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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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Gravity-inferred structure of the Rose Canyon fault zone from the San Diego River to La Jolla, California
The objective of this study is to determine the basement morhology along the Rose Canyon fault zone from the San Diego River to La Jolla. Several gravity surveys by previous S.D.S.U. students were compiled into a complete Bouguer anomaly contour map. Three, two to four mile long profiles were constructed perpendicular to the Rose Canyon Fault Zone. The data were modeled using a two­dimensional computer modeling program. We assumed values of 2.1 and 2.3 glee for the sedimentary rocks and 2.7 glee for the basement rock. These simple, two­dimensional models show several significant geologic features related to faulting in the Mission Bay and La Jolla area. The San Diego River models show two interesting features: first, a basement­low west of the Rose Canyon Fault Zone, suggesting a continuation of the nested graben under San Diego Bay northwestward into Mission Bay. Second, up-to-the­west offset on the Pt. Loma fault. The Mission Bay models imply a northward continuation of the Point Loma Fault where it had been previously unmapped. The most interesting feature of the Mission Bay models is the gravity minimum west of the Rose Canyon Fault Zone. This was modeled as a graben having over 3000 feet of throw, and a basement depth of 5000 feet. Most of the off set on the east side of the graben appears to be on the westernmost strand of the Rose Canyon fault zone, i.e., the Mission Bay fault. Both the Mission Bay and San Diego River models suggest that the nested graben under San Diego Bay extends northwestward into Mission Bay. This depression is probably the result of transtension produced by the fact that the strike of the Rose Canyon fault zone in this area, N15W, is more northerly than the ideal N45W direction for transforms on the Pacific Plate-North American Plate boundary. The La Jolla model shows the change in the nature of the Rose Canyon fault zone from a zone of tension in Mission Bay to a zone of compression producing uplift on reverse faults dipping steeply to the southwest under Mt. Soledad. The folding and reverse faulting of Mt. Soledad is probably the result of transpression, caused by the change in the strike of the Rose Canyon fault zone to N60W, resulting in a restraining bend in the Rose Canyon fault zone., San Diego State University
Ground motion directivity effects derived from 3D rough-fault earthquake simulations
Deterministic ground motion simulations in 3D crustal models are now computationally feasible up to frequencies needed by structural engineers for building design (0-10Hz). At frequencies above ~1Hz, seismic data indicate that simulations need to include frequency-dependent anelastic attenuation (Q(f)). Moreover, high-frequency simulations require small-scale complexity in both source description and crustal structure to generate realistic ground motions, which can be generated by statistical approaches. While such statistical (fractal) distributions of the small-scale variations on the fault and in the crust can be constrained from data, it is important to validate and calibrate the resulting high-frequency synthetic ground motions to observed seismic records. Here, we carry out one such validation test for ground motion directivity effects, an important feature that can significantly amplify and de-amplify the ground motions from earthquakes. The directivity effects are estimated for 0-1 0Hz ground motion simulations for a single M7.2 strike-slip earthquake scenario. We use various realizations of the scenario that include a geometrically rough-fault source (Shi and Day, 2013; Withers et al., 2013), a layered crustal model with and without small-scale heterogeneities included, and Q(f). Ratios of rotd100 and rotd50 estimates are used as a measure of directivity effects for the simulations, as suggested by the empirical study by Shahi and Baker (2012). Our results indicate that the small-scale heterogeneities in the media are necessary to reproduce the empirical trend in rotd 100/rotd50 ratios, while simulations with small-­scale geometrical complexity on the fault by itself do not reproduce the decrease in the ratios for periods shorter than ~ 1 s. The ratios generally increase for stations toward the fault (distances of 0-10 km, measured along 'race tracks'), in agreement with empirical data. Q(f) is found to have insignificant effect on the directivity estimates. As expected, the largest ratios are found toward the ends of the fault. However, another region of increased ratios is found perpendicular to the fault extending away from the epicentral area. Further analysis with additional source descriptions is needed to assess how general this effect is. Finally, our results may be used to generate an improved parameterized model for including directivity effects into ground motion estimates, such as Ground Motion Prediction Equations., San Diego State University
