High-resolution gravity and seismic-refraction surveys of the Smoke Tree Wash area, Joshua Tree National Park, California

Open-File Report 2016-1027
By: , and 

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Abstract

We describe high-resolution gravity and seismic refraction surveys acquired to determine the thickness of valley-fill deposits and to delineate geologic structures that might influence groundwater flow beneath the Smoke Tree Wash area in Joshua Tree National Park. These surveys identified a sedimentary basin that is fault-controlled. A profile across the Smoke Tree Wash fault zone reveals low gravity values and seismic velocities that coincide with a mapped strand of the Smoke Tree Wash fault. Modeling of the gravity data reveals a basin about 2–2.5 km long and 1 km wide that is roughly centered on this mapped strand, and bounded by inferred faults. According to the gravity model the deepest part of the basin is about 270 m, but this area coincides with low velocities that are not characteristic of typical basement complex rocks. Most likely, the density contrast assumed in the inversion is too high or the uncharacteristically low velocities represent highly fractured or weathered basement rocks, or both. A longer seismic profile extending onto basement outcrops would help differentiate which scenario is more accurate. The seismic velocities also determine the depth to water table along the profile to be about 40–60 m, consistent with water levels measured in water wells near the northern end of the profile.

Suggested Citation

Langenheim, V.E., Rymer, M.J., Catchings, R.D., Goldman, M.R., Watt, J.T., Powell, R.E., and Matti, J.C., 2016, High-resolution gravity and seismic-refraction surveys of the Smoke Tree Wash Area, Joshua Tree National Park, California: U.S. Geological Survey Open-File Report 2016–1027, 15 p., http://dx.doi.org/10.3133/ofr20161027.

ISSN: 2331-1258 (online)

Study Area

Table of Contents

  • Abstract
  • Introduction
  • Data Sets
  • Gravity Field
  • Computation Method for Modeling the Thickness of the Valley-Fill Deposits
  • Gravity Results
  • Comparison with the Seismic-Refraction Model
  • Acknowledgments
  • References

Additional publication details

Publication type Report
Publication Subtype USGS Numbered Series
Title High-resolution gravity and seismic-refraction surveys of the Smoke Tree Wash area, Joshua Tree National Park, California
Series title Open-File Report
Series number 2016-1027
DOI 10.3133/ofr20161027
Year Published 2016
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Geology, Minerals, Energy, and Geophysics Science Center
Description Report: iii, 15 p.; Dataset; Metadata; Read Me
Country United States
State California
Other Geospatial Joshua Tree National Park
Online Only (Y/N) Y
Additional Online Files (Y/N) Y