Abstract

Moment-tensor solutions of three earthquakes recorded in the 1982 Arkansas swarm area (Haar et al., 1984) are obtained. Since a correct model is essential in such analysis, the earthquake of 29 June 1982 (07h 00m 27.94s) was used as the calibration event for the final structural model. An essential component of the analysis consisted of low-pass filtering of both observed and predicted seismograms to minimize the effect of different P- and S-wave pulse shapes due to source dynamics. The choice of a 15-Hz corner frequency was governed by corner frequency estimates of 10 to 13 Hz for these events (Haar et al., 1984).

The focal mechanisms of these events are determined to be predominantly strike-slip, with east to northeast-trending pressure axes, compatible with single event focal mechanisms for other earthquakes in the swarm area (Johnston and Metzger, 1982; Chiu et al., 1984; Haar et al., 1984). The major difference is in the estimates of seismic moments, two to ten times smaller than those determined using frequency domain techniques (Haar et al., 1984). The value of this detailed analysis lies in its ability to calibrate local structure, which will hopefully permit deconvolution of the propagation effects to characterize the source properties.

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