Linking geomechanical simulation of induced seismicity to surface seismic observations

Abstract

Dynamic geomechanical modeling can generate the seismic wavefield caused by a fault rupture. In dynamic fault-rupture modeling, the source is considered to be finite, with a limited extent both in space and in time. This contrasts with the definition of a point source, which is generally assumed to explain the seismic wavefield caused by an earthquake. Most earlier seismic inversion studies, including those of the induced earthquakes caused by depletion of the Groningen gas field, were performed assuming a point source. Still, finding a point-source reference from the seismic wavefield, even when generated by finite faulting, is important in order to calibrate the geomechanical simulation with field-seismic observations. To this end, we have developed a workflow that links geomechanical forward modeling to seismic moment-tensor inversion. We have tested this workflow for the dynamic rupture considering a realistic 3D layered earth model. At first, we simulate the triggering of dynamic fault slip at the center of a fault plane. Next, we invert the seismograms recorded by receivers located on or near the surface to obtain the full moment-tensor point-source representation and the location of the earthquake. The results of inversion show similar waveforms for both the point source and the finite source. The location of the inverted point source is within 400 m from the center of the slip patch. The double-couple components of the inverted moment tensor also match with the strike and the dip of the fault plane.