Stress fields in the Antarctic plate inferred from focal mechanisms of intraplate earthquakes

Abstract

Typical directional features of intraplate stresses are extracted from focal mechanism solutions of earthquakes in the Antarctic plate. Typical directions of stresses are obtained in the following regions, 1) Bellingshausen Sea, 2) south of Juan-Fernandez microplate, 3) Balleny Island region and 4) Kerguelen region. P axes in regions 1) and 2) have been interpreted by ridge push force. However these interpretations are based on one focal mechanism for each event and on crude physical concept of ridge push. It is difficult to explain intraplate stress fields in these regions only by the local ridge push force. The stress direction in region 3) can be interpreted by both deformation near triple junction and deformation due to deglaciation. Earthquakes near region 4) appear to be normal fault event. Because normal fault events appear only in the younger ocean floor, the stress field may be affected by thermal features such as hot spots Quantitative modeling and superposition of various stress factors are required to discriminate among stress origins. It is difficult to discuss stress directions in and around Antarctic continent, because number of the earthquakes is not enough.