Dynamic triggering: Stress modeling and a case study

Changes in the static stress can trigger nearby earthquakes that occur within a few fault lengths from the causative event. Transient stresses caused by passage of surface waves commonly trigger events at remote distances, yet little is documented or understood about the processes and stresses necessary for remote triggering. To understand the causative stresses and environments behind remote, or dynamic, triggering, we must decipher the stresses caused by the passage of the surface waves in relation to the local stress field and fault conditions where the triggered events occur. In this study, we model the change in the stress field that the passing of Rayleigh and Love waves causes on a fault plane of arbitrary orientation relative to the direction of propagation of the waves, and we apply a Coulomb failure criterion to calculate the potential of these stress changes to trigger reverse, normal, or strike-slip failure. We compare these model results with data from dynamically triggered earthquakes in the Australian Bowen Basin, an area with low seismicity and mapped regional stress and that is at the margin of a stable continental craton. Our data analysis shows that for this region, surface waves arriving at 45 from the average strike direction are the most likely to trigger local seismicity. This agrees with our observations.