General Building Damage in the vicinity of Avcilar-Istanbul (click to enlarge)

Distribution of Peak Horizontal Ground Acceleration (data from: Bogazici Univ.and General Directorate of Disaster Affairs)

With the exception of Istanbul each city indicated has only one station. Some stations are located on competent ground and the motions may not be indicative of the prevailing motions in the city such as in Adapazari. The distribution of ground motion in Istanbul will be trated seperately. The near field and the directivity effects are evident in the records in Yarimca (YPT) and Duzce. It should be noted that the ground motion levels are not as high as would be expected from such a large magnitude earthquake with extensive fault rupture. It may be due to the somewhat slow release of the energy during the earthquake. The second shock visible in the YPT record is probably associated with an asperity between Sapanca lake and Izmit. Due to its very high frequency content it dissapeates very fast and can only be seen in neighboring records. Strong motion records indicate a double rupture starting from immediate east of Izmit and extending to the west towards Yalova and to the east towards Adapazari. We are trying to determine the location of the second shock. Future investigations will deal with the geotechnical conditions under the stations.

Strong Motion Stations in Istanbul and the Marmara Region operated by Bogazici University.

Acceleration, Velocity and Displacement Traces from YPT station and the Fourier Amplitude Spectra based on Preliminary Processing

Yarimca (YPT) Station is located about 10km northwest of Golcuk and 20km. northwest of USGS epicenter.

Bogazici University operates a strong motion array (structural and free field) in and around Istanbul. Information on the array is provided in Strong Motion Stations in Istanbul and the Marmara Region. The records are being collected and processed. The preliminary data on peak accelerations at selected stations are given below. The location of the stations can be found in the forementioned link. Note that Yarimca (YPT) station is in the epicentral area.

Station	Peak Ground Acceleration
	Max-Horizontal	Max-Vertical	ASCII Files
ARÇELİK (ARC)	211.365 mg	83.252 mg
AMBARLI (ATS)	252.564 mg	80.078 mg
BOTAŞ (BOT)	98.877 mg	23.560 mg
ÇEKMECE (CNA)	177.307 mg	57.678 mg
HAVA ALANI (DHM)	90.210 mg	55.115 mg
YAPI KREDİ (YKP)	41.07 mg	27.100 mg
YARIMCA (YPT)	322.205 mg	241.089 mg
FATİH (FAT)	189.392 mg	131.714 mg
HEYBELİADA (HAS)	110.230 mg	143.494 mg
BURSA (BUR)	100.891 mg	48.218 mg

Strong motion Accelerograms recorded in Istanbul and the Aegean Region operated by Earthquake Research Department of General Directorate of Disaster Affairs :ERD