Quantifying the erasure of earthquakes in desert landscapes

Seismic hazard analysis depends in part on understanding fault segmentation and slip distribution, which are partially recorded in the landscape during surface-rupturing earthquakes. Over time, surface processes degrade these features, challenging fault mapping. We use landscape evolution models to quantify this information loss in desert environments. Using post-earthquake lidar from the 2019 Ridgecrest (California) and 2010 El Mayor-Cucapah (Baja California) ruptures, we simulate landscape degradation using 2D linear diffusion in Landlab over 100, 1k, 5k, and 10k years, with a transport rate of 1 m²/kyr. We assess change in mappable fault trace length, fault zone width, and a “degradation coefficient” based on topographic slope change. Field validation in 2024 (Ridgecrest) supports the modeled degradation. Results show that 20–80% of original fault trace length remains after 10k years and fault zone width decreases from a mean of 30 m to ~2 m, causing older rupture zones to appear narrower and less complex than initially. Degradation is fastest in the first 100 years, then slows. Fault zones with simple, single-strand morphology retain more mappable length and degrade more slowly. Fault zone structure primarily controls degradation rate and fault trace visibility. These findings provide quantitative constraints on landform degradation, informing probabilistic displacement hazard models and fault mapping in tectonically active regions.