PRELIMINARY RESULTS FROM A SHALLOW, HIGH-RESOLUTION SEISMIC SURVEY AND POTENTIAL FIELD DATA FILTERING NEAR DEVIL'S HOLE AT ASH MEADOWS, NEVADA

In February 2005, Brigham Young University conducted a high-resolution seismic reflection P-wave survey at Ash Meadows, Nevada across the presumed location of the southern strand of the Gravity fault, which locally corresponds to a 16 km-long lineament of springs. Preliminary processing and interpretation of the seismic data reveal a zone of discrete shallow faults with offsets up to 10 m intersecting the trend of the springs. The seismic profile also shows a major damage zone just east of the springs nearer Devil's Hole. Available aeromagnetic and gravity data were re-analyzed with first and second vertical derivative, Butterworth, and downward continuation filters. This analysis indicates that the seismically detected fault and damage zone lies just south of where the gravity gradient is strongest, in a zone where the potential field signature is complex. Furthermore, the re-analyzed aeromagnetic and gravity data suggest that the Gravity fault, where coincident with the lineament of springs at Ash Meadows, represents a major crustal-scale feature. The deep-seated nature of the Gravity fault has been previously supported by a USGS deep seismic profile located 25 km north of Ash Meadows. Based on our integration of geophysical methods, we infer that the Gravity fault may act either as barrier to the flow of groundwater from the east, or as a conduit for the flow of water from the north, or both. Further geophysical surveying is needed to map the detailed shallow subsurface structure of the Gravity fault and related deformation zone.