New Theory for Calculating Strains Changes Caused by Dislocations in a Spherically Symmetric Earth

A new theory is presented for calculating co-seismic strain caused by four independent types of seismic source in a spherically symmetric, non-rotating, perfectly elastic, and isotropic (SNREI) Earth model. Expressions are derived by introducing strain Green’s functions. A proper combination of these expressions is useful to calculate co-seismic strain components resulting from an arbitrary seismic source at any position in the Earth. Numerical computations are performed for four independent sources at a depth of 32 km inside the 1066A Earth model. Results in the near field agree well with that calculated for a half-space Earth model. A case study is performed and Earth model effects are investigated. Furthermore, the effects of spherical curvature and the stratified structure of the Earth in computing co-seismic strain changes are also investigated using the present dislocation theory and Okada’s (1985) formulation. Curvature effects are small for shallow seismic events, but they are larger for greater source depths. Stratified effects are very large for any depth and epicentral distance, reaching a discrepancy greater than 30% almost everywhere.