Society Books Reviewing Procedures

8/10/2019 Society Books Reviewing Procedures

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Chapter 1

Introduction and previous research

A. J. BARBER, M. J. CROW & J. S. MILSOM

Sumatra, with an area of 473 ! "m # i$ the %are$t i$%an' in the In'one$ian ar(hi)e%ao an' the

fifth %are$t i$%an' in the wor%'.*he i$%an' $tret(he$ a(ro$$ the e+uator for 7! "m from -W to

SE, an' i$ u) to 4!! "m a(ro$$ /i. .0. A'mini$trati1e%2, an' for the )ur)o$e$ of thi$ Memoir,

Sumatra in(%u'e$ the Mentawaii$%an'$ from Simeu%ue to aai, whi(h with Enano form

aforear( (hain to the SW, an' the *in I$%an'$ of Ban"a an' Bi%%iton an' the Riau i$%an'$ to the

ea$t. *he 5a("5one of the main i$%an' i$ forme' of the Bari$an Mountain$, whi(h e6ten'the

who%e %enth of Sumatra in a narrow 5e%t, )ara%%e% to, an'enera%%2 on%2 a few ten$ of "i%ometre$,

from the SW (oa$t. *he main )ea"$ whi(h are main%2 uaternar2 or Re(ent

1o%(anoe$0(ommon%2 ri$e #!!! m a5o1e $ea %e1e%, (u%minatin in Mt8erin(i at 39!: m. Short,

$tee) ri1er (our$e$ 'rain the Bari$an$ towar'$ the SW, often (utttin 'ee) ore$, whi%e towar'$

the ea$t the ri1er$ fo%%ow %on mean'erin (our$e$ a(ro$$ 5roa' (oa$ta% )%ain$ an' $wam)$ to the

Ma%a((a Strait$, whi(h $e)arate Sumatra from the Ma%a2 enin$u%a, or to the Ja1a Sea.

Ea$twar'$, a(ro$$ the Ja1a Sea, %ie$ the a%mo$t e+ua%%2 %are i$%an' of BorneoIn'one$ian

8a%imantan0, an' Ja1a %ie$ imme'iate%2 to the SE a(ro$$ the narrow Sun'a Strait. *he Ma%a((a

Strait an' the Ja1a Sea form the $outhern )art$ of the Sun'a She%f /i. .0. A(ro$$ the $he%f the

$eaf%oor i$ $ha%%ow with a 'e)th of %e$$ than #!! m an' remar"a5%2 f%at. ;irtua%%2 the who%e ofthe $he%f wa$ e6)o$e' at the )ea" of the %a$t %a(iation. *o the SW, Sumatra i$ $e)arate' from a

%inear ri'e with emerent i$%an'$ e6ten'in from Simeu%ue in the north to Enano in the $outh,

52 marine 5a$in$ more than !!! m 'ee), whi(h in(rea$e to a 'e)th of more than #!!!m in the

$outh. *o the SW of the ri'e the $eaf%oor $%o)e$ $tee)%2 into the Sun'a *ren(h, :!!! m 'ee) in

the -W, 'ee)enin to


2/721

re%ati1e 7.7 (m a> --E>'ire(te' motion of the In'ian O(ean re$u%t$ in o5%i+ue (. 4: ?$u5'u(tion

at the Sun'a *ren(h. Sei$mi( )rofi%e$ a(ro$$ the %an'war' $i'e of the Sun'a *ren(h imae' the

remo1a% of )a("ae$ of $e'iment from the 'ownoin )%ate to 5ui%' a forear( ri'e a((retionar2

(om)%e6 =ami%ton @7@ 8ari et al. @9!0 /i. .30.O5%i+ue $u5'u(tion re$u%t$ in the

northwe$twar' mo1ement of a$%i1er )%ate Curra2 @9@0, 'e(ou)%e' 5oth from the 'ownoin

In'ian O(ean %ate an' the Sun'a%an' %ate, a%on the Wa'ati>Benioff $ei$mi( one, whi(h 'i)$

northea$twar'$ at (. 3! ? an' a%on the 1erti(a% Sumatran /au%t S2$tem. *he Wa'ati>Benioff

one inter$e(t$ the fau%t at a 'e)th of $ome #!! "m. *he a(ti1e Sumatran /au%t S2$tem run$ the

who%e %enth of the Sumatra, throuh the Bari$an Mountain$, from Ban'a A(eh to the Sun'a

Strait, an' i$ )ara%%e%e' 52 a %ine of uaternar2 1o%(anoe$, main%2 +uie$(ent, 5ut $ome (urrent%2

a(ti1e /i. .40.

eo%oi(a%%2, Sumatra form$ the $outhwe$tern marin of the

Sun'a Craton, whi(h e6ten'$ ea$twar'$ into enin$u%ar Ma%a2$ia

an' into the we$tern )art of Borneo /i. .#0. A re>*ertiar2

5a$ement i$ e6)o$e' e6ten$i1e%2 in the Bari$an Mountain$

/i. .40 an' in the *in I$%an'$ of Ban"a an' Bi%%iton. *he

o%'e$t ro("$ whi(h ha1e 5een re%ia5%2 'ate' are $e'iment$ of

Car5oniferou$>ermian ae, a%thouh De1onian ro("$ ha1e

5een re)orte' from a 5oreho%e in the Ma%a((a Strait, an'

un'ate' nei$$i( ro("$ in the Bari$an Mountain$ ma2 re)re$ent

a re>Car5oniferou$ (ontinenta% (r2$ta%%ine 5a$ement. A%% the

o%'er ro("$, whi(h %ie main%2 to the -E of the Sumatran

/au%t S2$tem, $how $ome 'eree of metamor)hi$m, main%2 to

%ow>ra'e $%ate$ an' )h2%%ite$, 5ut 2ouner ermo>*ria$$i( $e'iment$

an' 1o%(ani($ are %e$$ metamor)ho$e'. *he area to the

SW of the fau%t i$ (om)o$e' %are%2 of 1aria5%2 metamor)ho$e'

Jura$$i(>Creta(eou$ ro("$. *he re>*ertiar2 5a$ement i$ (ut 52

ranite )%uton$ that rane in ae from ermian to Late Creta(eou$.

Lo(a%%2 within the Bari$an$ the 5a$ement i$ intru'e' 52 *ertiar2

ineou$ ro("$ an' i$ o1er%ain to the -E an' SW 52 1o%(ani(%a$ti(

an' $i%i(i(%a$ti( $e'iment$ in h2'ro(ar5on> oi% an' a$0


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an' (oa%>5earin *ertiar2 $e'imentar2 5a$in$. *he$e 5a$in$ ha1e

5a("ar(, forear( an' interar( re%ation$hi)$ to the uaternar2 to

Re(ent 1o%(ani( ar(. La1a$ an' tuft$ from the$e 2oun 1o%(anoe$

o1er%ie the o%'er ro("$ throuhout the Bari$an$ an', in )arti(u%ar

(o1er an e6ten$i1e area in -orth Sumatra aroun' La"e *o5a

/i. .40. Re(ent a%%u1ia% $e'iment$ o((u)2 $ma%% ra5en$

within the Bari$an Mountain$, 'e1e%o)e' a%on the %ine of the

Sumatran /au%t an' (o1er %ower roun' throuhout Sumatra.

*he$e a%%u1ia% $e'iment$ are of f%u1ia% oriin imme'iate%2

a'a(ent to the Bari$an$, 5ut )a$$ into $wam), %a(u$trine an'

(oa$ta% 'e)o$it$ towar'$ the northea$tern an' $outhwe$tern

marin$ of the i$%an'.

History of geological research in

Sumatra before-WWII

Durin the %ate nineteenth an' ear%2 twentieth (enturie$ Sumatra

wa$ e6)%ore' 52 eo%oi$t$ an' enineer$ wor"in for minin

an' )etro%eum (om)anie$ un'er the au$)i(e$ of the Bureau of

Mine$ in the Dut(h Ea$t In'ie$ Co%onia% A'mini$tration. In @#:

a a%aeo5otani( E6)e'ition to Dam5i Jam5i0 wa$ un'erta"en

to (o%%e(t $am)%e$ of the Dam5i /%ora. *hi$ ear%2 wor" i$

$ummarie' 52 Rutten @#70 in hi$ Le(ture$ on the eo%o2

of the -ether%an'$ Ea$t In'ie$. Between @#7 an' @3 the

-ether%an'$ In'ie$ eo%oi(a% Sur1e2 (on'u(te' a ma))in

)roramme in South Sumatra with the )ro'u(tion of a $erie$ of

$i6teen F#!! !!! eo%oi(a% Ma) Sheet$ e.. Mu$)er @370,

an' (arrie' out other eo%oi(a% $tu'ie$ in Centra% an' -orthern

Sumatra Mu$)er @#@ Gwieri("i @##a, 5, @3!a0. Hnfortunate%2,

a$ a re$u%t of the %o5a% e(onomi( 'e)re$$ion, thi$

ma))in )roramme wa$ 'i$(ontinue' in @33, 5efore the

ma))in of the who%e i$%an' wa$ (om)%ete. =owe1er, the (e$$ation

of fie%'wor" )ro1i'e' an o))ortunit2 to )u5%i$h the re$u%t$


4/721

of the @#: a%aeo5otani( e6)e'ition to Dam5i Gwieri("i

@3!a Jonman$ & othan @3:0. E6)%oration 52 minin an'

)etro%eum (om)anie$ (ontinue' throuhout Sumatra, 5ut for

(ommer(ia% rea$on$ mo$t of the re)ort$ remaine' (onfi'entia%

an' un)u5%i$he'. =owe1er, $ome of the re$u%t$, nota5%2 for

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5/721

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wor" (arrie' out in Si5erut, -ia$ an' Simeu%ue an' the other Outer

Ar( I$%an'$ on 5eha%f of the -e'er%an'$ a(ifi( etro%eum

Maat$(ha))i an' the eo%oi(a% Ser1i(e of the Baataf$(he

etro%eum Maat$(ha))i 5efore WWII E%5er @3@ Den =arto

@4!a, 5 =o))er @4!0, were ma'e a1ai%a5%e to 1an Bemme%en

@4@, @7!0 'urin the )re)aration of hi$ maor $2nthe$i$ of

*he eo%o2 of In'one$ia.

;an Bemme%en 5ean wor" on thi$ (om)rehen$i1e an' ma$ter%2


6/721


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9/721

toothe' %ine $)rea'in (entre$ an'

tran$form fau%t$ are $hown in the An'aman

Sea after Curra2 et al. @7@0.

)ost-WWII research

Litt%e eo%oi(a% wor" wa$ )o$$i5%e 'urin the 2ear$ imme'iate%2

after the en' of WWII, 5ut fo%%owin In'one$ian In'e)en'en(e in

@47 the eo%oi(a% Sur1e2 of In'one$ia SI0 wa$ e$ta5%i$he' in

the o%' Bureau of Mine$ 5ui%'in in Ban'un. /rom @@ to @74

the Ma))in Di1i$ion of SI0 (ommen(e' a $2$temati( )roramme

of ma))in in the a'an area of We$t Sumatra, in (o%%a5oration

with the Hnite' State$ eo%oi(a% Sur1e2 HSS0, a$

)art of the /ir$t /i1e ear De1e%o)ment %an ELI*A I0.

Se1era% F#:! !!! eo%oi(a% Ma) Sheet$ were )u5%i$he' a$ a

re$u%t of thi$ )roramme Si%itona & 8a$towo @7: Ro$i'i

et al. @7 8a$towo & Leo @730. A$ )art of thi$ (o%%a5oration

a $enior eo%oi$t of the HSS, Warren =ami%ton, wa$ (ommi$$ione'

to )re)are a $erie$ of ma)$ an' a memoir re1iewin the

eo%o2 of the In'one$ian reion in )%ate>te(toni( term$

=ami%ton @77, @7@0. =ami%ton$ @7@0*e(toni( Ma), whi(h

in(%u'e$ Sumatra, $how$ (%ear%2 )re$ent 1iew$ of the te(toni(

$ettin of Sumatra.

SEA*AR )rogramme

In @73 a meetin wa$ (on1ene' 52 the Hnite' -ation$ Committee

for the Coor'ination of Joint ro$)e(tin for Minera% Re$our(e$

in A$ian Off>$hore water$ CCO0 in Ban"o" whi(h e$ta5%i$he'

the Stu'ie$ in Ea$t A$ian *e(toni($ an' Re$our(e$ SEA*AR0

roramme. At that time a re1iew of the (urrent un'er$tan'in

of the te(toni($ of ea$tern A$ia wa$ )re)are' 52 Der2(" Lamin

on 5eha%f of CCO>IOC @740. A$ a re$u%t of the meetin it

wa$ )ro)o$e' to (on(entrate re$ear(h a%on a $erie$ of tran$e(t$

a(ro$$ the i$%an' ar( $2$tem$ of Ea$t an' SE A$ia. Su5$e+uent%2


10/721

A. J. Bar5er Hni1er$it2 of Lon'on0 an' Der" Jon$ma BMR0

were enae' 52 CCO a$ *e(hni(a% Con$u%tant$ to )re)are a

re)ort on the (urrent $tate of "now%e'e a%on the %ine$ of

the$e tran$e(t$ CCO>IOC @9!0. One of the $e%e(te' tran$e(t$

ran from the Ma%a2 enin$u%a a(ro$$ northern Sumatra an' the

forear( i$%an' of -ia$ to the Sun'a *ren(h. A%thouh the fina%

re)ort for thi$ tran$e(t wa$ ne1er )u5%i$he', a reat 'ea% of

im)ortant re$ear(h wa$ (arrie' out 52 Ameri(an re$ear(her$

4 C=A*ER

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11/721

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:!

/i. .3. Diarammati( $e(tion a(ro$$ the Sumatran Su5'u(tion S2$tem from the f%oor of the

In'ian O(ean to the Ma%a2 enin$u%a, 'rawn to $(a%e.

un'er the au$)i(e$ of the SEA*AR roramme, )arti(u%ar%2 in -ia$

an' the $urroun'in $ea$ Curra2 et al. @9# 8ari et al. @9!

