Showing papers by "Barbara A. Bekins published in 2004"

Distributions of Microbial Activities in Deep Subseafloor Sediments

Abstract: Diverse microbial communities and numerous energy-yielding activities occur in deeply buried sediments of the eastern Pacific Ocean. Distributions of metabolic activities often deviate from the standard model. Rates of activities, cell concentrations, and populations of cultured bacteria vary consistently from one subseafloor environment to another. Net rates of major activities principally rely on electron acceptors and electron donors from the photosynthetic surface world. At open-ocean sites, nitrate and oxygen are supplied to the deepest sedimentary communities through the underlying basaltic aquifer. In turn, these sedimentary communities may supply dissolved electron donors and nutrients to the underlying crustal biosphere.

Re‐evaluation of heat flow data near Parkfield, CA: Evidence for a weak San Andreas Fault

Abstract: [1] Improved interpretations of the strength of the San Andreas Fault near Parkfield, CA based on thermal data require quantification of processes causing significant scatter and uncertainty in existing heat flow data. These effects include topographic refraction, heat advection by topographically-driven groundwater flow, and uncertainty in thermal conductivity. Here, we re-evaluate the heat flow data in this area by correcting for full 3-D terrain effects. We then investigate the potential role of groundwater flow in redistributing fault-generated heat, using numerical models of coupled heat and fluid flow for a wide range of hydrologic scenarios. We find that a large degree of the scatter in the data can be accounted for by 3-D terrain effects, and that for plausible groundwater flow scenarios frictional heat generated along a strong fault is unlikely to be redistributed by topographically-driven groundwater flow in a manner consistent with the 3-D corrected data. INDEX TERMS: 8130 Tectonophysics: Heat generation and transport; 8150 Tectonophysics: Plate boundary—general (3040); 8164 Tectonophysics: Stresses—crust and lithosphere. Citation: Fulton, P. M., D. M. Saffer, R. N. Harris, and B. A. Bekins (2004), Re-evaluation of heat flow data near Parkfield, CA: Evidence for a weak San Andreas Fault, Geophys. Res. Lett., 31 , L15S15, doi:10.1029/2003GL019378.