Deterministic Seismic Design Values for Istanbul Metropolitan and Sea of Marmara (Turkey) Region

 

Kalkan Gulkan GMPE

Multiple rupturing of Off-Tekirdag, Mid-Marmara and Islands faults can create ground shaking in Istanbul Metropolis as much as three times as compared to the shaking that the city experienced during the 1999 Mw 7.4 Kocaeli (Izmit) Eq.

 

Plain English Summary  

Istanbul, the largest urban sprawl in Turkey, is considered likely to experience a major earthquake during the next few decades. Using a deterministic approach, peak values of expected ground-motions are estimated for the Sea of Marmara (Turkey) region that encompasses the city based on six plausible earthquake scenarios. These scenarios consist of individual and multiple rupturing of the submarine fault segments along the western part of the North Anatolian Fault Zone (NAFZ) extending into the Sea of Marmara. To quantify the regional exposure on a set of hazard maps, a total of six ground motion prediction equations (GMPEs) have been used in a combinatorial approach to account for epistemic uncertainty. In lieu of subjectively weighting the expressions, the GMPEs were weighted proportional to their relative performance in predicting the measured peak ground motions of the 1999 M7.4 Kocaeli earthquake when it ruptured the Izmit segment of the NAFZ up to the eastern reaches of Istanbul. This computational approach has resulted in consistent but different weights for each GMPE at different spectral periods. The resultant high-resolution (0.002° by 0.002°, approx. 250 m by 250 m) deterministic seismic hazard maps, that implicitly incorporate site amplification due to softer sediments, provide peak horizontal ground acceleration (PGA) and spectral acceleration values at 0.2, 0.3, 0.5, 1, 1.5, 2, 3 and 4 seconds. The maximum spectral acceleration at 0.3 s computed is close to 1 g along the shoreline to the west of the Istanbul Metropolitan area, and 0.3 g near the financial district. The hazard results of this study can be used directly as design ground-motion levels for evaluating existing infrastructure, and design of new buildings and other critical systems in the Istanbul Metropolitan Area and its surroundings.

Turkce Ozet

Bu calismada, Istanbul ve cevresi icin beklenen yer hareketinin siddeti alti degisik deprem senaryosuna gore hesaplanmistir. Bu senaryolar Kuzey Anadolu Fay zonunun Marmara denizi altina uzana Adalar, Orta Marmara, Cinarcik ve Tekirdag faylarinin tekil ve beraber kirilmalarindan olusan depremleri temsil etmektedir. Bu faylar Istanbul ve cevresini etkileyecek moment magnitud olceginde 7 ila 7’den buyuk deprem uretebilecek potansiyeldedirler. Bu senaryo depremlere dayali yer hareketinin tahmini icin yerel ve yerel olmayan toplam alti ampirik denklem kullanilmistir. Olasi yer hareketi konusunda yetersiz bilgi ve veriden kaynaklanan belirsizlik denklemlerin tahmin ettigi yer hareketi degerlerinin degisik agirlik katsayilariyla birlestirilmesiyle dikkate alinmistir. Kullanilan agirlik katsayilari, bu denklemlerin 1999 Kocaeli depremi yer hareketi degerlerinin tahmin performanslarina gore belirlenmistir. Bu yaklasim her bir denklem icin farkli spektral periyotlarda farkli agirlik katsayilari vermektedir. Neticede elde edilen yuksek cozunurluklu (0.002° x 0.002° = 250 m x 250 m) deprem tehlike haritalari, yatay dogrultudaki en buyuk yer ivme degerleri ve 0.2, 0.3, 0.5, 1, 1.5, 2, 3, 4 saniye periyotlarindaki spektral ivme degerlerini sunmaktadir. Bu haritalar yumusak zeminden kaynaklanan yer hareketi buyutme etkisini de gozonune alir. 0.3 saniyedeki en buyuk spektral ivme degeri Bakirkoy, Atakoy ve Avcilar kiyi seridi buyunca 1 g (g = yer cekimi ivmesi), Maslak civarinda ise 0.3 g olarak hesaplanmistir. Bu calismada elde edilen sonuclar dogrudan tasarim depremi olarak, Istanbul ve cevresindeki mevcut yapilarin degerlendirilmesi ve yeni yapilacak binalarin ve diger muhendislik yapilarinin tasarimi icin kullanilabilir.

