The 1943 Lake Hawea earthquake—a large subcrustal event beneath the Southern Alps of New Zealand
Abstract A re‐assessment of both instrumental and macroseismic data for the earthquake felt widely in the South Island of New Zealand on 1943 May 08 indicates that it was a subcrustal ML 5.9 event c. 50 km deep located near the head of Lake Hawea. This location places it in the uppermost mantle beneath the crustal root of the Southern Alps, within the dipping seismic zone defined by well‐located smaller earthquakes. Both the rupture dimension of the 1943 earthquake and the planar nature of the dipping seismic zone itself imply that the uppermost mantle in this region is rigid on c. 10 km and c. 100 km length scales, consistent with recent numerical models of lithospheric deformation. Subduction of rigid mantle lithosphere provides an explanation for the unusual isoseismal pattern for the 1943 event.