Geophysics and Seismology Commons^™

Using Gravitational And Magnetic Data To Understand Interactions Between Active Seismic Zones Within The Interior Of Alaska, Shane M. Schinagel^, Diane I. Doser*

COURI Symposium Abstracts, Spring 2011

Differences in rock density, along with changes in the orientation of the magnetic field, provide vital information about the tectonic environment within the interior of Alaska in a region where outcrop exposure is poor due to recent glacial and fluvial activity.  Analysis of the gravity and magnetic field can help identify relationships between recent (1989-2008) and historic (pre-1971) seismicity and suspected strike-slip, reverse, and thrust faults within the region, as differences in density and magnetic properties of materials may be observed across fault zones.  Our overall objective is to better understand the complicated interactions between the strike-slip Denali fault system …

Seismic Study Of Carlsbad, Nm, Steven M. Espinosa^, Aaron A. Velasco*

COURI Symposium Abstracts, Spring 2011

Since January 1, 2000, there have been numerous earthquakes recorded in the vicinity of Carlsbad, NM.  Importantly, these shallow (10km) earthquakes with magnitudes < 4.3, do not have a fault or system of faults directly mapped to explain these events.  We will be relocating the largest and most recent earthquake, which occurred 25km west of Carlsbad, NM of magnitude 4.1 on March 28, 2010. Data recorded by seismic stations from the USArray, a large National Science Foundation project, and our local Kidd Observatory will be used for this analysis. The use of Standing Order of Data (SOD) allows us access seismograms, and the Seismic Analysis Code (SAC) helps in the analysis of the seismic data.   We will correlate the hypocenters of aftershocks to the main event hypocenter, allowing us to identify the fault plane.  Once a fault plane has been identified, we will begin work on relocating a second event, thereby identifying the responsible faults.  We believe that faulting in this area is related to the Rio Grande Rift extension and can be used as evidence for an active rift.

Possible Connections Between A Great Earthquake And An Earthquake Sequence: Samoa Islands (8.1) And Vanuatu Islands, Marissa Cameron^, Aaron A. Velasco*

COURI Symposium Abstracts, Spring 2011

Dynamic triggering describes the possibility that certain earthquakes cause, or ‘trigger’ new earthquakes at great distances. Static triggering is common and is known to cause aftershocks very near to the site, generally within two lengths of the ruptured fault.  Dynamically triggered events can occur at distances beyond two fault lengths, however the mechanism for how this can occur remains unknown. By examining seismic data collected from possible dynamically triggered events, we may gain a better understanding of the mechanisms at work. On September 29, 2009, an earthquake of magnitude 8.1 took place along a 175 km fault rupture in Samoa, …

On Constrained Optimization Schemes For Joint Inversion Of Geophysical Datasets, Uram Anibal Sosa Aguirre

Open Access Theses & Dissertations

In the area of geological sciences, there exist several experimental techniques used to advance in the understanding of the Earth. We implement a joint inversion least-squares (LSQ) algorithm to characterize one dimensional Earth's structure by using seismic shear wave velocities as a model parameter. We use two geophysical datasets sensitive to shear velocities, namely Receiver Function and Surface Wave dispersion velocity observations, with a choice of an optimization method: Truncated Singular Value Decomposition (TSVD) or Primal-Dual Interior-Point (PDIP). The TSVD and the PDIP methods solve a regularized unconstrained and a constrained minimization problem, respectively. Both techniques include bounds into the …

Gpu Based Parallel Smoothing Of Seismic Tomography Models, Ivan Gris

Open Access Theses & Dissertations

Three-dimensional models of the velocity structure of the Earth's crust are an important and relevant factor for several types of analyses across disciplines. Crustal velocity models are also commonly used to analyze and search for different materials of interest or to determine and differentiate many aspects of life on Earth during different eras.

Seismic tomography techniques, both in two and three dimensions, perform image reconstruction of the crust of the Earth. Seismic tomography algorithms can calculate crustal velocity structure through inversion of traveltimes of seismic waves produced by natural events, such as earthquakes, or controlled source experiments, such as explosions. …

Evidence Of Ancient Rifts Beneath Texas, Keisuke Irie

Open Access Theses & Dissertations

Continental rifts are defined as geological features where Earth's lithosphere is pulled away by surface expansion of the Earth. Their physiographic features include linear rift valleys associated with active volcanism. Many rifts fail to split a continent and ancient rifts that failed to split can be found by using seismic waves to image these ancient structures. Using seismic data collected by EarthScope USArray stations in Texas, teleseismic receiver functions was calculated and utilized surface wave dispersion curves to simultaneously invert for the 2D velocity structure beneath each seismic station. EarthScope is a scientific program funded by NSF that provides geophysical …

Evaluating Suspended Dust Particulate Matter From Anthropogenically - Altered Lands, Roberto Velarde

