Three-dimensional crustal structure of the southern Sierra Nevada from seismic fan profiles and gravity modeling

Journal Article · Mon Apr 01 04:00:00 EST 1996 · Geology

DOI:https://doi.org/10.1130/0091-7613(1996)024<0367:TDCSOT>2.3.CO;2· OSTI ID:420918

Fliedner, M M ^[1]; Ruppert, S ^[2]; Park, S K ^[3]; and, others

---

1. Stanford Univ., CA (United States)
2. Lawrence Livermore National Lab., CA (United States)
3. Univ. of California, Riverside, CA (United States)

Traveltime data from the 1993 Southern Sierra Nevada Continental Dynamics seismic refraction experiment reveal low velocities in the southern Sierra Nevada and Basin and Range province of California (6.0 to 6.6 km/s), as well as low upper mantle velocities (7.6 to 7.8 km/s). The crust thickens from southeast to northwest along the axis of the Sierra Nevada from 27 km in the Mojave Desert to 43 km near Fresno, California. A crustal welt is present beneath the Sierra Nevada, but the deepest Moho is found under the western slopes, not beneath the highest topography. A density model directly derived from the crustal velocity model but with constant mantle density satisfies the pronounced negative Bouguer anomaly associated with the Sierra Nevada, but shows large discrepancies of >50 mgal in the Great Valley and in the Basin and Range province. Matching the observed gravity with anomalies in the crust alone is not possible with geologically reasonable densities; we require a contribution from the upper mantle, either by lateral density variations or by a thinning of the lithosphere under the Sierra Nevada and the Basin and Range province. Such a model is consistent with the interpretation that the uplift of the present Sierra Nevada is caused and dynamically supported by asthenospheric upwelling or lithospheric thinning under the Basin and Range province and eastern Sierra Nevada. 20 refs., 4 figs.

• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 420918
• Journal Information: Geology, Journal Name: Geology Journal Issue: 4 Vol. 24; ISSN 0091-7613; ISSN GLGYBA
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
66 PHYSICS
EARTH CRUST
GEOLOGIC STRUCTURES
GEOLOGY
GRAVITATIONAL FIELDS
GRAVITY SURVEYS
MATHEMATICAL MODELS
SEISMIC SURVEYS
SEISMOGRAPHS
SIERRA NEVADA COLORADO