Publications

A band of seismicity transects the southern Sierra Nevada range between the northeastern end of the site of the 1952 MW (moment magnitude) 7.3 Kern County earthquake and the site of the 1946 MW 6.1 Walker Pass earthquake. Relocated earthquakes in this band, which lacks a surface expression, better delineate the northeast-trending seismic lineament and resolve complex structure near the...

The authors present a field study of estuarine turbulence in which profiles of Reynolds stresses were directly measured using an ADCP throughout a 25-h tidal day. The dataset that is discussed quantifies turbulent mixing for a water column in northern San Francisco Bay that experiences a sequence of states that includes a weak ebb and flood that are stratified, followed by a strong, and...

Ground water production wells commonly are designed to maximize well yield and, therefore, may be screened over several water-bearing zones. These water-bearing zones usually are identified, and their hydrogeologic characteristics and water quality are inferred, on the basis of indirect data such as geologic and geophysical logs. Production well designs based on these data may result in...

The development and distribution of phytoplankton blooms in estuaries are functions of both local conditions (i.e. the production-loss balance for a water column at a particular spatial location) and large-scale horizontal transport. In this study, the second of a 2-paper series, we use a depth-averaged hydrodynamic-biological model to identify transport-related mechanisms impacting...

Nitrogen-15/14 isotope ratios (δ15N) were measured in groundwater, infiltrating wastewater, and natural uncontaminated soil to determine the source of high NO3- concentrations in two desert basins at Fort Irwin National Training Center in the Mojave Desert. The abundance and isotopic composition of dissolved nitrogen gas were measured in some of the groundwater samples to determine the...

Acoustic swath mapping and sediment box coring conducted on the continental shelf near the mouth of the Eel River revealed regional variations in acoustic backscatter that can be related to the shelf sedimentology. The acoustic-backscatter variations observed on the shelf were unusually narrow compared to the response of similar sediment types documented in other areas. However, the...

ABSTRACT: Most of the application of the organophosphate insecticide diazinon in the San Joaquin River Basin occurs in winter to control wood-boring insects in dormant almond orchards. A federalstate collaborative study found that diazinon accounted for most of the observed toxicity of San Joaquin River water in February 1993. Previous studies focused mainly on west-side inputs to the...

An analytical method useful for the quantification of a range of pesticides and pesticide degradation products associated with suspended sediments was developed by testing a variety of extraction and cleanup schemes. The final extraction and cleanup methods chosen for use are suitable for the quantification of the listed pesticides using gas chromatography-ion trap mass spectrometry and...

This report describes the environmental setting and investigative activities of the Sacramento River Basin study unit of the National Water-Quality Assessment Program. The Sacramento River Basin is one of 60 study units located throughout the United States that has been scheduled for study as part of the National Water-Quality Assessment Program. The Sacramento River Basin is the most...

The city of Santa Barbara pumps most of its ground water from the Santa Barbara and Foothill ground-water basins. The Santa Barbara basin is subdivided into two storage units: Storage Unit I and Storage Unit III. The Foothill basin and Storage Unit I of the Santa Barbara basin have been studied extensively and ground-water flow models have been developed for them. In this report, the...

Interferometric synthetic aperture radar (InSAR) has great potential to detect and quantify land subsidence caused by aquifer system compaction. InSAR maps with high spatial detail and resolution of range displacement (±10 mm in change of land surface elevation) were developed for a groundwater basin (∼103 km2) in Antelope Valley, California, using radar data collected from the ERS-1...

Nutrients and suspended sediment in surface water of the San Joaquin-Tulare basins in California were assessed using 1972-1990 data from the U.S. Geological Survey's National Water Information System and the U.S. Environmental Protection Agency's STOrage and RETrieval database. Loads of nutrients and suspended sediment were calculated at several sites and the contributions from point and...