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Collection Description

The Department of Geological Sciences has a long-standing Senior Thesis research option for the B.S. Degree which involves a written thesis, and a public oral presentation done under the supervision of a faculty member. These independent research projects typically involve field work and laboratory analyses of samples, but can also include laboratory-based experimental projects, numerical modeling of geologic phenomena and literature reviews. Senior theses are kept in the permanent collection of the Malcolm A. Love Library on the SDSU campus.

Authors hold full copyright ownership of their original works. Please contact the repository manager at digital@sdsu.edu for any further questions.

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A GPR survey of the Danning Strand, Palm Springs, CA
Recent studies of the southern portion of the San Andreas Fault north of Palm Springs, CA call into question the slip rate and likelihood of the slip along the Banning Strand in the case of a seismic event. At Mission Creek, an arroyo crosses the Banning Strand and incises slightly into the surrounding older sediments. Outside of the modern channels, the land surface is covered with an aeolian drape of varying thickness (< 1 m to > 3 m). A GPR study of the Banning Strand was performed with the goal of obtaining a better understanding of its slip frequency. As part of the survey, 11 lines at varying orientations relative to the fault were collected using a 160 MHz antenna. Two lines, roughly perpendicular to the fault, were selected for further analysis and interpretation. Several discontinuities in the water table and buried braided channel deposits were found, while the overlying surface related to the modern arroyo was found to be continuous. These findings suggest that there are multiple faults in the survey area, but they have been obscured at the surface by an arroyo and aeolian deposits. This work highlights the need for more extensive testing in the area to obtain a better understanding of the Banning Strand and its interaction with nearby fault strands., San Diego State University
A Visual Basic solute transport program
In the past, most science and engineering computer models were done in DOS-based FORTRAN and BASIC languages. Solute transport models are no exception. The programs are generally not user friendly and may persuade users to avoid the programs. A Visual Basic, solute transport program was created to produce a friendlier environment to increase program use. The object­oriented program increases the ease in which the parameters are input and then output for analysis. The user may choose to peruse calculators or quickly experiment with various parameters. The basic mechanisms of the mass transport of solutes in groundwater are diffusion, advection, and mechanical dispersion. With analytical solutions available for solute transport, computer models are a convenient tool to illustrate the distribution of solute due to diffusion or advection-dispersion., San Diego State University
A comparison of the Toorongo weathering profile, south Australia, and weathered regolith at Santa Margarita Ecological Reserve: comparing weathering intensity factors derived from non-central principal component analysis
Compositional data derived from Cretaceous granodiorite at the Santa Margarita Ecological Reserve (SMER), southern California, are used to model a linear compositional weathering trend using non-­‐central principal component analysis. Unlike the Chemical Index of Alteration (CIA) typically used to determine weathering intensity, non-­‐central principal component analysis provides a translation invariant weathering intensity factor, thereby quantifying the degree of chemical weathering. This model yields a trend similar to that derived from modeling data from the classic Toorongo granodioritic weathering profile, south Australia. Both the SMER and Toorongo trends are directed away from the p(CN) apex and towards the p(A) apex in p(A) -­‐ p(CN) -­‐ p(K) ternary diagrams. Such trends are likely due to the removal of CaO and Na2O associated with the preferential weathering of plagioclase. Weathering intensity factors (t) of saprock at the SMER site range from 0.11-­‐ 0.91 with a mean of 0.32 ± 0.17. In contrast, these factors for the Toorongo site range from 0.03 -­‐ 3.94 with a mean of 1.29 ± 0.76. This difference in weathering intensity is likely a result of climatic variations between the two localities. Principal component 1 (PC1) accounts for 90.9% of the total variability of data along the adjusted weathering trend of the SMER site and 99.5% for the Toorongo site., San Diego State University
A gravity investigation of the western part of the La Jolla quadrangle, San Diego County, California
In the western part of the La Jolla 15-minute quadrangle, Upper Cretaceous and Cenozoic sediments lie upon the eroded surface of older basement rock. A pattern of gravity stations was established to determine the depth to and configuration of the top of the basement rocks. Contours of gravity anomalies were found to parallel axes of probable folds. In the Mission Bay area the anomalies indicate a depth of about 3,000 feet to basement, while beneath Soledad Mountain they reveal a more shallow depth of about 1,500 feet. North of Soledad Mountain the depth to basement increases, reaching 2,500 feet at a gravity low near Carmel Mountain. This trend reverses itself northeast of Del Mar., San Diego State University
A gravity study along University Avenue, San Diego, California
