Mechanism of the May 21–22, 1960, Chilean Earthquakes as derived from residual vertical displacements

Abstract

The great earthquakes of 21–22 May, 19 in west‐central Chile were accompanied tectonic displacements and intense, predominantly shallow (h≤70 km), aftershock activity. They affected a region more than 2 km wide and about 1000 km long that along the continental margin between 37° 46° S latitude. Studies of shorelines levelling data in this region indicate that vertical deformation involved a broad downwarp and two flanking upwarps. The structures lie roughly between and parallel the Peru‐Chile Trench and Andeanchain. Vertical tectonic displacements to sea level resulted in: (1) uplift of at least 5 m on offshore islands, at some points along mainland coast, and on at least part of contiguous continental shelf; (2) subsidence as much as 2.7 m in a zone 75–110 km that extends eastward from the vicinity of outer coast almost to the western margin of borders the downwarp on the east.