Seismic Source of 1966 Huacho Peru Earthquake (Mw 8.1) from Tsunami Waveform Inversion

In this research we estimated the slip distribution of the 1966 Huacho Peru earthquake, by inverting tsunami waveforms. This event took place offshore the central Peru region and produced severe ground shaking in the cities of Supe and Huacho, with intensities of VIII MM, leading to 100 fatalities. The coseismic seabed deformation produced by the earthquake triggered a regional tsunami that inundated some coastal areas, with major effects in Casma and Tortugas. We used the tsunami waveforms from three tidal stations located in Chimbote, Callao and Marcona, to obtain the parameters of the seismic source through an inversion process, whereby we compared the simulated and observed waveforms using the non-negative least square approach. Our results show a dislocation with a maximum slip of 5.5 m located around the epicentre. This implies that the asperity with maximum energy release was located offshore Barranca city. The seismic moment was calculated as 2.05× 10²¹ Nm, which is equivalent to a moment magnitude of 8.1 Mw. We suggest that there is a high potential for the generation of a tsunamigenic earthquake in the central region of Peru, despite the occurrence of the 1966 Peruvian earthquake, because this earthquake (together with the 1940, 1974 and 2007 earthquakes) has only released around the 20% of the energy accumulated from the 1746 earthquake (Mw9.0).