turkey earthquake risk model financing the risks of natural disasters world bank washington, dc,...
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Turkey Earthquake Risk Model
Financing the Risks of Natural Disasters
World Bank
Washington, DC , June 2-3, 2003
Dennis E. Kuzak
Senior Vice President, EQECAT, Inc
Overall Model Components
Portfolio of Insured TCIP ExposuresPortfolio of Insured TCIP ExposuresTurkish Census and building stock data, plus TCIP information
Turkish Census and building stock data, plus TCIP information
Seismotectonic Model - fault/source locations, magnitudes, frequenciesSeismotectonic Model - fault/source locations, magnitudes, frequencies
Professor Erdik, USGS Research Papers, historical catalogsProfessor Erdik, USGS Research Papers, historical catalogs
Seismic Hazard - Ground ShakingSeismic Hazard - Ground Shaking Attenuation Functions,Local Soil ConditionsAttenuation Functions,Local Soil Conditions
VulnerabilityVulnerabilityHistorical Building Performance, Engineering Analysis, Turkish construction practices
Historical Building Performance, Engineering Analysis, Turkish construction practices
Damage and Financial LossDamage and Financial Loss Policy Deductibles, LimitsPolicy Deductibles, Limits
Seismic Hazard Modeling Methodology
Source zonation model (location) Recurrence model (size and frequency) Ground motion model (ground shaking) Hazard curve (ground shaking vs.
probability) Soil model (ground shaking amplification)
The location, size, and frequency of rare catastrophic earthquakes and their associated ground shaking are modeled using a Probabilistic Seismic Hazard Analysis (PSHA), which is composed of the following elements:
Tectonic Setting of Turkey
White
Quaternary Faults of Turkey
Legend: M 5.0-5.9 (purple); M 6.0-6.9 (blue); M 7.0+ (red)
Earthquakes in Turkey, 1904-1992
Earthquake Sources of Turkey
White
Source: Erdik et al. (1999), “Assessment of earthquake hazard in Turkeyand neighboring regions,” Annali di Geofisica, Vol. 42, pp. 1125-1138.
Seismic Hazard Map of Turkey
PGA (g) with a 10% Probability of Exceedance in 50 Years(475-year Return Period) on soft rock
White
Istanbul
Ankara
Black Sea
Mediterranean Sea
Source: Erdik et al. (1999), “Assessment of earthquake hazard in Turkeyand neighboring regions,” Annali di Geofisica, Vol. 42, pp. 1125-1138.
EQECAT Source Zonation Model
Basic area-source model from Erdik et al. (1999)
Large characteristic earthquakes (M 6.5): North Anatolian Fault (NAF) Northern NAF (NNAF; Marmara Sea) Southern NAF (SNAF; south of Marmara Sea)
Distributed faulting on NNAF and SNAF Smaller earthquakes included as NAF,
NNAF and SNAF background seismicity zones
Marmara Sea Region
NAF
SNAF
NNAF
North Anatolian Fault System (NAF)
Potentially the largest contributor to seismic hazard in Istanbul and northwestern Turkey
Ruptures in a sequence of large earthquakes Previously known rupture sequences
occurred in 967-1050 and 1254-1784 Latest sequence began in 1939 and is still in
progress Latest events in current sequence are the
1999M 7.4 Izmit and M 7.2 Duzce earthquakes
Next event in sequence is likely to be in Marmara Sea (Yalova and/or Prince’s Islands Faults?)
Rupture History of the NAF to 1992
Note: Mean repeat time is now estimated to be 225 years east of NNAF/SNAF split and 280 years west of this split (Stein, personal comm., 2000; Parsons et al., 2000)
EQECAT Recurrence Model
Area and background sources Fault sources:
North Anatolian Fault (NAF) Northern NAF (NNAF; Marmara Sea) Southern NAF (SNAF; south of Marmara
Sea)
Recurrence: Area and Background Sources
Earthquake catalog from regional sources: All magnitudes converted to moment
magnitude Foreshocks, aftershocks and swarms
removed Corrected for incompleteness
Exponential (Gutenberg-Richter) recurrence law
Maximum magnitude from seismicity/tectonics
Recurrence: Fault Sources
Characteristic earthquake recurrence law Recurrence rates from previous historic
events Magnitudes on NAF from last historic
event Magnitudes on NNAF from length/historic
events Magnitudes on SNAF from largest historic
event Time-dependent probability on NAF and
NNAF
EQECAT Time-Dependent Model
Definition of Time-Dependent Probability
Time-dependent probability is the conditional probability that an earthquake will occur on a fault within some specified period of time in the future (i.e., 2000 to 2030), given that a similar earthquake has occurred on this fault at some known time in the past
Causes of Time-Dependent Behavior
Secular stress increase due to long-term strain accumulation
Permanent stress increase or decrease due to stress interaction from an earthquake on a nearby fault
