Observation and Signatures of Injection-induced Repeating Earthquake Sequences
J. Kummerow, C. Dinske, H. Asanuma and M. Häring
Event name: 76th EAGE Conference and Exhibition 2014
Session: Microseismic - Case Studies
Publication date: 16 June 2014
Info: Extended abstract, PDF ( 1.1Mb )
Price: € 20
We detect and analyze repeating earthquake sequences in the Basel 1 microseismic data set. Using a combination of waveform similarity and estimates of source radius we identify 144 repeating earthquake sequences with a total of 422 events. The specific spatio-temporal behaviour of the repeating events indicates clearly that they are more sensitive to pore pressure changes than the total induced seismicity, which is at larger distances (more than about 250-300m from the injection source in the Basel reservoir) not only affected by pore pressure variations, but presumably also by stress transfer from the larger (Mw>2.0) events. The results suggest that repeating earthquakes may contribute to identifying and differentiating the dominant triggering effects of recorded microseismicity. Furthermore, this study shows that a significant percentage of the fractures stimulated in the Basel reservoir ruptured repeatedly: More than 15% of all located events are repeaters. We anticipate that the occurrence of repeating events is a common feature in injection induced microseismic data sets, and that it is useful to incorporate repeating events in future statistical analyses of microseismic data, which so far generally assume that each potential source in the stimulated reservoir can only fail one-time.