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Polat Gulkan

Publications and source records attributed to Polat Gulkan.

6 recordsLinked to original sources
USGS2011

8 March 2010 Elazığ-Kovancilar (Turkey) Earthquake: observations on ground motions and building damage

An earthquake of M W = 6.1 occurred in the Elazığ region of eastern Turkey on 8 March 2010 at 02:32:34 UTC. The United States Geological Survey (USGS) reported the epicenter of the earthquake as 38.873°N-39.981°E with a focal depth of 12 km. Forty-two people lost their lives and 137 were injured during the event. The earthquake was reported to be on the left-lateral strike-slip east Anatolian fault (EAF), which is one of the two major active fault systems in Turkey. Teams from the Earthquake Engineering Research Center of the Middle East Technical University (EERC-METU) visited the earthquake area in the aftermath of the mainshock. Their reconnaissance observations were combined with interpretations of recorded ground motions for completeness. This article summarizes observations on building and ground damage in the area and provides a discussion of the recorded motions. No significant observations in terms of geotechnical engineering were made.

Seismological Research Letters↗
USGS2010

İhtimaller Hesabına Dayalı İstanbul ve Çevresindeki Deprem Tehlikesi (Seismic hazard assessment of Istanbul and its surroundings)

Bu yazının amacı, İstanbul ve yakın çevresinin maruz olduğu deprem tehlikesine dair 1999 depremlerinden bu yana devam eden tartışmalara bilimsel verilere ve hesaplara dayanan ve mümkün olduğu ölçüde kolay anlaşılır bir açıklama getirmektir. Depremlerin bir bölgede yaratabileceği tehlike, yani yerin sarsılması yüzünden yapılar üzerinde doğacak deprem etkileri, bölgenin deprem riskine, yani o bölgede olabilecek en yüksek deprem büyüklüğüne ve bölgenin zemin durumuna bağlıdır. Bu çalışmada, deprem oluşturma potansiyeline sahip aktif faylar ve son 500 yılda meydana gelmiş depremler ihtimal hesapları kullanılarak ilişkilendirilmiş ve Marmara Bölgesi’nde deprem sonucu doğacak yer hareketi şiddetinin dağılımı haritalanmıştır. Sunulan yeni deprem tehlike haritaları önceki bölgesel tehlike haritaları ile karşılaştırıldığında, Marmara Bölgesi’nde hissedilebilecek yer hareketi şiddetinde, benzer çalışmalara oranla % 10 ila % 15 arası artış görülmektedir.

Bilim ve Teknik (Science and Technology Magazine)↗
USGS2009

Reassessment of probabilistic seismic hazard in the Marmara region

In 1999, the eastern coastline of the Marmara region (Turkey) witnessed increased seismic activity on the North Anatolian fault (NAF) system with two damaging earthquakes (M 7.4 Kocaeli and M 7.2 D??zce) that occurred almost three months apart. These events have reduced stress on the western segment of the NAF where it continues under the Marmara Sea. The undersea fault segments have been recently explored using bathymetric and reflection surveys. These recent findings helped scientists to understand the seismotectonic environment of the Marmara basin, which has remained a perplexing tectonic domain. On the basis of collected new data, seismic hazard of the Marmara region is reassessed using a probabilistic approach. Two different earthquake source models: (1) the smoothed-gridded seismicity model and (2) fault model and alternate magnitude-frequency relations, Gutenberg-Richter and characteristic, were used with local and imported ground-motion-prediction equations. Regional exposure is computed and quantified on a set of hazard maps that provide peak horizontal ground acceleration (PGA) and spectral acceleration at 0.2 and 1.0 sec on uniform firm-rock site condition (760 m=sec average shear wave velocity in the upper 30 m). These acceleration levels were computed for ground motions having 2% and 10% probabilities of exceedance in 50 yr, corresponding to return periods of about 2475 and 475 yr, respectively. The maximum PGA computed (at rock site) is 1.5g along the fault segments of the NAF zone extending into the Marmara Sea. The new maps generally show 10% to 15% increase for PGA, 0.2 and 1.0 sec spectral acceleration values across much of Marmara compared to previous regional hazard maps. Hazard curves and smooth design spectra for three site conditions: rock, soil, and soft-soil are provided for the Istanbul metropolitan area as possible tools in future risk estimates.

Bulletin of the Seismological Society of America↗
USGS2008

Seismic hazard in the Istanbul metropolitan area: A preliminary re-evaluation

In 1999, two destructive earthquakes (M7.4 Kocaeli and M7.2 Duzce) occurred in the north west of Turkey and resulted in major stress-drops on the western segment of the North Anatolian Fault system where it continues under the Marmara Sea. These undersea fault segments were recently explored using bathymetric and reflection surveys. These recent findings helped to reshape the seismotectonic environment of the Marmara basin, which is a perplexing tectonic domain. Based on collected new information, seismic hazard of the Marmara region, particularly Istanbul Metropolitan Area and its vicinity, were re-examined using a probabilistic approach. Two seismic source and alternate recurrence models combined with various indigenous and foreign attenuation relationships were adapted within a logic tree formulation to quantify and project the regional exposure on a set of hazard maps. The hazard maps show the peak horizontal ground acceleration and spectral acceleration at 1.0 s. These acceleration levels were computed for 2 and 10 % probabilities of transcendence in 50 years.

Journal of Earthquake Engineering↗
USGS2005

An evaluation of the strong ground motion recorded during the May 1, 2003 Bingol Turkey, earthquake

An important record of ground motion from a M 6.4 earthquake occurring on May 1, 2003, at epicentral and fault distances of about 12 and 9 km, respectively, was obtained at a station near the city of Bingöl, Turkey. The maximum peak ground values of 0.55g and 36 cm/s are among the largest ground-motion amplitudes recorded in Turkey. From simulations and comparisons with ground motions from other earthquakes of comparable magnitude, we conclude that the ground motion over a range of frequencies is unusually high. Site response may be responsible for the elevated ground motion, as suggested from analysis of numerous aftershock recordings from the same station. The mainshock motions have some interesting seismological features, including ramps between the P- and S-wave that are probably due to near- and intermediate-field elastic motions and strong polarisation oriented at about 39 degrees to the fault (and therefore not in the fault-normal direction). Simulations of motions from an extended rupture explain these features. The N10E component shows a high-amplitude spectral acceleration at a period of 0.15 seconds resulting in a site specific design spectrum that significantly overestimates the actual strength and displacement demands of the record. The pulse signal in the N10E component affects the inelastic spectral displacement and increases the inelastic displacement demand with respect to elastic demand for very long periods.

Journal of Earthquake Engineering↗