Clustering and location of mining induced seismicity in the Ruhr Basin by automated master event comparison based on dynamic waveform matching (DWM)

Abstract

Most of the local seismicity in the Ruhr Basin can be separated into characteristic clusters of similar, mining induced earthquakes. Each cluster can be represented by a strong master event. Therefore, it is possible to associate weak events to the corresponding clusters by master event comparison. The seismic signal matching is performed by a nonlinear correlation termed DWM for the entire seismogram length. DWM permits stretchings and shortenings between the two signals and overcomes the ambiguities in phase correlation by a consistent matching path. The automatic cluster association searches for the best DWM-correlation between the actual event and all master events of the appropriate epicenter region. Knowing the P- and S-onsets of the master event, they can be transposed to the actual event by the correlation path with one sample accuracy. The method has been applied to all BUG small array recordings 1987–1990 of local events from the Hamm-region to investigate spatial and temporal clustering. Within the clusters, a high percentage of weak events could be located relative to its master event. The temporal clustering resolved seismic activities that typically last a few months per cluster, but single aftershocks occur in the following years.