Analysis of some aspects of locating sources with passive seismic data: synthetic examples

Leonid Vanyan

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ABSTRACT

Locating sources of seismic energy by computing the semblance along moveout trajectories requires knowledge of the velocity structure. Since our knowledge of the medium velocities is always imperfect, there will be errors in the location of sources. Using an incorrect average velocity results in a vertical shift of the semblance maximum as compared with the actual source location. The presence of random travel time fluctuations causes a decrease in the maximum semblance value without changing its location.
Sources can be located even if the data are aliased. Synthetic tests show that while some artifacts are introduced by the aliasing, meaningful results can still be obtained, especially when the source signal is broadband. For any proposed experiment, such synthetic tests should be run to see how well one can expect to locate sources given the proposed array geometry.