HR: 0800h
AN: H21E-1080    [Abstracts]
TI: A Geophysical Study of Fissures in Pahrump, Nevada
AU: * Hirsch, A C
EM: hirscha2@unlv.nevada.edu
AF: Geoscience Department, University of Nevada Las Vegas, 4505 Maryland Parkway, MS 4010, Las Vegas, NV 89154-4010 United States
AU: McEwan, M J
AF: Geoscience Department, University of Nevada Las Vegas, 4505 Maryland Parkway, MS 4010, Las Vegas, NV 89154-4010 United States
AU: Howley, R A
AF: Geoscience Department, University of Nevada Las Vegas, 4505 Maryland Parkway, MS 4010, Las Vegas, NV 89154-4010 United States
AU: Mehling, J B
AF: Geoscience Department, University of Nevada Las Vegas, 4505 Maryland Parkway, MS 4010, Las Vegas, NV 89154-4010 United States
AU: Snelson, C M
AF: Geoscience Department, University of Nevada Las Vegas, 4505 Maryland Parkway, MS 4010, Las Vegas, NV 89154-4010 United States
AU: Drohan, P
AF: Geoscience Department, University of Nevada Las Vegas, 4505 Maryland Parkway, MS 4010, Las Vegas, NV 89154-4010 United States
AB: Earth fissures are surface expressions of deep fracturing subsidence systems caused by groundwater withdrawl greater than aquifer recharge. This type of subsidence is most common in arid environments of the south western U.S. such as, Las Vegas, NV, Phoenix, AZ, and areas in New Mexico. In addition, fissures have recently been identified in the Pahrump Valley in southwestern Nevada just west of Las Vegas. The city of Pahrump has experienced an increase in population and economic growth. This growth has lead to a higher demand in the use of the areas natural resources. One major concern is groundwater pumping and over-watering of the land surface. Pahrump has experienced significant differential subsidence within the valley causing significant structural damage to infrastructure. This differential subsidence is most readily identified by its surface expression as fissures. Earth fissures are not only shallow surface features but can be 10's of meters deep and 100's of meters long. These ground failures can be exacerbated by faults at depth, shallow bedrock, and/or differential compaction. However, the most significant cause is from groundwater withdrawl. Several geophysical methods were performed on the fissures to better understand their subsurface expression, trend, and ultimately their affect on the city of Pahrump. Seismic refraction, reflection, ground penetrating radar (GPR), and gravity measurements were performed on the fissures and surrounding area including local faults. Our initial studies show the fissures propagating for long distances, in a variety of shapes, and trending in a north-south direction. Initial GPR studies show high fissure reflections at approximately 1 and 1.5 meters along with general slumping features below these reflections. Fissures are an unmitigatable problem. Our results will help identify fissures in the area that do not have a surface expression as well as mapping the current fissures and their extent. These results can be used to increase standards in the building of infrastructure and in designating land use zonation.
DE: 8107 Continental neotectonics
DE: 1815 Erosion and sedimentation
DE: 0850 Geoscience education research
DE: 0925 Magnetic and electrical methods
DE: 0935 Seismic methods (3025)
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting