1. Department of Geological Sciences, San Diego State University, San Diego, California 92182, trockwell@mail.sdsu.edu
2. Earth Observatory of Singapore, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore, meltzner@ntu.edu.sg
3. Also at Asian School of the Environment, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
4. G3SoilWorks, Inc., 350 Fischer Avenue Front, Costa Mesa, California 92626, ehaaker@g3soilworks.com