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Key Considerations in Modeling of Earthquake Risk in Turkey. Fouad Bendimerad, PhD, PE Christian Mortgat, PhD Financing the Risks of Natural Disasters World Bank Washington DC June 2-3, 2003. Background .

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Key Considerations in Modeling of Earthquake Risk in Turkey

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Key considerations in modeling of earthquake risk in turkey l.jpg

Key Considerations in Modeling of Earthquake Risk in Turkey

Fouad Bendimerad, PhD, PE

Christian Mortgat, PhD

Financing the Risks of Natural Disasters

World Bank

Washington DC

June 2-3, 2003


Background l.jpg

Background

  • Present key risk modeling consideration introduced in RMS RiskLink Turkey Earthquake Model

  • This presentation is mainly focused on impact of hazard parameters on modeling risk around Marmara Sea Region.

  • Illustration of variability of Loss Exceeding Probability (LEP) and Average Annual Loss (AAL) to residential exposure with respect to:

    • Source parameters

    • Rupture parameters

    • Recurrence parameters

  • The risk around the Marmara Sea is key to the insurance industry because a large proportion of the exposure is in this region, and because there is a large probability of a large earthquake hitting the region in the near future

Confidential


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Background

  • RMS RiskLink Turkey Earthquake model was released commercially in July 2001

  • Model and its applications were presented to the Turkish insurance industry during a seminar in Istanbul co-organized with the Association of Insurance and Reinsurance Companies of Turkey (TSRSB) on February 24, 2003

Confidential


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Number of Mahalles = 922

I s t a n b u l

(Mahalle Resolution)

B l a c k S e a

M a r m a r a S e a

Analysis Resolution

The loss analysis is performed at the Mahalle (I.e., neighborhood) level. About 10,000 stochastic events are simulated and loss is calculated for each event. An LEP is develop from the loss to each event. AAL is calculated accordingly

I s t a n b u l

Confidential


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Earthquake Exposure

  • Commercial lines constitutes the largest exposure

  • 58% of the total earthquake exposure is located around the Marmara Sea (Cresta Zones 1 to 4) ; including 40% in Cresta 1 (Istanbul). Hence, earthquake model warrants major focus on the risk around the Marmara Sea.

Confidential


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Seismic Activity In Turkey

  • Earthquake risk in Turkey is characterized both by high severity and high frequency

  • 1999 Izmit and Duzce earthquakes (M7.4 and 7.2, respectively) created the largest historical losses

Historical Earthquakes 1850-1999

Confidential


Earthquake threat to istanbul l.jpg

More than 10 million people and close to 60% of the economic value of Turkey would be impacted by an earthquake in the Marmara Sea region

Max magnitude could be as high as M7.7, potentially causing major losses

1992

1999

1967

1912

1957

1951

1944

1943

1942

1939

7.3

7.3

7.4

7.2

7.8

6.8

Earthquake Threat to Istanbul

  • The cluster of earthquakes on the North Anatolia Fault in the last century identifies a seismic gap around Istanbul

Seismic Gap

Marmara Sea

Confidential


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Historic Seismicity in the Marmara Sea

  • Ambraseys (2002) identifies 54 earthquakes of M>6.8 taking place in the Marmara Sea Region in the last 20 centuries

  • Earthquakes seemed to take place in sequences of clusters that repeat itself every 300 years approximately

Confidential


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Source Modeling and Rupture Modeling

  • Three source models are considered to take into consideration uncertainty in the NAFZ structure in the Marmara Sea

  • “Cascade” rupturing (I.e., potential for rupture of more than one segment) is considered in the study. Probability of cascade is determined by looking at ruptures in past events

Confidential


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Recurrence Modeling

  • In Model (a) eq. recurrence is modeled as Poisson

  • Model (b) and Model (c) consider characteristic events for M>6.5

    • Characteristic events are restricted on the fault segments

    • M<=6.5 occur within the area source following Poisson

  • In the Northwest Strand of the MSSZ, the rate of occurrence is estimated using four methods:

    • Slip rate

    • Slip rate + Time dependency (I.e., Renewal model)

    • Same as 2. + permanent stress migration due to the 1999 earthquakes

    • Same as 3. + transient stress migration due to the 1999 earthquakes

  • In the Southern Strand, occurrence is based on slip rate

Confidential


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Other Model Parameters

  • Uniform slip rate on the NAFZ is estimated at 2.4cm/year. About 2.0 cm/year is assigned to the Northwest strand of the MSSZ

  • Rate are calculated while preserving the energy balance in the fault

  • The time lapsed since the last occurrence and the average recurrence time are based on historical data. Investigation of historical seismicity for the last 2000 years

  • Maximum magnitude is adjusted to take into consideration the rupture length of “cascade” events

  • A background source of Mmax=6.5 is added to all models to account for the possibility of an earthquake outside of the geometry of the defined sources

  • Rate of earthquake occurrence in the background source is calculated using smoothed historical seismicity using and adaptive Gaussian Kernel technique

Confidential


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Combining Model

  • An event tree technique is used to combine different models and calculate an event rate

Confidential


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Probability Results

  • (1) and (2) are similar, but there only about 1/3rd of (6)

  • (3) increases probabilities significantly

  • (6) is very high for M>=7.0, but lowest for M>=7.5

  • Stress transfer (4) and (5) has a significant impact

Confidential


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Loss Results

  • Comparison of loss depends on the return period

  • (6) does not produce the highest losses

  • (1) produce the lowest losses

  • “Cascade” has a significant impact on increase losses for the high return periods

  • (5) produces the largest losses

Confidential


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Historical Loss Reconstruction

Calibration is achieved by successive approximation

Confidential


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Model Calibration: Historical Loss

99 Kocaeli (7.4)

Economic Loss -Residential

98 Adan Ceyhan (6.2)

Average

99 Duzce (7.2)

92 Erzincan(6.8)

Confidential


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Model Calibration: Scenario Analysis

Istanbul Max Scenario (M7.5)

D

C

B

Confidential


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Model Calibration: Industry Losses

Loss

Loss

Event

Magnitude

Calculated

Observed

1999

KOCAELI

7.4

$506

$410

1999

DUZCE

7.2

$124

$125

2002

Sultandagi

6.3

TCIP

$.80

Non-TCIP

$1.5

Repeat

1999 Kocaeli TCIP

7.4

$400

Repeat

1939 Erzincan

7.9

TCIP

$57

Non-TCIP

$67

Central Marmara

7.5

Worst

Case

TCIP

$1,100

Scenario

Non-TCIP

$2,000

Confidential


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Model Validation: Pure Premium

Pure Premium

Sub-Province Level

  • Model Resolution allows to identifies significant differences in risk within the different geographical regions of Turkey

High

Medium

Low

Confidential


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Model Validation: Modeled OEP versus Scenario Events

  • Model results are consistent with historical experience

  • Model allows relationship between individual scenarios and probabilistic losses

Confidential


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Conclusion

  • Model takes into consideration all the plausible scientific assumptions

  • In-depth treatment of the seismo-tectonic in the region

  • Thorough calibration of hazard and vulnerability components

  • Validation with respect to various benchmarks and historical experience

Confidential


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