| Title | Fault strength in Marmara region inferred from the geometry of the principle stress axes and fault orientations: A case study for the Prince’s Islands fault segment |
| Publication Type | Conference Proceedings |
| Year of Conference | 2015 |
| Authors | Pınar, A, Coşkun, Z, Mert, A, Kalafat, D |
| Conference Name | European Geophysical Union General Assembly |
| Volume | 17 |
| Abstract | The general consensus based on historical earthquake data point out that the last major moment release on the
Prince’s islands fault was in 1766 which in turn signals 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
Çınarcık basin and the other extending between offshore Bakırköy 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.
In the frame of the presentation we analyze seismological data acquired in Marmara region and interpret
the results in conjuction with the above mentioned weak fault model. |
