Japan Geoscience Union Meeting 2015

Presentation information


Symbol S (Solid Earth Sciences) » S-SS Seismology

[S-SS30] Earthquake Source Processes and Physics of Earthquakes

Mon. May 25, 2015 2:15 PM - 4:00 PM A05 (APA HOTEL&RESORT TOKYO BAY MAKUHARI)

Convener:*Ryosuke Ando(Graduate School of Science, University of Tokyo), Yuko Kase(Active Fault and Earthquake Research Center, AIST, GSJ), Chair:Bogdan Enescu(筑波大学大学院 生命環境科学研究科 ), Takahiko Uchide(Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology)

2:15 PM - 2:30 PM

[SSS30-14] Fault strength in Marmara region inferred from the geometry of the principle stress axes and fault orientations

*Ali PINAR1, Zeynep COSKUN1, Aydin MERT1, Dogan KALAFAT1 (1.Bogazici University Kandilli Observatory and Earthquake Research Institute)

Keywords:stress tensor, fault orientation, frictional coefficient

The general consensus based on historical earthquake data suggests that the last major moment release on the Prince’s islands fault was in 1766 which in turn points out an increased seismic risk for Istanbul Metropolitan area considering the fact that most of the 20 mm/yr GPS derived slip rate for the region is accommodated mostly by that fault segment.

The orientation of the Prince’s islands fault segment overlaps with the NW-SE direction of the maximum principle stress axis derived from the focal mechanism solutions of the large and moderate sized earthquakes occurred in the Marmara region. As such, the NW-SE trending fault segment translates the motion between the two E-W trending branches of the North Anatolian fault zone; one extending from the Gulf of Izmit towards C?narc?k basin and the other extending between offshore Bak?rkoy and Silivri.

The basic relation between the orientation of the maximum and minimum principal stress axes, the shear and normal stresses, and the orientation of a fault provides clue on the strength of a fault, i.e., its frictional coefficient. Here, the angle between the fault normal and maximum compressive stress axis is a key parameter where fault normal and fault parallel maximum compressive stress might be a necessary and sufficient condition for a creeping event. That relation also implies that when the trend of the sigma-1 axis is close to the strike of the fault the shear stress acting on the fault plane approaches zero. On the other hand, the ratio between the shear and normal stresses acting on a fault plane is proportional to the coefficient of frictional coefficient of the fault. Accordingly, the geometry between the Prince’s islands fault segment and a maximum principal stress axis matches a weak fault model.