Izmit Earthquake of 1999

The Izmit earthquake occurred at 00:01:39 UTC (3:01 a.m. local time), and was centered at 40.74 N., 29.86 E., which places the epicenter about 11 kilometers, or seven miles, southeast of the city of Izmit.

This location indicates that the earthquake occurred on the northernmost strand of the North Anatolian fault system. The earthquake originated at a depth of 17 kilometers, or about 10.5 miles, and caused right-lateral strike-slip movement on the fault. Preliminary field reports confirm this type of motion on the fault, and initial field observations indicate that the earthquake produced at least 60 kilometers (37 miles) of surface rupture and right-lateral offsets as large as 2.7 meters, or almost nine feet.

On 19 August at 14:16 and 15:18 UTC (5:16 and 6:18 PM local time), two light-to-moderate earthquakes with magnitudes of 4.8 and 5.0 occurred approximately 80 km to the west of the mainshock. Previous aftershocks of this size were centered to the east of the mainshock, further from the cities of Bursa and Istanbul. While this suggests the possibility of a larger earthquake occurring in this new location, it is also probable that the mainshock rupture extended into this region, into the Gulf of Izmit, making these events aftershocks. We have no means of predicting the likelihood of a larger event in this new location.

At least 17,118 people killed, nearly 50,000 injured, thousands missing, about 500,000 people homeless and estimated 3 to 6.5 billion U.S. dollars damage in Istanbul, Kocaeli and Sakarya Provinces. Felt as far east as Ankara. Felt (III) at Anapa, Russia; Chisinau, Moldova; Simferopol and on the south coast of Crimea, Ukraine. As much as 5 meters of right-lateral strike-slip displacement occurred along a 120-km zone of the North Anatolian Fault between Karamursel and Golyaka. Rupture proceeded from west to east in two subevents. Duration of strong shaking was 37 seconds with maximum acceleration 0.3-0.4g.

The August 17, Izmit (Kocaeli) earthquake is the largest earthquake of the 20th century that struck the Northwestern Turkey. It hit a densely populated area while most of the people were asleep. Both the severity and the extent of damage called for a colossal emergency response, search and rescue operation. The Turkish authorities were overwhelmed with the magnitude of this demand causing a delay in their response to this major disaster. The Turkish Government has been criticized heavily for failing to plan and respond quickly to the disaster.