EFFECT OF NEAR-FAULT TERRAIN UPON DISLOCATION MODELING

Coseismic surface deformation provides important information needed to determine source rupture geometry and slip distribution as well as to estimate seismic moment. In this study, numerical experiments were de signed to analyze and classify how free-surface topography affects sur face deformation. The investigation was performed by 3-D finite elemen t modeling. Results of this study show that crustal deformation induce d by near-fault terrain is significant and can be measured with presen t geodetic survey techniques. The characteristics of the terrain effec ts show that a hill structure produces more crustal deformation than a half-space model, and that the crustal deformation of a basin structu re is less than that of the half-space model. The topographic correcti on is in the order of five percent of the fault dislocation. On the ba sis of the relationship between fault offset and earthquake magnitude, it is suggested that the terrain effects on the coseismic crustal def ormation of shallow earthquakes with a magnitude greater than 5.6 shou ld be considered as one of the major errors in coseismic deformation m odeling which ignored the surface topography on the order of 300 meter s.