Tectonic interpretation of the Raniya earthquake, Kurdistan, northern Iraq

Abstract

The 23 August 2017 earthquake was the biggest recorded event in the Raniya region near the northeastern boundary of the Arabian plate in the Kurdistan region of Iraq over the last 37 years. It was felt in the city of Raniya and its surrounding areas in Erbil and Sulaimaniyah governorates. The Raniya earthquake was recorded by the USGS National Earthquake Information Centre with a magnitude of 5.1 (Mww). The rotational optimization method (Windows-Tensor software, version 5.8.8) was used to determine the present-day stress field by inversion of the fault plane solution. The results show that the Raniya earthquake was generated by the neotectonic reactivation of Late Precambrian northeast-dipping blind basement thrust fault, with a small amount of strike–slip motion, at a focal depth of 8 km. This indicates that the Raniya region is subjected to a present-day compressional deformation, with a northeast–southwest-oriented maximum horizontal stress axis (N47° E). The neotectonic activity along the Raniya basement thrust fault is in good agreement with the active shortening across the Zagros fold–thrust belt due to the Mid Miocene continental collision between the Arabian and Eurasian plates. Finally, a detailed seismic risk assessment is recommended for the Raniya region and surrounding areas.