ISTerre seminar

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The Importance of Damage Zones in Unifying Earthquake Slip Statistics and Dynamics

Tuesday 14 October 2025 - 10h30

Navid Kheirdast - ENS & ISTeP
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We present a minimal model that takes into account the geometry of fault zones, including the size distribution of fractures around a main fault. The model considers the spatial distribution of fractures, with high density near the main fault decreasing with distance from the fault plane, length-dependent strength against rupture, and rate-and-state friction as the constitutive behavior on every slip plane. This reproduces the full spectrum of slip behavior from slow to fast and exhibits all well-known earthquake statistics. Using quasi-dynamic simulations over several centuries of seismicity, we extract a catalog of events similar to those of real earthquakes: the magnitude-frequency distribution follows the Gutenberg-Richter law, the rate of aftershocks decreases according to Omori's law, and the rate of foreshocks increases following the inverse Omori law. We observe M–T scaling for slow events, while M–T³ is observed for fast events. Our model shows localization of seismic events toward the nucleation patch of the future event prior to the mainshock; however, after the event, activity returns to the fault zone. Without considering fluids in the simulation, during slow events, off-fault activity migrates like a fluid diffusion process. The energy density dissipated during rupture, G′, follows the same scaling as observed in data from real earthquakes, and the energy radiated from slow slip events mainly originates from off-fault areas, resembling tremor activity. We conclude that considering the interaction between the main fault and the surrounding damage zone is sufficient to reproduce all observed complexities of real earthquakes

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Organizing team : Géophysique des risques sismiques et gravitaires

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères