1. 1Geology Department, University of Puget Sound, Tacoma, Washington 98416-1048, USA
2. 2U.S. Geological Survey, Alaska Volcano Observatory, Anchorage, Alaska 99508, USA
3. 3College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA
4. 4Department of Earth and Space Sciences, University of Washington, Seattle, Washington 98195, USA
5. 5Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131, USA