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On The Depth Discrepancies between Downhole and Surface Monitoring
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 79th EAGE Conference and Exhibition 2017, Jun 2017, Volume 2017, p.1 - 5
Abstract
Systematic discrepancies in estimated focal depth estimates have been noted for induced seismicity monitoring using either surface broadband sensors or microseismic monitoring arrays. This report considers two possible sources of such discrepancies, namely dispersion associated with seismic attenuation and velocity model uncertainty. Synthetic modeling shows that while attenuation causes some changes in arrival time, it is not a viable explanation for the discrepancies. Velocity model error, however, can cause significant errors, especially if the source of the event is below a low velocity zone. With increasing velocity model error, there is a bias for the surface arrays to locate events deeper than necessary, and for the downhole arrays to locate events shallower than necessary.