Evidence for composite hydraulic architecture in an active fault system based on 3D seismic reflection, time‐domain electromagnetics and temperature data

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.