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Spatio-temporal Evolution of Seismicity Controlled by Damage Zone Architecture

Description: 

Seismic swarms and foreshocks occur both in laboratory experiments and on tectonic faults. However, their statistical properties and relation to the mainshock differ between the two: natural fault systems are dominated by Poissonian background seismicity, aftershocks and swarms, with rare foreshock activity; in contrast, laboratory experiments often produce a relatively quiescent interseismic phase and abundant foreshocks. To investigate these differences, here we use numerical earthquake cycle simulations to study seismicity patterns in a fault zone comprised of a main fault surrounded by damage, represented by an ensemble of discrete faults with a power-law decay with distance from the main fault. We find that during the interseismic period, seismicity takes place predominantly in the damage zone, and it consists of Poisson background events, episodic swarms, and foreshock sequences. The statistical behavior of seismicity varies systematically as a function of fault zone architecture: for broadly distributed damage, seismicity is dominated by background events and earthquake rates are constant in time, while more localized damage leads to an increase in temporal clustering. Clusters include aftershock sequences triggered by mainshocks on the main fault, isolated interseismic swarms, and accelerating foreshock sequences. Foreshock characteristics are also controlled by fault zone architecture: localized damage favors accelerating foreshock sequences and a progressive coalescence towards the main fault. Narrow damage zones produce a surplus of foreshocks relative to standard triggering models, as part of a cascade process and without requiring an aseismic precursor. These findings suggest that the abundance of foreshocks in laboratory experiments on smooth faults may due to the presence of narrow, rapidly decaying damage zones. On the other hand, broader and more slowly decaying damage produces episodic swarms and fewer foreshocks, consistent with seismicity in complex fault systems in nature.

Session: Advanced Geophysical Observations, Analytical Methods, and New Insights for Earthquake Swarms - I

Type: Oral

Date: 4/15/2025

Presentation Time: 02:45 PM (local time)

Presenting Author: Camilla

Student Presenter: No

Invited Presentation: Yes

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