Source parameters of regional earthquakes recorded by Israel Seismic Network: implications for earthquake scaling

The source properties and scaling relationships for small and moderate earthquakes occurring in Israel and adjacent areas are investigated. We determine source parameters such as corner frequency, seismic moment, static stress drop, and source radius using three-component short period and broadband seismograms recorded by the Israel Seismic Network from 1993 to 2010. In this study about 2000 seismograms from 300 regional earthquakes in the magnitude range of 1.5 ≤ M≤ 5.2 have been analyzed. To identify possible differences in source scaling depending on regional features the analysis is performed separately for three regional earthquake sequences that occurred in Southern Lebanon, Dead Sea basin and Gulf of Aqaba. The analyzed regional earthquakes exhibit corner frequencies ranging from 0.9 to 9.7 Hz, which correspond to seismic moments from 1.580E+11 to 5.82E+16 Nm. Our estimates of Brune’s stress drop for regional earthquakes are in the range of 0.005–19 MPa with a clear tendency to higher stress drops for larger events. Source radii for the earthquake range from ~100 to ~1600 m. Source spectra of small to moderate earthquakes are normally compared with the classical Brune one-corner spectral model, which includes a flat portion at low frequencies and decreasing as ω at high frequencies. However, some spectra in the dataset are complex and a second corner frequency is apparent, exhibiting substantial deviations of individual source spectra from the ideal ω spectral shape.