Anelastic processes in strike slip faulting: Application to the San Francisco earthquake of 1906

An analytic approximation to the Green's function for the displacements due to a strike slip point source in an elastic layer over a viscoelastic half space is developed. To represent the quasi-static displacements from a large crustal strike slip earthquake, a model is constructed which makes use of the approximate Green's function. Aseismic slip below the brittle seismic zone is also allowed in the model as well as a large scale relative plate velocity. The model is applied to explain the continual changes in geodetic triangulation angles observed during the 40 years following the 1906 San Francisco earthquake. The most important results are that viscoelastic relaxation can explain the data very well, and that the driving force of relative plate motion can be characterized by a horizontal distance scale perpendicular to the plate boundary of hundreds of kilometers.