 

EXPECTED GROUND SHAKING AS COMPARE TO 1999 Mw7.4 KOCAELI EARTHQUAKE

Ratio of maximum estimated horizontal ground shaking due to each scenario earthquake and that experienced during the 1999 Kocaeli event computed at central point of each district of the ?stanbul Metropolitan area. 

 

PEAK GROUND ACCELERATION AS COMPARE TO 1999 Mw7.4 KOCAELI EARTHQUAKE

Ratio of PGA values of scenario earthquakes to the 1999 Kocaeli Earthquake shows that west of the Istanbul Metropolitan area is expected to be shaken more than three times as it did during the Kocaeli Earthquake.

 

Peak ground acceleration (PGA) and spectral acceleration (SA) values (at 0.2, 0.3, 0.5, 1, 1.5, 2, 3 and 4 s for 5%-damping) computed at central point of districts in the I?stanbul Metropolitan area considering the worst- case earthquake scenario (that is, multiple rupturing of Off-Tekirdag?, Mid-Marmara and Islands fault segments). The districts, expected to experience the highest shaking, are highlighted.

DOWNLOADABLE HIGH-RESOLUTION MAPS

Deterministic Seismic Design Maps for Sea of Marmara Region (in TIF format)

PGA | SA (0.2 sec) | SA (0.3 sec) | SA (0.5 sec) | SA (1.0 sec) | SA (1.5 sec) | SA (2.0 sec) | SA (3.0 sec) | SA (4.0 sec)

Deterministic Seismic Design Maps for Istanbul Metropolis (in TIF format)

PGA | SA (0.2 sec) | SA (0.3 sec) | SA (0.5 sec) | SA (1.0 sec) | SA (1.5 sec) | SA (2.0 sec) | SA (3.0 sec) | SA (4.0 sec)

Ground Motion Ratio Map (Ratio = Marmara Scenario Eq. / 1999 Mw7.4 Kocaeli (Izmit) Earthquake) (in TIF format)

PGA | SA (0.2 sec) | SA (0.3 sec) | SA (0.5 sec) | SA (1.0 sec) | SA (1.5 sec) | SA (2.0 sec) | SA (3.0 sec) | SA (4.0 sec)

NOTE: Gridded deterministic seismic design values for Istanbul Metropolis and Sea of Marmara region may be available upon request (ekalkan@usgs.gov).

RELEVANT PUBLICATIONS AND WEB PAGES

Probabilistic Seismic Hazard Study for Sea of Marmara Region and Istanbul Metropolis (English / Turkce)

 

1. Kalkan, E. and Gulkan, P. (2010).“Earthquake Hazard in Istanbul and Its Surroundings”, Science and Technics, 513, Aug. 2010. (in-Turkish)
2. Kalkan E., Gulkan, P., Yilmaz, N. and Celebi, M. (2009). “Re-Examination of Probabilistic Seismic Hazard in the Marmara Sea Region”, Bulletin of Seismological Society of America, 99(4): 2127–2146.
3. Kalkan, E. and Gülkan, P. (2004). “Site-Dependent Spectra Derived from Ground Motion Records in Turkey”, Earthquake Spectra, 20(4): 1111-1138 [Download Erratum]
4. Kalkan, E. and Gülkan, P. (2004). “Empirical Attenuation Equations for Vertical Ground Motion in Turkey”, Earthquake Spectra, 20(3): 853-882.
5. Gülkan, P. and Kalkan, E. (2002). “Attenuation Modeling of Recent Earthquakes in Turkey”, Journal of Seismology, 6(3): 397-409.
6. Kalkan, E. (2001). Attenuation Relationships based on Strong Motion Data Recorded in Turkey, M.Sc. Thesis, Middle East Technical University, Ankara,Turkey.

 

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