1. Department of Geology, Bucknell University, Lewisburg, PA, 17837 (current address: Ashford, CT 06267)
2. Department of Geology, Bucknell University, Lewisburg, PA, 17837
3. Hager-Richter Geoscience, Inc., Orange, NJ 07050
4. Department of Geophysics, Stanford University, Stanford, CA 94305