Large Scale Detection of Fault Damage

Kelian Dascher-Cousineau, Emily E. Brodsky, Noah Finnegan, & Alison R. Duvall

Published August 14, 2019, SCEC Contribution #9588, 2019 SCEC Annual Meeting Poster #123

Fault damage zones are inherently difficult to measure, yet determining their presence and size is a cornerstone of earthquake mechanics. We develop tools to couple remote observations of the Earth's topography to deep-seated physical features of a crustal-scale fault damage zone. We iterate between empirical landscape observations and mechanical interpretation by utilizing a combination of high-resolution LIDAR of the San Andreas, landscape evolution models, and ground-truth campaigns. We first show that the presence of a fault quantifiably influences geomorphic processes. In test locales, proximity to the San Andreas Fault influences stacked topographic profiles, stream power erosion, and river orientation. On the scale of the San Andreas shear zone, rivers networks exhibit a strong bias to along mapped faults. These metrics reveal a length scale of on the order of 100m to 1km comparable to independent geophysical and ground measurements of damage zone width. The analysis reveals lateral heterogeneity in geomorphic processes along fault zones which correlate with the complexity of the fault trace along strike. Landscape evolution models incorporating active strike-slip offset and a damage zone with increased bed rock erosivity and distributed deformation qualitatively reproduce the observed statistics. We ground-truth our remote measurements with field observations of fault damage along sea-cliff exposure and bedrock streams. Our work clarifies the importance of fault damage in shaping landscapes over geomorphic time scales. Fault damage reduces rock cohesion, increases permeability, promotes bedrock detachment along river channels, and facilitates material flux through the critical zone. Thus, we build towards quantifying damage remotely.

Key Words
Damage Zone, Remote Sensing, Fault Zone Architecture, Distributed Deformation

Citation
Dascher-Cousineau, K., Brodsky, E. E., Finnegan, N., & Duvall, A. R. (2019, 08). Large Scale Detection of Fault Damage. Poster Presentation at 2019 SCEC Annual Meeting.

Related Projects & Working Groups
Earthquake Geology