1. 1Sandia National Laboratories, Geophysical Detection Programs, Albuquerque, New Mexico, U.S.A.
2. 2Wilson Alaska Technical Center & Geophysical Institute, University of Alaska Fairbanks, Fairbanks, Alaska, U.S.A.
3. 3Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, U.S.A.
4. 4U.S. Geological Survey, Cascades Volcano Observatory, Vancouver, Washington, U.S.A.
5. 5R&D Seismology and Acoustics, Royal Netherlands Meteorological Institute (KNMI), De Bilt, The Netherlands
6. 6Norwegian Seismic Array (NORSAR), Kjeller, Norway
7. 7Roy M. Huffington Department of Earth Sciences, Southern Methodist University, Dallas, Texas, U.S.A.