Groundwater and surface water interactions within Camp Pendelton, CA
A survey of the groundwater and surface-water interactions within drainages of Camp Pendleton was conducted. Stream flow was measured at several locations within the Santa Margarita, Las Flores and San Onofre Rivers. Stream flow, precipitation and groundwater levels from other sources were collected for the same time period. Stream flow and groundwater levels rose in response to precipitation events. Stream discharge increased by 2.7 - 38.7cfs and 0.4 - 2.4cfs for the Santa Margarita and Las Flores gaging locations, respectively. Groundwater levels rose 0.01 - 0.4ft and 0.01 - 0.1ft for the Santa Margarita and Las Flores, respectively. Differences in response could be explained by distance from river or size of drainage basin. Base flow or the stream flow contributed by groundwater was measured during fall 1998. Base flow ranged from 13.66 - 28.12cfs, 0.67 - 1.24cfs, and 0.7 - 1.02cfs for the Santa Margarita, Las Flores and San Onofre drainages respectively. Calculation of net loss or gain of flow along a stream stretch indicated regions of gaining and losing streams. A possible relationship of regions of gaining streams within areas of narrowing stream channels was observed., San Diego State University
Groundwater contour and monitoring well investigation of the North, South, and West Miramar landfills
Groundwater monitoring wells composing the North, South, and West Miramar Landfills groundwater monitoring program in San Diego, California are developed in erosional remnants of a Pleistocene-aged terraced mesa incised by San Clemente Canyon and its tributary canyons. The groundwater gradient reported for the vicinity comprising the North, South, and West Miramar Landfills is westward north of San Clemente Canyon and to the south, south of San Clemente Canyon (Ninyo and Moore, 1994). This disagreement between the two gradients separated by San Clemente Canyon could be caused by invalid water levels due to improper monitoring well development, well screen intervals completed in different formations, or to different depths between wells. Most wells were found to be completed to the same elevation and in the same formation (Friars). Water level measurements were taken from eight wells completed to the same elevation and screened in the Friars Formation. A slug test was then performed on the tested wells to determine if they are reflective of aquifer characteristics. Hydraulic conductivity values for the Friars Formation were determined and compared to existing data. Using water level measurements taken from these wells a site groundwater gradient contour map was constructed. The slug tests were successful in all but groundwater monitoring wells MW-1 and SMMW-2. Monitoring well MW-1 was found to be silted. The remainder of monitoring wells tested recovered to approximate static water height in 4 hrs or less. Hydraulic conductivity values obtained from the remainder of the tested wells for the Friars Formation ranged from 1.03 x 10-4 to 4.7 x 10-5 ft/min. The hydraulic gradient in the site vicinity is to the south. Calculated values for the hydraulic gradient ranged from 1.26 x 10-2 to 6.61 x 10-4 feet/foot. There appears to be mounded water in the vicinity of monitoring well MW-3 that could be influencing the ground water gradient in the site area. Settling ponds located on the Sim J. Harris property to the east of MW-3 may be causing the mounding by recharging the groundwater in the north east vicinity of the study site., San Diego State University
Groundwater monitoring optimization plan for the Chatham Brothers Barrel Yard, Escondido, California
The Chatham Brothers Barrel Yard (Site) is located in Escondido, California. The Site accepted chlorinated solvents, such as Tetrachloroethylene (PCE) and Trichloroethylene (TCE) for reclamation from 1941 to 1981. In 1982 the Department of Hazardous Substances (DHS), the Regional Water Quality Control Board (RQCB), and the Environmental Protection Agency (EPA) began investigating the Site for groundwater contamination. Groundwater monitoring data has been collected irregularly since 1994 in 69 monitoring wells and 24 water supply wells. This study focuses on a statistical approach to determine an appropriate monitoring frequency, for the offsite monitoring well network. The historical groundwater monitoring data was evaluated by using the Monitoring and Remediation Optimization System (MAROS) program. The MAROS program utilizes the Mann-Kendall statistical analysis (a nonparametric measure) and Linear Regression (Rate of Change) to determine a monitoring frequency for each well. Both the Mann-Kendal and linear Regression trend methods gave similar trend estimates for the offsite monitoring wells and water supply wells analyzed. Stable to decreasing trends were observed in offsite monitoring wells near the source area, while increasing trends were observed in some of the monitoring wells and water supply wells located near the center axis and tail end of the PCE and TCE plume. Based