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Map of Topographic Lineaments Interpreted As Recent Surface Ruptures Along the Bennett Valley and Southern Maacama Fault Zones, Sonoma County, California

Scientific Investigations Map 3529
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https://doi.org/10.3133/sim3529

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Abstract

This study documents lidar-illuminated topographic lineaments interpreted as evidence of recent surface fault ruptures and surface ruptures related to distributed deformation along the Bennett Valley Fault Zone and the southernmost Maacama Fault Zone in the northern San Francisco Bay area (fig. 1, on map sheet). Together, these fault zones form a structural connection across a right stepover between the main Maacama Fault Zone and the Rodgers Creek Fault, overlapping principal strands of the San Andreas plate boundary system north of San Francisco Bay (figs. 1, 2, on map sheet) that accommodate about a quarter of the ~40 millimeters per year of regional dextral tectonic slip (Parsons and others, 2013).

Although much of the Bennett Valley Fault Zone is seismically active (McLaughlin and others, 2012; Sowers and others, 2010), only the north end of the fault zone (the “Spring Valley strand,” indicated on southern map panel of map sheet and labeled “D” in figure 2, on map sheet) was previously known to have youthful geomorphic expression and to displace Holocene deposits (McLaughlin and others, 2008; Sowers and others, 2010; Sowers and others, 2016). Holocene activity along the length of the Bennett Valley Fault Zone and southernmost Maacama Fault Zone, with possible implications for rupture propagation, continuity, and slip transfer, had not been identified. However, fault splays that project eastward from the Rodgers Creek Fault have been mapped and hypothesized to accommodate slip transfer to the Bennett Valley Fault Zone (Hecker and Randolph Loar, 2018). The generally subtle and distributed nature of surface-rupture evidence along the Bennett Valley and southernmost Maacama Fault Zones, and extensive vegetation cover, had left recent faulting previously unmapped along most of the zone.

The map presented here represents a new compilation of inferred surface-rupture features detected using high-resolution topographic lidar data from an airborne lidar survey of Sonoma County, California (OpenTopography, 2014). These data, which enable subtle topographic features to be discerned, indicate that recent (likely Holocene) surface ruptures extend throughout the Bennett Valley and southernmost Maacama Fault Zones.

The rupture-lineament map was created using a GIS (geographic information system) framework and is included herein as an image map at a scale of 1:36,000 and as digital datasets (included as supplemental information to this report). The mapping is intended to lay the groundwork for future studies designed to better characterize how plate-boundary slip is accommodated on this important and complex system of faults.

Suggested Citation

Hecker, S., 2024, Map of topographic lineaments interpreted as recent surface ruptures along the Bennett Valley and Southern Maacama Fault Zones, Sonoma County, California: U.S. Geological Survey Scientific Investigations Map 3529, scale 1:36,000, pamphlet 5 p., https://doi.org/10.3133/sim3529.

ISSN: 2329-132X (online)

Study Area

Table of Contents

  • Acknowledgments
  • Introduction
  • Approach and Scope
  • Geomorphic Evidence of Surface Rupture
  • Distribution and Pattern of Recent Surface Ruptures within the Bennett Valley and southernmost Maacama Fault Zones
  • Implications for Rupture in Individual Earthquakes
  • References Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title Map of topographic lineaments interpreted as recent surface ruptures along the Bennett Valley and Southern Maacama Fault Zones, Sonoma County, California
Series title Scientific Investigations Map
Series number 3529
DOI 10.3133/sim3529
Year Published 2025
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Earthquake Science Center
Description Pamphlet: iv, 5 p.; 1 Sheet: 50.91 x 40.68 inches; Supplemental Information
Country United States
State California
County Sonoma County
Other Geospatial Bennett Valley and Southern Maacama fault zones
Online Only (Y/N) Y
Additional Online Files (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details