Content area
Full Text
On 17 August 1999 at 3:02 a.m. local time, northwest Turkey was shaken by a magnitude 7.4 earthquake, catching most people in their sleep. The earthquake's epicenter was located at latitude 41.81 deg N and longitude 30.08 deg E, and the earthquake had a depth of around 10 to 16 km. Records of the maximum ground motion varied between 0.3 and 0.4g. The earthquake lasted 37 s and consisted of two subevents, the first The nearest major city affected by the earthquake was Izmit at the eastern end of the Marmara Sea, but the earthquake also caused considerable damage in Istanbul, about 70 km away from the earthquake's epicenter. The earthquake's magnitude was initially estimated as 6.'7 by the Kandilli observatory, which operates a seismic network in the region. This estimate was considerably lower than the actual magnitude of 7.4 and initially gave a wrong impression of the likely damage to scientists and governmental officials.
During the first 2 days, the severity and extent of the damage and human loss were seriously underestimated. Rescue operations were delayed because of lack of communications and heavy damage on the major highway connecting Istanbul to Ankara. Alternate roads were blocked by people wanting to reach relatives and friends in the most of fected areas because all telephone communication had broken down. Many apartment blocks collapsed completely, causing the death of many people in the earthquake region. A fire in the Tupras oil refineries, which refine 86% of Turkey's oil, threatened to take over other industrial sites and took 5 and a half days to contain and extinguish. The navy base and shipbuilding yard at Golcuk were cut by surface faulting and displaced 4 m to the right, causing considerable damage and the death of at least 400 soldiers and high ranking officers. The total death toll has now reached 15,000, but thousands more are still missing.
The surface rupture caused by the earthquake consists of four segments (see the figure). Three of them-the Golcuk, Izmit-Sapanca, and Arifiye-Akyazi segments in the west-were caused by the first...