A kinematic viscoelastic model of the San Francisco earthquake of 1906

We construct a model of the San Andreas fault zone based on a rectangular fault in an elastic layer overlying a viscoelastic half-space. We alllow both steady and episodic aseismic slip at depth on the fault as well as a large-scale relative plate driving force. We use the model to explain the aseismic 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 kilometres.