Moore & 8ari @9!0. A%$o in (onun(tion with the SEA*AR roramme,

Co55in et al. @@#0 ma'e a 'etai%e' $tu'2, in(%u'in

i$oto)i( 'atin, of the ranite$ on the *in I$%an'$ of Ban"a an'

Bi%%iton, $u))orte' 52 the H8 O1er$ea$ De1e%o)ment A'mini$tration

a$ a (ontri5ution to the wor" of FCO.

Sin(e the effe(ti1e termination of the SEA*AR roramme,

HS re$ear(h in Sumatra ha$ 5een (on(entrate' on neote(toni($,

an im)ortant )art of whi(h ha$ 5een the monitorin of mo1ement

a%on the Sumatran /au%t S2$tem, u$in S %o(ation $2$tem$

rawiro'ir'o et al. @@70.

Indonesian )etroleum Association

In @7 the In'one$ian etro%eum A$$o(iation IA0 wa$ e$ta5%i$he'

52 )etro%eum (om)anie$ o)eratin in In'one$ia, in a$$o(iation

with the In'one$ian nationa% oi% (om)an2, ertamina.

Sin(e it$ in(e)tion the IA ha$ he%' Annua% Con1ention$ whi(h

(ontinue to the )re$ent 'a2. At the$e (on1ention$ )a)er$ on the

eo%o2 of In'one$ia are )re$ente' an' )u5%i$he' a$ the ro(ee'in$


12/721

of the In'one$ian etro%eum A$$o(iation. *he IA

ro(ee'in$ )ro1i'e an in1a%ua5%e $our(e of information on the

eo%o2 of In'one$ia. Mo$t of the )a)er$ 'ea% with *ertiar2 'e)o$it$

an' 'etai%$ of the $tratira)h2 an' $tru(ture of the oi% an'

a$ fie%'$ of In'one$ia, in(%u'in tho$e of Sumatra, 5ut more

enera% )a)er$ on eo%o2 an' te(toni($ ha1e a%$o 5een )u5%i$he'.

*he )u5%i(ation of the IA ro(ee'in$ ha$ re$o%1e' 1an Bemme%en$

@4@0 (om)%aint of the )re>WWII $ituation, in whi(h %are

amount$ of eo%oi(a% 'ata, a((umu%ate' 52 the oi% (om)anie$,

remaine' un)u5%i$he' for (ommer(ia% rea$on$, an' were not a1ai%a5%e

for the (om)i%ation of reiona% eo%oi(a% $2nthe$e$.

+ritish and Indonesian 0eological Surveys

Maor H8 in1o%1ement in the eo%o2 of Sumatra 5ean in

@7: when the In$titute of eo%oi(a% S(ien(e$ IS, now the

Briti$h eo%oi(a% Sur1e2, BS0, in (o%%a5oration with the

eo%oi(a% Sur1e2 of In'one$ia SI0, (ommen(e' a fi1e>2ear

ma))in an' re(onnai$$an(e eo(hemi(a% $ur1e2 of northern

Sumatra to the north of the e+uator -orthern Sumatra roe(t,

-S0. In @79 SI wa$ reoranie' into a num5er of $emi>autonomou$

'ire(torate$ an' the Dire(torate of Minera% Re$our(e$

DMR0 5e(ame the 'e$inate' In'one$ian (ounter)art orani$ation

in the -S. *he wor" of IS in the -orthern Sumatra roe(t,

an' $u5$e+uent )roe(t$ 52 BS in Sumatra, were fun'e' from

the *e(hni(a% A$$i$tan(e an' *e(hni(a% Coo)eration 5u'et$ of

the H.8. O1er$ea$ De1e%o)ment A'mini$tration ODA0.

*he $tru(tura%, $tratira)hi(, eo(hemi(a% an' te(toni( re$u%t$

of the -orthern Sumatra roe(t ha1e 5een )re$ente' in a $erie$

of )a)er$ ae et al. @79, @7@ Cameron et al. @9! Ro("

et al. @9# A%'i$$ & haa%i @940 an' un)u5%i$he' re)ort$.

In a (ontinuation of the -S, eo%oi(a% ma)$ an' re)ort$ re$u%tin

from the )roe(t were e'ite' 52 BS )er$onne%, an' )u5%i$he'


13/721

52 the In'one$ian eo%oi(a% Re$ear(h an' De1e%o)ment

Centre RDC0, one of the (on$tituent 'ire(torate$ of SI,

a$ a $erie$ of 9 eo%oi(a% Ma) Sheet$ at F#:! !!! $(a%e,

with a((om)an2in E6)%anator2 -ote$. /o%%ow>u) $tu'ie$ of

fo$$i% %o(a%itie$, with the 1iew of e$ta5%i$hin the $tratira)hi(a%

ae$ of the $e'imentar2 unit$ in Sumatra, were (arrie' out

52 Met(a%fe @93, @9, @9@a, 5 Met(a%fe et al. @7@0 an' 52

/ontaine an' hi$ (o%%a5orator$, un'er the au$)i(e$ of FCO

/ontaine & afoer @9@0. *he re$u%t$ of the reiona% eo(hemi(a%

$tream $e'iment $am)%in $ur1e2 were )u5%i$he' in a oint

ISNDMR eo(hemi(a% At%a$ Ste)hen$on et al. @9#0 an' $u5$e+uent%2

DMR )u5%i$he' $et$ of $in%e e%ement )ro)ortiona%

$2m5o% 'i$tri5ution ma)$ at F#:!!!!, for man2 of the

+ua'ran%e$ to the north of the e+uator. eo(hemi(a% anoma%ie$

foun' 'urin the -S were fo%%owe' u) 52 BS an' DMR

in the (o%%a5orati1e -orth Sumatra eo%oi(a% an' Minera%

E6)%oration roe(t -SME, @9:>@990. *he re$u%t$ of a

$e)arate )roramme of re$ear(h into the minera%iation in north

Sumatra, a%$o fun'e' 52 H8 ODA, ha1e 5een )u5%i$he' 52

Bow%e$ et al. @94, @9:0 an' Be''oe>Ste)hen$ et al. @970.

niversity of ondon Southeast Asian ,esearch 0roup%

+0S and "I0AS

In @79 mem5er$ of the Hni1er$it2 of Lon'on Southea$t A$ian

Re$ear(h rou) whi(h ha' )re1iou$%2 5een a(ti1e in Ea$tern

In'one$ia, (ommen(e' a )roramme of re$ear(h )roe(t$ in

Sumatra, in (o%%a5oration with BS, DMR an' RDC. In @94

a oint Hni1er$it2 of Lon'onNBS -orth Sumatra Ba$in$

Stu'2 roe(t, wa$ $et u) with fun'in from the H8 O1er$ea$

De1e%o)ment A'mini$tration, in (o%%a5oration with the In'one$ian

Re$ear(h an' De1e%o)ment Centre for Oi% an' a$ *e(hno%o2

LEMIAS0 8ir52 et al. @@30. *hi$ )roe(t 5ui%t on the maor


14/721

in1o%1ement 52 LEMIAS in thi$ )ro'u(ti1e 5a$in, where

one of the %are$t e6)%oration 5%o("$ i$ o)erate' 'ire(t%2 52

ertamina. *he o1era%% )roramme wa$ %are%2 (on(erne' with

the $tratira)h2, $e'imento%o2 an' eo)h2$i($ of the *ertiar2

5a$in$ in northern Sumatra, with the Hni1er$it2 (ontri5ution

Con(entratin on fie%' $tu'ie$ of the re%ation$hi) of the *ertiar2

ro("$ to the un'er%2in 5a$ement, with a 1iew to un'er$tan'in

the te(toni( e1o%ution, of the$e 5a$in$ *urner @93 *i%tman

@97, @@! 8a%%aher @@!0. More re(ent%2 the Hni1er$it2 of

Lon'on (ontri5ution, fun'e' 52 the H8 -atura% En1ironment

Re$ear(h Coun(i% -ERC0, ODA an' a num5er of oi% (om)anie$,

I-*RODHC*IO- :

I

@?

+andaAceh

I

@9 ?

I

1 #& /

4 ?

>!?

Line of

Se(tion

/i.%.3.

Nias

?2

>4 ?

.

uaternary-,ecent volcanics


15/721

?ertiary Sediments and volcanics

)re-?ertiary +asement

I

!# ?

A

! !!

. F . F . F . F . F . F . F . F .

. . . . . . . . . . . . V >F>F.F>F>F>F>F>F.F>F.F... ...>

FiF?iFiFiFiFiFiFiFiFiFi

I

!4 ?

Active $olcano

Sumatran Eault System

Deformation Eront of the

Sumatran Subduction

CompleF

#!! 3!! 4!!

..............

i i F i i % i F F F i F F F i i i F ? ? F F i i i i ? m 5 a n

?..iiFF..? FFFiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiIii iiiiiiiiiiii. Ben"u F F i ? > > >>>

I

! ?

? >

4 o .

:!!"m

# ? >

! o>

# ? >

@ / -

/)un

? >


16/721

@? @9 ? !! ? !# ? !4 ? ! ?

i I I : I I I

/i. .4. Sim)%ifie' eo%oi(a% ma) of Sumatra $howin the 'i$tri5ution of the main $tratia)hi(

unit$ an' the a(ti1e 1o%(anoe$. *oothe' %ine mar"$ the 'eformation

front of the Sumatran Su5'u(tion S2$tem. *he %ine of $e(tion in /i. .3 i$ a%$o $hown.

5e(ame in(rea$in%2 (on(entrate' in the forear( i$%an'$, where

a $erie$ of eo%oi(a% ma))in an' ra1it2 $ur1e2$ were

(om)%ete' Situmoran et al. @97 Mi%$om et al. @@! =ar5ur2

& 8a%%aher @@ Samue% & =ar5ur2 @@ Samue% et al.

@@70. At the $ame time LEMIAS (o%%a5orate' with the

/ren(h C-RS Centre -ationa% )our Re(her(he S(ientifi+ue0 in

a num5er of $tu'ie$ in the forear( reion u$in the In'one$ian

Marine Re$ear(h ;e$$e% Baruna Ja2a III Diament et al. @@#

Iart et al. @@40. Out$i'e the 5oun'$ of the -S, Hni1er$it2 of

Lon'on Staff an' re$ear(h $tu'ent$ with fun'in from -ERC,

ODA an' a Con$ortium of )etro%eum (om)anie$ (o%%a5orate'

with LEMIAS on $tu'ie$ on the Om5i%in interar( 5a$in

in (entra% Sumatra Lai%e2 @9@ Bartram & -urahanin$ih

@@! =owe%%$ @@750, the Wo2%a rou) in -orth Sumatra

Waer et al. @@ Bar5er #!!! M(Carth2 et al. #!!0 an' a

$tu'2 of the Sumatran /au%t S2$tem throuhout the i$%an'

M(Carth2 & E%'er$ @@70.

Southern Sumatra )roGect

eo%oi(a% ma))in, ra1it2 $ur1e2$ an' eo(hemi(a% )roramme$

in Sumatra $outh of the e+uator were (on'u(te' 52 RDC

an' DMR 'urin ELI*A II @74>7@0 an' in $u((e$$i1e fi1e

2ear 'e1e%o)ment )roramme$, (ontinuin into the @9!$. In

@99 the Southern Sumatra eo%oi(a% an' Minera% E6)%oration

roe(t SSME0 wa$ e$ta5%i$he', an' BS oine' DMR an'

RDC in the (om)%etion of the$e $ur1e2$ an' in re$ear(h

C=A*ER


17/721

r./i/o: d o

NB,,a n,.' a A...(..e.h N ? . Lho. ". .$.e. .u.m. awe

;GGGEGA

i?..o4. #o H.N

re5int)i I

t7

NSi'i"afan, ?,Nematan Baan$ia)ia)i

?NNNN? N $iantar . . N ( > ? N . N N N . N

a'an$i'em)uan

!IK 3!,

K5

-E Muara$i5erut

Sunai)enuh

an'

8etuan

., !@3 N ...

> ? t ? ? ? >?,..f?

t3 O! #!! 3!! ................. 4!! :!!"in 7 N

/i. .:. Co1erae, $heet num5er$ an' name$ of the F#:! !!! eo%oi(a% Ma)$ )u5%i$he' 52 the

In'one$ian eo%oi(a% Sur1e2, the eo%oi(a% Re$ear(h an'

De1e%o)ment Centre, In'one$ian Mini$tr2 of Mine$ an' Ener2.

)roramme$ with fun'in from H8 ODA *e(hni(a% Coo)oration

5u'et. *hi$ )roramme wa$ (om)%ete' in @@: with the )u5%i(ation

52 RDC of the %a$t of the fort2 three eo%oi(a% Ma)

Sheet$ at F#:!!!! $(a%e, (o1erin the who%e of Sumatra

/i. .:0 an' 9 F#:!!!! $(a%e Bouuer ra1it2 anoma%2

ma)$ of $outhern Sumatra, in(%u'in Ban"a an' Bi%%iton

i$%an'$, 5ut e6(%u'in the (oa$ta% $wam)$ an' the Bari$an

Mountain$. *he (o%%a5orati1e eo(hemi(a% $ur1e2 wa$ (om)%ete'

in @@4 with the )u5%i(ation 52 DMR of 4 +ua'ran%e 5o6e' $et$

of F#:! !!! $in%e e%ement )ro)ortiona% $2m5o% eo(hemi(a%


18/721

ma)$ u) to : e%ement$0 with a((om)an2in re)ort$ on the

eo(hemi$tr2, eo%o2 an' minera% o((urren(e$. Su5$e+uent%2

the Sumatra eo(hemi(a% 'ata wa$ ma'e a1ai%a5%e on CD>ROM

;er$ion # in @@@0. In @@: fo%%owin a one>2ear Su$taina5i%it2

ha$e of the SSME a eo(hemi(a% At%a$ of Southern

Sumatra wa$ i$$ue' in 'iita% form on CD>ROM Ma(ha%i et al.

