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Scientific Investigations Map 3059

Prepared in cooperation with the California Geological Survey and the San Luis Obispo County Planning and Building Department

Map of the Rinconada and Reliz Fault Zones, Salinas River Valley, California

By Lewis I. Rosenberg and Joseph C. Clark

2009

Introduction

Thumbnail of and link to map PDF (61 MB)

The Rinconada Fault and its related faults constitute a major structural element of the Salinas River valley, which is known regionally, and referred to herein, as the “Salinas Valley”. The Rinconada Fault extends 230 km from King City in the north to the Big Pine Fault in the south. At the south end of the map area near Santa Margarita, the Rinconada Fault separates granitic and metamorphic crystalline rocks of the Salinian Block to the northeast from the subduction-zone assemblage of the Franciscan Complex to the southwest. Northwestward, the Rinconada Fault lies entirely within the Salinian Block and generally divides this region into two physiographically and structurally distinct areas, the Santa Lucia Range to the west and the Salinas Valley to the east.

The Reliz Fault, which continues as a right stepover from the Rinconada Fault, trends northwestward along the northeastern base of the Sierra de Salinas of the Santa Lucia Range and beyond for 60 km to the vicinity of Spreckels, where it is largely concealed. Aeromagnetic data suggest that the Reliz Fault continues northwestward another 25 km into Monterey Bay, where it aligns with a high-definition magnetic boundary.

Geomorphic evidence of late Quaternary movement along the Rinconada and Reliz Fault Zones has been documented by Tinsley (1975), Dibblee (1976, 1979), Hart (1976, 1985), and Klaus (1999). Although definitive geologic evidence of Holocene surface rupture has not been found on these faults, they were regarded as an earthquake source for the California Geological Survey [formerly, California Division of Mines and Geology]/U.S. Geological Survey (CGS/USGS) Probabilistic Seismic Hazards Assessment because of their postulated slip rate of 1±1 mm/yr and their calculated maximum magnitude of 7.3.

Except for published reports by Durham (1965, 1974), Dibblee (1976), and Hart (1976), most information on these faults is unpublished or is contained in theses, field trip guides, and other types of reports. Therefore, the main purpose of this project is to compile and synthesize this body of knowledge into a comprehensive report for the geologic community. This report follows the format of Dibblee (1976) and includes discussions of the sections of the Rinconada Fault and of the Reliz Fault, as well as their Neogene history and key localities. Accompanying this report is a geologic map database of the faults, key localities, and earthquake epicenters, in ESRI shapefile format.

Version 1.0

Posted February 25, 2009

For additional information contact:
Lew Rosenberg

Western Earth Surface Processes Team

This report is available via print on demand.

Part or all of this report is presented in Portable Document Format (PDF); at least version 7 of Adobe Reader or similar software is required to view it. Download the latest version of Adobe Reader, free of charge.


Suggested citation:

Rosenberg, Lewis I., and Clark, Joseph C., 2009, Map of the Rinconada and Reliz Fault Zones, Salinas River Valley, California: U.S. Geological Survey Scientific Investigations Map 3059, scale 1:250,000 with pamphlet [http://pubs.usgs.gov/sim/3059/].



Pamphlet contents

Introduction

Acknowledgments

Sections of the Rinconada Fault Zone

Other Faults Possibly Related to the Rinconada Fault Zone

Sections of the Reliz Fault Zone

Seismicity of the Rinconada and Reliz Fault Zones

Neogene History of the Rinconada and Reliz Fault Zones

References Cited

Unpublished Reports Cited


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