Sundaland: Undeformed Lithospheric Block of Southeast Asia

A Review of published space geodetic data for Southeast Asia has been used to confirm the assumption that the central part of the region (the Sunda Plate) can be regarded as a rigid stable block with a continental lithosphere. The combined geodetic, geological, and seismological data make it possible to specify the position of the boundaries of this block (Sundaland). These boundaries are largely represented by subduction zones and areas of recent continental tectonic deformation of the Earth's crust. Here, the overwhelming proportion of deformation is concentrated precisely within the boundaries of Sundaland. Data on the sets of earthquake focal mechanisms have been used to assess the type of the seismotectonic deformation tensor (STD) within 21 spatial samples in the vicinity of various sections of the Sundaland boundary. Compared with existing geological and geodetic data, the results of this assessment showed a satisfactory agreement between them. The STD type has been assessed for the entire observable depth of subduction zones and the revealed variations in the STD type with depth have been interpreted.