Effects of Earth's curvature and radial heterogeneity in dislocation studies: Case studies of the 2008 Wenchuan earthquake and the 2004 Sumatra earthquake

Recently, effects of Earth’s curvature and radial heterogeneity on coseismic deformations are often investigated based on the 2004 Sumatra earthquake. However, such effects are strongly related to earthquake types. As a low dip angle event, the 2004 Sumatra earthquake is not a good seismic case for such a topic since the effects for moderate dip angle events are much bigger. In this study, the half-space and spherical dislocation theories are used, respectively, to calculate coseismic displacements caused by the 2008 Wenchuan earthquake and the 2004 Sumatra earthquake. Effects of Earth’s curvature and stratification are investigated through the discrepancies of results calculated using the two dislocation theories. Results show that the effects of Earth’s curvature and stratification for the 2008 Wenchuan earthquake are much larger than those for the 2004 Sumatra earthquake. Ignoring the effects will cause errors up to 100%–200% in far field displacements for a moderate dip angle event like the 2008 Wenchuan earthquake. Such great effects are much bigger than those conclusions of previous studies. Besides, comparison with observations verifies that spherical dislocation theories yield better results than half-space ones in far fields.