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Two models of the Climax and Gold Meadows stocks were generated using a new method of magnetic inversion modeling based on the pseudogravity anomaly. The first model examined the shape of the two stocks and their connection at depth, concluding that the stocks are connected-4000 m below the ground surface. The second model reexamined the shape and depth of the Climax stock using a two-layer model and new magnetic data collected from drill hole ER-8-1. Existing and new magnetic data support a model of a zoned pluton with increasing magnetization with depth. A model of a zoned pluton was generated and adjusted to fit the magnetic anomaly measured over the stock. The model has an upper layer that extends to a depth of 1,700 m and is magnetized at 0.06 A/m, and a lower layer that extends to a maximum depth of 7,600 m and is magnetized at 0.17 A/m. The model matches the outcrop data, but was unable to match the intercept of the Climax stock from drill hole ER-8-1.

Certain naturally occurring minerals can be hazardous to human health and the environment when disturbed by human development. Because certain minerals, such as asbestos and serpentinite, are associated with specific geologic units, geologic maps that show the subsurface distribution of those units can be used to regionally delineate the potential hazard. 4. Education and scientific inquiry. A 3D geologic map allows the user to explore the shapes of the geologic units and structures, in isolation or as an integrated whole. Geologic features can be viewed from different angles, individually or in aggregate, and slices through the map can easily be constructed. This allows the user to grasp complex spatial relationships quickly and easily. Thus, 3D geologic maps are an excellent teaching aid and interpretive tool. This 3D map can be used by the academic community and by the public to understand the geology of the Hayward Fault at a regional scale. Uses of this map database are limited by compilation scale and content, therefore the map is not intended for site-specific studies. Refer to the fault maps of the California Geological Survey (http://www.consrv.ca.gov/cgs/) for site-specific studies of fault activity.

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The depth of the basin beneath Frenchman Flat is estimated using a gravity inversion method. Gamma-gamma density logs from two wells in Frenchman Flat constrained the density profiles used to create the gravity inversion model. Three initial models were considered using data from one well, then a final model is proposed based on new information from the second well. The preferred model indicates that a northeast-trending oval-shaped basin underlies Frenchman Flat at least 2,100 m deep, with a maximum depth of 2,400 m at its northeast end. No major horst and graben structures are predicted. Sensitivity analysis of the model indicates that each parameter contributes the same magnitude change to the model, up to 30 meters change in depth for a 1% change in density, but some parameters affect a broader area of the basin. The horizontal resolution of the model was determined by examining the spacing between data stations, and was set to 500 square meters.