International Insurance-Reinsurance Forum 2012 Managing catastrophic risks From Seismic Hazard Analysis to Seismic Risk mitigation C.O.Cioflan Ph.D., Senior.

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

2001 hazard map2010 M7 earthquake shaking

much greater than predicted for next 500 years

? 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 Design Ground Accelerations

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

Common imput for PSHA & NDSHA

NDSHA results – max I VIII+ MSK scale

The ongoing DACEA Cross Border Cooperation Project RO-BG

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 !!!!!

Seismic Risk

Vulnerability

Site EffectsSeismic Hazard

Practical ways to decrease Seismic Risk : Shake Maps

• Real Time Shake Map

Practical ways to decrease Seismic Risk : Vulnerability Studies

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.

THANK YOU FOR

YOUR KIND ATTENTION