For additional information                     Copies of this report can 
write to:                                      be purchased from: 
 
 
 
                                               U.S. Geological Survey  
                                               Earth Science Information Center 
District Chief                                 Open-File Reports Section 
U.S. Geological Survey                         Box 25286, MS 517  
3916 Sunset Ridge Road                         Denver Federal Center  
Raleigh, NC 27607                              Denver, CO 80225