Global CMT analysis of moderate earthquakes, Mw ≧ 4.5, using intermediate-period surface waves

Abstract

Abstract A new method for calculating centroid moment tensor (CMT) solutions for moderate-sized earthquakes is presented and tested. In the new algorithm, which is a modification to the standard Harvard CMT method, intermediate-period surface waves are included in the inversion for source parameters. The dispersion of teleseismic surface waves in the period range 40 to 150 sec is predicted by interpolation of recent global phase velocity maps. The method is tested on a set of 20 moderate and large (5.2 ≦ Mw ≦ 7.2) earthquakes with known mechanisms. The retrieved mechanisms are similar to the previous results, even when noise is added to the seismograms to simulate earthquakes of a smaller magnitude (Mw ∼ 4.5). The inversion algorithm is applied to the 1993 Klamath Falls mainshock and aftershock sequence, and the results compare well with earlier results. A catalog of Mw ≧ 4.5 focal mechanisms for Greece and surrounding areas for the first six months of 1995 is derived using the new method of analysis.