Physical Sciences and Mathematics Commons^™

Geophysical Constraints On The Hueco And Mesilla Bolsons: Structure And Geometry, Victor Manuel Avila

Open Access Theses & Dissertations

The Hueco and Mesilla Bolsons are part of the intramountain basins of the Rio Grande Rift system. These bolsons are the primary source of groundwater for the El Paso-Ciudad Juarez metropolitan area and contain faults that show evidence of repeated earthquakes during the Quaternary. The region is also associated with has low-level (M<4) seismicity. The collection and analysis of precision gravity data, coupled with information from water wells, multichannel analysis of surface waves (MASW) studies and previously published seismic reflection lines, have been used to examine the structure and faulting within these bolson. This study reveals that the Hueco and Mesilla Bolsons are very different structurally. The southern Mesilla Bolson contains about 500 m of sediment. Faults are difficult to trace and have less than 50-100 m of displacement across them. The southernmost bolson contains numerous Tertiary intrusions and the thickness of Cretaceous bedrock appears to decrease from south to north, possibly delineating the edge of Laramide age deformation within the bolson. The northern Hueco Bolson contains 1800 to 2500 m of basin fill. Displacement along the East Franklin Mountains fault (EFMF), a fault with evidence for repeated earthquakes within the past 64,000 years, is about 1500 m, and displacement on intrabasin faults is 200-300 m. Several intrabasin faults appear to control the saline to freshwater contact within the bolson. The EFMF may extend over 30 km south of the end of its mapped trace at the end of the Franklin Mountains and a number of intrabasin faults also extend south into the urbanized regions of the study area. The EFMF and other basin structures appear to be offset or disrupted at the speculated edge of Laramide deformation that lies beneath the bolson. Horizontal Gradient Methods (HGM) were applied to the gravity data and were successful for tracing faults and older Laramide features within the Hueco Bolson beneath the urbanized regions of the cities. HGM were not as successful at tracing faults within the Mesilla Bolson, however they were helpful for tracing the subsurface extent of igneous intrusions including the Mt. Cristo Rey, River, Three Sisters, and the Westerner outcrops. Some of these features appear linked at depth by a series of dikes and faults. MASW data were used to determine the average shear wave velocity in the upper 30m (Vs 30) at ~70 sites within the Hueco Bolson. These observations were combined with similar data collected previously in Juarez to produce regional velocity and site classification maps. The results show low velocities are found close to the river within fluvial deposits with higher velocities close to the Franklin Mountains where bedrock is close to the surface and higher velocities in upland regions of northeast El Paso were soils appear to be more highly cemented. These data will be used in conjunction with information on bolson geometries to model the expected effects of strong ground motion from earthquakes in the El Paso-Ciudad Juarez region.

Geophysical Model Of The Cu-Mo Porphyry Ore Deposit At Copper Flat Mine, Hillsboro, Sierra County, New Mexico, Adrian Emmanuel Gutierrez

Open Access Theses & Dissertations

A 3D gravity model of the Copper Flat Mine was performed as part of the exploration of new resources in at the mine. The project is located in the Las Animas Mining District in Sierra County, New Mexico. The mine has been producing ore since 1877 and is currently owned by the New Mexico Copper Corporation, which plans o bringing the closed copper mine back into production with innovation and a sustainable approach to mining development. The Project is located on the Eastern side of the Arizona-Sonora-New Mexico porphyry copper Belt of Cretaceous age. Copper Flat is predominantly a Cretaceous …

Geophysical Investigation Of Hot Springs In The Vicinity Of Shoshone, California, Felix Dziedzorm Ziwu

Open Access Theses & Dissertations

Magnetic and gravity surveys were conducted in the vicinity of Shoshone, California to test a hypothesis from investigating hotsprings within Tecopa and Saratoga which states that deep faults must intersect with a specific orientation relative to the regional stress field in order to create hot springs along the Amargosa River.

Three isolated basalt flows with different gravity and magnetic properties were identified near the Shoshone hot spring. Two of the flows have very low magnetic anomalies and the remaining one has a high magnetic anomaly. The high magnetic anomaly basalt flow also has a significantly higher Bouguer anomaly than the …

An Investigation Of The Seismic Hazards Of The El Paso-Juarez Region: The Nature And Extent Of The Southern East Franklin Mountains Fault Zone, Victor Manuel Avila

Open Access Theses & Dissertations

ABSTRACT

The El Paso-Ciudad Juarez Region is situated at the southern end of the active Rio Grande Rift within the Mesilla and Hueco basins. The Hueco basin is separated from the eastern Franklin Mountains by a prominent fault, the Eastern Boundary Fault. Studies of this fault have revealed fault scarps that displace Quaternary deposits (Keaton et al., 1995; Raney and Collins, 1990; Lovejoy, 1976). This fault is cataloged as an active fault in the National Seismic Hazard Map with an estimated slip rate of 0.1 mm/yr. A fault with similar characteristics as the Eastern Boundary Fault extends further to the …

Characterizing The Deformation Of Reservoirs Using Interferometry, Gravity, And Seismic Analyses, Cara Schiek

Open Access Theses & Dissertations

In this Dissertation, I characterize how reservoirs deform using surface and subsurface techniques. The surface technique I employ is radar interferometry, also known as InSAR (Interferometric Synthetic Aperture Radar). The subsurface analyses I explore include gravity modeling and seismic techniques consisting of determining earthquake locations from a small-temporary seismic network of six seismometers. These techniques were used in two different projects to determine how reservoirs deform in the subsurface and how this deformation relates to its remotely sensed surface deformation.

The first project uses InSAR to determine land subsidence in the Mimbres basin near Deming, NM. The land subsidence measurements …