1. Department of Geosciences, Pennsylvania State University, 201 Old Main, University Park, Pennsylvania 16802 U.S.A., dcb31@psu.educhrisjmarone@gmail.com
2. Department of Engineering Science and Mechanics, Pennsylvania State University, 201 Old Main, University Park, Pennsylvania 16802 U.S.A., pxs990@psu.edu, jvr5626@psu.edu
3. Geophysics Group, Los Alamos National Laboratory, 30 Bikini Atoll Road, Los Alamos, New Mexico 87545 U.S.A., bertrand.rouetleduc@gmail.com, claudia.hulbert@gmail.com, paj@lanl.gov