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Predictable recovery rates in near-surface materials after earthquake damage
Luc Illien1, Jens M Turowski2, Christoph Sens-Schönfelder2
1GFZ Helmholtz Centre for Geosciences, Potsdam, Germany. lillien@gfz-potsdam.de.
Nature Communications
|February 20, 2025
Summary
Earthquakes cause subsurface damage that recovers over time through relaxation. The recovery time is an intrinsic property of the material, predictable regardless of earthquake intensity.
Area of Science:
- Geophysics
- Seismology
- Material Science
Background:
- Earthquakes cause transient mechanical damage in the shallow subsurface, leading to postseismic hazards and long recovery times.
- This phenomenon is linked to relaxation, but systematic controls on recovery duration after seismic shaking remain unclear.
- Understanding these recovery dynamics is crucial for assessing earthquake risks and subsurface stability.
Purpose of the Study:
- To investigate the systematic controls on relaxation time scales in the shallow subsurface following seismic events.
- To determine if the relaxation time scale is dependent on the intensity of ground shaking.
- To provide insights into the predictability of earthquake damage dynamics in geological materials.
Main Methods:
- Analysis of seismic velocity changes using ambient noise interferometry.
- Examination of data from two successive large earthquakes and their aftershocks.
- Application of relaxation models to understand subsurface property recovery.
Main Results:
- The relaxation time scale was found to be a constant intrinsic property of the substrate.
- This time scale is independent of the intensity of the earthquake ground shaking.
- The study demonstrates the predictability of earthquake damage recovery dynamics.
Conclusions:
- Earthquake damage recovery in the shallow subsurface follows predictable relaxation time scales.
- These findings have implications for understanding material behavior under stress and predicting post-earthquake hazard evolution.
- The results can be reconciled with existing frameworks by considering multiple populations of damaged contacts.
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