The Chelyabinsk meteor: joint interpretation of infrasound, acoustic, and seismic waves

International Data Centre

The Chelyabinsk meteor: joint interpretation

of infrasound, acoustic, and seismic waves

I. Kitov, D. Bobrov, and M. Rozhkov

International Data CentrePreparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty OrganizationProvisional Technical SecretariatVienna International CentreP.O. Box 1200A-1400 ViennaAUSTRIA

[email protected]


Outline

• Sources of signals

• Peak energy release. Acoustic (low-amplitude shock) wave

• Infrasound source vs. seismic source

• Seismic waves: Pn, Lg

• Acousto-seismic waves: LR, LQ

• Comparison with atmospheric nuclear tests: Love and Rayleigh

waves

• Comparison with the 1987 Chulym meteorite


Source and energy

Ek = mV2/2 Ek = 2.35 · 1016 J

m0 = 1.3 · 107 kg 1 kt = 4.18 · 1012 J

V0 = 1.9 ·104 m/s W = 560 kt

Dynamic traction Pdyn = ρ(h)CDV2

Aerodynamic deceleration dV/dt = - ρ CDV2 /m(t)

Dissipation of kinetic energy dE = 0.5V2dm + mVdV

Ablation dm/dt = AρV3

Energy release history

Total energy


Source and energy

Flight time ~20 s; Flight distance ~350 km

Flight height change ~90 km

Height of peak light emission ~ between 30 km and 20 km

Duration of peak emission ~ 3 s

Length of peak emission ~ 35 km

Average energy release per km 560kt/350km =1.5 kt/km (1.5 t/m)

Peak energy release ~9 kt/km or 300 kt in total


Source and energy

V(1km) = 2500 m/s

m(1km) = 3,700 tons

Ek(1km) = 27 kt

E30 to 20 = 220 kt


Seismic source

(P2-P1)/P1 < 0.1 (high altitude explosion)

P1 - surface atmospheric pressure; P 2 – shock wave pressure

ΔP(r,t)/P1 = (ΔP(R0)/P1 )max(1-ta/L+)exp(-ta/L+)

ΔP = P2-P1 ; R0 – radius of peak overpressure; t – time;

a – sound speed near the surface; L+ - the length of shock wave

Source shape and evolution

Shock wave


Seismic observations:

ML=2.4; (ML(REB)=2.2)

Z

ARU N

E

Z

AKTO N

E

BVAR

KURK

MKAR

REB is the Reviewed Event Bulletin, a CTBTO product available to States Parties


Seismic observations: Pn


Location. SSSC- Source Specific Station Corrections

Pn : 55.06 º N, 60.92º E. Ellipse: Smax=23.5 km, Smin =15.3 km

MKAR AKTO ARU

KURK BVAR


Seismic observations: Lg


Seismic observations:

Lg waves magnitude estimation

5 stations: ARU, AKTO, BVAR, KURK, and MKAR

Station A, nm log(A) Δ, deg 0.83*log(Δ)

Q=400, V=3.5,

f=0.5 Hz mLg

ARU 116 2.064 1.9 0.231 0.001 3.11

AKTO 39 1.591 5 0.580 0.004 2.98

BVAR 17.5 1.243 5.9 0.640 0.004 2.70

KURK 17.3 1.238 11.5 0.880 0.008 2.94

MKAR 12.2 1.086 15.8 0.995 0.012 2.90

mLg = log(A) + 0.81+ 0.83log(Δ) + γ(Δ-0.09)0.434 ; Nuttly, 1986

mLg = 2.93 ± 0.15


Seismic observations: LR

ARU

AKTO

BVAR

KURK

AAK

OBN

MKAR

KBZ


Seismic observations: LR

magnitude estimation

# STA Phase Delta, deg Ms Ms res

1 BVAR LR 5.22 4.21 0.25

2 ZALV LR 13.53 4.35 0.39

3 AAK LR 14.17 4.11 0.15

4 OBN LR 14.65 3.20 -0.76

5 MKAR LR 14.91 4.35 0.39

6 KVAR LR 16.05 3.91 -0.05

7 KBZ LR 16.12 4.02 0.06

8 GNI LR 18.05 3.94 -0.02

9 NRIK LR 19.33 4.07 0.11

10 AKASG LR 20.07 4.06 0.11

11 FINES LR 20.23 3.23 -0.73

12 BRTR LR 23.79 3.72 -0.24

13 MLR LR 24.47 4.18 0.22

14 HFS LR 26.33 4.02 0.07

15 NOA LR 27.41 3.96 0.00

16 VRAC LR 28.05 4.00 0.05

17 SPITS LR 28.88 3.75 -0.21

18 GERES LR 29.95 4.21 0.26

19 EIL LR 31.17 3.87 -0.09

20 DAVOX LR 33.22 4.28 0.32

21 JMIC LR 34.09 3.71 -0.24

22 BORG LR 40.55 3.91 -0.05

23 CMAR LR 45.55 3.79 -0.17

24 KSRS LR 47.21 4.23 0.27

25 BBB LR 73.81 3.87 -0.09

25 IMS stations

(also detected at ARU,

AKTO, and KURK)

Ms(IDC) = 3.95 ± 0.06

Ms(IDC)max = 4.35 (ZALV

and MKAR)

Ms(IDC)min =3.20 (OBN)

Ms > Ms(DPRK2013)=3.9

Δmax= 74º !

