Relative Moment Tensor Analysis of the OTN3 Stimulation Seismicity: A new method for the micro-structural investigation of earthquake clusters

We present the relMT algorithm to estimate relative seismic moment tensors (MT) of small seismic events and apply it to the 2018 stimulation seismicity of the DEEP EGS project in Espoo, Finland. Relative MTs are tied to an absolute reference MT. They can be computed for clustered events for which the subsurface Green’s function can be assumed equal and do not require detailed knowledge of the subsurface velocity structure. We triple the number of resolved MTs from 283 to 864 and lower the magnitude threshold to -0.5. Future developments of the algorithm promise to contribute consistent S-wave cross-correlation lag times to re-localization efforts.