1. Formerly Colorado School of Mines, Department of Geophysics, Golden, Colorado, USA; presently ExxonMobil Technology and Engineering Company, Spring, Texas, USA. (corresponding author)
2. Colorado School of Mines, Department of Geophysics, Golden, Colorado, USA.
3. Formerly Kuwait Oil Company, Ahmadi, Kuwait; presently Qatar Energy, Doha, Qatar.
4. Kuwait Oil Company, Ahmadi, Kuwait.