@@:0. u5%i(ation in 5oo" form fo%%owe' in @@7, with te6t in

5oth Baha$a In'one$ia an' En%i$h Ma(ha%i et al. @@70. An

e1a%uation of te(toni( mo'e%$ for the re>*ertiar2 hi$tor2 of

Sumatra 5a$e' on BSNDMRNRDC an' Hni1er$it2 of Lon'on

re$ear(h )roramme$ ha$ 5een )u5%i$he' 52 Bar5er & Crow

#!!30.With the (om)%etion of thi$ maor )ha$e of H8

in1o%1ement in the $tu'2 of the eo%o2 of the Sumatra, the

time i$ ri)e to re1iew the 1a$t in(rea$e in our "now%e'e of

the eo%o2 of Sumatra $in(e 1an Bemme%en$ @4@, @7!0

$2nthe$i$.

Chapter 7

Seismology and neotectonics

JO=- MILSOM

Sumatra i$ an a(ti1e An'ean0 (ontinenta% marin that wou%' 5e

%in"e' 52 %an' to SE A$ia if $ea %e1e% fe%% 52 a$ %itt%e a$ :! m.

re$ent>'a2 te(toni( )ro(e$$e$ are (ontro%%e' 52 three maor

fau%t $2$tem$, the mo$t o51iou$ of whi(h i$ the $u5'u(tion thru$t

whi(h (ro)$ out in the Sun'a *ren(h. *he tren(h (ur1e$ 1er2

%itt%e in the 9!! "m 5etween Enano an' -ia$, i.e. off (entra%

Sumatra /i. #.0, 5ut i$ mar"e'%2 (on1e6 towar'$ the In'ian

O(ean 5oth further north an' further $outh. Water 'e)th$ of

more than !!! m are rea(he' in the $outh 5ut the ma6imum in

the north ma2 5e %e$$ than :!!! m. *he 'ifferen(e i$ u$ua%%2,

an' (on1in(in%2, attri5ute' to the )re$en(e on the In'ian O(ean

)%ate of the -i(o5ar /an, (on$i$tin of $e'iment$, 'eri1e'


19/721

u%timate%2 from ero$ion of the =ima%a2a$, whi(h in(rea$e $tea'i%2

in thi("ne$$ towar'$ the north e.. =ami%ton @7@0. Continuin

$u5'u(tion i$ atte$te' 52 a Wa'ati>Benioff Gone WBG0 that

e6ten'$ to 'e)th$ of the or'er of #!! "m e.. -ew(om5 &

M(Cann @970 an' 52 1o%(ani( a(ti1it2 in the Bari$an mountain$,

the )ea"$ of whi(h enera%%2 %ie within a few ten$ of "i%ometre$

of the (oa$t. *he (hane, of more than 4: ? in the tren' of the

tren(h 5etween @? an' @7? the -ia$ E%5ow0 ma2 ha1e

5een initiate' 52 $u5'u(tion of the # "m hih In1e$tiator Ri'e

In1e$tiator /ra(ture Gone0, whi(h tren'$ a))ro6imate%2 north$outh

at a5out @9? Sieh & -atawi'aa #!!!0 'efine' a

Centra% Domain of main%an' Sumatra 5etween the -ia$ E%5ow

an' the ri'e inter$e(tion a$ anoma%ou$ in a num5er of wa2$

nota5%2 in the 'ifferin tren'$ of the Sumatran /au%t an' the

1o%(ani( %ine0 an' a$ 'i$tin(t from more reu%ar -orthern an'

Southern 'omain$ on either $i'e /i. #.0.

In%an', the 'e6tra% tran$(urrent Sumatran /au%t run$ the entire

%enth of the i$%an', from Ban'a A(eh to the Sun'a Strait

/i. #.0. A 1ariet2 of name$ ha1e 5een u$e' for 5oth the

o1era%% fau%t $2$tem an' )art$ of it, an' new nomen(%ature

'e1e%o)e' 52 Sieh & -atawi'aa #!!!0 'i1i'e' it into @ in'i1i'ua%

$ement$. E1en thi$ 'etai%e' $tu'2 fai%e' to an$wer man2

fun'amenta% +ue$tion$, an' e$timate$ of tota% %atera% 'i$)%a(ement

$ti%% 1ar2 from $e1era% hun're' "i%ometre$ to a$ %itt%e a$ twent2

"i%ometre$. *he :!"m $ue$te' 52 M(Carth2 & E%'er$

@@70 $eem$ to 5e a5out the mean of the )u5%i$he' 1a%ue$. *he

fau%t tra(e (oin(i'e$ rouh%2 with the water$he' of the Bari$an$

an' with the 1o%(ani( %ine, a%thouh mo$t of the 1o%(anoe$ %ie

$omewhat to the -E of the fau%t an' on%2 nine of the fift2 2oune$t

(entre$ %ie within # "m of it Sieh & -atawi'aa #!!!0. A more

)re(i$e (orre%ation i$ with the $u5'u(tion thru$t, $in(e for mo$t


20/721

of it$ %enth the 'i$tan(e 5etween the Sumatran /au%t an' the

tren(h a6i$ 'iffer$ 52 no more than 3! "m from the a1erae

1a%ue of #@! "m. *he %are$t 'e1iation$ are a narrowin within

the 5iht of the -ia$ E%5ow an' a 5roa'enin in the reion

further to the -W.

*he thir' an' mo$t enimati( of Sumatra$ maor fau%t $2$tem$

i$ the Mentawai /au%t, at the outer marin of the forear( 5a$in

/i. #.0. In man2 )u5%i(ation$ the name i$ re$er1e' for the

$ement e6ten'in from the Sun'a Strait to -ia$ Samue% &

=ar5ur2 @@0 or the Batu I$%an'$ Diament et al. @@#0, 5ut the

$ame 'i$tur5an(e one (ontinue$ at %ea$t a$ far a$ the An'aman

Sea Ma%o' & 8ema% @@0 an' )o$$i5%2 to the An'aman an'

-i(o5ar I$%an'$. Mo1ement ha$ 5een 1ariou$%2 inter)rete' a$

norma%, $tri"e $%i) or re1er$e Sieh & -atawi'aa #!!!0. *here

are (on$i'era5%e (hane$ in a))earan(e on $ei$mi( $e(tion$

e1en within the reion from -ia$ $outhwar'$ the $tru(ture wa$

'e$(ri5e' 52 Sieh & -atawi'aa #!!!0 a$ a homo(%ine an' 52

8ari et al. @9!0 a$ a fau%t>f%e6ure.

Maneti( anoma%ie$ in the In'ian O(ean $outh of Sumatra

tren' ea$t>we$t an' were inter)rete' 52 S(%ater & /i$her @740

a$ in'i(atin a%aeoene ae$ for mo$t of the (ru$t a'a(ent to

the tren(h, with a )o$$i5i%it2 of Late Creta(eou$ (ru$t in the

e6treme SE. *ran$form$ $u(h a$ the In1e$tiator /ra(ture Gone,

whi(h ma2 off$et the anoma%ie$ 52 $e1era% hun're' "i%ometre$,

run a%mo$t )re(i$e%2 north>$outh. With the tren' of the tren(h

1ar2in from -4!? to -!? an' the 'ire(tion of the In'ian

O(ean>Sumatra (on1eren(e 1e(tor 5ein a5out -:? /i. #.0,

Sumatra ha$ %on 5een re(onie' a$ a "e2 area for $tu'ie$ of

the )artitionin of $train 5etween thru$t an' tran$(urrent fau%t$

'urin o5%i+ue (on1eren(e /it(h @7# M(Caffre2 @@#, @@

Ma%o' & 8ema% @@0. *he $ue$tion, oriina%%2 ma'e 52


21/721

/it(h @7#0, that the o5%i+ue motion i$ to a fir$t a))ro6imation

a((ommo'ate' 52 orthoona% $u5'u(tion at the tren(h an'

'e6tra% $%i) a%on the Sumatran /au%t, i$ now wi'e%2 a((e)te'.

*o the e6tent that thi$ i$ true, the forear( reion mu$t 5e 'e(ou)%e'

from 5oth the In'ian O(ean an' Eura$ia. *he (ommon%2 u$e'

term $%i1er )%ate e.. Curra2 @9@0 $ue$t$ more $trenth an'

rii'it2 than (ou%' rea$ona5%2 5e e6)e(te' of $u(h a %on an'

narrow $tri) of %itho$)here, an' an2 ana%2$i$ of $u5'u(tion

5eneath Sumatra mu$t ta"e into a((ount the )ro5a5i%it2 of in'e)en'ent

mo1ement$ of forear( frament$ e.. M(Caffre2 @@0.

E$timate$ of the mo1ement$ of the In'ian O(ean re%ati1e

to Sumatra are $hown in /iure$ #. an' #.4. Chane$ in manitu'e

an' 'ire(tion from -W to SE are 'i(tate' 52 the Ea$t

Afri(an %o(ation of the )o%e of rotation Lar$on et al. @@70. If )artitionin

of orthoona% an' tran$(urrent $train 5etween, re$)e(ti1e%2,

the tren(h an' the Sumatran /au%t were (om)%ete an'

mo1ement o((urre' on%2 a%on the$e feature$0, then $ite$ in the

forear( $%i1er wou%' mo1e )ara%%e% to the Sumatran /au%t re%ati1e

to SE A$ia, 5ut at riht an%e$ to the tren(h re%ati1e to the

In'ian O(ean. *ren(h>norma% re%ati1e motion im)%ie$ that the

forear( $%i1er tra("$ a(ro$$ %inear feature$ on the In'ian O(ean

%ate, $u(h a$ the In1e$tiator /ra(ture Gone, whi(h ha1e north$outh

tren'$ /i. #.0. If the %on term mo1ement 5etween the

forear( an' the In'ian O(ean ha$ a(tua%%2 5een a))ro6imate%2

orthoona%, the inter$e(tion )oint of the In1e$tiator /ra(ture

Gone with the tren(h, now near the Batu I$%an'$, wou%' ha1e

5een north of -ia$ %e$$ than ! mi%%ion 2ear$ ao. *he re%ief, of

more than # "m, on the In1e$tiator /ra(ture Gone miht not

on%2 im)e'e $u(h tra("in 5ut (ou%' 5e re$)on$i5%e for (2(%i(a%

u)%ift an' $u5$i'en(e in the forear( 5a$in an' ri'e.

S%i) )artitionin an' $u5'u(tion of In'ian O(ean %itho$)here


22/721

)ro'u(e hih %e1e%$ of $ei$mi(it2 in the Bari$an Mountain$, in

the forear( 5a$in an' a%on the forear( ri'e /i. #.#0. *he )otentia%

for e6treme%2 'e$tru(ti1e earth+ua"e$ wa$ mo$t re(ent%2

'emon$trate' 52 the Manitu'e @ e1ent near Simeu%ue in De(em5er

#!!4 an' 52 the re$u%tin t$unami, whi(h a1e ri$e to one of

the wor$t natura% 'i$a$ter$ in re(or'e' human hi$tor2. =owe1er,

an' 'e$)ite the eo%oi(a% e1i'en(e for a %on hi$tor2 of $u5'u(tion

e.. ae et al. @7@0, $ho("$ 'ee)er than #!! "m are rare

/i. #.30. E1ent$ 5e%ow 3!! "m are (onfine' to the e6treme SE

an' ma2 5e a$$o(iate' with north>'ire(te' $u5'u(tion 5eneath

Ja1a rather than -E>'ire(te' $u5'u(tion 5eneath Sumatra. *he

a5ru)t (hane in orientation of the a(ti1e marin 5etween the$e

two i$%an'$ mu$t )ro'u(e (on$i'era5%e $tre$$ in the 'ownoin

9 C=A*ER #

Northern Domain

Central Domain

Southern Domain

1&&& / LI-E >>?%

4#>43 Batu

)ora -.

E%5ow

Eig3 #.. SumatraF the neote(toni( $ettin. *he fiure ha$ 5een oriente' on the main fau%t

'ire(tion. *he In'ia>SE A$ia (on1eren(e 1e(tor (hane$ $inifi(ant%2 in 5oth

'ire(tion an' manitu'e o1er the %enth of the i$%an', from :# mm a> 'ire(te' at -!? at #?

@:? to ! mm a>% 'ire(te' at - 7? at ? !#? Con1eren(e

'ata an' main%an' $tru(tura% 'omain$0 are from Sieh & -atawi'aa #!!!0. E%onate'

re(tan%e$ in the forear( reion in'i(ate the %o(ation$ of the ero$ on the $ei$mi(it2

(ro$$>$e(tion$ in /iure #.3. *he $ei$mi( imae a%on Line 4#>43 i$ $hown in /iure #.7. *he

white $tar$ mar" the e)i(entre$ of the Enano #!!! an' Simeu%ue

#!!4 reat Earth+ua"e$. Bath2metri( (ontour$ at #!!, !!!, 3!!!, :!!! an' !!! m are from

EBCO @@70. Sha'in in'i(ate$ $ea f%oor 'ee)er than !!! m. I./.G.,


23/721

In1e$tiator /ra(ture Gone. On$hore to)ora)h2 'eri1e' from the %o5a% Re%ief Data CD>ROM

'i$tri5ute' 52 the -ationa% eo)h2$i(a% Data Center, Bou%'er, Co%ora'o.

$%a5 5ut thi$ i$ not o51iou$ in the )attern$ of $ha%%ow $ei$mi(it2

$hown in /iure #.# an' 'i$(u$$e' 5e%ow.

Shallo seismicity

A$ in mo$t a(ti1e (ontinenta% marin$, $ha%%ow K! "m 'e)th0

earth+ua"e$ in Sumatra are 'i$tri5ute' o1er wi'e area$ of the

u))er )%ate an' are not re$tri(te' to the WBG /i. #.#0.