Open Access Theses & Dissertations

Substantial dust loads are transported from drylands including the Saharan, Asian, and Chihuahuan Desert deposits by localized to planetary-scale processes to nearby and distal sites. These dusts may carry harmful constituents. To evaluate dust movement patterns and characteristics relative to carried constituents, three studies are presented comprising (A) Localized displacement of uranium and progeny radionuclides from high-grade uranium ore storage piles at Peña Blanca, Chihuahua, Mexico; (B) Long-distance transport of plutonium via Saharan and Asian aeolian pathways; and (C) Dust movement patterns in military maneuvering and non-maneuvering areas at White Sands Missile Range (WSMR), New Mexico. Study (A) evaluated surface …

Joint Geophysical Data Analysis For Geothermal Energy Exploration, Antony Munika Wamalwa

Open Access Theses & Dissertations

Geophysical data modelling often yields non-unique results and hence the interpretation of the resulting models in terms of underlying geological units and structures is not a straightforward problem. However, if multiple datasets are available for a region of study, an integrated interpretation of models for each of the geophysical data may results to a more realistic geological description. This study not only demonstrates the strength of resistivity analysis for geothermal fields but also the gains from interpreting resistivity data together with other geophysical data such as gravity and seismic data. Various geothermal fields have been examined in this study which …

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 …

Software Development For A Three-Dimensional Gravity Inversion And Application To Study Of The Border Ranges Fault System, South-Central Alaska, Rolando Cardenas

Open Access Theses & Dissertations

The Border Ranges Fault System (BRFS) bounds the Cook Inlet and Susitna Basins, an important petroleum province within south-central Alaska. A primary goal in the research is to test several plausible models of structure along the Border Ranges Fault System using a novel three-dimensional inversion utilizing gravity and magnetic data, constrained with other geophysical, borehole and surface geological information. This research involves the development of inversion modeling software using a Borland C++ compiler as part of the Rapid Application Development (RAD) Studio. The novel inversion approach directly models known geology, and "a priori" uncertainties on the geologic model to allow …

The East Jhomolari Fault System And The Timing Of East-West Extension In Northwest Bhutan, John Matthew Cannon

Open Access Theses & Dissertations

This investigation documents a little known, regionally significant, high angle, southeast dipping, system of normal faults in northwest Bhutan, the East Jhomolari Fault System (EJFS). The EJFS trends parallel to the Yadong Gulu rift (YG) and can be traced from Mt. Jhomolari to the northern border with Tibet. This fault zone has been demonstrably active since the last glacial maximum and there is geomorphic evidence of Holocene activity on some fault segments. The structurally lowest EJFS fault, the Lingshi fault appears on some published maps, but the full geographic extent, displacement, onset of faulting, and most recent activity have not …

An Integrated Geological And Geophysical Study Of The Fresh And Brackish Water Boundary In The Hueco Bolson, West Texas, Sandy Stephanie Marrufo

Open Access Theses & Dissertations

The Hueco Bolson in West Texas is located in the Rio Grande rift basin and provides water to El Paso County, Texas and Juarez, Mexico. El Paso Water Utilities (EPWU) drilled many wells up to 1000 ft (305) m into this aquifer, which provide 40% of El Paso's water supply. Stratigraphy and sedimentation in active extensional basins have received little study because they are usually buried and this research helped document these processes. The study area within the West Texas region of the Hueco Bolson Aquifer (HBA) lies within a transition zone between the fresh and brackish water sections of …

Seismological Studies In South-Central Alaska And Northern Mexico, Oscar Mario Romero De La Cruz

Open Access Theses & Dissertations

The work in this study is focused on two different areas, south-central Alaska and northern Mexico. In the first study area, I calculated dynamic stress drops for moderate sized earthquakes and performed receiver function analyses. The goal of the stress drop studies was to determine if events occurring within the more strongly coupled portion of the subducting slab have higher stress drops. My results shows that higher stress drops correspond to the locked and strongly coupled region in Prince William Sound, and lower stress drops are associated with the Cook Inlet region, a zone of relaxation of the plate interface. …

Bagc.M: Three Dimensional Gravity Modeling Software With An Application In Death Valley, Ca, Brian Eugene Eslick

Open Access Theses & Dissertations

Basin Anomaly Gravity Calculator (BAGC.m) is a 3D interactive gravity modeling package designed to create, edit, and calculate the gravitational attraction of basin models entirely within the MATLABTM environment. Gravity anomalies are calculated using the Rectangular Prism Method (Bott, 1960; Kane, 1962; and Plouff, 1966) which subdivides earth models into regularly spaced rectangular prisms. This approach requires large 3D matrices to store most realistic earth models. The process of model editing is simplified by storing basins as 2D gridded files which define the depth to the boundary between basement rock and sedimentary fill for each model cell. In order to …

Studies Of Earthquakes Stress Drops, Seismic Scattering, And Dynamic Triggering In North America, Christian Rene Escudero Ayala

Open Access Theses & Dissertations

I use the Relative Source Time Function (RSTF) method to determine the source properties of earthquakes within southeastern Alaska-northwestern Canada in a first part of the project, and earthquakes within the Denali fault in a second part. I deconvolve a small event P-arrival signal from a larger event by the following method: select arrivals with a tapered cosine window, fast fourier transform to obtain the spectrum, apply water level deconvolution technique, and bandpass filter before inverse transforming the result to obtain the RSTF. I compare the source processes of earthquakes within the area to determine stress drop differences to determine …

