thumbnail

Shallow-depth location and geometry of the Piedmont Reverse splay of the Hayward Fault, Oakland, California

Open-File Report 2016-1123
By: , , , , , , and 
https://doi.org/10.3133/ofr20161123

Links

Abstract

The Piedmont Thrust Fault, herein referred to as the Piedmont Reverse Fault (PRF), is a splay of the Hayward Fault that trends through a highly populated area of the City of Oakland, California (fig. 1A). Although the PRF is unlikely to generate a large-magnitude earthquake, slip on the PRF or high-amplitude seismic energy traveling along the PRF may cause considerable damage during a large earthquake on the Hayward Fault. Thus, it is important to determine the exact location, geometry (particularly dip), and lateral extent of the PRF within the densely populated Oakland area. In the near surface, the PRF juxtaposes Late Cretaceous sandstone (of the Franciscan Complex Novato Quarry terrane of Blake and others, 1984) and an older Pleistocene alluvial fan unit along much of its mapped length (fig. 1B; Graymer and others, 1995). The strata of the Novato Quarry unit vary greatly in strike (NW, NE, and E), dip direction (NE, SW, E, and NW), dip angle (15° to 85°), and lithology (shale and sandstone), and the unit has been intruded by quartz diorite in places. Thus, it is difficult to infer the structure of the fault, particularly at depth, with conventional seismic reflection imaging methods. To better determine the location and shallow-depth geometry of the PRF, we used high-resolution seismic imaging methods described by Catchings and others (2014). These methods involve the use of coincident P-wave (compressional wave) and S-wave (shear wave) refraction tomography and reflection data, from which tomographic models of P- and S-wave velocity and P-wave reflection images are developed. In addition, the coincident P-wave velocity (VP) and S-wave velocity (VS) data are used to develop tomographic models of VP/VS ratios and Poisson’s ratio, which are sensitive to shallow-depth faulting and groundwater. In this study, we also compare measurements of Swave velocities determined from surface waves with those determined from refraction tomography. We use the combination of seismic methods to infer the fault location, dip, and the National Earthquake Hazards Reduction Program (NEHRP) site classification along the seismic profile. Our seismic study is a smaller part of a larger study of the PRF by Trench and others (2016).

Suggested Citation

Catchings, R.D., Goldman, M.R., Trench, David, Buga, Michael, Chan, J.H., Criley, C.J., and Strayer, L.M., 2017, Shallow-depth location and geometry of the Piedmont Reverse splay of the Hayward Fault, Oakland, California: U.S. Geological Survey Open-File Report 2016–1123, 22 p., https://dx.doi.org/10.3133/ofr20161123.

ISSN: 2331-1258 (online)

Study Area

Table of Contents

  • Introduction
  • Seismic Data Acquisition
  • P-Wave Refraction Tomography Velocity Model
  • S-Wave Refraction Tomography Velocity Model
  • VP/VS Model
  • Poisson’s Ratio Model
  • Seismic Reflection Images
  • MASW and MALW S-Wave Velocity Models
  • Summary and Seismic Interpretation
  • Acknowledgments
  • References Cited
  • Figures
Publication type Report
Publication Subtype USGS Numbered Series
Title Shallow-depth location and geometry of the Piedmont Reverse splay of the Hayward Fault, Oakland, California
Series title Open-File Report
Series number 2016-1123
DOI 10.3133/ofr20161123
Year Published 2017
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Earthquake Science Center
Description iii, 22 p.
Country United States
State California
City Oakland
Other Geospatial Hayward Fault
Online Only (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details