1. Department of Geosciences, Universidad Nacional de Colombia at Bogotá, Bogotá, Colombia 321111, cavargasj@unal.edu.co
2. Department of Geosciences, University of Arizona, 1040 East 4th Street, Tucson, Arizona 85721 U.S.A., slbeck@email.arizona.edu
3. Observatorio Vulcanológico y Sismológico de Costa Rica, Universidad Nacional, Heredia, Costa Rica, marino.protti.quesada@una.cr
4. Geophysics Department, Faculty of Physical and Mathematical Sciences, University of Chile, Blanco Encalada 2002, Santiago, Chile, jaime@dgf.uchile.cl