Ma6imum $ha%%ow earth+ua"e a(ti1it2 o((ur$ within the $%i1er

'efine' 52 the Sumatran /au%t in the ea$t an' 52 the $u5'u(tion

thru$t in the we$t an' at 'e)th, an' i$ mo$t inten$e a%on the

%ine of the forear( ri'e. *here mu$t 5e (on$i'era5%e forear(

e6ten$ion $ee M(Caffre2 @@ 0 if the e$timate$ of %are 1ariation$

in rate$ of tran$(urrent $%i) more than 4!! "m of off$et in A(eh

5ut ne%ii5%e 'i$)%a(ement$ in the Sun'a Strait Curra2 et al.

@790 are (orre(t $ee a%$o Be%%ier & Se5rier @@:0. A%thouh

there ha1e 5een re%ati1e%2 few $ho("$ of Manitu'e or reater

5eneath the main%an', $ome ha1e o((urre', mo$t nota5%2 in

the 1i(init2 of the e+uatoria% 5ifur(ation in the Sumatran /au%t

i'entifie' 52 rawiro'ir'o et al. #!!!0.

*he in$et$ to /iure #.# attem)t to $how $e)arate%2 the 'i$tri5ution$

of e1ent$ within the u))ermo$t 4! "m of the (ru$t an'

at 'e)th$ of 5etween 4! an' ! "m. Be(au$e of the un(ertaintie$

inherent in 'eterminin the 'e)th$ of $ha%%ow earth+ua"e$ $ee

'i$(u$$ion in En'ah% et al. @@90, there wi%% 5e e1ent$ on one

ma) that $hou%' )ro)er%2 ha1e 5een )%otte' on the other, 5ut the

o1era%% 'ifferen(e$ 5etween the )%ot$ are %i"e%2 to 5e rea%. *he

4!>! "m e1ent$ are (on(entrate' in a narrow one (entre' on

the forear( 5a$in an' mo$t are )ro5a5%2 'ire(t%2 a$$o(iate' with

the $u5'u(te' o(eani( %itho$)here, i.e. with the WBG. *here are,

howe1er, $ome $imi%aritie$ with the )attern$ of $ha%%ower e1ent$,


24/721

noti(ea5%2 in the ten'en(2 for e)i(entre$ to 5e (on(entrate' in

$hort %inear one$ at riht an%e$ to the tren(h, )re$uma5%2 'ue

to $ome form of forear( $ementation. *he mo$t o51iou$ e6am)%e$

(an 5e $een aroun' Enano an' we$tern Simeu%ue, i.e. (%o$e to

the $ite$ of the reat Earth+ua"e$ 'efine' a$ earth+ua"e$ with

MW manitu'e$ reater than a5out 7.90 in June #!!! an' De(em5er

#!!4 re$)e(ti1e%2. Intere$tin%2, the Simeu%ue e1ent$ (%u$ter

a%on the (re$t of a 5a$ement ri'e that 'efine$ the northwe$tern

5oun'ar2 of a marine an' $e'imentar2 5a$in Simeu%ue Ba$in0

where ma6imum water 'e)th$ e6(ee' !!! m. *he tren' of the

%inear a%inment$ (hane$ $%iht%2 north of the -ia$ E%5ow to

)art%2 mat(h the (hane in orientation of the tren(h 5ut, $ur)ri$in%2,

-E>SW a%inment$ of e)i(entre$ (an 5e $een ea$t of the

e1en more 'ramati( (hane 5etween Sumatra an' Ja1a /i. #.#0.

A $e(on' feature of the $ha%%ow $ei$mi(it2 i$ the $e)aration

of the $ha%%owe$t earth+ua"e$ /i. #.# %ower in$et0 into two

'i1erent one$, one a%on the forear( ri'e with a 5en' or

off$et where the In1e$tiator /ra(ture Gone enter$ the $u5'u(tion

one near the Batu i$%an'$0, the other 1er2 a))ro6imate%2 a%on

the we$t (oa$t of Sumatra. *he forear( 5a$in it$e%f i$ re%ati1e%2

+uiet $ei$mi(a%%2 at the$e 'e)th$. *he off$et at the In1e$tiator

/ra(ture Gone i$ intere$tin 5e(au$e -ew(om5e & M(Cann

@970 note' that ru)ture$ a$$o(iate' with reat Earth+ua"e$ 'o

not )ro)aate a(ro$$ thi$ reion. In 933 a Manitu'e Mw0 9.7

e1ent fau%te' the )%ate marin for a5out !! "m from Enano

to the Batu I$%an'$, whi%e the effe(t$ of the Mw 9.4 e1ent in

9 were (onfine' to a 3!! "m $ement 5etween the Batu an'

Ban2a" I$%an'$.

?he Wadati-+enioff one JW+;

In "ee)in with the (ontinenta% marin $ettin, $ei$mi(it2 5eneath

Sumatra i$ more 'iffu$e than 5eneath a t2)i(a% intra>o(eani( ar(.


25/721

*hi$ i$ i%%u$trate' in /iure #.3, whi(h $how$ h2)o(entre 'i$tri5ution$

within three t2)i(a% $wathe$, ea(h #!! "m wi'e. In the

e6treme -E /i. #.3a0 the WBG form$ the %ower 5oun'ar2 to a

$ei$moeni( one that e6ten'$ u) to the $urfa(e o1er a 'i$tan(e

of a))ro6imate%2 3!! "m from the tren(h. *he reate$t (on(entration

of e1ent$ i$ at a5out I!! "m from the tren(h an' at

'e)th$ of a5out :! "m. In the $wathe imme'iate%2 $outh of the

e+uator, near the i$%an'$ of Si5erut an' Si)ora, there i$ a mu(h

SEISMOLO & -EO*EC*O-ICS @

i =2)o(entre$ a5o1e 4! "m o

oe L a t e > . N=2)o(entre$ 4!>! "m

N e,++"

.N

,i.

Kuator

B

.XX?X

LLL@o - =o Bm on4y

!,? o

3!! "in > N !

oX

XI? COo ,

o #o

o

#o o o

, , > ,

N

? N o ,

'( %!6 L 1

. . . . N Xo N

4!"u, o,,? Q o ?!$/ o


26/721

X XXXFX X?X I / 2 2 3 LI / o / .

I X ? ,e F ?

X @ ........ ? X , X X

X,X XXXX FXX XX XXX XX.XF. .. I ... /oo'|r e, +o o "


27/721

A more (om)rehen$i1e )i(ture of Sumatra $ei$mi(it2 than i$

)ro1i'e' 52 /iure #.3 wa$ )re$ente' 52 =anu$ et al. @@0,

who )%otte' h2)o(entre$ within :! "m wi'e, -E>SW $wathe$

that toether (o1ere' the who%e of the i$%an'. Arua5%2 their

mo$t intere$tin )%ot wa$ A:, whi(h in(%u'e' the northern )art

of the forear( i$%an' of -ia$ an' mu(h of the *o5a (a%'era

/i. #.0. *he WBG in thi$ reion 'i)$ at an an%e of a %itt%e

more than 3! ? an' the 'ee)e$t $ho("$ o((ur 5etween #!! an'

#:!"m. *here i$ a $ma%% 5ut noti(ea5%e a) in $ei$mi(it2

5eneath the 1o%(ani( %ine at 'e)th$ of a5out :! to 9! "m an'

a (orre$)on'in reion of $ha%%ow $ei$mi(it2 imme'iate%2

5eneath the 1o%(anoe$.

In 'etai%, the )i(ture )ro1i'e' 52 =anu$ et al. @@0 i$ $u$)e(t

5e(au$e of the re%ian(e on Internationa% Sei$mo%oi(a% Centre

* R /

#!! !! ! !! #!! 3!!

o &L/L3% oL33LL / I o 0 o +to oXo..? ? .

o o o?. o,? ? ? . o F .

o !// 6 o

o o o O!

-orth

o P o

* R o o / ? I %? #!!

o . . .e o ? . . ?, . . F o F F > i I I o

. . . . . . ? > F,? o o,?, o F

> 3 - & & 36 / a;

'( '( '( o

Simeu%ue

* R /

#!! !! ! !! #!! 3!!

o o0o o o o


28/721

o / > e/

6 6 3 3 3 3 o%% o /o% / o

o

. . . . . . . . . . . . . . . . . . . . .

O

Centra%

I!!

#!!

?! * !! RO !! /#!! 3!

o o 5o !

oo F o ! o

/ o '( oi/o3#o O l l 3 ' % % 3 3 o 6

2 L 3 3 3 3 3 3 6 6 3o/ O2P>/l,m/-?/33%% /

6 6% 3333 i / L%/%3/ 3

3 %/o /LL/'/l5llm/ o . . . . Ioo

. . . . F? F F A?o 7K


29/721

'ata were 'own%oa'e' from $u))%ementar2 materia% to En'ah% et al. @@90.

Di$tan(e$ in "i%ometre$, no 1erti(a% e6aeration.

ISC, *hat(ham, H80 h2)o(entre %o(ation$. *he$e, 5ein

'eri1e' from inter)retation$ of te%e$ei$mi( 'ata 5a$e' on %o5a%

1e%o(it2 mo'e%$, are ine1ita5%2 of fair%2 %ow a((ura(2. *he $inifi(an(e

of thi$ %imitation ha$ 5een 'emon$trate' 52 /aui et al.

@@0, who u$e' a''itiona% 'ata from a new%2 e$ta5%i$he' 5ut

now )ermanent0 networ" of $hort>)erio' 'iita% $ei$mometer$ to

$tu'2 earth+ua"e$ in the 1i(init2 of *o5a. *he )rimar2 aim of

the wor" re)orte', whi(h (o1ere' the )erio' from O(to5er @@!

to A)ri% @@3, wa$ to in1e$tiate a h2)othe$ie' 5rea" in the

'ownoin $%a5 'ue to $u5'u(tion of the In1e$tiator /ra(ture

Gone. Sei$mi( a(ti1it2 wa$ foun' to 5e unu$ua%%2 hih in the

a))ro)riate area 5ut no 'i$(ontinuit2 wa$ 'ete(te' an' a %imit

of #! "m wa$ )%a(e' on the manitu'e of an2 )o$$i5%e 'i$)%a(ement.

*here wa$ more $u((e$$ with a $u5$i'iar2 o5e(ti1e of

'efinin the $ha)e of the WBG a$ it fo%%owe' the 5en' in the

off$hore tren(h 5etween -ia$ an' Simeu%ue. In (ontra$t to 5oth

the ISC an' En'ah% et al. @@90 'ata, h2)o(entre$ 'eri1e'

from the %o(a% $tu'2 an' )%otte' for narrow (ro$$>$tri"e $wathe$

! C=A*ER #

/3aBe

!

+atu

IS.

I Indian ~

: [Ocean/

S !ia

con#er$ence

. . . . . . . . . . . . . . . . . . . . . . # e c t o r %

&2 /(r


30/721

! 3!! "m

Sipor

B%)-tra ih? ?f? S?

- ?%?a%

Convergence velocity scale .... Y

Q&mm.yr ? ?

Contour$ on the WBG

in the *o5a reion, after .

/. au.i et a.%., @.@ . )~ I n d i a n .

June 7&&& nggano earthKuaBe ? Ocean/ I

Main ? After$ho("$? ?? con#eSr$!enciae [ /

$ho("$ ? ". ? #ector I

December 7&&@ Simeulue & ? &* / # r / .. ..

"arch 7&&Q Nias ,IL N

earthKuaBes Main $ho("$ ? ?

f

Kuator

i

en$l1

. . . . . o

ngganc

o !

........ ............................. S

Eig3 #.4. Mo1ement$ of $ite$ in Sumatra a$ 'etermine'

52 S o5$er1ation$ 'urin the )erio' @9@>@@3

rawiro'ir'o et al. @@70. ;e(tor$ $how rate$ of

mo1ement re%ati1e to a $ta5%e SE A$ia. *he2 im)%2 $tre$$

a((umu%ation in )art$ of the forear( reion, $ome

of whi(h wou%' ha1e 5een re%ea$e' 52 the June

#!!! earth+ua"e near Enano, the De(em5er

#!!4 earth+ua"e near Simeu%ue an' the Mar(h #!!:


31/721

earth+ua"e near -ia$. *he %o(ation$ an' me(hani$m$ of

the$e earth+ua"e$ are in'i(ate' 52 the (entre$ of the

%ower hemi$)here )roe(tion 5ea(h5a%%$, from

A5er(rom5ie et al. #!!30 for Enano an' from -EIC

#!!:0 for Simeu%ue an' -ia$. Lo(ation$ of after$ho("$

of the Enano earth+ua"e for whi(h fau%t>)%ane

$o%ution$ were (a%(u%ate' 52 A5er(rom5ie et al. #!!30

are a%$o $hown. Maor after$ho("$ to the Simeu%ue

earth+ua"e o((urre' a%mo$t entire%2 -W of the %imit$ of

the ma). MS, Muara Si5erut. S, Sina5an, B, u%au

Ba5i. *he )e("e' re2 %ine$ $how the %o(ation$ of

5arrier$ to )ro)aation of ru)ture$ from reat

Earth+ua"e$ inferre' 52 -ew(om5 & M(Cann @970.

were foun' to 5e tiht%2 (on(entrate' in 1er2 narrow one$ that

(hane' in 'i) $(ar(e%2 at a%% aroun' the 5en' /i. #.40. E$timate'

'e)th$ a%$o ten'e' to 5e $ma%%er than tho$e 5a$e' on%2 on

te%e$ei$mi( 'ata, e$)e(ia%%2 5eneath the forear( 5a$in.

A more re(ent $ei$mo%oi(a% $tu'2 of the *o5a area u$e' a tem)orar2

networ" (om)ri$in 3! $hort>)erio' an' ! 5roa'>5an'

$ei$mora)h$ 'e)%o2e' for four month$ in the fir$t ha%f of @@:

Ma$tur2ono et al. #!!0. *omora)hi( metho'$ were u$e'

to 'efine 1e%o(it2 1ariation$ 5eneath the (a%'era. *he re$u%t$

$u))ort the h2)othe$ie' e6i$ten(e of two 'i$tin(t eru)ti1e

(entre$, one in the $outh>(entra% )art of the %a"e an' the other at

it$ northern en', whi(h eru)te' at 'ifferent time$ 8niht et al.

