Effect of thermal refraction on heat flow near the San Andreas Fault, Parkfield, California

Patrick M. Fulton, Demian Saffer

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

Heat flow data near the San Andreas Fault (SAF) do not reveal a near-fault anomaly as expected from frictional heat generation, an observation interpreted to indicate that the fault slips at a depth-averaged shear stress <20 MPa. The data also contain large unexplained scatter, which has been a separate major issue in the analysis of heat flow within the California Coast Ranges. Here we use numerical models of heat conduction to evaluate the hypothesis that thermal refraction, due to contrasts in thermal conductivity in the subsurface, both produces the observed scatter in heat flow and as a result obscures the thermal signature from frictional heating on a fault that supports large shear stress during slip. Our study focuses on the region around the San Andreas Fault Observatory at Depth (SAFOD) near Parkfield, California. Our results show that surface heat flow is most sensitive to the contrast between Tertiary sediments and basement rocks and to wavelengths of basement topography of ∼10 km. With realistic thermal conductivity contrasts and a reasonable interpretation of this geologic contact, we show that thermal refraction is a plausible explanation for the observed heat flow scatter. However, refraction effects are unable to mask frictional heat generation in a manner consistent with observations. We show that even with large refraction effects, low background heat flow, a regional NW-SE decrease in heat flow, or nonsteady state heat conduction, the data are most consistent with a fault that produces little to no frictional heat.

Original languageEnglish (US)
Article numberB06408
JournalJournal of Geophysical Research: Solid Earth
Volume114
Issue number6
DOIs
StatePublished - Jan 1 2009

Fingerprint

San Andreas Fault
Refraction
refraction
heat transmission
heat flow
Heat transfer
heat generation
Heat generation
thermal conductivity
basements
Heat conduction
conductive heat transfer
shear stress
Shear stress
Thermal conductivity
slip
Fault slips
fault slip
Observatories
basement rock

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

Cite this

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abstract = "Heat flow data near the San Andreas Fault (SAF) do not reveal a near-fault anomaly as expected from frictional heat generation, an observation interpreted to indicate that the fault slips at a depth-averaged shear stress <20 MPa. The data also contain large unexplained scatter, which has been a separate major issue in the analysis of heat flow within the California Coast Ranges. Here we use numerical models of heat conduction to evaluate the hypothesis that thermal refraction, due to contrasts in thermal conductivity in the subsurface, both produces the observed scatter in heat flow and as a result obscures the thermal signature from frictional heating on a fault that supports large shear stress during slip. Our study focuses on the region around the San Andreas Fault Observatory at Depth (SAFOD) near Parkfield, California. Our results show that surface heat flow is most sensitive to the contrast between Tertiary sediments and basement rocks and to wavelengths of basement topography of ∼10 km. With realistic thermal conductivity contrasts and a reasonable interpretation of this geologic contact, we show that thermal refraction is a plausible explanation for the observed heat flow scatter. However, refraction effects are unable to mask frictional heat generation in a manner consistent with observations. We show that even with large refraction effects, low background heat flow, a regional NW-SE decrease in heat flow, or nonsteady state heat conduction, the data are most consistent with a fault that produces little to no frictional heat.",
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Effect of thermal refraction on heat flow near the San Andreas Fault, Parkfield, California. / Fulton, Patrick M.; Saffer, Demian.

In: Journal of Geophysical Research: Solid Earth, Vol. 114, No. 6, B06408, 01.01.2009.

Research output: Contribution to journalArticle

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