Seismic Investigation Of The Southern Rio Grande Rift, Lennox Emmanuel Thompson

Open Access Theses & Dissertations

Competing models exist to explain what caused the Earth's crust to spread apart 29 million years ago to create a region known today as the Rio Grande Rift (RGR). The RGR extends from central Colorado through New Mexico to northern Mexico, near El Paso. The RGR has different geologic features that distinguish it from most other valleys (e.g., the RGR was not cut by a river nor does a river branch upstream). A growing body of evidence shows that geologic activity still occurs in the RGR, with a continuation of faulting, seismicity and widening at a small rate of about …

Insight Into The Physics Of Rupture: Dynamic Triggering Seismicity, Hector Gonzalez-Huizar

Open Access Theses & Dissertations

Seismic waves can trigger earthquakes and tremor at large distances from the causable event. Dynamic triggering occurs when the surface waves from large earthquakes change the stresses conditions on previously overstressed faults, promoting failure. To understand the causative stresses and environments behind dynamic triggering, we model the change in the stress field that the passing of Rayleigh and Love waves cause on a fault plane of arbitrary orientation relative to the direction of propagation of the waves, and apply a Coulomb failure criterion to calculate the potential of these stress changes to trigger seismicity. We apply our model to three …

Resistivity And Conductivity Studies Of The Rattlesnake Springs, New Mexico Watershed, Claudia Santiago

Open Access Theses & Dissertations

Rattlesnake Springs are a high-discharge artesian springs situated in the upper Black River Valley in southwestern Eddy Country, New Mexico. The aquifer that supplies the Rat- tlesnake Springs has been the main water source for domestic use by visitors of Carlsbad Caverns National Park and residents of neighboring ranches since the 1930s. Several ge- ological studies relying on surface geology and limited water wells had previously been conducted in the area to examine the trend of ground water flow. In this study I used con- ductivity and resistivity geophysical techniques to identify possible locations of fractures in the subsurface of …

Analysis Of Shallow Seismicity And Stress Fields In Southeastern Alaska, Hugo Rodriguez

Open Access Theses & Dissertations

Southeastern Alaska is dominated by strike-slip motion along the Queen Charlotte-southern Fairweather fault system (QCFS) in the south and transitions to oblique convergent motion partitioned between strike-slip motion along the Denali and northern Fairweather fault systems and thrusting along faults of the St. Elias region. Geologic complications are further increased by the subduction of the Yakutat microplate beneath North America and glacial processes. By studying regional background seismicity we intend to better determine the current state of stress of southeastern Alaska from the Dixon Entrance to Yakutat Bay. Phase data was gathered for over 4000 earthquakes of depths <20 km and magnitude <5 that occurred from 1973-2005 from Alaskan and Canadian databases. We relocated these earthquakes using the Double-Difference joint hypocenter method. Two areas of interest were identified with high concentrations of seismicity after relocation calculations for the entire southeast Alaska region; Glacier Bay through Yakutat (GBY) and the area surrounding Mt. Ogden (MOG). Earthquake locations in GBY are diffuse with some isolated clusters. The MOG subregion is dominated by a large northeast to southwest trending cluster that trends along the Speel River. We used these relocations and first motion data to estimate the stress fields for earthquake clusters that formed. Only a few of the calculated stress tensors were successful in representing the region's overall tectonic signature. We combined the calculated stress information with GPS, magnetic and gravity data in order determine how plate motion is partitioned in this region and to identify other potentially active faults.

Two-Dimensional Gravity Modeling Of The Rattlesnake Springs Watershed, Carlsbad Caverns National Park, New Mexico, Nikolay D. Boykov

Open Access Theses & Dissertations

A series of non-invasive geophysical investigations at the Rattlesnake Springs part of Carlsbad Caverns National Park, New Mexico, were performed in an effort to better delineate the watershed of the springs. The goal of this project is to determine possible locations of fractures and faults that may control the distribution of groundwater that feeds Rattlesnake Springs. Once the water flow paths are identified, the park will be able to better protect Rattlesnake Springs from environmental hazards, such as oil and gas drilling, as well as from upstream water development. As part of this effort I conducted a precision gravity survey …

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 …

Integrated Geophysical Data Processing And Interpretation Of Crustal Structure In Ethiopia With Emphasis On The Ogaden Basin And Adjacent Areas, Ketsela Tadesse

Open Access Theses & Dissertations

The combined effects of magmatism and stretching due to asthenosphere upwelling modifies the crustal structure of the Earth as seen in the Ethiopian rift and adjacent areas. The Ethiopian rift provides unique opportunities to understand the nature of rifted crust and the intensity of its modification by magmatic processes. I used geological and geophysical data to conduct an integrated study in and around the Ethiopian rift including the northern Kenyan rift and the northern part of the Kenyan dome. New gravity, controlled source seismic, and teleseismic data from the EAGLE (Ethiopia-Afar Geoscientific Lithospheric Experiment) were used as additional constraints in …