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U.S. Geological Survey
Miscellaneous Field Studies Map MF-2196

Map of Recently Active Traces of the Hayward Fault, Alameda and Contra Costa Counties, California

By James J. Lienkaemper

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The purpose of this map (pl. 1) is to show the location of and evidence for recent movement on active fault traces within the Hayward Fault Zone. The mapped traces represent the integration of three different types of data: (1) geomorphic expression, (2) creep (aseismic fault slip), and (3) trench exposures. The location of the mapped area is shown on figure 1 on plate 1.

A major scientific goal of this mapping project was to learn how the distribution of fault creep and creep rate varies spatially, both along and transverse to the fault. The results related to creep rate are available in Lienkaemper and others (1991), and are not repeated here. Detailed mapping of the active fault zone contributes to a better understanding of the earthquake source process by constraining estimates of: (1) the probable recurrence times of major earthquakes, (2) the size of expected surface displacements, and (3) the expected length of ruptures accompanying these earthquakes. Now that the 1989 Loma Prieta earthquake has occurred on the San Andreas Fault, the Working Group on California Earthquake Probabilities (1990) considers the Hayward Fault the most probable source of a major earthquake (magnitude 7 or larger) in the San Francisco Bay region in the next few decades.

This map also is of general use to engineers and landuse planners. The traces shown on the map are those that can be expected to have the most intense ground rupturing from fault slip in future major earthquakes on the Hayward Fault. However, the small scale of the map (1:24,000) does not provide sufficient details of the local complexities of the fault zone for site development purposes. The term "recently active fault trace" is defined here as a fault trace that has evidence of movement in the Holocene or approximately the last 10,000 years. This definition also satisfies the legal definition of active fault used in the implementation of the Alquist- Priolo Act of 1972 (Hart, 1990).

This map provides a starting point for planners by showing locations of fault creep and trench exposures of active traces. However, minor fault traces may not be recognized because many sections of the fault were already urbanized by 1939, the date of the earliest aerial photography for the entire fault. Thus, geomorphic features indicative of active faulting have been degraded or destroyed by human activity, especially secondary traces that have minor cumulative slip. For this reason, subsurface investigations will continue to be the main method of recognizing and precisely locating active fault strands in sites that lack reliable creep evidence. Mapping of creep evidence and monitoring of fault creep can be the most definitive methods to precisely locate active traces. Because important subsurface and creep monitoring investigations are now in progress or planned, this map must be considered an interim report of data available on January 1, 1992.

Note: Note: MF2196 has been superceded by USGS Data Series 177. The map was originally printed with two colors. This site allows download of grayscale scanned images of the original paper map. Some variation from the original 1:24,000 scale may result from the scanning of a non-scale-stable materials.

Map Sheet 1 JPG file (8.8 MB)

For viewing and printing. (Good image resolution for most purposes)

Map Sheet 1 PDF file (5.1 MB)

For viewing and printing. (Good image resolution for most purposes like JPG above)

Map Sheet 1 JPG file (56 MB)

For viewing and printing. (Higher resolution; very large download)

The pamphlet accompanying the map (280 KB PDF file)

For viewing and printing.

For questions about the content of this report, contact Jim Lienkaemper

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Maintained by: Michael Diggles
Created: March 6, 2006
Last modified: March 7, 2006 (mfd)