1. Geosciences Montpellier, UMR5243, Université de Montpellier, Place E. Bataillon, F-34095 Montpellier, France. E-mail: cattin@gm.univ-montp2.fr
2. Seismology and Geophysics Division, Department of Geology and Mines, Ministry of Economic Affairs, Post Box 173, Thimphu, Bhutan