Displacement and Geometrical Characteristics of Earthquake Surface Ruptures: Issues and Implications for Seismic Hazard Analysis and the Process of Earthquake Rupture

Steven G. Wesnousky

Accepted 2007, SCEC Contribution #1095

There now exist about 3 dozen historical earthquakes for which investigators have constructed maps of earthquake rupture traces accompanied by data describing the coseismic slip observed along fault strike. The compilation of that data presented here places observational bounds on aspects of both seismic hazard analysis as well as fault mechanics. Analysis leads to an initial statistical basis to predict the endpoints of rupture and the amount of surface slip expected at sites along strike during earthquakes on mapped faults. The observations also give support to the ideas that there exists a process zone or volume of about 3-4 km dimension at the fronts of large laterally propagating earthquake ruptures within which stress changes may be sufficient to trigger slip on adjacent faults, and that the ultimate length of earthquake ruptures is controlled primarily by the geometrical complexity of fault traces and variations in accumulated stress levels along faults that arise due to the location of past earthquakes. To this may be added the observation that the form of earthquake surface slip distributions is better described by asymmetric rather than symmetric curve forms and that earthquake epicenters do not appear to correlate in any systematic manner to regions of maximum surface slip observed along strike.

Citation
Wesnousky, S. G. (2007). Displacement and Geometrical Characteristics of Earthquake Surface Ruptures: Issues and Implications for Seismic Hazard Analysis and the Process of Earthquake Rupture. Bulletin of the Seismological Society of America, (accepted).