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


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?


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


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







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


Amplitude Function that depends on distance

Local (Richter) Magnitude

ML = log A – log A0


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.






Sydney source zone • Newcastle, Sydney,

Wollongong, Orange, Dubbo.

• Earthquakes distributed relatively uniformly over most of the zone

• But, no recorded earthquakes in Sydney basin


Sydney source zone • Newcastle, Wollongong,

Orange, Dubbo. • Could exclude Sydney


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






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








Impact of the Scenarios


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?


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


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


Melbourne • Many long faults

around city • M 6.8 under city

possible • M ≥ 7.0 possible on

city edge.


Perth • Deep M 6.3 possible

under city. • M ≥ 7.0 possible to

west and east of city.


Sydney • M 6.3 possible

under city • M ≥ 7.0 possible on

western edge


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.


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



Any Questions?

• Thank you



Fault Scaling – Length vs Slip


Fault Scaling – Length vs Slip

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Seismic Hazard in Australia, - Actuaries