1. 1Swiss Seismological Service (SED), ETH Zurich, Zurich, Switzerland
2. 2California Institute of Technology (Caltech), Pasadena, California, U.S.A.
3. 3United States Geological Survey, University of Washington, Seattle, Washington, U.S.A.
4. 4Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California, U.S.A.
5. 5University of California, Berkeley, Berkeley, California, U.S.A.
6. 6United States Geological Survey, Moffett Field, California, U.S.A.