New local magnitude scales for Egypt

Abstract

Local magnitude (ML) scales have been developed for Egypt based on 14,453 normalized Wood–Anderson amplitudes from 1670 earthquakes. These events were recorded by at least four seismic stations, with hypocentral depths of less than 40 km and earthquake magnitudes ranging from 0.1 to 6.5 ML. The dataset was processed using recordings from the two horizontal components. Egypt was divided into four sub-tectonic regions: South Egypt, North Egypt, the Red Sea, and the Mediterranean Sea. The decay of amplitudes with distance was examined across the entire dataset, providing attenuation characteristics segmented into three sections, with transition distances at 90 km and 175 km. Within each sub-tectonic region, the coefficients of the distance correction term (− log A0) and the station correction term (S) were determined using a trilinear geometrical scattering model and singular value decomposition, respectively. The newly derived relationship for Egypt has resulted in unbiased ML magnitude estimates over a substantial distance range (10–1000 km), thus ensuring consistent magnitude estimates from the ENSN network.