Robert B. Herrmann C.A. Langston H. Benz C.J. Ammon 1998 <p><span>Two events dominated the January 1994, Wyomissing, PA earthquake sequence, an&nbsp;</span><i>M_w</i><span>&nbsp;4.0 foreshock, followed by an&nbsp;</span><i>M_w</i><span>&nbsp;4.6 mainshock. We modeled regional waveforms to estimate the event depth and the moment tensors for the two largest events in the sequence, and examine teleseismic waveforms recorded on the ARCESS short-period seismic array to estimate the depth and source time function of the mainshock. Our data constrain the depth of the events to be shallower than 5 km, and prefer a depth of 3–5 km. For an assumed depth of 3 km, the mainshock moment tensor is 75% double couple, with (the major double couple) planes striking at 135°N, 347°N, dips of 49°, 46°, and rakes of 68°, 114°. The estimated moment is 8.9 × 10</span>²²<span>&nbsp;dyne-cm. The&nbsp;</span><i>P</i><span>&nbsp;axis strikes 241°N and plunges 2°, the Tension axis strikes 336°N and plunges 73°. The foreshock inversion results are virtually identical to the mainshock results; for a source depth of three km, we find a major double couple with a strike, dip, and rake of 121°N, 60°, and 66°, respectively. The seismic moment for the foreshock is 1.2 × 10</span>²²<span>&nbsp;dyne-cm, which is approximately 13% of the mainshock moment release. These events did not excite high-frequency&nbsp;</span><i>Lg</i><span>&nbsp;waves as effectively as typical eastern North American events, and the mainshock had a stress drop in the range of 25–50 bars.</span></p> application/pdf 10.1785/gssrl.69.3.261 en GeoScienceWorld Faulting parameters of the January 16, 1994 Wyomissing Hills, Pennsylvania earthquakes article