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Seismic Images and Subsurface Structures of Northeastern Edwards Air Force Base, Kern County, California

Open-File Report 2023-1018
Prepared in cooperation with the U.S. Air Force
By: , , , , and 
https://doi.org/10.3133/ofr20231018

Links

  • Document: Report (20 MB pdf)
  • Figures:
    • Figure 4A (1.5 MB pdf) - Two-dimensional compressional-wave velocity tomography model along the Edwards seismic profile (Edwards Air Force Base, California), generated using a subset of the seismic data with short offset distances between the shots and the receivers.
    • Figure 5 (1.5 MB pdf) - Two-dimensional shear-wave velocity model along the Edwards seismic profile (Edwards Air Force Base, California) developed from Rayleigh surface waves and the multichannel analysis of surface waves modeling technique.
    • Figure 6A (1.5 MB pdf) - Two-dimensional model of the ratio of compressional-wave velocity to shear-wave velocity along the Edwards seismic profile (Edwards Air Force Base, California), derived from the tomographic compressional-wave velocity model and the multichannel analysis of surface waves shear-wave velocity model.
    • Figure 7A (1.5 MB pdf) - Two-dimensional Poisson’s ratio model along the Edwards seismic profile (Edwards Air Force Base, California), derived from the tomographic compressional-wave velocity model and the multichannel analysis of surface waves shear-wave velocity model.
    • Figure 8A, B, C (7 MB pdf) - Unmigrated reflection image of the upper 400 meters (depth) along the Edwards seismic profile, Edwards Air Force Base, California.
    • Figure 8D, E, F (11 MB pdf) - Unmigrated reflection image of the upper 400 meters (depth) along the Edwards seismic profile, Edwards Air Force Base, California.
    • Figure 13 (2 MB pdf) - Two-dimensional model of the ratio of compressional-wave velocity to shear-wave velocity along the Edwards seismic profile (Edwards Air Force Base, California), annotated with interpretive faults shown in figure 11
    • Figure 14 (2 MB pdf) - Two-dimensional Poisson’s ratio model along the Edwards seismic profile (Edwards Air Force Base, California), annotated with interpretative faults shown in figure 11.
  • Data Release: Data release for a 2020 high-resolution seismic survey across northeastern Edwards Air Force Base, Kern County, California
  • Download citation as: RIS | Dublin Core

Abstract

We used multi-component seismic data (including two-dimensional images of compressional-wave velocity [vP], shear-wave velocity [vS], the ratio of compressional-wave velocity to shear-wave velocity [vP/vS ratio], Poisson’s ratio [μ], and seismic reflections) along a transect across northeastern Edwards Air Force Base to investigate the upper few hundred meters of the subsurface. The shallow subsurface there is characterized by unconsolidated sediments (vP of less than 2,500 meters per second [m/s]; vS of less than 1,500 m/s) in the upper 40 meters (m), underlain by weathered granitic basement rock (vP of 2,500–4,000 m/s; vS of 1,500–2,700 m/s) to about 100 m depth and unweathered granitic basement rock (vP of 4,000–6,000 m/s; vS of 2,700–4,000 m/s). The depth to basement rock varies laterally along the transect by as many as tens of meters. The top of groundwater, as indicated by both the 1,500-m/s vP contour and measurements in five wells along the transect, is located 8–30 m below the surface. In places, the top of groundwater is vertically offset over short lateral distances, likely the result of fault barriers. Faults mapped at the surface along the northeastern part of the transect correlate with multiple seismic indicators of faulting at the same locations. These same indicators show evidence for faulting in several other places along the transect beneath the alluvium. A major zone of faulting is apparent near the center of the seismic profile and is characterized by offsets in the top of groundwater; diffractions on the reflection image; a near-vertical zone of low vS; a corresponding near-vertical, shallow-depth zone of high vP relative to adjacent rocks (indicating high saturation); a near-vertical zone of high vP/vS ratios; and a near-vertical zone of high Poisson’s ratios (also indicating saturation). Many of these anomalies extend at least 400 m deep, reaching into granitic basement rock and indicating that the fault zone is water-saturated to those depths. There is likely vertical flow of contaminants along these fault zones, which are apparently barriers to the lateral flow of groundwater. The major central fault zone marks a boundary beyond which contaminant flow is apparently impeded. Along the southwestern part of the transect, there are also areas with similar indicators of faulting, but these appear to be smaller fault zones.

Suggested Citation

Catchings, R.D., Goldman, M.R., Chan, J.H., Sickler, R.R., and Criley, C.J., 2023, Seismic images and subsurface structures of northeastern Edwards Air Force Base, Kern County, California: U.S. Geological Survey Open-File Report 2023–1018, 29 p., https://doi.org/10.3133/ofr20231018.

ISSN: 2331-1258 (online)

Study Area

Table of Contents

  • Acknowledgments 
  • Abstract 
  • Introduction 
  • Methodology and Background Information 
  • Interpretations 
  • References Cited 
  • Appendix. One-Dimensional Velocity Models for the Edwards Seismic Profile, Edwards Air Force Base, California
Publication type Report
Publication Subtype USGS Numbered Series
Title Seismic images and subsurface structures of northeastern Edwards Air Force Base, Kern County, California
Series title Open-File Report
Series number 2023-1018
DOI 10.3133/ofr20231018
Year Published 2023
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Earthquake Science Center
Description Report: vii, 29 p.,; Data Release; 8 Figures
Country United States
State California
County Kern County
Other Geospatial Edwards Air Force Base
Online Only (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details