International Insurance-Reinsurance Forum 2012 Managing catastrophic risks From Seismic Hazard Analysis to Seismic Risk mitigation C.O.Cioflan Ph.D., Senior.
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International Insurance-Reinsurance Forum 2012Managing catastrophic risks
From Seismic Hazard Analysis to Seismic Risk
mitigation
C.O.Cioflan Ph.D., Senior Sci.Res.Engineering Seismology Dept.
National Institute for Earth Physics
PSHA DSHAStep 1 Seismic sources
Identification of Seismogenic Zones and Capable Faults;Epicenters; Geometry and Focal mechanism;
Step 2 Recurrence rate can be represented by a linear
relation only if the size of the study area is large with respect to linear
dimensions of sources.
• Scenario Earthquakes - fixed magnitude and distance
• Choice of the Controlling Earthquake
Step 3 Attenuation relations -they represent the functional dependency of the random spectral acceleration on the random variables, magnitude,
distance and measurement error and thus are source of systematic error in the seismic hazard assessment
Step 4 Seismic hazard assessment Probability of exceedance of
a given ground motion measure
Seismic hazard assessment Fixed Ground Motion
Measure
Horizontal Peak Ground Acceleration seismic hazard map representing stiff site conditions for an exceedance or occurrence rate of 10% within 50 years for the Mediterranean region.
GSHAP: PSHA, 475 years return period
Expected PGA(GSHAP)
ObservedPGA with a probability of exceedance of 10% in 50 years (return period 475 years)
• Kobe 0.40-0.48 0.7-0.8
• Gujarat 0.16-0.240.5-0.6
• Boumerdes 0.08-0.160.3-0.4
• Bam 0.16-0.24 0.7-0.8• Wenchuan 0.16-0.24
0.6-0.7Kobe (17.1.1995), Gujarat (26.1.2001), Boumerdes (21.5.2003), Bam (26.12.2003), Wenchuan (12.05. 2008)
IS PSHA (alone) RELIABLE ???
2008 Wenchuan earthquake (Mw=7.9) was not expected:
map showed low hazard
Bad assumptions or bad luck: Why natural hazard maps
often fail and what to do about it??? by Seth Stein, Northwestern University Robert Geller, University of Tokyo Mian Liu, University of Missouri
? GSHAP ? - PSHA• The detail given by the probabilistic maps proposed by
GSHAP is, in general, an artefact of the processing. • This limitation to the practical use of probabilistic maps is
particularly severe when dealing with large urban settlements or special objects.
The main advantage of the neo-deterministic procedure is the simultaneous treatment of the contribution of the seismic source and seismic wave propagation media to the strong motion at the target site/region, as required by basic physical principles.
NDSHA
PSHA DSHA NDSHAStep 1 Seismic sources
Identification of Seismogenic Zones and Capable Faults;Epicenters; Geometry and Focal mechanism;
Step 2 Recurrence rate can be represented by a linear relation only if the size
of the study area is large with respect to linear
dimensions of sources.
• Scenario Earthquakes - fixed magnitude and distance
• Choice of the Controlling Earthquake
• Scenario Earthquakes - fixed magnitude and distance
• Choice of the Controlling Earthquake
Step 3 Attenuation relations -they represent the functional dependency of the random
spectral acceleration on the random variables, magnitude, distance and measurement error and thus are source of systematic error in the seismic hazard
assessment
Synthetic ground motions.
no need of attenuation relations.
Step 4 Seismic hazard assessment Probability of exceedance of
a given ground motion measure
Seismic hazard assessment
Fixed Ground Motion Measure
Seismic hazard assessment
Envelopes of PGA or other Ground Motion
Measure
In 2000, finalizing the UNESCO-IGCP Project 414 and exploiting the existing CEI Network, neo-determinsitic maps of seismic hazard (peak amplitudes of the horizontal ground motion - displacement, velocity and design ground acceleration) were published (Panza & Vaccari, 2000). Shallow seismicity has been considered as a rule, limiting the computations to epicentral distances ≤ 90 km. The hypocentral depth considered is 10 km for events with magnitude Mw<7 and 15 km for larger events. For the Vrancea intermediate-depth events spectral properties especially determined for the Romanian these earthquakes have been considered and the computations have been performed over the Romanian, Northeastern Croatian and Hungarian territory, within a circle of 350 km of radius centered on Vrancea. The hypocentral depths considered are 90 km for M< 7.4 and 150 km for larger quakes.
Neo Deterministic Seismic Hazard Assessment
Mercea’08, Reggio CalabriaRecorded PGA : 1977,1986, 1990after Lungu, D. & Aldea, A., 1999
Seismic zoning of the Romanian territory in terms of maximum
DGA for Tr=100y; P100-1/2006
Seismicity of Romania ROMPLUS catalogue 984-2011
The ongoing DACEA Cross Border Cooperation Project RO-BG
PSHA results – max I=VIII in MSK scale different distribution !!!!!!
General Problems in SHA
• Uncertainties are hard to assess and generally underestimated
• Systematic errors often exceed measurement errors
• Map depends greatly on assumptions & thus has large uncertainty
General Problems in SHA
Hazard maps depend dramatically on unknown and difficult-to-assess parameters and hence on the mapmakers’ preconceptions
thus have large uncertainties that are generally underestimated and not communicated to public
sometimes either underpredict hazard in areas where large earthquakes occur
or overpredicting hazard
Without objective testing, maps won’t improve !!!!!
Practical ways to decrease Seismic Risk: Early Warning System
Detection & magnitude computation algorithm of the NIEP EWS
References
Klügel, J.-U., 2007. Error inflation in probabilistic seismic hazard analysis. Engineering Geology 90, 186–192.
Panza, G. F., Cioflan, C.O., Kouteva, M., Paskaleva, I., Romanelli, F., Marmureanu, G., (2002). An innovative assessment of the seismic hazard from Vrancea intermediate-depth earthquakes: case studies in Romania and Bulgaria. Proc. 12 ECEE, Ref. No. 230, Elsevier.
Panza, G.F., Radulian, M. and Trifu, C.-I., Editors (2000). Seismic hazard of the Circum-Pannonian Region, PAGEOPH topical volume, 157, 279 pp.
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