Regional moment tensor determination in the European-Mediterranean area - initial results

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 approximate to 3.0 earthquakes. In areas far from broadband seismic stations, the lower bound is M-W approximate to 4.5-4.8, still considerably lower than the teleseismic analysis threshold (about M-W approximate to 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 approximate to 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. (C) 2002 Elsevier Science B.V. All rights reserved.