Diapositivo 1 - Swiss Seismological Service · 2017-09-27 · 1 –Laboratório Nacional de...
1
Recurrence interval for great earthquakes in mainland Portugal: a critical overview A. Carvalho 1,2 and N. Malfeito 2 1 – Laboratório Nacional de Engenharia Civil (LNEC), Lisboa, Portugal 2 – Sociedade Portuguesa de Engenharia Sísmica (SPES), Lisboa, Portugal [email protected] Introduction Seismic source zones, and its characterization, have major impact in Probabilistic Seismic Hazard Analyses (PSHA). In 2006, a model with eleven seismogenic zones was considered to re-evaluate the seismic hazard for Mainland Portugal, supporting decisions for the seismic zonation map presented in the Portuguese Annex of Eurocode 8. Between 2008 and 2009, in the aim of projects ERSTA and SHARE, there were alternative area source models developed, together with the estimate of activity rates parameters and magnitude distribution. These different proposals (together with ground motion prediction equations assumptions) result in quite different seismic hazard levels, leading to a need, among decision makers, to understand the origin of such differences. The national earthquake engineering society (SPES) promoted, among scientific community, a study to evaluate the origin of such differences. In this work the earthquake activity rates, b-values and magnitude distribution for the mentioned source zones proposals are analysed, with particular emphasis on its implications for the recurrence period of large seismic events. Hazard maps are also assessed, for different ground motion prediction equations, and a comparison analysis was carried out. Models Conclusions ERSTA (2008-2011) SHARE (2009-2013) b_value EC8 (2006) 1 2 3 4 5 Períodos de Retorno Magnitude 100 475 1000 5000 5.5 6 7 EC8 6.1 6.8 7.0 7.1 EC8 30 80 1300 ERSTA 6.2 6.8 6.9 7.1 ERSTA 20 60 2000 SHARE 6.0 6.7 7.0 7.3 SHARE 35 100 1300 6.6 – 6.7 6.9 – 7.0 7.2 – 7.4 1100-1700 Lower Tagus Valley 1 2 3 4 5 Zona 7 Zona J Zona 253 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 EC8 ERSTA SHARE a Zona 7 Zona J Zona 253 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 EC8 ERSTA SHARE b Zona 7 Zona J Zona 253 0 1 2 3 4 5 6 7 8 9 10 EC8 ERSTA SHARE Mmáx 0.00001 0.0001 0.001 0.01 0.1 1 10 4 5 6 7 8 9 Número Eventos / Ano Magnitude EC8 ERSTA SHARE Mmáx-EC8 Mmáx-ERSTA Mmáx-SHARE Períodos de Retorno Magnitude 100 475 1000 5000 7 8 8.4 EC8 6.5 7.4 7.8 8.4 EC8 200 1600 5000 ERSTA 7.1 7.9 8.2 8.6 ERSTA 90 550 1700 SHARE 6.7 7.4 7.7 8.3 SHARE 200 2100 9000 8.2 - 8.3 1900-1400 6500-19000 0.00001 0.0001 0.001 0.01 0.1 1 10 4 5 6 7 8 9 Número Eventos / Ano Magnitude EC8 ERSTA SHARE Mmáx-EC8 Mmáx- ERSTA Zona 5 Zona B Zona 251 0 1 2 3 4 5 6 7 8 EC8 ERSTA SHARE Zona 5 Zona B Zona 251 0 0.5 1 1.5 2 2.5 3 3.5 4 EC8 ERSTA SHARE a Zona 5 Zona B Zona 251 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 EC8 ERSTA SHARE b Horseshoe Fault Períodos de Retorno Magnitude 100 475 1000 5000 6 6.5 7 EC8 6.0 