on the MAROS analysis, 4 monitoring wells and 2 water supply wells were recommended for a quarterly (Q) monitoring frequency. These wells all received an Increasing (I) trend from the Mann-Kendall analysis and the Linear Regression analysis except for 2 wells that received No Trend (NT) for both. The confidence in this trend was 100% or near 100%, and had a positive and large magnitude Mann-Kendall S statistics. MAROS determined that the sampling frequency for the remaining monitoring wells and water supply wells could be sampled on a less than quarterly frequency without loss of confidence in plume definition. This was based on stable to decreasing trends and a low rate of change along with concentrations at or below the cleanup goal. After further data collection after the next two years, the MAROS analysis can be reevaluated to determine if a reduction in monitoring intensity is appropriate. Additionally, further evaluations and investigations must be performed to determine if the increase and/or reduction of groundwater monitoring is appropriate for the offsite monitoring program., San Diego State University
Growth dynamics in the intertidal barnacle Megabalanus: Assessment of a subseasonal paleoceanographic archive
The barnacle Megabalanus sp. is indigenous to coastal Baja California, but migrated north to San Diego during to an El Nino event in the early 1980s (Newman and McConnaughey 1987). This barnacle genus dates back to the Miocene (Doyle et al. 2007), and therefore potentially is useful for paleoenvironmental reconstruction. Megabalanus’ shell structure can potentially indicate exposure and submergence intervals by the production of growth patterns in its calcium-carbonate shell. This barnacle was used to compare tidal cycles with its exposure history in the littoral zone off the coast of San Diego. After four spring tide events, outplant samples were collected from the number 17 piling of the Scripps pier, along with a temperature data logger, and thin sectioned using an Isomet Precision saw. A calcein dye was incorporated to bond with the calcium-carbonate shell before the outplant to mark the initial growth of the experiment. A fluorescence scope showed multiple fluorescence lines (excitation/emission configuration of 495/515nm), not a singular line, indicating discrepancies in dye bonding or shell flourescence. Transmitted light microscopy through the anterior carinal shell section of the specimens revealed darker U-shaped growth lines taken to represent subaerial exposure intervals. For the outplant interval, the relative distribution of growth lines within the shells show a general correspondence with a predicted relative distribution of exposure-related growth lines, though absolute growth rates vary among specimens. These preliminary results, though far from conclusive, call for additional analyses assisted by a greater ability to mark exact outplant dates within the shell. Such studies may provide a framework for geochemical microsampling and paleoenvironmental reconstruction., San Diego State University
Heavy metal contaminants at the famosa slough
Thirteen samples were collected from the main pond of Famosa Slough, San Diego, CA and analyzed for the concentrations of the metals Cu, Ag, Zn, Cd and Pb. Loss on ignition and the percent detrital minerals were analyzed to indicate the metal concentrations independent of the detrital fraction. Loss on ignition was higher on the south and east sides indicating an accumulation of organics in the back of the slough. Cu appeared to be a general pollutant of the pond, while Ag was only detectable on the east side of the slough. These metals could enter the slough via the numerous drains, storm pipes and surface streets that discharge into the slough. Ag most likely enters via a fresh water stream at the south end of the main pond. Zn had generally high concentrations with the samples taken at the inlet to the slough from its channel containing the highest concentrations. This inlet is the main source of water into the slough and serves as a pathway for tidal ebb and flow from the San Diego River. Pb was the most concentrated contaminant in the slough. The highest value of 3300 ppm (leachable fraction only) also occurred at the culvert leading into the main pond. This indicates that leaded gasoline from automobile traffic on West Point Loma Blvd., which crosses over the slough where the channel and pond meet, and Interstate 8, which passes over the channel where it meets the San Diego river, are the most likely sources of lead to the Famosa Slough., San Diego State University
High-resolution drone imaging of Adobe Falls Region around SDSU: Use of geologic imaging for assisting decision makers trying to understand complex issues through time involving geology, crime, and critical infrastructure protection
