Determination of earthquake source parameters using the inversion of waveform data: A case of small earthquakes around High Dam Lake, Aswan region, Egypt

Abstract

Abstract The earthquake source parameters of 310 seismic events recorded by Aswan broadband seismic network with local magnitude ranges from 0.9 to 3.5 are determined. The Generalized Inversion Technique (GIT) assuming that a reference site was applied to isolate the source one, site, and path effects from the observed displacement P-wave spectra by means of linear least square analysis. The inversion technique was formulated based on Brune s omega-squared source model. The long period asymptote and the corner frequency are two essential parameters to achieve the desired goals of the current study. The source parameters are estimated (seismic moment, static stress drop, dislocation area, corner frequency and source radius), using the displacement source spectra from P wave portion. The determined stress drop values range from 0.03 to 2.9\xa0MPa, with an average of 0.3\xa0MPa. The lower stress drop values obtained may reflect that reservoir–induced earthquakes have a lower stress drop. The stress drop doesn t show significant dependence on the earthquake depth in Aswan region. Seismic moment, source radius, and corner frequency range from, 1.50E+17 to 2.18E+20\xa0dyne-cm, 31.7–194.3\xa0m, and 6 to 34 HZ, respectively. The seismic wave attenuation through propagation, expressed by a quality factor indicated its frequency dependence with regression relation proportional to Q p = 128 f 0.58 for P wave spectra. The low Q 0 (quality factor at reference frequency f 0 ) value indicate that Aswan region is a seismically active region. The site responses obtained using the inversion technique show that the stations sites have peak amplitudes in high frequency from 10 to 40\u202fHz.