CO2 degassing along the San Andreas fault, Parkfield, California

Jennifer L. Lewicki, Susan L. Brantley

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59 Scopus citations


The fluxes, concentrations, and carbon isotopic compositions of soil CO2 were measured along the Parkfield segment of the San Andreas fault (SAF). Single or double-peak CO2 flux anomalies (> 18 g m-2 d-1) were observed along 12 of 16 fault-crossing transects at five sites. Flux anomalies did not coincide with concentration anomalies. Flux anomalies paralleled the fault trace, suggesting zones of high diffusivity/permeability. One flux anomaly may have been accentuated by a 0.3 mm creep event. However, values of δ13C (-23.7 to -21.6 ‰) and 14C (110.5 to 111.9 pmC) for soil gas CO2 are characteristic of CO2 of biogenic origin. The CO2 flux anomalies are therefore consistent with fault-related biogenic gas flow and do not yield evidence for degassing of deeply derived CO2.

Original languageEnglish (US)
Pages (from-to)5-8
Number of pages4
JournalGeophysical Research Letters
Issue number1
StatePublished - Jan 1 2000

All Science Journal Classification (ASJC) codes

  • Geophysics
  • General Earth and Planetary Sciences


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