1. Department of Geology; Bucknell University; Lewisburg Pennsylvania USA
2. On leave at the Office of Ground Water, Branch of Geophysics; U.S. Geological Survey; Storrs Connecticut USA
3. Office of Ground Water, Branch of Geophysics; U.S. Geological Survey; Storrs Connecticut USA
4. Department of Geophysics; Stanford University; Stanford California USA
5. Department of Geological and Environmental Sciences, Braun Geology Corner; Stanford University; Stanford California USA