This data set is a series of polylines denoting fault lines mapped in USGS Publication MF-1790, "Geologic Map of the Late Cenozoic Deposits of the Sacramento Valley and Northern Sierran Foothills, California" (Helley and Harwood,1985). This data set was created by scanning the five- original sheets from USGS Publication MF-1790 (Helley and Harwood, 1985), the five sheets were georeferenced individually and the geologic information was digitized using AutoCAD 2006. The accuracy of the digitized lines was deemed to be within acceptable error tolerances, with the digitized lines accurately matching the original drafted lines in USGS Publication MF-1790 (Helley and Harwood, 1985). In general, the width of the contact lines on the paper copy, accounting for scale, ranged up to about 20 meters (66 feet). During the original digitization, minor topological mistakes (such as identical rock units on both sides of a lithologic contact or unclosed polygons) and omissions (such as unidentified lithologic units) were applied according to the best available knowledge. Comparisons were made between the original mylar and colorized field sheets (as available), in addition to the Geologic Map of the Battle Creek Fault Zone, Northern Sacramento Valley, California (USGS Map MF-1298, 1981), the Geologic Map of the Chico Monocline and Northeastern Part of the Sacramento Valley, California (USGS Miscellaneous Investigations Series Map I-1238, 1981), and the Geologic Map of the Red Bluff 30' X 60' Quadrangle, California (USGS Geologic Investigation Series Map I-2542, 1995). The correlation and description of geologic units were excerpted from USGS Publication MF-1790m (Helley and Harwood, 1985).

The U.S. Geological Survey (USGS) entered into a cooperative study with the California Department of Water Resources and the Ramona Band of Cahuilla to characterize the hydrogeology of the Cahuilla Valley and Terwilliger Valley groundwater basins and surrounding water-bearing units, with the ultimate goal of developing a calibrated integrated hydrologic model to manage the groundwater supplies on a sustainable basis. A three-dimensional geologic framework model (GFM) was developed to quantify the structural geometry and distribution of water-bearing units in the groundwater basins, using borehole lithology and hydraulic information, geologic maps, and gravity-derived depth-to-basement information. This dataset includes (1) tabular data of selected boreholes with their location and construction information, (2) borehole lithology information, (3) a geographic information systems (GIS) shapefile of a cellular array containing interpolated elevations and thicknesses of modeled geologic units from the GFM in the format of a polygon feature class, (4) and a table of summary textural classes for the alluvial fill unit from borehole logs and summary textural classes used in geologic framework model.

These data present a ground-water inventory of existing geospatial data and other information needed to determine the extent and characteristics of the aquifers in the Tahoe Basin. Geospatial and other data include geologic maps and soil surveys of the entire basin and for specific watersheds within the basin at the best available scales; vegetation remote-sensing datasets; well information from various local, state, and federal agencies; geophysical surveys; and results of available ground-water studies. The compilation and development of a ground-water inventory geospatial database will assist the United States Forest Service in better assessing the present and future impacts on ground-water resources within the Lake Tahoe Basin.

Approximate locations of faults crossing the California Aqueduct, Coastal Branch, North Bay Aqueduct, and South Bay Aqueduct. Taken from "State Water Project, California Aqueduct Fault Crossings" report (PG Report 50-00-06) and supplemental maps (PG Report 50-00-06A) dated November 18, 1965. Fault crossings were collected before and during construction of the State Water Project (SWP) to inform design, and have been compiled in this database for future use in repairs and design. This compilation covers the SWP from North of San Francisco Bay in Solano County to Riverside County, and includes the California Aqueduct, North and South Bay Aqueducts, Coastal Branch, and West Branch.

This dataset contains simplified fault traces, derived from the lineament mapping, for the Pit River region, northeastern California.

,