A gravity survey which measured minute changes in gravity at the land surface was conducted along University Avenue in San Diego, California. The gravity line consisted of 103 stations at one block intervals (~250 feet) covering a total length of approximately eight miles. This data set is at the northern extent of a gravity survey conducted for the San Diego County Water Authority. The purpose of the survey was to attempt to determine the thickness of the San Diego Formation which acts as an aquifer underlying downtown San Diego. Standard calculations were used in the reduction of the gravity data. Taken into accuont were elevation, latitude, and a surface rock density of 2.3 gm/cc which resulted in values of the Simple Bouguer anomaly. The data show a decrease in gravity (~7 mGal) from the easternmost station, at University Ave. and 69th St. to the base station, at Washington St. and Pacific Hwy. These results coincide with the changes in the depth to basement which crops out one mile east of the gravity line and drops to a depth of 3,000-4,000 feet on the west end of the survey. The data were then evaulated by constructing 2-d computer models which illustrated the subsurface geology based on the changes in gravity, elevation, and distance from the base station. The change of thickness in the San Diego formation, and older sedimentary rocks, is controlled by the various faults that intersect the field area. The La Nacion fault has an apparent throw of 1,000 feet, down-to-the-west. The Texas Street and Florida Canyon faults form a structural graben which has down-dropped approximately 500 feet. And, finally, the Rose Canyon Fault Zone (Old Town fault) resulted in 2,000-3,000 feet of throw, causing a juxtaposition of deeper basement on the west to more shallow basement on the east side of the fault. The San Diego Formation is thickest on the west side of the Rose Canyon Fault Zone, with a modeled thickness of 1,500-1,800 feet., San Diego State University
A gravity study of the southern portion of the Elsinore Fault Zone, Ocotillo, California
A gravity survey was performed through a portion of the southern Elsinore fault zone where the fault has been obscured by a thick accumulation of alluvium. The purpose of this sur­vey was to try to delineate the exact location of the Elsinore fault as it crosses old highway. 80, east of Ocotillo, California. One traverse consisting of 55 stations was performed, beginning 0.6 miles southwest of this town of Ocotillo, following old high­way 80 4.2 miles to the northeast. The resulting profile shows a marked increase of 17 milligals from west to east, suggesting a normal step-fault structure. The profile was not carried out far enough to the east to determine the exact amount of throw and the exact position of the fault, but a western-most limit and a minimum throw of 3300 feet can be concluded from the available data., San Diego State University
A gravity survey along the north side of the agua blanca fault, Baja California
The Aguo Blanca Fault is a major transverse fault of Baja California. Geothermal activity is associated with this fault in the Punta Banda area along the Pacific Coast. The gravity survey described in this paper covers the areal extent of the Valle de Maneadero and port of the Todos Santos Plain north of the northern extension of the fault. Two gravity lows occur in the vicinity of the fault. One low occurs ot the east end of the Volle de Maneadero along the Agua Blanca Fault, and the other occurs north of the fault in the Todos Santos Plain. In oil probability, the eastern low is due to lithologic changes in the basement rock. The gravity low in the Todos Santos Plain is most likely due to a thick sequence of sediments overlying the basement rock. A general east-west trending linearity of the gravity anomaly occurs in the locality of the fault. The exact location of the Agua Blanca Fault as deter­mined by interpretation of the gravity data coincides with the fault location specified by previous geophysical investigations. In addition, from the gravity data, the depth to basement rock is calculated to be approximately 6000 feet, assuming a density contrast of 0.3 gm/cm3. The thick sedimen­tary fill of the Todos Santos Plain may be acting as a heat resevoir., San Diego State University
A gravity survey of Rosecrans Boulevard and the Point Loma Peninsula, San Diego, California
A single gravity line was run along Rosecrans Boulevard for approximately 6 miles extending from Pacific Highway to approximately one mile north of the tip of the Poin Loma Peninsula. A 12 milligal anomaly on the northern, northeast trending pard of the traverse suggests a steeply northeastward sloping basement. The gravity anomaly supports previous data that the basement here has been downfaulted by a series of en echelon faults that represent an extension or branch of the Rose Canyon Fault Zone. Three additional minor faults are also indicated on the gravity profile on the Point Loma Peninsula. The location of two of these agrees with those previously mapped. The third gravity indicated fault is unmapped., San Diego State University
A gravity survey of the coyote creek fault in the ocotillo badlands, ocotillo wells, San Diego County, California
This thesis studies the relationships between the basement topology and the surface structures in the Ocotillo Badlands, in the western Salton Trough area of southern California. Gravity surveys were conducted during the summer of 1994 by Jerry Bell and Allen Porter under the direction of Dr. Monte Marshall. Three east-west lines between 4 and 7 miles long were surveyed, one immediately to the north of the badlands, one through the central badlands, and one just to the south. The topology of the gravity-inferred crystalline basement is an east-west trough in which the badlands lie over the northern side. This northern side slopes about 7° S from a depth of around 500 ft beneath the northern line along Hwy 78 to a depth over 2,500 ft beneath the southern line. The badlands are flanked by two en echelon strands of the right-lateral strike-slip Coyote Creek Branch of the San Jacinto Fault. These strands ruptured in the magnitude 6.8 Borrego Mt. earthquake on April 9, 1968. The obvious surface structure of the area is an east-west trending anticlinorium that makes up the core of the badlands. Computer modeling shows an east-west trending fault with 500-1,000 ft of throw and with the north side up. This fault is almost directly beneath the fold axis of the anticlinorium. One interpretation of this model is that this fault is responsible for the deformation in this area. Compression across the step causing thrust faulting is the probable mechanism for this uplift. This compressional uplift on the northern side is further expressed as a gravitational high and exposure of bedrock at Squaw Peak to the north of the study area. On the southern side of the thrust fault, the bedrock has been forced down creating a trough, which is reflected in the gravity., San Diego State University
