Seismic images of the deep structure of the San Andreas fault system, Central Coast Ranges, California.

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Abstract

Three-dimensional inversion of teleseismic P wave travel time residuals recorded at the US Geological Survey central California array has resolved small-scale (?? tens of kilometers) crustal and upper mantle heterogeneity down to depths of 90 km beneath the California coast ranges. Upper crustal lateral velocity variations of +-8% correlate closely with surface geology. Lower-than-average velocities are associated with thick Tertiary sedimentary fill and higher-than-average velocities with basement exposures. Lower crustal velocity heterogeneity of +-4% appear to reflect crustal thickness variations. A thinner crust is indicated southwest of the San Andreas fault and northwest of San Pablo Bay. A linear zone of low-velocities (0 to 4%) subparallel to the San Andreas fault was resolved in the upper mantle. The preferred interpretation is that the low-velocities indicate a narrow upwarp of asthenosphere to unusually shallow depths (??45 km) beneath the coast ranges. Such an unusual mantle structure may have been produced by the northwestward migration along the California coast of a transiently unstable Mendocino triple junction. The inversion results also indicate the possibility of partial decoupling of the crust from the upper mantle. -Author

Original languageEnglish (US)
Pages (from-to)5039-5052
Number of pages14
JournalJournal of Geophysical Research: Space Physics
Volume86
Issue numberB6
StatePublished - 1981
Externally publishedYes

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San Andreas Fault
coasts
Coastal zones
Earth mantle
coast
low speed
upper mantle
crusts
inversions
geological surveys
asthenosphere
geology
basements
P waves
decoupling
crust
travel
teleseismic wave
Geological surveys
mantle structure

ASJC Scopus subject areas

  • Earth and Planetary Sciences(all)
  • Environmental Science(all)

Cite this

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title = "Seismic images of the deep structure of the San Andreas fault system, Central Coast Ranges, California.",
abstract = "Three-dimensional inversion of teleseismic P wave travel time residuals recorded at the US Geological Survey central California array has resolved small-scale (?? tens of kilometers) crustal and upper mantle heterogeneity down to depths of 90 km beneath the California coast ranges. Upper crustal lateral velocity variations of +-8{\%} correlate closely with surface geology. Lower-than-average velocities are associated with thick Tertiary sedimentary fill and higher-than-average velocities with basement exposures. Lower crustal velocity heterogeneity of +-4{\%} appear to reflect crustal thickness variations. A thinner crust is indicated southwest of the San Andreas fault and northwest of San Pablo Bay. A linear zone of low-velocities (0 to 4{\%}) subparallel to the San Andreas fault was resolved in the upper mantle. The preferred interpretation is that the low-velocities indicate a narrow upwarp of asthenosphere to unusually shallow depths (??45 km) beneath the coast ranges. Such an unusual mantle structure may have been produced by the northwestward migration along the California coast of a transiently unstable Mendocino triple junction. The inversion results also indicate the possibility of partial decoupling of the crust from the upper mantle. -Author",
author = "George Zandt",
year = "1981",
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volume = "86",
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journal = "Journal of Geophysical Research: Space Physics",
issn = "2169-9380",
publisher = "Wiley-Blackwell",
number = "B6",

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TY - JOUR

T1 - Seismic images of the deep structure of the San Andreas fault system, Central Coast Ranges, California.

AU - Zandt, George

PY - 1981

Y1 - 1981

N2 - Three-dimensional inversion of teleseismic P wave travel time residuals recorded at the US Geological Survey central California array has resolved small-scale (?? tens of kilometers) crustal and upper mantle heterogeneity down to depths of 90 km beneath the California coast ranges. Upper crustal lateral velocity variations of +-8% correlate closely with surface geology. Lower-than-average velocities are associated with thick Tertiary sedimentary fill and higher-than-average velocities with basement exposures. Lower crustal velocity heterogeneity of +-4% appear to reflect crustal thickness variations. A thinner crust is indicated southwest of the San Andreas fault and northwest of San Pablo Bay. A linear zone of low-velocities (0 to 4%) subparallel to the San Andreas fault was resolved in the upper mantle. The preferred interpretation is that the low-velocities indicate a narrow upwarp of asthenosphere to unusually shallow depths (??45 km) beneath the coast ranges. Such an unusual mantle structure may have been produced by the northwestward migration along the California coast of a transiently unstable Mendocino triple junction. The inversion results also indicate the possibility of partial decoupling of the crust from the upper mantle. -Author

AB - Three-dimensional inversion of teleseismic P wave travel time residuals recorded at the US Geological Survey central California array has resolved small-scale (?? tens of kilometers) crustal and upper mantle heterogeneity down to depths of 90 km beneath the California coast ranges. Upper crustal lateral velocity variations of +-8% correlate closely with surface geology. Lower-than-average velocities are associated with thick Tertiary sedimentary fill and higher-than-average velocities with basement exposures. Lower crustal velocity heterogeneity of +-4% appear to reflect crustal thickness variations. A thinner crust is indicated southwest of the San Andreas fault and northwest of San Pablo Bay. A linear zone of low-velocities (0 to 4%) subparallel to the San Andreas fault was resolved in the upper mantle. The preferred interpretation is that the low-velocities indicate a narrow upwarp of asthenosphere to unusually shallow depths (??45 km) beneath the coast ranges. Such an unusual mantle structure may have been produced by the northwestward migration along the California coast of a transiently unstable Mendocino triple junction. The inversion results also indicate the possibility of partial decoupling of the crust from the upper mantle. -Author

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M3 - Article

VL - 86

SP - 5039

EP - 5052

JO - Journal of Geophysical Research: Space Physics

JF - Journal of Geophysical Research: Space Physics

SN - 2169-9380

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