Assessment of the size of large and great historical earthquakes in Peru

A critical reappraisal of great historical earthquakes in Peru is made in order to obtain quantitative estimates of rupture length, seismic moment, tsunami magnitude M_t, and moment magnitude M_w. Newly collected information concerning several historical earthquakes permits the evaluation of macroseismic zones and from the size of these zones, the estimation of length of rupture, seismic moment and magnitude M_w. It is found that local tsunami data provide good quantitative estimates of M_t, and therefore an independent way of verifying macroseismic estimates of rupture length and seismic moment. A space-time diagram of great historical earthquakes shows the existence of three zones roughly corresponding to the segmentation of the Nazca plate (Hasegawa and Sacks, 1981) subducting under Peru. The northern zone looks aseismic. The central one is very complex; it breaks either completely or in smaller segments, and it may go through long quiescence periods. The recurrence time for the southern segment, the more regular one, is of the order of one century.