How far did the surface rupture of the 1999 Izmit earthquake reach in Sea of Marmara?

Type Article
Date 2011-02
Language English
Author(s) Gasperini Luca1, Polonia Alina1, Bortoluzzi Giovanni1, Henry Pierre2, Le Pichon Xavier2, Tryon Michael3, Cagatay Namik4, Geli LouisORCID5
Affiliation(s) 1 : CNR, ISMAR, I-40129 Bologna, Italy.
2 : CEREGE, F-13545 Aix En Provence, France.
3 : Univ Calif San Diego, Scripps Inst Oceanog, La Jolla, CA 92093 USA.
4 : ITU, Fac Min, EMCOL, TR-34469 Istanbul, Turkey.
5 : Ifremer, F-29280 Plouzane, France.
Source Tectonics (0278-7407) (Amer Geophysical Union), 2011-02 , Vol. 30 , P. 11 p.
DOI 10.1029/2010TC002726
WOS© Times Cited 14
Abstract An open problem concerning the Mw 7.4, 1999 Izmit earthquake along the North Anatolian Fault (NAF) system is the apparent conflict between estimates of strike-slip deformation based on field and remote sensing data. This is due to the fact that the main strand of the NAF west of the epicenter lies below the Sea of Marmara. Seismological evidence and models based on synthetic aperture radar interferometry suggest that coseismic and early postseismic displacement accumulated after the earthquake could have reached the western end of the Izmit Gulf and possibly the southern edge of the Cinarcik Basin, tapering off along the northern coast of the Armutlu Peninsula, more than 60 km from the epicenter. This scenario is not confirmed by onshore field observations that point toward a termination of the surface rupture around 30 km to the east. These discrepancies convey high uncertainties in the estimate of the tectonic load produced by the Izmit earthquake on the adjacent fault segment toward Istanbul. We analyzed data from different sources, including high-resolution marine geophysical surveys and two Nautile dives along the fault-controlled canyon that connects Izmit Cinarcik basins. Our observations suggest that the surface rupture of the 1999 Izmit earthquake propagated through the shallow Gulf but did not reach the deep Marmara basins. In fact, along the slope between Cinarcik and the western end of the Izmit Gulf, we do not observe fault-related ruptures affecting the sea-floor but rather a series of active gas seeps and "black patches" that mark the presence of known active faults. Our findings have implications for seismic risk assessment in the highly populated region of Istanbul, both for the estimate of tectonic load transferred to the next fault segments and the location of the next earthquake. Citation: Gasperini, L., A. Polonia, G. Bortoluzzi, P. Henry, X. Le Pichon, M. Tryon, N. Cagatay, and L. Geli (2011), How far did the surface rupture of the 1999 Izmit earthquake reach in Sea of Marmara?, Tectonics, 30, TC1010, doi: 10.1029/2010TC002726.
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