Seismic Hazard in Australia, - Actuaries
Transcript of Seismic Hazard in Australia, - Actuaries
Seismic Hazard in Australia, uncertainties and extreme events
Mark Leonard Geoscience Australia
Earthquakes in Australia o The National hazard map
Primary sources of Uncertainty o Mmax o Recurrence rates o Zonation o Ground Motion model
Extreme events Conclusion
CATRisk, Sydney 2014
Outline
CATRisk, Sydney 2014
Plate velocity/stress
– 60-70
Why do we have earthquakes? Northerly velocity • 60-70 mm/yr
Complex stress field • resistance to motion
creates stress • Stress -> EQs
Ignite – EMH (Feb 2013)
+ + =
Where do earthquakes occur?
How often and how big?
How much do they shake the earth?
CATRisk, Sydney 2014
o Earthquakes in Australia → The National hazard
map o Primary sources of Uncertainty
• Mmax → Solved! • Recurrence rates → Catalogue magnitudes • Zonation → Seismotectonic Model • Ground Motion model → Constrained with Australian
data o Extreme events o Conclusion
Mmax varies with crustal geology. • Old crust 7.25 • Newer 7.45 • Extended 7.65
CATRisk, Sydney 2014
Effect Mmax on Hazard in Sydney o Minor for
7.0 ≤ Mmax ≥ 7.8 o Significant for
change from the 5.5 ≤ Mmax ≤ 6.5 of 1980’s
o Mostly solved
CATRisk, Sydney 2014
o Earthquakes in Australia → The National hazard
map o Primary sources of Uncertainty
• Mmax → Solved! • Recurrence rates → Catalogue magnitudes • Zonation → Seismotectonic Model • Ground Motion model → Constrained with Australian
data o Extreme events o Conclusion
CATRisk, Sydney 2014
ABE Abe (1981, 1982, 1984) Catalog of Large Earthquakes, 1897-1980.
ADE Adelaide (University of Adelaide, Flinders University, PIRSA, DMITRE)
AGSO Australian Geological Survey Organisation
AUST Australian Geological Survey Organisation Geoscience Australia
BCIS Bureau Central International Seismologique BJI Beijing, China Earthquake Administration BMR Bureau of Mineral Resources BRS University of Queensland, Brisbane BurkeG Burke-Gaffney, Riverview Observatory, Sydney CAN Australian National University, Canberra Cotton L. A. Cotton, University of New South Wales CQU Central Queensland University, Rockhampton Denham David Denham DES Doyle, Everingham and Sutton, 1968, Jnl GSA, 15, pt2, 295-312 DJA Lembaga Meteorologi dan Geofisika, Jakarta, Indonesia Doyle Hugh Doyle Drake Laurie Drake, Riverview Observatory, Sydney E.T. Everingham and Tilbury, 1972, Jnl Royal Soc of WA, 55, 3, 90-96 EHB Centennial Catalogue (Engdahl-Hilst-Buland) EIDC Experimental International Data Center ERL Earthquake Research Lab, San Francisco, California G&R Gutenberg and Richter (1954) catalogue, 1904-1952. Garran GG Gary Gibson, Environmental Systems and Services Gliddon GSQ Geological Survey of Queensland HDR unknown agency code, Indonesia 1993 Holmes Holmes, W.M., 1933, Trans Royal Soc Vic, 45, 2, 150-151 IDC International Data Center ISC International Seismological Centre
ISM Unknown source quoted by BMR, 1972 February and March (NOT ISC)
ISS The International Seismological Summary, 1918-1963 JMA Japan Meteorological Agency, Tokyo, 1926-present
Joklik Gunning NSW earthquakes, Joklik and Casey 1952
Jones Unknown source, Queensland, 1950-1957
KMcC Kevin McCue, Canberra
Leiba Marion Leiba, Canberra
LEM Lembang, Indonesia, 1959-1961, see DJA
Malpas Katherine Malpas, Adelaide
McArdle Alison McArdle, Adelaide
MEL Seismological Research Centre, Melbourne, Victoria
MELOBS Melbourne Observatory
MGO Mundaring Geophysical Observatory, Western Australia
MOS Institute of Physics of the Earth, Moscow, Russia
MUN Mundaring Geophysical Observatory, Western Australia
NEIC National Earthquake Information Center
NEIS National Earthquake Information Service
Osburne Unknown source, Warrnambool earthquake, 1848
PEK Peking, until 1987-12-31, recoded as BJI, Beijing, from 1988-01-01
Qld Met Meteorological Bureau, Queensland, 1866-1912
RC Russell Cuthbertson, Environmental Systems and Services, Brisbane
RobUnd Rob Underwood
Rynn Jack Rynn, Centre for Earthquake Research in Australia, Brisbane
SEQW South East Queensland Water, Brisbane
Spennemann Dirk Spennemann, Charles Sturt University, New South Wales
Sykes Catalogue of SCR earthquakes, 1900-1989, Pacheco and Sykes (1992)
TAU University of Tasmania, Australia
Underwood Rob Underwood
UQ University of Queensland (Now deleted, references re-coded as BRS)
USCGS US Coast and Geodetic Survey
USGS US Geological Survey
Inconsistent Magnitudes
CATRisk, Sydney 2014
Amplitude Function that depends on distance
Local (Richter) Magnitude
ML = log A – log A0
CATRisk, Sydney 2014
Magnitude Effects Recurrence Distribution
Effect Recurrence on Hazard in Sydney o Log(N) = A + log(M*b) o Magnitude b ± 0.15 o Recurrence method
b ± 0.15 o b+0.2 → hazard * 1.75
o Requires a consistent
catalogue with new Australian specific magnitudes.
