Assessment of Earthquake Hazard in Turkey and Neighboring Regions.

Turkey lies within the Mediterranean sector of the Alpine-Himalayan orogenic system, which extends from Italy to Burma.Turkey. This system, identified with high mountain ranges and shallow, somewhat diffuse seismicity, constitute one of the most seismically active continental regions of the world with a long and well documented history of earthquakes. The study is initiated in connection with the GSHAP (Global Seismic Hazard Assessment Program) encompasses the region that extends from the Adriatic Sea in the west to Caspian Sea in the East, and from the middele Black Sea in the North to the Cyprus in the South. Portrayal of the seismicity and the tectonics of a region provides the essential information towards the assessment of seismic source zones. The epicentral maps of the historical damaging earthquakes in Turkey and vicinity clearly identifies the West, North and Southeast Anatolian regions as hazardous zones. The diffused character of the epicenters is partly due to the location inaccuracies associated with small magnitude events and hinders the detailed correlation of the epicentral locations with the neo-tectonic features. To present a clearer picture, a macroseismic epicentral map of all large, magnitute (Ms) greater than or equal to 5.9, or damaging, epicentral intensity (Io) greater than equal to VII, earthquakes of this century is considered. Almost all earthquakes in Turkey and its vicinity is associated with these tectonic elements (or faults). The correlation of seismicity with the tectonic elements (seismo-tectonics) constitutes an important phase of the earthquake hazard assessment and, as such, several micro-plate tectonics models have been proposed. The following major earthquake sources zones have beencan be identifed. Anatolian Trough Zone North Anatolian Fault Zone Caldiran Zone North-East Anatolian Fault Zone East Anatolian Fault Zone Bitlis Suture Zone West Anatolian Graben Complex Zone Cyclades and Fethiye Zone Cyprus Zone Black Sea Escarpment Intra microplate regions such as Central Anatolia does not possess major tectonic elements capable of generating high magnitude earthquakes. Such regions are markedly less seismic than the other seismic zones, however, they are not aseismic as evidenced by the occurrences of infrequent damaging events. The seismicity exhibited by these sporadic events were treated as elements of the background seismicity, i.e. the seismicty of the region excluding the source zones. For the assessment of the recurrence relationships in these source zones the rates of occurrence in different magnitude groups are adjusted by determination of the period over which the data in a given magnitude group are completely reported. For depicting earthquake ground motion severity, predictive empirical relationships for MSK intensity (attenuation relationships developed for the region) , peak accelerations and spectral amplitudes (regression analysis based mostly on California data) are considered. Probabilistic hazard is computed by SEISRISK III routine. The stochastic model in this routine assumes a homogenous Poisson process for earthquake generation. The pros and cons of this assumption are discussed. The contour maps provided for intensities, peak ground acceleration and 5% damped 0.3 and 1.0 s pseudo acceleration spectral amplitudes with a 10% probability of exceedance in 50 years can be used for rational construction of the site-specific design basis response spectrum.