1. Colorado School of Mines, Department of Geophysics, Golden, Colorado, U.S.A. .
2. Harvard University, Division of Applied Science and Engineering, Cambridge, Massachusetts, U.S.A. .
3. Colorado School of Mines, Division of Engineering, Golden, Colorado, U.S.A. .
4. Colorado School of Mines, Petroleum Engineering Department, Golden, Colorado, U.S.A. .