Evaluation of earthquake triggering during the 2005-2008 earthquake sequence on Qeshm Island, Iran

Abstract

Coseismic static Coulomb stress changes may either advance or retard the timing of subsequent earthquakes on nearby faults in a manner that depends both on the relative orientations of faults within the vicinity of the primary rupture, as well as on the postseismic redistribution of stress. Here we examine interferometric synthetic aperture radar (InSAR) data spanning two earthquakes that occurred in close temporal and spatial proximity on Qeshm Island in southern Iran. Remote observations of earthquakes such as ground deformation or seismic waves allow us to infer earthquake source parameters, but in general, a nonunique family of solutions is consistent with the data, given our understanding of data noise and the limitations of our ability to model the real Earth. Here, we explore methods for assessing and propagating InSAR noise through our entire analysis of the stress triggering potential between these two earthquakes. We generate a range of source models for each earthquake based both on InSAR and seismic observations and assess whether the expected static Coulomb stress change during the first earthquake is likely to have brought the second event closer to or further from failure. Some combinations support the hypothesis that the first earthquake brought the second fault closer to failure, whereas some do not. Fault plane geometries that agree with InSAR constraints are more likely to suggest that the first earthquake increased the likelihood of the second earthquake, those based on the Harvard and global centroid moment tensor tend to not support triggering between the two events. Copyright 2010 by the American Geophysical Union.