A possible mechanism for the spatial distribution of seismicity in northern Gulf of Mexico

In an aseismic part of northern Gulf of Mexico (GOM), three earthquakes of M-s 5.2, M-w 4.6 and M-w 5.8 occurred between 2006 February and September. These earthquakes raised concerns because of their proximity to locations of active hydrocarbon production, and potential for tsunami generation, prompting investigations about their causes. Herein, we test a hypothesis using 2-D and 3-D models, where stress concentration due to contrast in mechanical properties between the salt deposits and surrounding sediments in the northern GOM, driven by background tectonic loading, may have triggered these earthquakes in particular, and cause earthquakes in the northern GOM in general. We perform the mechanical modelling by a 'distinct element method' implemented through commercially available computer programmes called 'Universal Distinct Element Code (UDEC)' and 'Three-Dimensional Distinct Element Code (3DEC)'. Our models consist of a simplified regional outline of the salt bodies surrounded by sediments. We assign mechanical properties to the salt and sediments based on known geology and seismic velocities. We load the models tectonically for a year, and observe the patterns of resulting shear stresses. The results of modelling suggest that some locations of relatively high shear stress correlate well with the spatial distribution of seismicity in the northern GOM, thereby suggesting a possible causal association.