1. Institute for Geophysics; University of Texas at Austin; Austin; Texas; USA
2. Department of Earth and Atmospheric Sciences; Purdue University; West Lafayette; Indiana; USA
3. Laboratoire de Tectonique, CNRS-UMR 7578; Institut de Physique de Globe de Paris; Paris; France
4. Department of Geology and Geophysics; University of Wisconsin; Madison; Wisconsin; USA
5. Department of Geosciences; University of Arkansas; Fayetteville; Arkansas; USA
6. Department of Geology; University of Puerto Rico; Mayaguez; Puerto Rico