a deep Geophysical Observatory at the North Anatolian Fault
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To monitor the microseismic activity in the North Anatolian Fault Zone offshore of Istanbul below the Çinarcik Basin (ÇB) a permanent seismic array (PIRES, see pdf) was installed on the Prince Islands in 2006, at a very close proximity to the main fault. The array consists of two subarrays installed on the two outermost islands (Yassiada and Sivriada) of the Princes Islands group offshore Istanbul.

Figure: Location map of the PIRES array on Sivriada and Yassiada deployed within 2-3 km distance to the main branch of the NAFZ.

PIRES subarrays consist of five seismic stations at the surface which are spaced in a cross-shape layout. The network has recently been enlarged towards the other Princes Islands in order to improve the azimuthal control of the focal area. We additionally integrate data from local permanent stations of the Turkish network (KOERI) and the ARNET seismic network. Combined data allowed obtaining a well-resolved scale for the hypocentral map to better understand the existing seismically active structures and their role in local tectonic settings. This allowed resolving the major fault branches beneath the ÇB providing insights into separation of seismically active/inactive segments along the western seismic gap and down-dip geometry of the seismically active faults. Spatiotemporal analysis of the seismicity based on well-constrained hypocenters is performed to understand the interaction between the sub-segments of the NAFZ along the ÇB.

Key references:
Bulut et al, JGR, 2009
Bulut et al, BSSA, 2011