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Quantifying the Erasure of Earthquakes From Desert Landscapes: Implications for Interpreting the Geomorphic Record of Faulting in Hazard Assessment

Description: 

Seismic hazard analysis relies on knowledge of the timing of past earthquakes, the length and segmentation of faults, the distribution of slip, and the partitioning of that slip between primary and distributed fractures. This information is recorded in the landscape coseismically and erased over time by surface processes. The surface process clock starts ticking immediately after the earthquake so that the time elapsed since the most recent event and surface process vigor dictates the level of detail available for mapping the fault. We use landscape evolution models (transport-limited 2D linear diffusion) to quantify the information loss due to surface processes from the record of surface-rupturing earthquakes in desert landscapes. For the original landforms, we rely on lidar topography collected following the surface ruptures from the 2019 Ridgecrest (California) and 2010 El Mayor-Cucapah (Baja California) earthquakes. We sample a range of rupture styles and rock types. We simulate the effect of surface processes over a 10,000 year time series since the scarp-forming event, mapping the discernible fault traces at five time steps within this series. We rely on two metrics to characterize the information loss associated with surface processes: the change in mappable fault trace length over time and a degradation coefficient that quantifies the evolution of topographic slopes. Only 20-70% of the original fault trace length remains mappable at 10k years. This variability and the rate at which information is lost is primarily controlled by the geometry of the original surface rupture structure. Our findings provide quantitative constraints on the loss of information that can be incorporated into probabilistic displacement hazard assessment.

Session: The Landscape Record of Earthquakes and Faulting - I

Type: Oral

Date: 4/16/2025

Presentation Time: 08:00 AM (local time)

Presenting Author: Alba

Student Presenter: No

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