Turkey Earthquake
Introduction
The terrible earthquake that struck western Turkey on August 17, 1999
measured a massive Mw7.4 on the Richter scale (also known as the
Kocaeli, Turkey, earthquake) Turkey has had a long history of large
earthquakes that often occur in progressive adjacent earthquakes.
Starting in 1939, the North Anatolian fault produced a sequence of
major earthquakes, of which the 1999 event is the 11th with a
magnitude greater than or equal to 6.7. Starting with the 1939 event
in western Turkey, the earthquake locations have moved both eastward
and westward. The westward migration was particularly active and
ruptured 600 km of contiguous fault between 1939 and 1944. This
westward propagation of earthquakes then slowed and ruptured an
additional adjacent 100 km of fault in events in 1957 and 1967, with
separated activity further west during 1963 and 1964.
The August 17, 1999 event fills in a 100 to 150 km long gap between
the 1967 event and the 1963 and 1964 events. This gap was first noted
by Toksoz, Shakal, and Michael in 1979 and it's hazard was later
analyzed by Stein, Barka, and Dieterich in 1997. The latter paper
estimated that there was a 12% chance of this earthquake occurring in
the 30 years from 1996 to 2026.
The Cause
[IMAGE]The earthquake originated at a shallow depth of about 10.5
miles (17 km) and generated strong ground motion (and moderate to high
accelerations) in a zone along the Gulf of Izmit of the Sea of Marmara
to east of Adapazari. It occurred along the northernmost strands of
the North Anatolian fault system. Turkey lies upon 3 major plates, two
of which forms the North Anatolian fault one of the world's longest
and best-studied strike-slip (horizontal motion) faults. The Eurasian
and Anatolian/Aegean plates were the cause of the earthquake. They had
overlapped along a distance of 68 miles (110 kilometres). This
particular earthquake occurred on the east-west trending. This
particular quake was due to conservative actions. This is when two