@90. Low 1e%o(it2 one$ un'er%2in the$e two (entre$ an'

e6ten'in 'own into the mant%e are $e)arate' 52 a reion with a

more t2)i(a% (ru$ta% 1e%o(it2 $tru(ture.

,elative horiRontal movements

*he information on )re$ent>'a2 te(toni( )ro(e$$e$ in Sumatra )ro1i'e'

52 $ei$mo%o2 i$ now 5ein $u))%emente' 52 eo'eti( 'ata


32/721

from %o5a% o$itionin S2$tem S0 $ate%%ite$. Re)eate'

mea$urement$ at fi6e' )i%%ar$ )ro1i'e an e$$entia% (om)%ement

to earth+ua"e $tu'ie$, whi(h re(or' on%2 e)i$o'i(, a%thouh $ometime$

1er2 %are, 'i$)%a(ement$. Durin $ei$mi(a%%2 +uiet )erio'$,

S mea$urement$ monitor a$ei$mi( (ree) an' (an in'i(ate

reion$ in whi(h $tre$$ i$ in(rea$in an' ma2 5e re%ea$e' (ata$tro)hi(a%%2

at $ome time in the future. Be(au$e of the $hort time

inter1a%$ o1er whi(h o5$er1ation$ are ma'e t2)i(a%%2 3 to :

2ear$0, S mea$urement$ mu$t a%wa2$ 5e (on$i'ere' in the

(onte6t )ro1i'e' 52 e$timate$ of %on term re%ati1e )%ate motion$.

Mo$t of the S $ite mar"er$ in Sumatra were e$ta5%i$he' 52

BA8OSHR*A-AL, the In'one$ian ma))in an' eo'eti( $ur1e2

authorit2, wor"in in (o%%a5oration with 1ariou$ HS in$titute$, an'

mo$t are %o(ate' 5etween #? an' #? rawiro'ir'o et al. @@7

enri(h et al. #!!!0. A''itiona% mea$urement$ were ma'e at $ite$

near Ben"u%u an' Me'an an' on -ia$ an' Bi%%iton in the (our$e

of the EODSSEA $tu'2, whi(h (o1ere' the who%e of SE A$ia.

*he EODSSEA re$u%t$ 'efine' a Sun'a B%o(" that in(%u'e$

Borneo, the Ma%a2 enin$u%a an' In'o(hina an' mo1e$ ea$t re%ati1e

to Eura$ia at 7>! mm a > Chamot>Roo"e & Le i(hon

@@@ Mi(he% et al. #!!0. Bi%%iton I$%an' an' Me'an are (%ear%2

within thi$ 5%o(", a$ i$ mu(h of Sumatra ea$t of the Sumatran

/au%t, 5ut motion$ near an' to the we$t of the fau%t are mu(h

more (om)%e6. *he main BA8OSHR*A-AL (am)ain $ite$

$hown in /i. #.40 5ean in @9@. Detai%e' ana%2$e$ of the 'ata

o5taine' to @@ in the Centra% Domain /i. #.0 ha1e 5een )ro1i'e'

52 M(Caffre2 et al. #!!!0 an' 52 enri(h et al. #!!!0. *o

$u))%ement the$e ana%2$e$, rawiro'ir'o et al. #!!!0 a%$o (on$i'ere'

the re$u%t$ of (on1entiona% trianu%ation $ur1e2$ e6ten'in

o1er a )erio' of !! 2ear$ in the $ame area. *he$e enera%%2 (onfirme'

the S e$timate$ of #!>3! mm a> of 'e6tra% mo1ement


33/721

SEISMOLO & -EO*EC*O-ICS

on thi$ )ortion of the Sumatran /au%t, 5ut re1ea%e' 1er2 (on$i'era5%e

'ifferen(e$ in 'etai% in 5oth mo1ement manitu'e$ an'

'ire(tion$.

/iure #.4 $how$ the $ite motion$ re%ati1e to SE A$ia a$

inter)rete' 52 rawiro'ir'o et al. @@70 an' a%$o re%ati1e to

SE A$ia0 the a1erae' %on term In'ian O(ean mo1ement

1e(tor$ Demet$ et al. @@!0. Strain )artitionin wa$ e1i'ent%2

on%2 )artia%%2 a(hie1e', at %ea$t o1er the $hort time inter1a%

in1o%1e', nor were mo1ement$ (onfine' to the main fau%t

$2$tem$. Site$ ea$t of the Sumatran /au%t 5ut within :! "m of it

were not $tationar2 with re$)e(t to SE A$ia 5ut re(or'e' $ma%%

5ut $inifi(ant 'i$)%a(ement$ to the north an' -W. Simi%ar )attern$

near other maor $tri"e>$%i) feature$ ha1e 5een inter)rete'

a$ re(or'in $tre$$ a((umu%ation$ in wi'e reion$ of 'eforme'

ro(" that are u%timate%2 re%ea$e' 52 fau%tin e.. Armio et al.

@@@0.

Site$ in the forear( e6)erien(e' mu(h %arer tren(h>)ara%%e%

'i$)%a(ement$, 5ut M(Caffre2 et al. #!!!0 arue' that on%2

a5out two>thir'$ of the ne(e$$ar2 $%i) wa$ a((ounte' for an'

that mo$t of the remain'er mu$t ha1e 5een a((ommo'ate' o(eanwar'

of the (re$t of the forear( ri'e. =owe1er, the $ituation

1arie' (on$i'era5%2 from )%a(e to )%a(e. On forear( i$%an'$ in

the Centra% Domain 5etween the Batu an' Ban2a" I$%an'$0 the

tren(h>norma% (om)onent$ were $ma%%, $ue$tin $tron )artitionin

of (on1erent an' tran$(urrent mo1ement$, 5ut it $eem$

that the forear( wa$ %are%2 (ou)%e' to the 'ownoin $%a5 e1er2where

to the $outh of the Batu I$%an'$. *he 5oun'ar2 5etween

the two reime$ o((ur$ in the reion where the In1e$tiator

/ra(ture Gone enter$ the tren(h. rawiro'ir'o et al. @@70 tentati1e%2

inter)rete' the northwe$twar'$ 'e(rea$e in (ou)%in a$ a


34/721

(on$e+uen(e of the $u5'u(tion of thi(", water>ri(h $e'iment$ of

the -i(o5ar /an, re$u%tin in hih )ore )re$$ure$ in the forear(

we'e an' wea"enin of the u))er )%ate 52 the intro'u(tion of

h2'rotherma% f%ui'$. *he (hane in (ou)%in wou%' thu$ 5e 'ue

to the 5arrier to $e'iment f%ow from the -W )re$ente' 52 the

In1e$tiator /ra(ture Gone, rather than 'ire(t%2 to it$ )re$en(e a$

an a$)erit2 on the %ower )%ate. =owe1er, the manitu'e of the

De(em5er #!!4 Simeu%ue earth+ua"e $ue$t$ a $ti("2, rather

than we%%>%u5ri(ate', fau%t one.

*he (om5ination of ra'ua% (hane in the orientation of the

In'ian O(eanNSE A$ia (on1eren(e 1e(tor an' the (hane in

tren(h orientation at the -ia$ E%5ow im)%ie$ a%mo$t orthoona%

(on1eren(e a(ro$$ the tren(h in the 1i(init2 of Simeu%ue

an' the Ban2a" I$%an'$. *he Sumatran /au%t, howe1er, (hane$

'ire(tion mu(h %e$$ noti(ea5%2, an' the 'ifferen(e$ in (ur1ature

of $tru(ture$ on the main%an' an' a%on the forear( ri'e

)ro'u(e a wi'enin an' 'ee)enin of the forear( 5a$in -W of

Simeu%ue. Rather $ur)ri$in%2, the S motion$ of the two $ite$

in the Ban2a" I$%an'$ were a%mo$t )erfe(t%2 )ara%%e% to the tren'

of the Sumatran /au%t, an' $o to the tren(h further $outh. *he

%a(" of S $ite$ on Simeu%ue mean$ that $hort>term neote(toni(

)attern$ in thi$ (riti(a% area remain, for the moment, un'efine'.

*he 'ata from S mea$urement$ an' trianu%ation $ur1e2$

(an 5e (om)are' with %on>term $%i) e$timate$ 5a$e' on eo%oi(

an' to)ora)hi( off$et$ at the Sumatran /au%t. S%i) rate$ e$timate'

from $tream off$et$ on SO* imaer2 1ar2 from

! mm a > at the Sun'a Strait to #3 mm a > near La"e *o5a

Be%%ier & Se5rier @@:0. Mu(h of thi$ (hane o((ur$ in the

Centra% Domain, where the rate$ e$timate' 52 Sieh & -atawi'aa

#!!!0 u$in eo%oi(a% off$et$ in(rea$e from mm a i in

the SE to #7 mm a> in the -W. S%i) rate$ e$timate' from S


35/721

o5$er1ation$ 1ar2 mu(h %e$$, in(rea$in 52 on%2 4 mm a >, from

#3 mm a> to #7 mm a>, o1er the $ame 'i$tan(e enri(h et al.

#!!!0. Sieh & -atawi'aa #!!!0 $ue$te' that the eo%oi(a%%2

in'i(ate' (hane$ in $%i) rate$ a%on the fau%t mu$t ha1e

'e1e%o)e' on%2 'urin the %a$t !! "a, 5e(au$e of the a5$en(e

of (om)re$$iona% a((ommo'ation $tru(ture$, 5ut %eft the eo%oi(a%>

S 'i$(re)an(2 une6)%aine'. *he2 a%$o $ue$te'

that the tota% $%i) on the Sumatran /au%t miht 5e %itt%e more

than the #! "m of the ma6imum 1erifia5%e eo%oi(a% off$et,

an' that the remain'er of the rouh%2 !! "m off$et re+uire'

52 $tret(hin in the Sun'a Strait miht ha1e 5een a((ommo>

renc3-ort3o$onal motion renc3-4arallel motion

1 2

Eig3 #.:. S 1e(tor$ an' the reat Earth+ua"e of June

#!!!. *he u))er 'iaram $how$ o1era%% mo1ement

1e(tor$ re%ati1e to SE A$ia an' their tren(h>)ara%%e% an'

tren(h>orthoona% re$o%1e' (om)onent$. *he %ower

'iaram$ (om)are the$e (om)onent$ in'i1i'ua%%2.

;e(tor i$ the reiona% (on1eren(e 1e(tor, after

Demet$ et al. @@!0. *he remainin 1e(tor$ are S

1e(tor$ from the @@>@@3 (am)ain at $ite$ at the

5a$e$ of the arrow$, after rawiro'ir'o et al. @@70.

Bea(h5a%%$ $how the %o(ation$ of the two $u5e1ent$

)ro)o$e' 52 A5er(rom5ie et al. #!!#0 for the June #!!!

earth+ua"e.

# C=A*ER #

'ate' 52 $%i) on the Mentawai /au%t. *heir )ro)o$e' 'eformation

hi$tor2 whi(h the2 em)ha$ie' wa$ on%2 one of a mu%titu'e

of )o$$i5i%itie$0 in1o%1e' ar(>)ara%%e% $tret(hin 'urin the

%ei$to(ene 5ut )ro1i'e' no ro%e for the $ement of the Mentawai

/au%t north of the -ia$ E%5ow.


36/721

0)S data% the nggano and Simeulue earthKuaBes and the

"entaai Eault

Durin the )erio' (o1ere' 52 )u5%i$he' S mea$urement$,

the $outhern forear( i$%an'$ Si5erut to Enano0 were mo1in

-W re%ati1e to Sumatra at rouh%2 the $ame rate a$ the un'er%2in

In'ian O(ean %ate /i. #.40. Enano, in )arti(u%ar, )arti(i)ate'

in 1irtua%%2 a%% of the motion of the In'ian O(ean 'urin the )erio'

of o5$er1ation, whi(h unfortunate%2 in thi$ )arti(u%ar (a$e

e6ten'e' on%2 from @@ to @@3 /i. #.:0. Mu(h $ma%%er re%ati1e

motion$ were re(or'e' at two $ite$ on the a'a(ent (oa$t of the

main%an' an' therefore on%2 a $ma%% )art of the tren(h>)ara%%e%

motion re+uire' a((ommo'ation further in%an', in the 1i(init2

of the Sumatran /au%t. More than ha%f the tren(h>)ara%%e% motion

an' an e1en reater )ro)ortion of the tren(h>norma% motion

mu$t ha1e 5een a5$or5e' 5etween Enano an' the (oa$t, either

at one or more 'i$(rete fau%t$ or 52 'i$tri5ute' $train o1er the

wi'th of the forear( 5a$in.

Sei$mi( ref%e(tion $e(tion$ from man2 )art$ of the 5a$in

fa1our %o(a%ie' fau%tin in the forear( 5a$in, $in(e 'eformation

of Late -eoene $e'iment$ i$ enera%%2 (onfine' to the narrow

one (%o$e to the ea$tern (oa$t$ of the forear( i$%an'$ whi(h wa$

name' the Mentawai /au%t 52 Diament et al. @@#0. =owe1er,

the now numerou$ )u5%i$he' imae$ of thi$ feature o5taine' on

(ro$$in$ re)orte' 52 8ari et al. @9!0, Diament et al. @@#0

/i. #.a0, Ma%o' & 8ema% @@0 an' S(h%fiter et al. #!!#0

/i. #.50 an' the e6(e%%ent mu%ti(hanne% imaer2 o5taine'

52 the S(ri))$ In$titution of O(eanora)h2 SIO0 $outh of

-ia$ /i. #.70, in'i(ate a 1er2 (om)%e6 an' 1aria5%e $tru(ture.

