Seismicity and Focal Mechanism Analysis of The Local Earthquakes in the Zagros Fold-Thrust Belt of the Iraqi Kurdistan Region

Abstract

During the period of 2020 to May 2022, the Iraqi Kurdistan region experienced several small to moderate size earthquakes. The seismic waveform data of these earthquakes were collected from regional and local broadband seismic stations. Waveform data was analyzed for seventy earthquakes to determine their source parameters, which may contribute to the active tectonics in those areas. Moment tensor inversion is estimated for the detected local earthquakes by analysis of observed seismic waveforms in different selected areas. The waveform inversion determines the seismic moment, depth, and kind of rupturing fault at the source. A grid search is employed as part of the inversion procedure across the strike, dip, and rake angles for each depth between 0.5 and 40 Km in increments of 1 Km. Waveform modeling is used to correlate the observed and created waveforms by applying bandpass filters and a suitable velocity model for Green's function using computer programs in seismology and the ISOLA code" Isolated asperities" for multiple-point source modeling. The results show that the earthquakes with M ≥ 4 have a focal depth ranging between 7 and 20 Km. Furthermore, the regional stresses were identified and the mechanism for the optimum fit was determined. The source mechanisms in the study area are most likely a combination of strike-slip, oblique-slip, and thrust.