Regional moment tensor determination in the European–Mediterranean area — initial results

Abstract

The broadband seismic network in the European–Mediterranean area provides high-quality data. We invert these regional three-component data for the source parameters of moderate-to-strong earthquakes in the entire European–Mediterranean area. Regional seismograms have a good signal-to-noise ratio even for moderate-sized events that are too small for teleseismic analysis. The magnitude threshold for source parameter determination can, thus, be significantly lowered. The threshold depends on the average event–station distances. Within dense broadband networks, we analyze M W≈3.0 earthquakes. In areas far from broadband seismic stations, the lower bound is M W≈4.5–4.8, still considerably lower than the teleseismic analysis threshold (about M W≈5.0–5.3). For larger events, we perform rapid moment tensor analysis using near-real-time data; solutions are posted within hours after event occurrence. In a second step, we merge near-real-time and later available data to obtain a regional moment tensor catalog of moderate-to-large earthquakes for the entire European–Mediterranean area. Within less than 1 year, we have analyzed 67 earthquakes ranging in size from M W=2.9 to 7.5. The solutions cover the seismically active areas of the European–Mediterranean area. Particularly important are solutions for slowly deforming regions where large earthquakes, that could be analyzed with teleseismic data, occur infrequently. The solutions are reliable: for events with independent source parameter estimates, the agreement is generally high. The solutions are robust: variations in epicentral parameters, source depth, or exact choice of stations do not affect source parameter estimates strongly. The moment magnitudes provide a unified estimate of earthquake size for the European–Mediterranean area. We perform regression analyses to link our moment magnitudes with local, body, and surface wave magnitudes.