Con$i'era5%e un(ertaintie$ remain a$ to it$ true nature. On $ome

$ei$mi( $e(tion$ e.. Diament et al. @@#0 it a))ear$ to 5e a

$im)%e fau%te' anti(%ine, whi%e in other area$ the one of wea"ne$$


37/721

ha$ 5een e6)%oite' 52 $ha%e 'ia)ir$ whi(h (on(ea% fun'amenta%

$tru(ture$ Mi%$om et al. @@:0. *he e6treme %inearit2 ha$ 5een

u$e' a$ an arument for a fun'amenta%%2 tran$(urrent ro%e

Sieh & -atawi'aa #!!!0 5ut $u5$i'en(e of the forear( 5a$in

an' e%e1ation of the forear( ri'e im)%2 either norma% or thru$t

(om)onent$. Where it emere$ on %an', in $outhea$tern -ia$, the

fau%t wa$ inter)rete' 52 Samue% & =ar5ur2 @@0 a$ an oriina%%2

e6ten$iona% fau%t that ha$ $uffere' %io(ene to Re(ent $u5'u(tionre%ate'

in1er$ion. Sinifi(ant tran$(urrent mo1ement wa$ rear'e'

a$ im)ro5a5%e. Intere$tin%2, howe1er, $ei$mi( $e(tion )re$ente'

52 S(h%titer et al. #!!#0 /i. #.50 $how$ the 'i$tur5an(e

a$ ha1in mo1e' awa2 from the %an'war' $i'e of the forear(

ri'e whi(h i$ it$e%f framente' in thi$ reion $ee /i. 3.0 to a

N? ? ? ? r a0

% i . . . . . . . . @ #.:

Seismic sections from Diament et al. @@#0 ?

/i. #.. a0 Inter)rete' $in%e>(hanne% $ei$mi( ref%e(tion

$e(tion$ a(ro$$ the Mentawai /au%t in the $outhern )art of

the Sumatra forear( 5a$in after Diament et al. @@#0. Line

%o(ation$ a$ $hown. 50 Mu%ti>(hanne% $ei$mi( ref%e(tion

$e(tion a(ro$$ the Mentawai /au%t $outh of Enano, after

S(h%titer et al. #!!#0. Lo(ation $hown on a0. *he reater

)enetration a(hie1e' on the more re(ent $ur1e2 $ue$t$ a

tran$(urrent oriin for the feature whi(h, in the near52

$outhernmo$t $in%e>(hanne% $e(tion, a))ear$ to 5e a

$im)%e fau%te' anti(%ine.

SEISMOLO & -EO*EC*O-ICS 3

/i. #.7. SIO Line 4#>43, $howin the Mentawai /au%t

imme'iate%2 $outh of -ia$. Se(tion )ro1i'e' 52 S(ri))$

In$titution of O(eanora)h2.


38/721

)o$ition within the forear( 5a$in. *hi$ fa(t, an' the imae it$e%f,

are more (om)ati5%e with tran$(urrent than 1erti(a% motion.

In'ee', S(h%titer et al. #!!#0 $ue$te' that the tran$(urrent

fun(tion of the Sumatran /au%t miht 5e in the )ro(e$$ of

$hiftin to the Mentawai /au%t. *hi$ i$ an attra(ti1e h2)othe$i$

5ut 'iffi(u%t to re(on(i%e with the $ue$tion 52 Sieh &

-atawi'aa #!!!0 that the tota% off$et on the Sumatran /au%t i$

rather $ma%%, 'e$)ite the a5un'ant e1i'en(e in(%u'in o((a$iona%

%are earth+ua"e$ Hntun et al. @9:0 for re(ent an' (ontinuin

off$et$ a%on it.

A further (om)%i(ation i$ intro'u(e' 52 a )o$$i5%e re%ation$hi)

5etween the Mentawai /au%t an' the Batee /au%t. *he %atter i$ a

'e6tra% $)%a2 from the Sumatran /au%t that tren'$ off$hore

near the Ban2a" I$%an'$ an' wa$ inter)rete' 52 8ari et al.

@9!0 a$ 'i$)%a(in or terminatin the Mentawai /au%t near

-ia$ /i. #.0. *he Mentawai /au%t i$ often $hown a$ either

en'in near -ia$ e.. Diament et al. @@#0 or merin with the

Batee /au%t, 5ut a 1er2 $tron ra1it2 ra'ient in'i(ate$ a maor

$tru(tura% 'i$(ontinuit2 5etween the two we$ternmo$t i$%an'$ in

the Ban2a" rou) $ee /i. 3.:0. *hi$ i$ rouh%2 the )o$ition

where a Mentawai /au%t (ontinuation wou%' 5e e6)e(te' if

the Batee /au%t were not )re$ent. Moreo1er, the e6i$ten(e of

Mentawai>t2)e $tru(ture$ $ti%% further north ha$ 5een (onfirme'

52 Iart et al. @@40 an' 52 Ma%o' & 8ema% @@0 u$in

$in%e>(hanne% ref%e(tion 'ata.

A''itiona% in$iht$ into the ro%e of the Mentawai /au%t in

the Enano area were )ro1i'e' in June #!!! 52 an Mw 7.@ earth+ua"e

fo%%owe' 52 a train of $tron after$ho("$ /i. #.:0. an' S

wa1e $tu'ie$ of the )rimar2 e1ent $ue$te' that thi$ (om)ri$e'

two $u5e1ent$, in1o%1in $tri"e>$%i) within the In'ian O(ean

%ate fo%%owe' 52 thru$t motion on the $u5'u(tion fau%t


39/721

A5er(rom5ie et al. #!!30. *he e1ent$ were too 'ee), an' in the

wron )%ate, to 5e 'ue to fai%ure on the Mentawai /au%t, 5ut

the2 'o )ro1i'e im)ortant 'ata on it$ re%ation$hi) to the tran$ition

5etween the a((retionar2 we'e an' the (ontinenta% marin.

Mat$on & Moore @@#0 $ue$te' that thi$ tran$ition o((ur$

near the ea$t (oa$t of -ia$ in the Centra% Domain an' that the

$u5'u(tion fau%t oriina%%2 rea(he' the $urfa(e in thi$ area. It$

$u5$e+uent miration o(eanwar'$ wa$ inter)rete' a$ a (on$e+uen(e

of the 'e1e%o)ment of the a((retionar2 we'e that now

form$ the forear( ri'e. *hi$ i$ (on$i$tent with the Ma%o' &

8ema% @@0 inter)retation of the Mentawai /au%t a%on it$

entire %enth a$ mar"in the tran$ition 5etween the we'e an'

a rii' 5a("$to) of )re>e6i$tin 5a$ement. On thi$ h2)othe$i$,

the %inearit2 of the fau%t i$ a (on$e+uen(e of the %inearit2 of the

oriina% $u5'u(tion tra(e, whi(h wou%', in turn, ha1e 5een (ontro%%e'

52 the %inearit2 of the former )a$$i1e marin.

*he $inifi(an(e of the Enano (om)o$ite earth+ua"e to the

5a("$to) (on(e)t i$ that the S re$u%t$ $hown in /iure #.: in'i(ate

that in thi$ area, an' )o$$i5%2 on%2 for $hort )erio'$, the a((retionar2

we'e mo1e$ with the $u5'u(tin )%ate an' mu$t therefore

(om)re$$ aain$t the 5a("$to), re$u%tin in fo%'in an' re1er$e

fau%tin. otentia% ener2 $tore' in thi$ fo%'e' an' fau%te' one

(an 5e re%ea$e' in %are earth+ua"e$ in whi(h the we'e mo1e$

o(eanwar'$ an' 'eformation near the 5a("$to) i$ re1er$e'. re$uma5%2

$u(h re1er$a%$ are on%2 )artia%, $o that 'eformation ra'ua%%2

in(rea$e$. At no )oint in thi$ $ti(">$%i) (2(%e wou%' %are

earth+ua"e$ ne(e$$ari%2 o((ur within the we'e, 5e(au$e a((rete'

materia% i$ u$ua%%2 too wea" to $u$tain %are %o(a% $tre$$. Lare

earth+ua"e$ wi%% therefore 5e a$$o(iate' )rin(i)a%%2 with the

un$ti("in of the we'e from the 5a("$to) or from the 'ownoin

$%a5 a%on the main $u5'u(tion thru$t an' with re%ati1e %atera%


40/721

mo1ement 5etween %o("e' an' un%o("e' $ement$ of

the forear(. E1ent$ of 5oth t2)e$ a))ear to ha1e o((urre' in

June #!!!, with the mo1ement 5etween $ement$ of the In'ian

O(ean )%ate in(rea$in the $tre$$ an' trierin fai%ure a%on

the $u5'u(tion thru$t A5er(rom5ie et al. #!!30.

*he re$u%t$ of future S mea$urement$ in the Enano>Ben"u%u

area there ha1e, unfortunate%2, 5een no mea$urement$ on

Enano $in(e the earth+ua"e0 are thu$ %i"e%2 to 5e 1er2 'ifferent

from tho$e o5taine' 5etween @@ an' @@3. Amon$t other

thin$, the2 (an 5e e6)e(te' to )ro1i'e in$iht$ into the hih%2

(ontro1er$ia% +ue$tion of the e6tent to whi(h tren(h>)ara%%e%

motion i$ a((ommo'ate' 52 the Mentawai /au%t. It $eem$ )ro5a5%e

that the new 1e(tor$ wi%% re$em5%e the 1e(tor$ $hown in

/iure #.4 for the i$%an'$ north of Si5erut, i.e. the2 wi%% $how

a%mo$t entire%2 tren(h>)ara%%e% motion, im)%2in a )rimari%2 tran$(urrent

%on>term fun(tion. *he (hara(teri$ti($ of 5oth the main

earth+ua"e an' the e6ten$i1e after$ho(" $e+uen(e $ue$t that

effe(t$ of the Enano reat Earth+ua"e are un%i"e%2 to 5e $een

in the forear( north of Ben"u%u A5er(rom5ie et al. #!!30, an'

in fa(t no $u(h effe(t$ ha1e 5een o5$er1e' in )o$t>earth+ua"e

S $tu'ie$ in the Centra% Domain Bo(" et al. #!!30. If thi$ i$

the (a$e, then 'anerou$ %e1e%$ of $tre$$ mu$t 5e a((umu%atin

in the reion from South aai to Si5erut.

*he June #!!! Enano earth+ua"e wa$ (om)%ete%2 o1er$ha'owe'

52 the De(em5er #!!4 Simeu%ue e1ent, information on

whi(h wa$ )o$te' on the -ationa% Earth+ua"e Information

4 C=A*ER #

Center we5$ite within a few 'a2$ -EIC #!!:0. *he $ue$te'

ma6imum 'i$)%a(ement wa$ : m, in a reion where (on1eren(e

i$ more near%2 orthoona% to the tren(h than it i$ further $outh $ee

/i$ #. an' #.40. Biarre%2, in 1iew of thi$ %atter fa(t, the re$u%t$


41/721

from the on%2 S $ite -W of the (hane of $tri"e, on u%au Ba5i

B on /i. #.40, $ue$t that 'urin the @9@>@@3 )erio' the

forear( mo1e' $%iht%2 further in a 'ire(tion )ara%%e% to the

tren(h than 'i' the In'ian O(ean, the $u))o$e' 'ri1er of the

forear( motion. It a%$o $eem$ that a5out ha%f of the In'ian O(ean

tren(h>norma% motion wa$ a((ommo'ate' 5etween u%au Ba5i

an' Sumatra, whi(h i$ %e$$ than at Enano, 5ut mu(h more

than )re'i(te' 52 $im)%e $%i1er>)%ate mo'e%$. *he motion of

Simeu%ue, a few ten$ of "i%ometre$ to the -W, miht, of (our$e,

ha1e 5een 'ifferent 5ut there i$ no 5ath2metri( or other e1i'en(e

for the )%a(ement 52 -EIC #!!:0 of an e6ten$iona% or an2 other0

5oun'ar2 to a Burma %ate imme'iate%2 ea$t of u%au Ba5i.

/au%t>)%ane $o%ution$ for the Simeu%ue earth+ua"e are (on$i$tent

with either SW>'ire(te' thru$tin 'i))in at a5out ! ? to the

-E or -E>'ire(te' re1er$e fau%tin 'i))in at a5out 9! ? -EIC

#!!:0. *he fir$t of the$e i$ mu(h the more %i"e%2, 5ut thru$tin

on a $urfa(e $o near%2 horionta%, when the Benioff Gone 'i)$ at

a5out 3! ? in the 1i(init2 of the h2)o(entre, rai$e$ $ome +ue$tion$.

*he =ar1ar' Centroi' Moment *en$or $o%ution, howe1er, )%a(e$

the (entroi' we$t of the forear( ri'e an' 5eneath the ea$tern

wa%% of the tren(h at 3.!@? @4.#? (f. the -EIC e)i(entre at

3.3!? @:.@E? Sin(e, $u5e(t to error$ intro'u(e' 52 fau%t2 1e%o(it2

mo'e%$, h2)o(entre$ (orre$)on' to )oint$ of ru)ture intiation

wherea$ (entroi'$ re)re$ent weihte' a1erae %o(ation$ of

moment re%ea$e Mere'ith -ett%e$ )er$. (omm. #!!:0, the re$u%t$

(an 5e inter)rete' a$ 'e$(ri5in an e1ent initiate' in the 1i(init2

of the Mentawai /au%t an' )ro)aatin o(eanwar'$ an' a%$o

-W a%on the forear(. *he (om)%e6it2 of $tre$$ )attern$ in the e)i(entra%

area i$ in'i(ate' 52 the mu%ti)%i(it2 of )re1iou$ $ma%%er

$ho("$, $ome of whi(h ha' $tri"e>$%i) $o%ution$ an' other$ $o%ution$

$imi%ar to that of the De(em5er #!!4 e1ent $ee


42/721

-ew(om5 & M(Cann @97, /i. #0. *he fa(t that the reion

aroun' the Mentawai /au%t a))ear$ to re$)on' to $tre$$ in 'ifferent

wa2$ at 'ifferent )%a(e$ an' at 'ifferent time$ i$ (on$i$tent with the

fau%t it$e%f 5ein the e6)re$$ion of a fun'amenta% eo%oi(a% 'i$(ontinuit2

rather than a $im)%e 5rea" throuh an e$$entia%%2 homoeneou$

ro(" ma$$.