Adobe Falls is a place name for the falls north of Interstate 8 on land owned by Caltrans, San Diego State University (SDSU), and the City of San Diego on adjoining sections of Alvarado Creek. The ownership is convoluted so names like the “Upper Falls” for the Caltrans property and “Lower Falls” for the SDSU property have been coined to clarify, in some part, the relative location of each territory. Additional owners such as the City of San Diego, individual homeowners, and the Smoke Tree Condominium Association make collaboration and cooperation extremely difficult if people don't understand the components and history of development. On June 12, 2016, a 74-year old woman was killed in the neighborhood adjacent to the SDSU land and her daughter sexually assaulted, further launching a major conflict between SDSU and the Del Cerro neighborhood. How decisions can best be made to help solve this controversy using geology as a tool was one of the goals of this project. The Santiago Peak Volcanics that make up most of the Del Cerro hill near SDSU is the solid rock on which parts of SDSU are built with overlying Friars Formation and Stadium Conglomerate. When Cal-Trans built Interstate 8, much of the current architecture of storm water drainage, sewage drainage, and roads was constructed that equates to the modern Adobe Falls. Construction berms of boulders of Santiago Peak were used to alter the original course of Alvarado Creek on both the north side (Alvarado Road) and the north side of the freeway, with the water passing under the freeway in a large Caltrans tunnel, as it also crosses under College Avenue. The main sewage line was place in the Creek area and a cement “sidewalk” placed over it. Infrastructure like sewage and roads were built in tandem with the Santiago Peak boulders used as the building materials for the storm water conduit forming the north side of campus, Interstate 8, and aspects of the Del Cerro neighborhood. Additional challenges of a large landslide related to the Friars Formation near the Smoke Tree Condominiums and Adobe Falls Road cul-de-sac as well as smaller slides that destroyed or damaged homes several decades ago are also part of the subtle geologic setting. Also present across the SDSU property is a highpressure gas line that also crosses part of Del Cerro and connects to the SDSU power generating system and is a potential risk if its location, including beneath Alvarado Creek and into SDSU. High-resolution drone imagery and video help provide a common situation awareness to decision makers without visiting the Falls, as well as recording the progress of the fences, further graffiti, and change of invasive species along Alvarado Creek. These efforts to gather, understand, and share the imagery and geologic insight helps solve the controversy between SDSU and the Del Cerro neighborhood. It also helps demonstrate how involvement with the community and sharing geology and tools for discovery can wonderfully benefit the school and neighborhood. It is a “Geologic Ambassadorship” to provide imagery and suggested solutions to school, city, Caltrans, and community leaders. Real and high-resolution information are far better than simple maps or acrimony around historic perceptions of unreality, or words expressing vague and jargon descriptions of the geology and geotechnical setting as would generally be used to satisfy compliance requirements like Environmental Impact Reports., San Diego State University
Hydrogeological investigation near the Sweetwater River using dc resistivity
A hydrogeological investigation was done next to the Sweetwater River in Bonita, San Diego County using a dc resistivity method to determine subsurface geology. Five test lines were conducted with a standard Schlumberger array. The contact between the unsaturated zone above the water table and the saturated zone was the only feature detected. None of the layers detected by a previous down-hole resistivity survey in the wells were resolved., San Diego State University
Impacts of geology on major ions in springs located in Cuyamaca Rancho State Park
Last year a geochemical evaluation of groundwater springs in the upper portion of the Sweetwater watershed was completed by a SDSU student Steve Phillips (Phillips, 2014). Phillips collected water samples from various locations including: Deer Spring, Cold Spring, Azalea Spring, Japacha Spring, Dyar Spring, Granite Spring, and Green Valley Falls. Field measurements were taken to determine the pH, temperature, and alkalinity of the springs. These locations were chosen due to the variations in the underlying geology, which includes the Cuyamaca Gabbro, Harper Creek Gneiss, Pine Valley Monzogranite, and the East Mesa Quartz Diorite. In order to gain a better understanding of the watershed and variations between the different springs, further lab analysis were needed to determine the major ion composition of the water samples. This new data will distinguish the differences in bedrock composition based on the geologic location of the springs. The major ions that this study analyzed include: calcium, magnesium, sodium, potassium, chloride, and sulfate. To determine the ion concentrations in the spring water samples this study utilized a chloride probe, a Spectrophotometer, and flame atomic absorption spectroscopy., San Diego State University