A gravity survey of the la nacion fault zone of East San Diego, California
Gravity surveys can be an excellent technique for studying relief in the basement underlying sedimentary rocks. Using a LaCoste-Romberg gravity meter for the measurements and a computer modeling program for interpretation, an east-west survey was run along Main Street and Otay Valley Road in San Diego, CA to determine basement depth and to locate possible faults in the La Nacion Fault Zone. This survey line is important because there is an old oil well which bottoms in basement at the west end and the basement outcrops at the surface at the east end, thus providing depth control. Utilizing a computer modeling program it was possible to determine the average density contrast between the sediments and the basement. Originally suspected to be about -0.5 glee, use of the modeling program showed that the average density contrast 1s about -0.32 glee. The modeling also showed two large and a couple of minor steps along the survey line which are believed to be faults. One of the major steps in the basement model is close to the main trace of the La Nacion fault, but the other large step dosen't coincide with any mapped faults. The unnamed "fault" is located 5000 ft west , and the La Nacion strand is about 1000 ft east of Interstate 805. The throw on the western fault is about 1200 ft and it is about 1400 ft on the La Nacion strand. This survey demonstrates the effects of the different corrections involved in completing a gravity survey. Graphs show how each correction effects the theoretical gravity calculations during each step of the data reduction. The different models that were created using the computer program show the ambiguous nature of geophysical data interpretation., San Diego State University
A gravity survey to determine aquifer geometry in Warner Valley Groundwater Basin, San Diego County, California
A detailed description of subsurface geology is a fundamental factor to understanding the quantity of water-bearing material (aquifer) available in a groundwater basin. In order to define the subsurface aquifer geometries, a gravity survey was conducted in Warner Valley Groundwater Basin (Basin), located in North County San Diego. By assuming a simple two-layer model consisting of an aquifer and bedrock, the survey aimed to delineate bedrock topography by measuring the minute changes in Earth’s gravitational attraction, which are a direct result to changes in subsurface densities. Over 300 gravity measurements were taken during the course of several weeks using a LaCoste & Romberg Model D gravimeter. Three survey lines ranging up to 3.0 kilometers in length were conducted in the northeast region of the Basin, with each observation point spacing measured from 50 – 100 meters apart. Observation data was corrected using standard gravity survey reductions including instrument drift, Earth tidal variation, latitude variation (Normal Gravity), excessive mass (Bouguer correction), and changes in elevation (Free Air correction). The corrected values resulted in a relative Bouguer Anomaly that was modeled using GRAVMAG software to determine the geometry of the subsurface aquifer. The results of the survey showed relative gravity measurements differences of up to 1.6 mGals in some areas of the Basin. By using known bedrock depths obtained from well logs, depth controls were possible in select areas. A model of the subsurface assumed an average density contrast of -0.22 g/cc between aquifer and bedrock. Also observed in the survey were areas interpreted as faults, which were shown by abrupt changes in the trend of the Anomaly. The accuracy of the model showed that gravity surveying is a viable technique for determining aquifer geometry in a simple two-layered model. This information may be used to fill data gaps from using well logs alone, and may contribute to an overall better understanding of aquifer material available for groundwater resources., San Diego State University
A hydological overview of the San Luis Rey River Basin
The San Luis Rey River, located in the northern region of San Diego County, has its head waters at Lake Henshaw and ends in the city of Oceanside, just before reaching the Pacific Ocean. The area of study is the alluvial basin, up to one and one-half miles south east of the town of Bonsall. This hydrologic study concentrates on the time period from December 1965 through April 1966. The basin is comprised of Holocene deposited, unconsolidated alluvium surrounded by Pleistocene and Miocene consolidated sedimentary rocks and Cretaceous crystalline rocks. The climate is semiarid receiving only 13.45 inches of rain from July 1965 to June 1966. The San Luis Rey River flows continuously December through January in the eastern, or upstream portion of the basin and December through April in the western, or downstream portion of the basin. Water contours show groundwater movement southwesterly in the basin except just east of San Luis Rey Mission were there is a cone of depression. Water table elevations range from 138.5 feet in the east to 9.8 feet in the west and as low as 2.5 feet in the cone of depression. Hydraulic gradients ranged from 0.004 to 0.010. Hydraulic conductivities were not estimated for the alluvium in this basin, but adjacent basins had hydraulic conductivities ranging from 43.2 feet per day to 668 feet per day. Assuming a hydraulic conductivity of 200 feet per day and a porosity of 0.30, pore water velocities will range from 2.67 to 6.67 feet per day. Overall the water table in the basin is higher in December 1965 through April 1966 than shown in a previous report for the year 1957, which had a cone of depression as low as 50 feet below mean sea level., San Diego State University