6.7 6.8 7.0 EC8 50 200 3000 ERSTA 6.3 7.0 7.2 7.4 ERSTA 60 140 445 SHARE 5.5 6.2 6.4 6.9 SHARE 300 1100 6600 6.2 - 6.3 6.3 - 6.5 6.7 - 7.1 970 - 1800 3600 - 6600 1 2 3 4 5 0.00001 0.0001 0.001 0.01 0.1 1 10 4 5 6 7 8 9 Numero Eventos / Ano Magnitude EC8 ERSTA SHARE Mmáx-EC8 Mmáx-ERSTA Mmáx-SHARE Zona 9 Zona H Zona 254 0 0.5 1 1.5 2 2.5 3 3.5 4 EC8 ERSTA SHARE a Zona 9 Zona H Zona 254 0 0.2 0.4 0.6 0.8 1 1.2 EC8 ERSTA SHARE b Zona 9 Zona H Zona 254 0 1 2 3 4 5 6 7 8 9 EC8 ERSTA SHARE Mmáx Gulf of Cadiz ERSTA SHARE 475 YEARS 2475 YEARS 475 YEARS 2475 YEARS EC8 ERSTA SHARE 2475 YEARS Sources OFFSHORE Sources INLAND • Gutenberg –Richter law lead to important differences among the three source models analysed, considering the recurrence period of large seismic events. • ERSTA took advantage of a revised instrumental catalogue. • Higher b_values considered by SHARE in offshore area-source zones lead to an underestimation of the recurrence periods for larger magnitude, and they are not representative of long-term seismicity for Portugal mainland. • The impact of uncertainties on source models and recurrences models (that rely on different datasets and assumptions) on hazard results cannot be ignored. • The zonation map presented in the portuguese national annex of EC8 should be revised, as well. Total hazard
Transcript of Diapositivo 1 - Swiss Seismological Service · 2017-09-27 · 1 –Laboratório Nacional de...
Recurrence interval for great earthquakes in mainland Portugal: a
critical overviewA. Carvalho1,2 and N. Malfeito2
1 – Laboratório Nacional de Engenharia Civil (LNEC), Lisboa, Portugal 2 – Sociedade Portuguesa de Engenharia Sísmica (SPES), Lisboa, [email protected]
Introduction
Seismic source zones, and its characterization, have major impact in Probabilistic Seismic Hazard Analyses (PSHA).
In 2006, a model with eleven seismogenic zones was considered to re-evaluate the seismic hazard for Mainland Portugal, supporting decisions for the seismic zonation map
presented in the Portuguese Annex of Eurocode 8. Between 2008 and 2009, in the aim of projects ERSTA and SHARE, there were alternative area source models developed,
together with the estimate of activity rates parameters and magnitude distribution.
These different proposals (together with ground motion prediction equations assumptions) result in quite different seismic hazard levels, leading to a need, among decision makers,
to understand the origin of such differences.
The national earthquake engineering society (SPES) promoted, among scientific community, a study to evaluate the origin of such differences.
In this work the earthquake activity rates, b-values and magnitude distribution for the mentioned source zones proposals are analysed, with particular emphasis on its implications
for the recurrence period of large seismic events. Hazard maps are also assessed, for different ground motion prediction equations, and a comparison analysis was carried out.