*he Simeu%ue e1ent a%$o $)e(ta(u%ar%2 (onfirme' the e6treme

$ementation of the forear(. After$ho("$ o((urre' a%on #!!

"m of the ar(, from the $ite of the main $ho(" a$ far a$ the northern

ti) of the An'aman$, 5ut there wa$ 1irtua%%2 no a(ti1it2 to the SE

-EIC #!!:0. *he 5ath2metri( hih northwe$t of Simeu%ue where

the e)i(entre wa$ %o(ate' ma2 therefore 5e the $urfa(e e6)re$$ion

of a 'i$(ontinuit2 $imi%ar to tho$e a$$o(iate' with the Ban2a" an'

Batu hih$ further $outh. *he e6tent$ of reat Earth+ua"e ru)ture$

are $tron%2 (orre%ate' with the e6tent$ of 'ee) marine 5a$in$

5etween Sumatra an' the forear( ri'e an', i1en that the -W

%imit of the ru)ture one of the 9 e1ent wa$ not at Simeu%ue

5ut at the Ban2a" I$%an'$ -ew(om5 & M(Cann @970, it $eem$

)o$$i5%e that $tre$$ i$ $ti%% 5ui%'in u) in a Simeu%ue Ba$in

$ement, to 5e (ata$tro)hi(a%%2 re%ea$e' at $ome time in the not

too 'i$tant future.

$ertical movements

It i$ more 'iffi(u%t to monitor 1erti(a% mo1ement$ with S than

horionta% mo1ement$, 5oth 5e(au$e of the enera%%2 $ma%%er

'i$)%a(ement$ an' 5e(au$e the a((ura(2 i$ inherent%2 %ower.

At )re$ent, more re%ia5%e e$timate$ of rate$ of 1erti(a% motion

are 5ein o5taine' 52 o5$er1in $hort>term (hane$ in re%ati1e

$ea %e1e%. -atawi'aa et al. #!!!0 $tu'ie' the $u5meren(e an'

emeren(e of (ora%$ an' 'e'u(e' a )attern of )rore$$i1e

%an'war' ti%tin of the forear( ri'e, with u)%ift within a5out

: "m of the tren(h a6i$ an' $u5$i'en(e at a%% reater 'i$tan(e$.


43/721

In$tantaneou$ 1erti(a% mo1ement$ of ten$ of (entimetre$ a$$o(iate'

with %are earth+ua"e$ were $u)erim)o$e' on thi$ )attern.

In'i1i'ua% i$%an'$ in the northern )art of the forear( often re(or'

$imi%ar ti%tin. I$%et$ $hown on Dut(h (o%onia% ma)$ a$ )rote(tin

Sina5an har5our, at the ea$tern en' of the north (oa$t of Simeu%ue

S in /i. #.40, are now )ermanent%2 $u5mere', an' )a%m tree$

are '2in a%on mu(h of the (oa$t a$ $a%t water in1a'e$ the $oi%

aroun' their root$. Muara Si5erut, the main town on Si5erut

MS on /i. #.40, i$ reu%ar%2 f%oo'e' at hih ti'e an' $ome

near52 off$hore i$%an'$ (on$i$t entire%2 of manro1e$ with

their root$ $u5mere' e1en at %ow ti'e.

On -ia$ the $ituation i$ more (om)%i(ate', $in(e the we$t (oa$t

(an 5e 'i1i'e' into two 1er2 'ifferent $e(tor$. In the north the

(oa$ta% reion i$ f%at an' $wam)2 an' the 5ea(h i$ 5roa' an'

ent%2 $%o)in, 5ut in the $outh there are (%iff$ :!>!! m hih

an' the $ea f%oor $he%1e$ $tee)%2. *hi$ $e(tion of the (oa$t%ine i$

(on(a1e $eawar'$ an' a))ear$ to 5e a $(ar) (reate' 52 fai%ure of

an un$ta5%e $%o)e $ee /i. #.0. *he re%ati1e%2 %ow ra1it2 fie%'

a%on the (oa$t an' off$hore $ee /i. 3.:0 $ue$t$ %o$$ of ma$$

from thi$ reion an' a%$o $u))ort$ the (on(e)t of fai%ure of a

$%o)e that ha$ 5een u)%ifte' to un$u$taina5%e e%e1ation$. On

the o))o$ite ea$tern0 $i'e of the i$%an', ri1er$ ha1e 5een in(i$e'

in narrow 1a%%e2$ to 'e)th$ of :>! m within a 5roa' (oa$ta%

)%ain ea$t of the Mentawai /au%t, $ue$tin re(ent an' ra)i'

u)%ift, 5ut further north there i$ e1i'en(e of 5oth u)%ift an'

$u5$i'en(e.

*he u)%ift of the (oa$ta% )%ain on -ia$ (ou%' ha1e 5een a$$o(iate'

with reat earth+ua"e$. Ga(haria$en et al. @@@0 inter)rete'

the re$u%t$ of a 'etai%e' $tu'2 of (ora% hea'$ e6)o$e' aroun'

the Mentawai I$%an'$ of Si)ora an' -orth an' South aai,

$outh of Si5erut, a$ re(or'in a$ei$mi( $u5$i'en(e fo%%owe' 52


44/721

(o>$ei$mi( u)%ift re%ate' to the reat earth+ua"e of 933. In thi$

area, an' in (ontra$t to area$ further north, 5oth a$ei$mi( an'

(o>$ei$mi( mo1ement$ a))ear to ha1e in1o%1e' ti%tin towar'$

the tren(h. De'u(in %on>term reiona% 'i$)%a(ement )attern$

from mea$urement$ of mo1ement$ o1er a few 2ear$, or e1en

o1er ten$ of 2ear$, i$ (%ear%2 ne1er oin to 5e a $im)%e e6er(i$e.

Note added in proof

*he earth+ua"e a(ti1it2 in the (entra% Sumatra forear( 5etween #

De(em5er #!!4 an' the en' of A)ri% #!!: i$ $ummarie' in /iure

#.9. *he fir$t four )%ot$ $how how the $ei$mi(it2 a$$o(iate' with

the # De(em5er e1ent ra'ua%%2 'ie' awa2 'urin the $u((ee'in

three month$. It i$ (%ear that e1en a$ %ate a$ Mar(h #!!:, the

maorit2 of e1ent$ were )art of the after$ho(" $e+uen(e.

=owe1er, on #9 Mar(h #!!: there wa$ a further reat Earth+ua"e,

with an e)i(entre u$t we$t of the Ban2a" I$%an'$ an' an e$timate'

manitu'e of 9.. *he 'i$tri5ution of after$ho("$ to thi$ e1ent in'i(ate'

that ru)ture e6ten'e' throuhout the who%e of the reion

5etween the Ban2a"$ an' the De(em5er # e)i(entre. It wa$, in

fa(t, 5ein +uite wi'e%2 )re'i(te' in the fir$t few month$ of

#!!: that thi$ wou%' 5e where the ne6t 5rea" wou%' o((ur.

=owe1er, an' une6)e(te'%2, the one of after$ho("$ a%$o e6ten'e'

$outh a$ far a$ the Batu I$%an'$ /i. #.9e0. It $eem$ therefore that

not on%2 ha' the %a$t remainin $ement that ha' no hi$tori( re(or'

of reat Earth+ua"e$ fai%e', 5ut that the $ement that ru)ture' in

9 mo1e' with it.

/au%t )%ane $o%ution$ 52 5oth the -EIC an' the =ar1ar' rou)

in'i(ate' a $ha%%ow thru$t, at an e1en $ma%%er an%e of 'i) than

ha' 5een the (a$e the )re1iou$ De(em5er. On(e aain, mo1ement

$eem$ to ha1e 5een initiate' (%o$e to where the Mentawai /au%t

a$$ume' to 5e near 1erti(a%0 wou%' rea(h the $u5'u(tion fau%t at

'e)th, an' on(e aain there wa$ a $inifi(ant 'i$)%a(ement


45/721

5etween the (a%(u%ate' )o$ition$ of the e)i(entre an' the (entroi'.

In thi$ (a$e, howe1er, the (entroi' %a2 $outh rather than we$t of the

SEISMOLO & -EO*EC*O-ICS :

? ? ?%( ? F De(em5er # > De(em5er 3, #!!4 I

o#/#- o o-%: %o/ !3% / 333333 /I

,o. E7>

?0 .....

o -3 : I

!o F F F ..................................................... ............ .....

a 6 ! 6

. . . . ? o >, a,,,i,,,,?., #!o$%

3 o , ........... ...............

. . . . . . . . . . . . . . . . . . . . . . . . . . .

o o ? ...............? ............... .......... ............. F Eebruary% 7&&Q

& ................... ? ...............>..?. , . ,

. . . . . ., . ? . . . . . . ..................... .................. ........... ...............X .. ................? . 3

. . . . . . . . . . . . . . . . . . . .

? ? ? Mar(h > Mar(h #7. #!!:

o .? ,.? o

. . . . . . . . . . O ? . . . . . . . . . . . R .................P.. ...... ? ,4-

2 > >l

. . . . . . . . . . . . . . . . . . . . . . . f 33333333333333333333>333 33373

.C. 0. . . . ?. . . . . ? .............A. )r i % ! > A)ri%3!, #!!:

'

# . . . . . . . . . . . . . . . , ........................?., .... ............ F ........ io?

. . . . oo .............................#.?.. ..

I /; ? ? .....?. .............,..,..?... ,? ?F %

/i. #.9. Centra% Sumatra $ei$mi(it2,

De(em5er # #!!4 to A)ri% 3! #!!:.

E)i(entre$ )%otte' from (ata%oue$ a1ai%a5%e

on the Internet from htt)FNN


46/721

www.n'(.noaa.o1. -ote that the )erio'$

(o1ere' $hown in the to) fiht han' (orner

of ea(h 'iaram0 are not of uniform %enth,

5ein 'i(tate' in )art 52 the 'ate$ of

initiation of $inifi(ant earth+ua"e $warm$.

*he (ir(%e$ (orre$)on'in to the -EIC

e)i(entre$ of the two reat Earth+ua"e$ in

)%ot$ a an' e0 are $ha'e' an' the %o(ation$ of

the (entroi'$ of their =ar1ar' CM*

$o%ution$ are in'i(ate' 52 fau%t>)%ane

$o%ution 5ea(h5a%%$.

e)i(entre, an' wa$ $ti%% a (on$i'era5%e 'i$tan(e from the tren(h.

A%$o, an' a$ miht ha1e 5een e6)e(te' in 1iew of the $ma%%er manitu'e

of the $ho(", an' hen(e the )ro5a5%e $ma%%er wi'th of the

$%i) one, the 'i$)%a(ement 5etween (entroi' an' h2)o(entre

wa$ (on$i'era5%2 %e$$ than in De(em5er. *he reater 'i$tan(e of

the (entroi' from the tren(h, toether with the $ma%%er manitu'e,

ma2 5e $uffi(ient e6)%anation for the mu(h $ma%%er a$$o(iate'

t$unami, whi(h wa$ on%2 a5out 3 metre$ hih on e6)o$e' (oa$t$

of -ia$ an' Simeu%ue an' 'e(rea$e' ra)i'%2 in am)%itu'e at

more remote %o(ation$. It i$ a%$o )o$$i5%e that $u5marine $%i'e$,

whi(h ma2 ha1e (ontri5ute' to the 'e$tru(ti1e )ower the De(em5er

wa1e, 'i' not o((ur in Mar(h 5e(au$e of the a5$en(e of an2

remainin )otentia%%2 un$ta5%e $%o)e$. *he after$ho(" $e+uen(e

/iure$ #.9e an' f0 wa$ nota5%e for 5ein mu(h more tiht%2 (on$traine'

to the reion imme'iate%2 5eneath the forear( ri'e than

ha' 5een the (a$e fo%%owin the De(em5er e1ent.

A new train of e1ent$ 5ean $ti%% further $outh an' u$t $eawar'

of Muara Si5erut in the fo%%owin wee"$. *here were a few re%ati1e%2

wea" $ho("$ in thi$ area in the )erio' imme'iate%2 after

Mar(h #9 /iure #9e0, 5ut the fir$t maor e1ent MwT.70 too"


47/721

)%a(e on A)ri% !, an' wa$ fo%%owe' three +uarter$ of an hour

%ater 52 another $tron MwT.:0 $ho(". On(e aain, the Mentawai

/au%t a))ear$ to ha1e (ontro%%e' the %o(ation at whi(h

fai%ure wa$ initiate'. Both e1ent$ were (om)re$$iona% 5ut, in (ontra$t

to the two reat Earth+ua"e$, the $%i) )%ane$ were mu(h

$tee)er from 3! ? to !? *here fo%%owe' numerou$ wea"er

e1ent$ in the $ame area 5ut, aain in (ontra$t to the )attern a$$o(iate'

with the reat Earth+ua"e$, there wa$ no $inifi(ant ru)ture

)ro)aation /i. #9f0. It i$ to 5e ho)e' that the earth+ua"e$ in

thi$ i$o%ate' (%u$ter wi%% )ro1e to 5e the %a$t maor e1ent$ in the

(urrent )ha$e of $outhwar'>)ro)aatin uni))in of $u5'u(tion

we$t of Sumatra.