CATRisk, Sydney 2014
o Earthquakes in Australia → The National hazard
map o Primary sources of Uncertainty
• Mmax → Solved! • Recurrence rates → Catalogue magnitudes • Zonation → Seismotectonic Model • Ground Motion model → Constrained with Australian
data o Extreme events o Conclusion
Sydney source zone • Newcastle, Sydney,
Wollongong, Orange, Dubbo.
• Earthquakes distributed relatively uniformly over most of the zone
• But, no recorded earthquakes in Sydney basin
CATRisk, Sydney 2014
Sydney source zone • Newcastle, Wollongong,
Orange, Dubbo. • Could exclude Sydney
CATRisk, Sydney 2014
Effect of Zonation on Hazard in Sydney and Perth • Decrease hazard in
Sydney 30% • Currently uses seismicity
with minor geological input.
• Requires a seismotectonic model that combines seismicity, geology, tectonics and geodesy
CATRisk, Sydney 2014
o Earthquakes in Australia → The National hazard
map o Primary sources of Uncertainty
• Mmax → Solved! • Recurrence rates → Catalogue magnitudes • Zonation → Seismotectonic Model • Ground Motion model → Constrained with Australian
data o Extreme events o Conclusion
Ground-Motion Models ≈ Attenuation Function
Source: Bommer 2010 Source: USGS CATRisk, Sydney 2014
Effect of GM Prediction Equation on Hazard in Sydney • If the collection of blue
GMPEs correct, effect is minor
• I not and one of the brown GMPEs applies, effect is significant
• Evidence for blue and not brown is weak.
• Needs much more study into the properties of the Australian crust
CATRisk, Sydney 2014
o Earthquakes in Australia → The National hazard
map o Primary sources of Uncertainty
• Mmax → Solved! • Recurrence rates → Catalogue magnitudes • Zonation → Seismotectonic Model • Ground Motion model → Constrained with Australian
data o Extreme events o Conclusion
CATRisk, Sydney 2014
CATRisk, Sydney 2014
Impact of the Scenarios
CATRisk, Sydney 2014
Earthquake Magnitude
Minor Injuries
Major Injuries
Deaths
6.4 4,400 600 150
7.5 30,000 3,800 950
A catastrophic event might be: > M6.8 under a city or > M7.1 next to a city For reference Newcastle was M5.6
What is a catastrophic event?
CATRisk, Sydney 2014
Damage MMI Damage MMI g Mag #
Moderate VII Moderate VII ≥ 0.2 5.3
Moderate to Heavy
VIII Moderate to Heavy
VIII ≥ 0.4 6.0
Heavy IX Heavy IX ≥ 0.75 6.8 Very Heavy X Very
Heavy X ≥ 0.13 7.2
• Mag# - Magnitude required for a damage area of 10km
• Return Rate for capital Cities • Per Year • Per 10,000 km2
Mag. Adelaide Melbourne Sydney Canberra Perth Brisbane Hobart
6.5 8500 4400 5600 7000 6500 4700 50000 6.8 17500 7600 10200 13900 12200 8000 100000 7.0 28000 11000 15000 21000 19000 11000 164000
CATRisk, Sydney 2014
o Large earthquakes require long faults
o Likely only occur on existing faults
o So catastrophic earthquakes in an Australian city requires a fault in or near the city
Fault Scaling
Adelaide • Long faults under
and next to city • M ≥ 7.0 possible
under city • M7.0
CATRisk, Sydney 2014
Melbourne • Many long faults
around city • M 6.8 under city
possible • M ≥ 7.0 possible on
city edge.
CATRisk, Sydney 2014
Perth • Deep M 6.3 possible
under city. • M ≥ 7.0 possible to
west and east of city.
CATRisk, Sydney 2014
Sydney • M 6.3 possible
under city • M ≥ 7.0 possible on
western edge
CATRisk, Sydney 2014
Sydney Zone Return Periods Per 10,000km2 M6.5 – 5400 yr M7.1 – 18000 yr M7.1 -1σ 7000 yr M7.1 +1σ 44000 yr Assumes regional Poisson process but individual faults likely have memory.
CATRisk, Sydney 2014
Conclusion • There is considerable uncertainty in the earthquake hazard in
Australia. – ±1σ is about a factor of 2 (50% to 200%), perhaps a factor of 3 – We observe factors of two in site specific hazard studies (e.g. RAH)
and that is ignoring the full range of GMPEs – Only more research into magnitudes, attenuation of the Australian
crust and seismo-tectonic models in stable continents will reduce this uncertainty. Just adopting US models wont.
• Large earthquakes (≥M6.3) can occur in all Australian cities with a return period 5000-7000 years
• Catastrophic earthquakes (>M7.0) can occur in or near most Australian cities with a return period 15000-25000 years
CATRisk, Sydney 2014
CATRisk, Sydney 2014
Any Questions?
• Thank you
CATRisk, Sydney 2014
CATRisk, Sydney 2014
Fault Scaling – Length vs Slip
CATRisk, Sydney 2014
Fault Scaling – Length vs Slip