Size and jog characteristics of the segments of 1999 Izmit and Duzce surface ruptures, North Anatolian Fault, Turkey implications to the future Marnara earthquakes
Abstract
Fault segmentation plays an important role to evaluate the magnitude and cascade of the future earthquakes on a long active fault. Correlation between behavioral segments and rupture process of the 1999 Izmit and Duzce earthquakes provide the size and jog characteristics of the segments of the North Anatolian Fault. From this point of view, we have been carrying out very detailed investigations about those surface ruptures both onland and offshore including the Izmit Bayand the Sapanca Lake. A 145 km-long Izmit rupture is divided into 6 segments; the Hersek, Golcuk, Tepetarla, Arifiye, Karadere and Aksu segments, and a 43 km-long Duzce rupture into 2 segments; the Lake Efteni and Beykoy segments, based on its geometry and sip-distribution. These segments vary between 15 and 35 km and average at about 25-km in length, and are bounded by the 3--15 km-long jogs. Large amount of subsidence in a pull-apart structure at the east end of the Izmit Bay suggests that those jogs bounding the segments reach down into the seismogenic layer. A single segment further divided into sections of several-kilometers long bounded by a few hundred-meters long jogs. The jogs bounding the sections are one-order smaller than that bounding segments,and are probably surficial structures sallower than several-hundred-meters deep. It is notable that the average length of segments is almost twice as much of the thickness of seismogenic layer along the NAF. Correlation between segment structure and rupture process of the Izmit and Duzce earthquakes implies that large jogs with significant bend can delay or terminate the rupture propagation effectively. The NAF in the Maramara Sea between the 1912 and the 1999 earthquake ruptures has remained as a seismic gap of about 150 km-long, and has a complicated geometry with step-overs and bends. Comparing with the size and jog characteristics of the 1999 ruptures, it is pointed out that the gap has a tendency to produce more than one successive large earthquakes in near future like an earthquake sequence during the 18th century.
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA....14181A