Constraining Fault Geomechanics Using Elastic Waveform Inversion and Dynamic Rupture Modelling

Summary The results from microseismic event locations, derived using an elastic full waveform matching algorithm, have been used to constrain dynamic rupture models to better understand induced fault rupture geomechanics. This workflow has been applied to events recorded by the shallow borehole network installed at the Groningen gas field in The Netherlands. Focal angles derived from moment tensor inversion are seen to provide a good match to the fault strike angles, but fault dip is poorly constrained along with the seismic interpretation. This is due to the limited vertical resolution of the available datasets. Dynamic rupture modelling was performed to constrain the slip patch size and displacement, using a linear slip weakening relationship. On one example fault, where several events have occurred over the past few years, microseismic activity from small magnitude events likely transferred stress to neighboring areas of the fault, which accumulated over time and finally resulted in a larger magnitude earthquake which ruptured over a 350m length of the fault.