Models
Conclusions
ERSTA (2008-2011) SHARE (2009-2013)
b_value
EC8 (2006)
1
2
3
4
5
Períodos de Retorno Magnitude 100 475 1000 5000 5.5 6 7
EC8 6.1 6.8 7.0 7.1 EC8 30 80 1300
ERSTA 6.2 6.8 6.9 7.1 ERSTA 20 60 2000
SHARE 6.0 6.7 7.0 7.3
SHARE 35 100 1300
6.6 – 6.7 6.9 – 7.0 7.2 – 7.4 1100-1700
Lower Tagus Valley
1
2
3
4
5
Zona 7
Zona J
Zona 253
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
EC8 ERSTA SHARE
a
Zona 7 Zona
J
Zona 253
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
EC8 ERSTA SHARE
b
Zona 7
Zona J
Zona 253
0
1
2
3
4
5
6
7
8
9
10
EC8 ERSTA SHARE
Mm
áx
0.00001
0.0001
0.001
0.01
0.1
1
10
4 5 6 7 8 9
Nú
mero
Ev
en
tos / A
no
Magnitude
Falha da Ferradura
EC8
ERSTA
SHARE
Mmáx-EC8
Mmáx-ERSTA
Mmáx-SHARE
Períodos de Retorno Magnitude
100 475 1000 5000 7 8 8.4
EC8 6.5 7.4 7.8 8.4 EC8 200 1600 5000
ERSTA 7.1 7.9 8.2 8.6 ERSTA 90 550 1700
SHARE 6.7 7.4 7.7 8.3
SHARE 200 2100 9000
8.2 - 8.3 1900-1400 6500-19000
Zona 5
Zona B
Zona 251
0
1
2
3
4
5
6
7
8
EC8 ERSTA SHARE
Mm
áx
Zona 5
Zona B
Zona 251
0
0.5
1
1.5
2
2.5
3
3.5
4
EC8 ERSTA SHARE
a
Zona 5
Zona B
Zona 251
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
EC8 ERSTA SHARE
b
0.00001
0.0001
0.001
0.01
0.1
1
10
4 5 6 7 8 9
Nú
mero
Ev
en
tos / A
no
Magnitude
Falha Vale Inferior do Tejo
EC8
ERSTA
SHARE
Mmáx-EC8
Mmáx-ERSTA
Zona
5
Zona
B
Zona
251
0
1
2
3
4
5
6
7
8
EC8 ERSTA SHARE
Zona
5
Zona
B
Zona
251
0
0.5
1
1.5
2
2.5
3
3.5
4
EC8 ERSTA SHARE
a
Zona
5
Zona
B
Zona
251
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
EC8 ERSTA SHARE
b
Horseshoe Fault
Períodos de Retorno Magnitude
100 475 1000 5000 6 6.5 7
EC8 6.0 6.7 6.8 7.0 EC8 50 200 3000
ERSTA 6.3 7.0 7.2 7.4 ERSTA 60 140 445
SHARE 5.5 6.2 6.4 6.9
SHARE 300 1100 6600
6.2 - 6.3 6.3 - 6.5 6.7 - 7.1 970 - 1800 3600 - 6600
1
23
4
5
Zona 9
Zona H
Zona 254
0
0.5
1
1.5
2
2.5
3
3.5
4
EC8 ERSTA SHARE
a
Zona 9 Zona
H
Zona 254
0
0.2
0.4
0.6
0.8
1
1.2
EC8 ERSTA SHARE
b
Zona 9
Zona H
Zona 254
0
1
2
3
4
5
6
7
8
9
EC8 ERSTA SHARE
Mm
áx
0.00001
0.0001
0.001
0.01
0.1
1
10
4 5 6 7 8 9
Nu
me
ro E
ven
tos
/ A
no
Magnitude
Golfo de Cádis
EC8
ERSTA
SHARE
Mmáx-EC8
Mmáx-ERSTA
Mmáx-SHARE
Zona
9Zona
H
Zona
254
0
0.5
1
1.5
2
2.5
3
3.5
4
EC8 ERSTA SHARE
a
Zona
9 Zona
H
Zona
254
0
0.2
0.4
0.6
0.8
1
1.2
EC8 ERSTA SHARE
b
Zona
9
Zona
HZona
254
0
1
2
3
4
5
6
7
8
9
EC8 ERSTA SHARE
Mm
áx
Gulf of Cadiz
ERSTA SHARE475 YEARS 2475 YEARS 475 YEARS 2475 YEARS
EC8 ERSTA SHARE
24
75
YE
AR
S
Sourc
es
OF
FS
HO
RE
Sourc
es
INLA
ND
• Gutenberg –Richter law lead to important differences among the three
source models analysed, considering the recurrence period of large
seismic events.
• ERSTA took advantage of a revised instrumental catalogue.
• Higher b_values considered by SHARE in offshore area-source zones lead
to an underestimation of the recurrence periods for larger magnitude, and
they are not representative of long-term seismicity for Portugal mainland.
• The impact of uncertainties on source models and recurrences models
(that rely on different datasets and assumptions) on hazard results cannot
be ignored.
• The zonation map presented in the portuguese national annex of EC8
should be revised, as well.
To
tal h
azard
