Preservation and interpretation of the geomorphic record of earthquakes

Malinda G. Zuckerman, Alba M. Rodriguez Padilla, Chelsea P. Scott, & Ramon Arrowsmith

Submitted August 30, 2026, SCEC Contribution #15607, 2026 SCEC Annual Meeting Poster #TBD

Surface-rupturing earthquakes leave a geomorphic record that serves as the foundation for fault mapping and probabilistic fault displacement hazard analyses. Over time, the record degrades as surface processes modify fault-related landforms. Both the progressive degradation of fault-related landforms and uncertainty in interpreting the remaining tectonic evidence limit our ability to reconstruct past coseismic ruptures from the modern landscape.

Landscape evolution models based on post-earthquake lidar digital elevation models from the 2019 M6.4 and M7.1 Ridgecrest earthquake sequence and 2010 M7.2 El Mayor-Cucapah ruptures suggest that fault zone morphology changes rapidly during the first century after rupture and progressively simplifies over millennial timescales, with only 20–80% of the original fault trace remaining after 10 kyr and apparent fault zone width decreasing from ~30 m to ~2 m. Older ruptures are represented in the geomorphic record by narrower fault zones and fewer preserved fault traces. We conducted a complementary regional mapping experiment that quantifies interpretation uncertainty, showing that even when fault-related landforms are well preserved, independent mappers place faults a median of 34 m from geomorphic indicators of rupture and commonly miss subtle indicators of future rupture. Together, these findings show that the geomorphic record becomes progressively less complete as time since rupture increases. Consequently, reconstructions of older surface ruptures based on human interpretation underestimate the original width, distribution of fault strands, and extent of surface faulting, with important implications for fault characterization and probabilistic fault displacement hazard analyses.

Key Words
tectonic geomorphology, fault scarp degradation, uncertainty

Citation
Zuckerman, M. G., Rodriguez Padilla, A. M., Scott, C. P., & Arrowsmith, R. (2026, 08). Preservation and interpretation of the geomorphic record of earthquakes. Poster Presentation at 2026 SCEC Annual Meeting.

Related Projects & Working Groups
Earthquake Geology