1. 1Alaska Volcano Observatory and Wilson Alaska Technical Center, Geophysical Institute, University of Alaska Fairbanks, Fairbanks, Alaska, U.S.A.
2. 2Wilson Alaska Technical Center, Geophysical Institute, University of Alaska Fairbanks, Fairbanks, Alaska, U.S.A.
3. 3Department of Earth Science and Earth Research Institute, University of California, Santa Barbara, California, U.S.A.