A GIS-based tool for assessing and visualizing well-informed uncertainty on mapped fault location

Chelsea P. Scott, Raswanth Prasath, Ramon Arrowsmith, Christopher M. Madugo, Robert Givler, Stephen Thompson, & Albert R. Kottke

Submitted September 7, 2025, SCEC Contribution #14838, 2025 SCEC Annual Meeting Poster #TBD

Accurately characterizing uncertainty in future earthquake surface rupture location is critical for fault displacement hazard analyses and for developing engineering solutions that mitigate coseismic risk to infrastructure. Geologists commonly predict potential rupture locations using regional-scale mapping of tectonic faults and landforms interpreted from remote sensing datasets. Standardized approaches to fault mapping and location uncertainty assessment enable mappers to apply consistent methods, document the landscape evidence supporting the mapped fault location and attributes such as confidence, and justify a well-informed fault location uncertainty with reference to the scientific literature.

We developed a GIS-based tool (for ArcGIS Pro and QGIS: https://plugins.qgis.org/plugins/faultbuffertool/) to support a fault mapper’s work to define, justify, and visualize a well-informed uncertainty in mapped fault location. The uncertainty values are derived from published fault maps and are calculated as the separation distance between fault traces in maps completed prior to the earthquake and the future coseismic rupture traces. These uncertainties account for (1) surface processes such as erosion and deposition that obscure and erase evidence of past faulting, (2) mapper interpretations where landforms provide partially ambiguous evidence for faulting or data quality limits the interpretations, and (3) aleatoric variability including the formation of new faults and the possibility that existing faults may not rupture in the subsequent earthquake.

We envision that this tool will facilitate fault location uncertainty analysis by the broader fault mapping community and will meet several needs of this community defined through interviews with geologists working in industry, agencies, and academia. The tool promotes a deeper understanding of fault location uncertainty targeted toward an audience of geologists, geotechnical engineers, and civil engineers. With the tool’s user-friendly approach, the mapper can iteratively and efficiently refine the uncertainty assigned to mapped fault locations based on insights in the scientific literature as well as professional judgment informed by data quality and surface processes. We designed versions of the tool in QGIS and ArcGIS and developed a user-manual to guide mappers using the tool. We demonstrate the tool’s application to regional-scale fault mapping across several fault types and climates.

Key Words
Fault mapping, fault location uncertainty

Citation
Scott, C. P., Prasath, R., Arrowsmith, R., Madugo, C. M., Givler, R., Thompson, S., & Kottke, A. R. (2025, 09). A GIS-based tool for assessing and visualizing well-informed uncertainty on mapped fault location. Poster Presentation at 2025 SCEC Annual Meeting.

Related Projects & Working Groups
Earthquake Geology