Ground truth events with source geometry in Eurasia and the Middle East

Abstract:

Accurate seismic source locations and their geometries are important to improve ground-based system monitoring; however, a few number of Ground Truth (GT) events are available in most regions within Eurasia and Middle East. In this study GT event locations were found for several earthquakes in the Middle East and Africa, including Saudi Arabia and Tanzania, with location errors of less that 5 km. These events were acquired through analyzing several local and near-regional waveforms for hundreds of earthquakes in these areas. A large number of earthquakes occurred beneath the Harrat Lunayyir in northwest Saudi Arabia in 2009. From the 15 Lunayyir GT events recorded on three-component seismographs, 5 with Mw between 3.4 and 5.9 were used for successfully obtaining source parameters. A moment tensor inversion was applied on filtered surface wave data to obtain the best-fitting source mechanism, moment magnitude, and depth. The uncertainty in the derived parameters was investigated by applying the same inversion to selected traces and frequency bands. Focal mechanism for these earthquakes demonstrates normal faulting with a NW-SE trend for all of the events except one, which has a NE-SW trend. The shallow 3 km depth obtained for all the events is consistent with previous studies of dyke intrusion in the area. Spectral analysis of S waves and source parameters for these earthquakes are in progress to find static stress drop, corner frequency and radiated energy.