1. Ms(IDC) = 3.95

2. ML (REB)=2.2

3. IDC rule: no LR associated for large Ms-mb differences

4. IDC rule: no LR associated without mb

5. Ignores physics of seismic wave generation

6. Ignores historical observations from atmospheric tests

7. What CTBT monitoring misses?

• Accurate epicenter location of atmospheric tests

with LR azimuths and travel times

• Altitude estimate from periods of LR and LQ

• Size estimate from amplitudes and periods

• Fusion of seismic and infrasound wavefield

• Interpretation of the event nature (nuclear tests vs. meteorites)

A serious gap in IDC processing at the development stage


Seismic observations, LR


Seismic observations, LQ

NRIK

SPITS


Atmospheric nuclear test:

seismic observations, LQ

E-W

Z

time

LQ

LR

Δ =3660 km

1 min

From: Pasechnik, I.P. (1970). Characteristic of seismic waves from nuclear explosions

and earthquakes, Nauka (in Russian)


Location

Pn : 55.06 º N, 60.92º E, Smax=23.5, Smin=15.3

LR/LQ : 54.81º N, 62.23º E, Smax=2.5 km, Smin =1.6 km (no modelling error)

I : 53.52º N, 66.59º E, Smax=376 km, Smin=197 km

REB : 54.06º N, 61.80º E, Smax=51 km, Smin=13 km

Disintegrated

meteorite

impact zone.

Expected

trajectory:

yellow line

International Data Centre International Data Centre Page 18

Comparative SSSC-corrected Pn-location for 5 and 3 IMS station (yellow and red),

and IASPEI-based location (blue)

Lake Chebarkul

Location


Trajectories published

by Universidad de

Antioquiahttp://urania.udea.edu.co/sitios

/facom/research/chelyabinsk-

meteoroid.php?#

Location

http://urania.udea.edu.co/sitios/facom/research/chelyabinsk-meteoroid.php?






Trajectory by BS2013-IAU

and YC2013-NASA, and

Universidad de Antioquia

Location


Chulym meteorite, 1984

26.02.1984, 13:40:00

57.5º N, 85.1º E

Ek ~10 kt

mLg = 3.39

Yield = 0.33kt

(From: Ovchinnikov and Pasechnik, Meteoritika 47,1988)


Chulym, 1984, and Chebarkul,

2013 meteorite locations


Comparing Chulym, 1984, Chebarkul, 2013, and

DPRK 2013 nuclear test

Mag Chulym Chebarkul Effect from

ML Not measured 2.4 Hitting the ground

MLg 3.31 2.93 Hitting the ground

Ms Not measured 3.95 Shock wave

What could we say about Chebarkul event if we would have only seismic observations?

“UNE case”:

• UNE manifestations at regional seismic stations: Pn, Lg and LR waves.

• Pn and LR locations give different coordinates and can’t be associated as a single source.

Comparing ML with the one determined by IDC from the DPRK-2013 event

(ML(IDC)=4.5).

• The DPRK-2013 yield was around 10kt.

• The explosion yield is proportional to the signal amplitude measured when estimating a

magnitude.

• From the magnitude measurements we can see that the Cheb is almost 100 times smaller

(2 magnitude units).

• The approximate yield of the explosion generating same body waves as Cheb is 0.1 kt.




Mag Chulym Chebarkul Effect from

ML Not measured 2.4 Hitting the ground

MLg 3.31 2.93 Hitting the ground

Ms Not measured 3.95 Shock wave

If Cheb were an atmospheric nuke.

• ATM test phenomena: prominent surface waves (Rayleigh and Love waves).

• UNE: a ratio R of energy transmitted to LR waves to total explosion energy is:

RUNE=ELR/EUNE = 10-6

RAIR= 4*10-8 for Air Nuclear Test

DPRK-2013: Ms = 3.9

• Cheb event Ms = 3.95

DPRK-2013 was an underground explosion, Cheb was an air explosion, so the

equivalent yield of this meteor explosion must be 25 times higher than the DPRK-

2013 test:

Ru/Ra = 25.

So the yield of the air explosion which would generate such waves must be 250Kt.




MLg discussion

• We estimated MLg=2.9 for Chebarkul event.

• To generate waves with such magnitude, UNE with the yield Y=0.2 kt must be conducted

(according to Nuttly magnitude scale).

• Though the numbers for Pn and Lg magnitudes are different (0.1kt and 0.2kt), the yields

estimated according to these magnitudes are really close taking into account uncertainties

of M to Y conversion for Lg based measurements.

• Estimation of a kinetic energy corresponding to such explosion gives the mass of the

space body which has hit the ground between 1 and 100 t (the range is due to uncertain

meteor velocity and some other parameters).

• Different mechanisms of wave generation (Pn and LR) in Cheb and Chul cases produce

difference in energy release as respectively 1/2 and 50:

MLg1 – MLg2 = 3.31 – 2.93 (2.99 by Ovchinnikov) = 0.38 which corresponds

approx. to yield ratio of 2.5 (2).

The meteorite energy estimated by us as ~500kt. Ovchinnikov and Pasechnik (1988)

estimated Chulym meteor yield as 10 kT, so the shock wave energy ratio for these

two events is 50.


Conclusions

• The energy of infrasound and seismic sources

associated with a meteorite may differ by a factor

of 2.

• Just a small part of the meteorite hit the surface

as debris.

• There were at least three sources separated in

space and time: (1) infrasound, (2) LR and LQ,

and (3) Pn, Sn, and Lg waves.

• These three sources are located along the

meteorite trajectory.

• There is a major hole in automatic and interactive

processing in the IDC. Atmospheric nuclear tests


Thank You!

The Chelyabinsk meteor: joint interpretation of infrasound, acoustic, and seismic waves

Technology

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