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Full-Text Articles in Physical Sciences and Mathematics
Spatial Variations Of Upper Crustal Anisotropy Along The San Jacinto Fault Zone In Southern California: Constraints From Shear Wave Splitting Analysis, Enyuan Jiang, Kelly H. Liu, Yuan Gao, Xiaofei Fu, Stephen S. Gao
Spatial Variations Of Upper Crustal Anisotropy Along The San Jacinto Fault Zone In Southern California: Constraints From Shear Wave Splitting Analysis, Enyuan Jiang, Kelly H. Liu, Yuan Gao, Xiaofei Fu, Stephen S. Gao
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
To discern spatial and explore possible existence of temporal variations of upper crustal anisotropy in an ∼15 km section of the San Jacinto Fault Zone (SJFZ) that is composed of the Buck Ridge and Clark faults in southern California, we conduct a systematic shear wave splitting investigation using local S-wave data recorded by three broadband seismic stations located near the surface expression of the SJFZ. An automatic data selection and splitting measurement procedure is first applied, and the resulting splitting measurements are then manually screened to ensure reliability of the results. Strong spatial variations in crustal anisotropy are revealed by …
Overpumping Leads To California Groundwater Arsenic Threat, Ryan G. Smith, Rosemary Knight, Scott Fendorf
Overpumping Leads To California Groundwater Arsenic Threat, Ryan G. Smith, Rosemary Knight, Scott Fendorf
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
Water resources are being challenged to meet domestic, agricultural, and industrial needs. To complement finite surface water supplies that are being stressed by changes in precipitation and increased demand, groundwater is increasingly being used. Sustaining groundwater use requires considering both water quantity and quality. A unique challenge for groundwater use, as compared with surface water, is the presence of naturally occurring contaminants within aquifer sediments, which can enter the water supply. Here we find that recent groundwater pumping, observed through land subsidence, results in an increase in aquifer arsenic concentrations in the San Joaquin Valley of California. By comparison, historic …
Lessons Learned From The St. Francis Dam Failure, J. David Rogers
Lessons Learned From The St. Francis Dam Failure, J. David Rogers
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
The St. Francis Dam (Fig. 1), a curved concrete gravity structure 209-feet high, located in the mountains about 35 miles north of downtown Los Angeles, failed catastrophically near midnight just before March 12, 1928. The failure released 36,180 acre-feet of water down San Francisquito Canyon on a turbulent 55-mile journey to the Pacifica Ocean near Ventura, killing 450 people. As the deadliest American civil engineering failure of the 20th century, the city of Los Angeles paid more than $7 million in restitution to the victims' families and affected landowners. The sudden failure of a new concrete dam constructed by a …
Field-Scale Estimation Of Volumetric Water Content Using Ground-Penetrating Radar Ground Wave Techniques, Katherine R. Grote, Susan Sharpless Hubbard, Yoram N. Rubin
Field-Scale Estimation Of Volumetric Water Content Using Ground-Penetrating Radar Ground Wave Techniques, Katherine R. Grote, Susan Sharpless Hubbard, Yoram N. Rubin
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
Ground-penetrating radar (GPR) ground wave techniques were applied to estimate soil water content in the uppermost ∼10 cm of a 3 acre California vineyard several times over 1 year. We collected densely spaced GPR travel time measurements using 900 and 450 MHz antennas and analyzed these data to estimate water content. The spatial distribution of water content across the vineyard did not change significantly with time, although the absolute water content values varied seasonally and with irrigation. The GPR estimates of water content were compared to gravimetric water content, time domain reflectometry, and soil texture measurements. The comparisons of GPR-derived …
Analysis Of Deformation Data At Parkfield, California: Detection Of A Long-Term Strain Transient, Stephen S. Gao, Paul G. Silver, Alan T. Linde
Analysis Of Deformation Data At Parkfield, California: Detection Of A Long-Term Strain Transient, Stephen S. Gao, Paul G. Silver, Alan T. Linde
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
Analysis of more than a decade of high-quality data, particularly those from the two-color electronic distance meter (EDM), in the Parkfield, California, area reveals a significant transient in slip rate along the San Andreas Fault. This transient consists of an increase in fault slip rate of 3.3 ± 0.9 mm/yr during 1993.0 to 1998.0. The most reliable fault creep instruments show a comparable increase in slip rate, suggesting that the deformation is localized to the fault which breaks the surface. There was also an increase in precipitation around 1993. It is unlikely, however, that this anomaly is due directly to …