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Multi-Cycle Evolution of Seismicity and Fault Zone for a Fault Network

Description: 

Seismic activity exists in a variety of scales from small tremors to large earthquakes resulting in severe economic and societal impacts. It is crucial to understand the mechanism behind the rupture of complex fault systems and how it evolves with time to better inform the seismic hazard models. Here, we model sequences of earthquakes and aseismic slip for a fault network having a primary fault and multiple secondary faults with different size and orientations. We incorporate Drucker-Prager plasticity with pressure dependent yield criterion to capture the off-fault bulk response. The friction is modelled by a rate and state dependent friction law. We assume 2D plane strain deformation and utilize an in-house hybrid numerical scheme, FEBE, combing finite element (FEM) and spectral boundary integral (SBI) methods to resolve both fast dynamic events and slow interseismic deformation.

The simulation results show emergence of complex seismicity including spatiotemporal clustering, foreshocks, and aftershocks. We observe co-seismic activation of the secondary faults during the rupture propagation on the primary fault as well as the migration of aseismic slip between the nearby secondary faults. Foreshocks happen on the secondary faults when the length of the secondary faults is greater than the nucleation length. The initial phase of the seismic cycle exhibits partial ruptures on the primary fault with more distributed seismicity on the secondary faults. Later, the seismicity tends to become more concentrated on the primary fault with full fault spanning rupture. The evolution of off-fault plasticity for the fault network shows more plastic deformation near the ends of the secondary faults that experiences activation. This plastic strain is indicative of off-fault damage and demonstrate the possible non-equilibrium evolution of seismicity and fault zone hosing a network of faults. Our findings may enlighten the understanding of the seismic source mechanics for complex fault zones and the long-term evolution of the fault zone with multi-cycle earthquakes.

Session: Learning Across Geological, Geophysical & Model-Derived Observations to Constrain Earthquake Behavior - II

Type: Oral

Date: 5/1/2024

Presentation Time: 11:15 AM (local time)

Presenting Author: Md

Student Presenter: No

Invited Presentation: 

Authors