Transient stress increase or decrease due to stress interaction from an earthquake on a nearby fault (decays with time)
Time-Dependence from Secular Stress
Lognormal Probability Model
Last Earthquake
PARAMETERS
Te = Elapsed Time
T = Exposure Period
Conditional Probability = A/(A + B)
A
B
Note: We use recurrence intervals of 225 years east of NNAF/SNAF split and 280 years west of split; exposure period of 1 year; elapsed time from last historic event
Time-Dependence from Secular Strain
Sensitivity to Total Variability
Note: We use = 0.5
Time-Dependence from Fault Interaction
Transient Stress for NAF
Source: Parsons et al. (2000)
Time-Dependenc
e from Fault
Interaction
Progressive Effect of
1939-1992 Earthquake Sequence
Source: Stein et al. (1997)
Time-Dependenc
e from Fault
Interaction
Effect of 1999 Izmit Earthquake
Source: Parsons et al. (2000)
Time-Dependence from All Effects
Faults within 50 km of Istanbul
Source: Parsons et al. (2000); Our results give 50% smaller probability
Time-Dependence from All Effects
Istanbul
30-year (%) 10-year (%) 1-year (%)Fault
Interaction Secular Interaction Secular Interaction Secular
Yalova 33 21 22 18 14 11 7 7 1.7 1.7 0.8 0.8
Prince’s Is. 35 15 26 12 16 9 10 6 2.1 1.6 1.1 0.7
Marmara 13 9 11 8 5 5 4 4 0.6 0.7 0.5 1.0
Combined 62 15 49 15 32 12 20 9 4.4 2.4 2.3 1.5
Earthquake Probabilities of M 7 for Faultswithin 50 km of Istanbul Beginning in May 2000
(Interaction includes Secular and Interaction Stress Effects)
Note: 30-year time-averaged (Poisson) probability is 20 10%
Source: Parsons et al. (2000); Our results give 50% smaller 1-year combined probabilities
EQECAT Ground Motion Model
Four attenuation relationships for shallow crustal earthquakes: Abrahamson and Silva (1997) Boore et al. (1997) Campbell (1997) Sadigh et al. (1997)
One attenuation relationship for subduction earthquakes: Youngs et al. (1997)
1999 Izmit earthquake validation
PGA Estimate for 1999 Izmit Event
Note: PGA in g; Values are consistent with limited strong-motion recordings
EQECAT Soil Model
NEHRP soil classifications (A-E) were derived from a 1:500,000-scale geologic map of Turkey
Correlation with geology was based on extensive studies relating shear-wave velocity and geologic units in California
PGA amplification factors were based on empirical and theoretical studies relating shear-wave velocity and amplification
Turkish Soil Map
EQECAT Hazard Results
Seismic hazard curves: Istanbul (Bakirkoy) Izmit Ankara
Seismic hazard maps: All of Turkey Marmara Sea Region
Seismic Hazard Curves
Lowest hazard in Ankara, located in more stable central region of Turkey
Hazard in Izmit is approximately the same as that in Istanbul (Bakirkoy) because:
Time-dependent probability effects have increased hazard in Istanbul
Time-dependent probability effects have decreased hazard in Izmit0.01 0.1 1
Peak Ground Acceleration (g)
10
100
1000R
etu
rn P
eri
od
(ye
ars
)
AnkaraIstanbulIzmit
Soft Rock
Seismic Hazard Map for Turkey
0.05 - 0.100.10 - 0.150.15 - 0.200.20 - 0.250.25 - 0.300.30 - 0.350.35 - 0.400.40 - 0.450.45 - 0.500.50 - 0.550.55 - 0.600.60 - 0.650.65 - 0.700.70 - 0.750.75 - 0.800.80 - 0.850.85 - 0.90
PGA (g)
PGA with 10% Probability of Exceedance in 50 Years(475-year Return Period)
Soft Rock
Seismic Hazard Map for Marmara Sea
PGA with 10% Probability of Exceedance in 50 Years(475-year Return Period)
0.05 - 0.100.10 - 0.150.15 - 0.200.20 - 0.250.25 - 0.300.30 - 0.350.35 - 0.400.40 - 0.450.45 - 0.500.50 - 0.550.55 - 0.600.60 - 0.650.65 - 0.700.70 - 0.750.75 - 0.800.80 - 0.850.85 - 0.90
PGA (g)Soft Rock
Building Vulnerability
Good building codes- poor construction practices Non ductile concrete frames, soft story Limited/No claims data for residential multi-family EQECAT approach- use aggregate residential
damage data from Izmit, select damage curve consistent with Izmit data.
Summary
Turkish Model incorporates current research on time-dependent studies of North Anatolian Fault Raises hazard in Istanbul Lowers hazard east of Izmit epicenter
Recognizes uncertainty in NAF location in the Marmara Sea
Incorporates poor building practices into vulnerability assumptions
Fully probabilistic damage and loss model consistent with other EQECAT earthquake models for the US, Japan, Taiwan, etc.
TCIP RISK ANALYSIS RESULTS
Portfolio exposures estimated as of 31-10-2002
Estimated Annual Damage = .138% (1.38 per mill)
Exceedance Frequency
Return Period (Years)
Damage as a % Replacement
Value10.0% 10 0.18 9.0% 11 0.21 8.0% 13 0.25 7.0% 14 0.30 6.0% 17 0.36 5.0% 20 0.46 4.0% 25 0.63 3.0% 33 0.92 2.0% 50 1.38 1.0% 100 2.28 0.9% 111 2.43 0.8% 125 2.62 0.7% 143 2.89 0.6% 167 3.04 0.5% 200 3.38 0.4% 250 3.87 0.3% 333 4.61 0.2% 500 5.61 0.1% 1000 7.26