Evidence for Composite Hydraulic Architecture in an Active Fault System Based on 3D Seismic Reflection, Time-Domain Electromagnetics and Temperature Data

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Fault hydrology is a topic of scientific and practical importance but considerable uncertainty exists regarding the nature of structural controls on fluid flow. Here we use seismic reflection and time-domain electromagnetic data to develop a three-dimensional model of hydraulic architecture in a predominantly dip-slip normal fault system and we predict the architectural elements based on subsurface fluid flow patterns inferred from near-surface temperature measurements. Our observations indicate the presence of high-permeability flow paths parallel to fault planes in poorly-lithified sediments. These results are best explained using a combination of elements from commonly accepted conceptual models of fault architecture, a finding that exhibits the heterogeneous nature of the geologic materials comprising the site. These insights may be useful as a guide to future studies of active fault systems, where multiple-mode investigations (geophysical, hydrologic, thermal, geochemical) will be required to better understand subsurface fluid/fault interactions.