Abstract: Faulting and Ground Subsidence at the Ford-Otosan Plant near Golcuk, Turkey as a Result of the August 17, 1999 Kocaeli Earthquake

GONZALEZ, TANIA, Earth Consultants International, Orange, CA; KERRY SIEH, Earth Consultants International Earth Consultants International, Pasadena, CA; TIMOTHY DAWSON, Earth Consultants International, San Diego, CA; ERHAN ALTUNEL, Osmangazi University, Eskisehir, Turkey; A. BARKA, Instabul Technical University, Istanbul, Turkey

The M 7.4 Kocaeli Earthquake that occurred on August 17, 1999 caused considerable damage at the Ford-Otosan automobile assembly plant, which was under construction at the time. Surface fault rupture, with vertical offsets of between 1 and 2.35 meters, and lateral offsets of as much as 1.2 meters, occurred along the southern perimeter of the property. The area where the main plant buildings were located subsided about 1.5 meters and experienced synclinal warping and secondary faulting associated with a step in the main fault. The northern portion of the property, along the Sea of Marmara, experienced lateral spreading and slumping into the bay. Management halted construction and undertook a seismic risk analysis of the site to evaluate the probability of another similar earthquake occurring during the lifetime of the plant. Paleoseismic trenching and review of historical records indicated that at least two other similar earthquakes occurred in the area of the Ford Otosan plant in the last 500 years, in AD 1509, and AD 1719, suggesting a predictable and regular pattern of surface rupture. Based on these findings, we concluded that the Ford-Otosan plant has a low probability of experiencing another similar earthquake in the next 50 to 100 years. However, it is likely to experience smaller earthquakes (aftershocks) generated by the same fault system, and lower, attenuated ground motions as a result of earthquakes on other faults some distance from the site.

AAPG Search and Discovery Article #90911©2000 AAPG Pacific Section and Western Region Society of Petroleum Engineers, Long Beach, California