Abstract

The slip distribution of the Mw 7.7 Tocopilla earthquake was obtained from the joint inversion of teleseismic and strong-motion data. Rupture occurred as underthrusting at the base of the seismically coupled plate interface, mainly between 35 and 50 km depth. From the hypocenter, located below the coast 25 km south of the town of Tocopilla, the rupture propagated 50 km northward and 100 km southward. Overall, the slip distribution was dominated by two slip patches, one near the hypocenter and the other 70 km to the south where slip reached its maximum value (3 m). An additional branch of moderate slip propagated at shallower depth toward the west near the northern tip of the Mejillones peninsula. Rupture velocity remained close to 2.8 km/sec, with a total rupture duration of 45 sec. The first 2 weeks of aftershocks located with a local seismic network display a strong correlation with the slip distribution. The 2007 rupture ended below the Mejillones peninsula, where the 1995 Antofagasta rupture also ended (Ruegg et al., 1996; Delouis et al., 1997; Pritchard et al., 2006). This corroborates the role of barrier played by this structure. The downdip end of the seismically coupled zone at 50 km depth, evidenced by previous studies for the 1995 event, is also confirmed. The 2007 Tocopilla earthquake contributed only moderately to the rupturing of the great northern Chile seismic gap, which still has the capacity for generating a much larger underthrusting event.

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