Preliminary potential-field constraints on the geometry of the San Fernando basin, Southern California

Open-File Report 2000-219

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Gravity and magnetic data provide new insights on the structural underpinnings of the San Fernando Basin region, which may be important to ground motion models. Gravity data indicate that a deep basin (>5 km) underlies the northern part of the San Fernando Valley; this deep basin is required to explain the lowest gravity values over the Mission Hills thrust fault. Gravity modeling, constrained by well data and density information, shows that the basin may reach a thickness of 8 km, coinciding with the upper termination of the 1994 Northridge earthquake mainshock rupture. The basin is deeper than previous estimates by 2 to 4 km; this estimate is the result of high densities for the gravels of the Pliocene-Pleisocene Saugus Formation. The geometry of the southern margin of the deep basin is not well-constrained by the gravity data, but may dip to the south. Recently acquired seismic data along the LARSE (Los Angeles Regional Seismic Experiment) II profile may provide constraints to determine the location and attitude of the basin edge. Gravity and aeromagnetic models across the eastern margin of the San Fernando Valley indicate that the Verdugo fault may dip to the southwest along its southern extent and therefore have a normal fault geometry whereas it clearly has a thrust fault geometry along its northern strand.

Suggested Citation

Langenheim, V.E., Griscom, A., Jachens, R.C., and Hildenbrand, T.G., 2000, Preliminary Potential-Field Constraints on the Geometry of the San Fernando Basin, Southern California: U.S. Geological Survey Open-File Report 00-219, 22 pp.,

ISSN: 2331-1258 (online)

Study Area

Table of Contents

  • Abstract
  • Introduction
  • Geologic Setting
  • Gravity, Aeromagnetic, and Physical Property Data
  • Discussion of Potential-Field Anomalies and Modeling Results
  • Discussion and Conclusions
  • Acknowledments

Additional publication details

Publication type:
Publication Subtype:
USGS Numbered Series
Preliminary potential-field constraints on the geometry of the San Fernando basin, Southern California
Series title:
Open-File Report
Series number:
Year Published:
U.S. Geological Survey
Publisher location:
Reston, VA
Contributing office(s):
Geology, Minerals, Energy and Geophysics Science Center
36 p.
United States
Other Geospatial:
San Fernando Basin