Source characteristics of the 22 january 2003 M_w = 7.5 tecomán, Mexico, earthquake: New insights

摘要

Aftershock locations, source parameters and slip distribution in the coupling zone between the overriding North American and subducted Rivera and Cocos plates were calculated for the 22 January 2003 Tecomán earthquake. Aftershock locations lie north of the El Gordo Graben with a northwest-southeast trend along the coast and superimposed on the rupture areas of the 1932 (M_w = 8.2) and 1995 (M_w = 8.0) earthquakes. The Tecomán earthquake ruptured the northwest sector of the Colima gap, however, half of the gap remains unbroken. The aftershock area has a rectangular shape of 42 ± 2 by 56 ± 2 km with a shallow dip of roughly 12° of the Wadati-Benioff zone. Fault geometry calculated with the Nábělek (1984) inversion procedure is: (strike, dip, rake) = (277°, 27°, 78°). From the teleseimic body wave spectra and assuming a circular fault model, we estimated source duration of 20 ± 2 s, a stress drop of 5.4 ± 2.5 MPa and a seismic moment of 2.7 ±.7 9 1020 Nm. The spatial slip distribution on the fault plane was estimated using new additional near field strong motion data (54 km from the epicenter). We confirm their main conclusions, however we found four zones of seismic moment release clearly separated. One of them, not well defined before, is located toward the coast down dip. This observation is the result of adding new data in the inversion. We calculated a maximum slip of 3.2 m, a source duration of 30 s and a seismic moment of 1.88 × 10~(20) Nm.