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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. Turkish Census and building stock data, plus TCIP information.

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turkey earthquake risk model

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
Overall Model Components

Turkish Census and building stock data, plus TCIP information

Portfolio of Insured TCIP Exposures

Professor Erdik, USGS Research Papers, historical catalogs

Seismotectonic Model - fault/source locations, magnitudes, frequencies

Attenuation Functions,Local Soil Conditions

Seismic Hazard - Ground Shaking

Historical Building Performance, Engineering Analysis, Turkish construction practices

Vulnerability

Policy Deductibles, Limits

Damage and Financial Loss

seismic hazard modeling methodology
Seismic Hazard Modeling Methodology

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:

  • 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)
earthquakes in turkey 1904 1992
Earthquakes in Turkey, 1904-1992

Legend: M 5.0-5.9 (purple); M 6.0-6.9 (blue); M 7.0+ (red)

earthquake sources of turkey
Earthquake Sources of Turkey

White

Source: Erdik et al. (1999), “Assessment of earthquake hazard in Turkey

and neighboring regions,” Annali di Geofisica, Vol. 42, pp. 1125-1138.

seismic hazard map of turkey
Seismic Hazard Map of Turkey

PGA (g) with a 10% Probability of Exceedance in 50 Years

(475-year Return Period) on soft rock

Black

Sea

Istanbul

Ankara

Sea

Mediterranean

Source: Erdik et al. (1999), “Assessment of earthquake hazard in Turkey

and neighboring regions,” Annali di Geofisica, Vol. 42, pp. 1125-1138.

White

eqecat source zonation model
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
north anatolian fault system naf
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
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
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
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
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
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
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
Time-Dependence from Secular StressLognormal Probability Model

PARAMETERS

Te = Elapsed TimeT = Exposure Period

A

B

Conditional Probability = A/(A + B)

Last Earthquake

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 fault interaction progressive effect of 1939 1992 earthquake sequence
Time-Dependence from Fault InteractionProgressive Effect of1939-1992 Earthquake Sequence

Source: Stein et al. (1997)

time dependence from fault interaction effect of 1999 izmit earthquake
Time-Dependence from Fault InteractionEffect of 1999 Izmit Earthquake

Source: Parsons et al. (2000)

time dependence from all effects faults within 50 km of istanbul
Time-Dependence from All EffectsFaults within 50 km of Istanbul

Source: Parsons et al. (2000); Our results give 50% smaller probability

time dependence from all effects istanbul
Time-Dependence from All EffectsIstanbul

Earthquake Probabilities of M  7 for Faults

within 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
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
PGA Estimate for 1999 Izmit Event

Note: PGA in g; Values are consistent with limited strong-motion recordings

eqecat soil model
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
eqecat hazard results
EQECAT Hazard Results
  • Seismic hazard curves:
    • Istanbul (Bakirkoy)
    • Izmit
    • Ankara
  • Seismic hazard maps:
    • All of Turkey
    • Marmara Sea Region
seismic hazard curves
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 Izmit

Soft Rock

seismic hazard map for turkey

PGA (g)

0.05 - 0.10

0.10 - 0.15

0.15 - 0.20

0.20 - 0.25

0.25 - 0.30

0.30 - 0.35

0.35 - 0.40

0.40 - 0.45

0.45 - 0.50

0.50 - 0.55

0.55 - 0.60

0.60 - 0.65

0.65 - 0.70

0.70 - 0.75

0.75 - 0.80

0.80 - 0.85

0.85 - 0.90

Seismic Hazard Map for Turkey

PGA with 10% Probability of Exceedance in 50 Years

(475-year Return Period)

Soft Rock

seismic hazard map for marmara sea

PGA (g)

0.05 - 0.10

0.10 - 0.15

0.15 - 0.20

0.20 - 0.25

0.25 - 0.30

0.30 - 0.35

0.35 - 0.40

0.40 - 0.45

0.45 - 0.50

0.50 - 0.55

0.55 - 0.60

0.60 - 0.65

0.65 - 0.70

0.70 - 0.75

0.75 - 0.80

0.80 - 0.85

0.85 - 0.90

Seismic Hazard Map for Marmara Sea

PGA with 10% Probability of Exceedance in 50 Years

(475-year Return Period)

Soft Rock

building vulnerability
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
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
TCIP RISK ANALYSIS RESULTS

Portfolio exposures estimated as of 31-10-2002

Estimated Annual Damage = .138% (1.38 per mill)