BASEMENT FAULT REACTIVATION IN THE ZAKHO– SILOPI REGION, IRAQI KURDISTAN – TURKEY BORDER

Abstract

The nature and orientation of underlying Late Precambrian basement structures, and their relationships to the seismic distribution and surface linear structures has provided a basis for studying the basement fault reactivation in the Zakho – Silopi region. This border region between Iraqi Kurdistan and Turkey is located in the north-eastern boundary of the Arabian plate and covers some parts of the Zagros fold-thrust belt as well as the high folded and foothill zones of Iraq. The Zakho – Silopi region is characterized by moderate-sized earthquakes of shallow-focus that caused mostly by the neotectonic reactivation of Late Precambrian thrust and strike-slip basement faults due to the on-going active continental collision between Arabia and Eurasia. Four potential NE- and NW-trending seismic lineaments were identified, based on the epicentral alignments of major earthquake and the orientation of nodal fault planes, to be the most seismically active basement faults in the Zakho - Silopi region. Any potential for the future damaging earthquakes throughout this region will be more likely associated with the reactivation of the basement faults along these active seismic lineaments. Therefore, a detailed seismic hazard assessment is recommended for the major cities and urban localities. The present-day stress-field orientation inferred from the inversion of fault plane solutions and lineament analysis indicates that the Zakho – Silopi region is undergoing a continuous state of nearly N-S (N05°E) compression. The trend analysis of lineament patterns and seismic lineaments reveals three dominant basement fault trends in the Zakho - Silopi region; roughly N-S, NE-SW, and NW-SE. These basement faults were probably initiated in Late Precambrian as normal faults, and subsequently inverted into thrust faults with a significant strike-slip component, and reactivated continuously from Late Cretaceous to present-day.