1. Department of Earth and Planetary Sciences, University of California, Santa Cruz, Santa Cruz, CA, USA.
2. Earthquake Science Center, U.S. Geological Survey, Moffett Field, CA, USA.
3. Seismological Laboratory, California Institute of Technology, Pasadena, CA, USA.
4. Institut Terre et Environnement Strasbourg, Université de Strasbourg/CNRS, Strasbourg, France.