Chapter

?he gravity field

JO=- MILSOM & ADRIA- WAL8ER

Data sources

*he ra1it2 fie%' of Sumatra an' the $urroun'in marine area$ i$

$hown in /iure 3.. Contour$ in the on$hore area of Bouuer

ra1it2, 5ut off$hore are of free>air ra1it2. *errain (orre(tion$

ha1e not 5een a))%ie'. A%thouh marine ra1it2 mea$urement$

ha1e 5een ma'e in the forear( 5a$in an' e%$ewhere on a num5er

of re$ear(h (rui$e$ e.. 8ie("hefer et al. @90, the 'ata from

the$e enera%%2 wi'e%2 $)a(e' %ine$ ha1e not 5een u$e' in )re)arin

the ma)$ 5e(au$e free>air ra1it2 1a%ue$ o5taine' from

in1er$ion of $ate%%ite ra'ar a%timetr2 )ro1i'e more $2$temati(

(o1erae an' (an re$o%1e anoma%ie$ with wi'th$ of a$ %itt%e a$

7 "m San'we%% & Smith @@70. *he on$hore an' $ate%%ite'eri1e'

off$hore 'ata were mat(he' at (oa$t%ine$ without un'ue

'iffi(u%t2, a$ $hou%' 5e the (a$e 5e(au$e 5oth free>air an'

Bouuer (orre(tion$ are ero at $ea %e1e%. =owe1er, ra'ient$

ten' to 5e $tee) at the (oa$t$ in the forear( reion, )art%2


48/721

5e(au$e of the (hane from free>air ra1it2, whi(h i$ $tron%2

(orre%ate' with %o(a% 5ath2metr2, to Bouuer ra1it2, whi(h i$ (orre(te'

for %o(a% to)ora)h2.

/iure 3.# $how$ the %o(ation$ of the on$hore $tation$ u$e' in

)re)arin /iure 3., 5ut not of the off$hore e$timate$, 'i$tri5ute'

on a reu%ar # minute ri'. On$hore 'ata were o5taine' from a

1ariet2 of $our(e$, 5ut unfortunate%2 the re$u%t$ of the man2

'etai%e' ra1it2 $ur1e2$ (arrie' out 52 oi% (om)anie$ remain

(onfi'entia%. *he %are$t $in%e a1ai%a5%e 'ata $et wa$ a$$em5%e'

a$ )art of the (o%%a5oration 5etween the Briti$h eo%oi(a%

Sur1e2 BS0 an' the eo%oi(a% Re$ear(h an' De1e%o)ment

Centre RDC0 'urin the )erio' @99>@@:. A%mo$t a%% of

Sumatra $outh of the e+uator wa$ (o1ere' at a re(onnai$$an(e

%e1e%, a%thouh there are $inifi(ant a)$ in a few area$ where

a((e$$ wou%' ha1e 5een e$)e(ia%%2 'iffi(u%t. In a''ition to the

Sumatra main%an', mea$urement$ were ma'e on Ban"a an'

Bi%%iton i$%an'$ in the northea$t an' the Mentawai i$%an'$ in the

we$t /i. 3.#0. RDC ha1e )u5%i$he' numerou$ Bouuer

ma)$ at F#:! !!! $(a%e $howin (ontour$, enera%%2 at # ma%

inter1a%$, an' $tation %o(ation$. *here are a%$o two $ummar2

ma)$ at !!! !!! $(a%e a'an an' a%em5an $heet$0, (ontoure'

at : ma% inter1a%$ an' without $tation )o$ition$. *errain

(orre(tion$, of u) to # ma%, were a))%ie' in )re)arin the

$ummar2 ma)$ 5ut were not u$e' for an2 of the F#:! !!! 'etai%e'

ma)$. *he two 1er$ion$ of Bouuer ra1it2 are therefore $%iht%2

'ifferent in the mountainou$ area$ (%o$e to the Sumatran /au%t

5ut ra'ient$ in the$e area$ are in an2 (a$e $tee), an' o1era%%

)attern$ are 1er2 $imi%ar.

Co1erae north of the e+uator, )rin(i)a%%2 52 RDC an'

LEMIAS the In'one$ian etro%eum Re$ear(h In$titute0, i$ %e$$

(om)%ete than in the $outh 5ut i$ )rore$$in ra)i'%2. Moreo1er,


49/721

Ja)ane$e uni1er$itie$ wor"in 5etween @77 an' @7@ o5taine'

'ata a%on man2 of the more im)ortant roa'$ in the La"e *o5a

area /i. 3.#0. In the northern forear( LEMIAS (o%%a5orate'

with the Hni1er$it2 of Lon'on in $ur1e2$ of a%% of the maor

i$%an'$ Mi%$om et al. @@0. Station$ were main%2 a%on the

(oa$t$, e6(e)t on -ia$. LEMIASNHofL $tation$ on Si5erut

were re$tri(te' to the $outhea$tern (orner, 5ut the i$%an' wa$

$u5$e+uent%2 (o1ere' at a re(onnai$$an(e %e1e% 52 RDC.

In @@ an' @@#, $tation$ were e$ta5%i$he' a%on maor roa'$

throuhout Sumatra 52 BA8OSHR*A-AL, the In'one$ian

eo'eti( $ur1e2 authorit2. A ma) $howin the %o(ation$ of the

BA8OSHR*A-AL $tation$ an' Bouuer ra1it2 (ontour$ after

the a))%i(ation of a $e1ere hih>(ut fi%ter ha$ 5een (ir(u%ate'

on a 1er2 %imite' 5a$i$, 5ut the$e $tation$ are not in(%u'e' in

/iure 3.#. An unfi%tere' 5ut 1er2 $ma%% $(a%e 1er$ion of the

BA8OSHR*A-AL Bouuer ma) wa$ )u5%i$he' 52 8a'ir et al.

@@0, an' the 'ata ma2 a%$o ha1e 5een u$e' 52 RDC in )re)arin

the F!!!!!!! Bouuer anoma%2 ma) of In'one$ia

So5ari et at. @@30. BA8OSHR*A-AL Bouuer 1a%ue$ aroun'

the *o5a (a%'era are enera%%2 !>#!ma% hiher than tho$e

re)orte' 52 the Ja)ane$e rou)$, a 'ifferen(e )ro5a5%2 'ue to

the %a(" of terrain (orre(tion$ in the Ja)ane$e wor".

*he on$hore (ontour$ in /iure 3. are 5a$e' on a(tua% )oint

ra1it2 'ata where a1ai%a5%e, $u))%emente' where ne(e$$ar2 52

1a%ue$ e$timate' at "nown BA8OSHR*A-AL $tation )o$ition$

u$in the (ontour$ of 8a'ir et al. @@0. A((ura(2 i$ ine1ita5%2

%ow where thi$ ha$ 5een 'one, an' e1en $o $ome $inifi(ant a)$

remain. *he )ro5%em of ma"in fu%% u$e of oo' reiona% (o1erae

where thi$ e6i$t$ an' at the $ame time 'i$)%a2in in an a((e)ta5%e

wa2 the re$u%t$ of inter)o%ation a(ro$$ %arer a)$ ha$ 5een

a''re$$e' 52 o1er%a2in the ma) 5a$e' on a re%ati1e%2 fine


50/721

!. ? ri', whi(h i$ 5%an" in area$ of ina'e+uate (o1erae, on a

ma) )ro'u(e' u$in a mu(h (oar$er ri' an' a reater 'eree of

inter)o%ation. *hi$ i$ o51iou$%2 un$ati$fa(tor2 a$ a +uantitati1e

metho', 5ut /iure 3. i$ inten'e' to 5e u$e' on%2 +ua%itati1e%2

an' the enera% )attern$ (an 5e (on$i'ere' $uffi(ient%2 we%% e$ta5%i$he'

to $u))ort reiona% inter)retation. It i$ u$t )o$$i5%e on

/iure 3. to i'entif2 'i$(ontinuitie$ in the (o%our )attern$ at the

e'e$ of area$ where the (oar$e ri' ha$ 5een u$e'.

E6ten'in /iure 3. to in(%u'e Bi%%iton ha$ 5rouht we$tern

Ja1a within the 5oun'arie$ of the ma). *he 'ata u$e' were

o5taine' in @7! 52 the BS, wor"in in (onun(tion with the

eo%oi(a% Sur1e2 of In'one$ia. *he re$u%t$ of re(ent more

'etai%e' wor" on Ja1a 52 RDC are not $hown 5ut are enera%%2

(om)ati5%e with the BS $ur1e2.

,egional gravity patterns

*he mo$t )rominent feature$ in /iure 3. are off$hore. ra1it2

hih$ with north>$outh or --E>SSW tren'$ are a$$o(iate'

with fra(ture one$ an' $eamount (hain$ on the In'ian O(ean

%ate an' the$e (ontro% the )o$ition$ of in'i1i'ua% (u%mination$

on the 5roa' f%e6ura% hih at the outer marin of the Sumatra

*ren(h. *wo 'ee) -W>SE>tren'in free>air %ow$, a$$o(iate'

re$)e(ti1e%2 with the tren(h an' the forear( 5a$in, inter1ene

5etween thi$ o(eani( 'omain an' the Sumatran main%an' an'

are $e)arate' from ea(h other 52 a hih a%on the forear( ri'e.

*he %ow o1er the tren(h e6i$t$ 5e(au$e the ma$$ 'efi(it of the

water (o%umn i$ not in %o(a% i$o$tati( e+ui%i5rium 5ut i$ 5a%an(e'

e%a$ti(a%%2 52 the off$et ma$$ of the $u5'u(tin $%a5.

A%thouh the a1ai%a5%e ra1it2 (o1erae i$ mu(h %e$$ (om)%ete

north of the e+uator than in the $outh, there (an 5e no 'ou5tin

the e6i$ten(e of fun'amenta% 'ifferen(e$ 5etween SE an' -W

Sumatra. In the $outh the Bari$an mountain$ are a$$o(iate' with


51/721

a narrow, 'i$(ontinuou$ an' rather wea" Bouuer %ow that,

where it e6i$t$, (oin(i'e$ +uite )re(i$e%2 with the a6i$ of the

mountain rane, 5ut in the north the %ow 'ee)en$ an' e6)an'$ to

RA;I* /IELD 7

/i. 3.. *he ra1it2 fie%' of Sumatra an' the $urroun'in $ea$, 5a$e' on 'ata from $our(e$

'i$(u$$e' in the te6t. Contour$ are of free>air ra1it2 off$hore an' Bouuer

ra1it2 on$hore. *he Bouuer re'u(tion 'en$it2 i$ #.7 M m >3. /aint white (ontour$ are

5ath2metr2, at #!! m an' at inter1a%$ of :!! m thereafter, from the EBCO 'iita%

at%a$ )re)are' 52 the Briti$h O(eanora)hi( Data Centre. *he (ontinuou$ 5%a(" %ine runnin the

%enth of Sumatra mar"$ the a))ro6imate $urfa(e tra(e of the Sumatran /au%t.

*he 2e%%ow %ine (ro$$in the forear( 5a$in near the e+uator mar"$ the %o(ation of the inter)rete'

)rofi%e of /iure 3.. *he 5%a(" out%ine$ en(%o$in the %etter$ O an' B

in'i(ate the %o(ation$ of the ra1it2 $ur1e2$ of the Om5i%in an' Ben"u%u 5a$in$ $hown in

/iure$ 3.3 an' 3.4 re$)e(ti1e%2. *he %etter B a%$o in'i(ate$ the a))ro6imate

)o$ition of the town of Ben"u%u. *S an' * in'i(ate, re$)e(ti1e%2, La"e *o5a in(%u'in Samo$ir

I$%an'0 an' La"e *awar. *he %etter$ I/G at a5out @7 ? 3!E mar" the (entra%

trouh of the In1e$tiator /ra(ture Gone. *he in$et $how$ the EM>*3 %on wa1e%enth ra1it2

fie%' in the Sumatra reion $ee Ler(h et al. @@40.

9 C=A*ER 3

= 3 3 3 3 3 3 3 3 3 3 3 3 3 % 2 2 o / I o >,

E .EL/ Ft !# SOH*. SE , !9 E

>-. Z?.,, ? &7. 0?


52/721

,#,,~ ~ .... .22 ? t ? >>, F F>F> . @

.?>F. .. >F. >r;77? >? ?# ? ?

? ?F.,FFF i Ff,. .?. ..F7?. !

? 3 ? ? , , ? FF . . . . . ? . t . , . . . . ..(.. < ??a4 ,?.?K .. ?N S?= EL/

.??. 0I8? FF t F % % % a m a % % ( $ ?? ? > FF ,?FF,.1>J

Z .F. ,?. F $

-t! tAU@-'/ ; ;V />2/>-Q /%tP/R-F/F - / / a3/%>2>2!%4 3333 %4 33333 >R

# 3 ! - .. ...................... ............... . . . . . . . . . . . . . . . . . . . . . . . . . . .? 1 .r > F ? ? OCEA- K ?

imeu%ue

@,E @3! I

. . . . . . .

/i. 3.#. Di$tri5ution of reiona% ra1it2 $tation$ on Sumatra an' the a'a(ent i$%an'$. In$etF the

ra1it2 fie%' of Simeu%ue, $howin %o(ation$ of the $ma%% e6)o$ure$ of

o)hio%iti( ro("$.

o((u)2 mo$t of the wi'th of the i$%an' /i. 3.0. ;a%ue$ 5e%ow

>! ma% are a$$o(iate' with the *o5a (a%'era an' with an

e1en 'ee)er %ow or, rather, a 'ee)er (u%mination of the $ame

%ow0 that o((ur$ farther north an' e6ten'$ a$ far a$ La"e *awar

$ee /i$ 3. an' 3.#0. *he un(tion 5etween the two ra1it2

)ro1in(e$ a))ro6imate%2 a%on a %ine runnin --W from

Ben"u%u0 'oe$ not (orre$)on' to an2 of the terrane 5oun'arie$

re(onie' in )u5%i$he' a((retion mo'e%$ of Sumatra (f.

u%unono & Cameron @940 or to tho$e i'entifie' in Cha)ter

4, an' ma2 ref%e(t entire%2 )o$t>ama%amation )ro(e$$e$. It i$,

howe1er, a%$o )o$$i5%e that a maor 5ut hitherto unre(onie'

$uture i$ 5ein re(or'e' 52 the

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