Abstract

A procedure to locate seismic events uses the value of the crosscorrelation coefficient between waveforms of different events. First, an empirical relation between spatial event separation and maximum crosscorrelation coefficient is established for a subset of a priori located reference events. Then this relation is used to determine the hypocenters of an increasing number of events by a grid-search strategy. Measured arrival-time differences between S- and P-waves also constrain the location. Although the reference events are located by a standard method using the arrival-time measurements at three or more receivers, the correlation-based location requires only one receiver. The method has been applied to microseismic data recorded at a single borehole sensor during the 2004/05 injection experiment at the Continental Deep Drilling Site (KTB) in Germany. With the approach, significantly more weak seismic events were located, compared to the number of events recorded by a near-surface receiver array and by inversion of arrival times. The proposed location method is particularly well suited to locate small-magnitude earthquakes within dense event clouds when too few arrival-time observations for part of the events are available and standard location methods fail. These conditions are frequently met in the case of microseismic monitoring of geothermal or enhanced oil recovery experiments.

You do not currently have access to this article.