Estimation of seismic momemts from local magnitudes and coda durations for the Cairo earthquake aftershocks recorded at Kottamyia (KEG) Broadband station

Abstract

The spectral analysis of fifty-five KEG VBB records from the October 12, 1992 Cairo earthquake source region was performed to obtain the seismic moment. We obtained this parameter in turn to develop empirical local magnitude (ML), seismic moment (Mo, coda duration (D) relations for that region. In this study the data consist of Lg-waves on the vertical component seismograms for the recorded earthquakes with ML ranging from 1.7 to 4.7. The derived empirical relation between the seismic moment (Mo) and magnitude ML for the aftershocks sequence with 1.7 ≤ ML < 3.5 is Log (Mo) = (0.96 ± 0.05) ML + (17.88 ± 0.13). We found a correlation between the coda duration (D) and Log of the moment (Log (Mo)) as follows: Log (Mo) = (2.35 ± 0.27) Log (D) + (16.33 ± 0.48).