Research & Projects

Project 1

3-D Visco-elastic Seismic Cycle Model

Low viscosity on one side of the fault results in a smaller rupture area but with a higher Coulomb stress drop on the ruptured fault region.

Low viscosity also leads to a small Coulomb stress accumulation rate and further increases the earthquake recurrence interval by approximately 10% and the earthquake moments by about 30% when the low viscosity is related to a geothermal gradient of 30 K/km.

In addition, across-strike viscosity variation causes asymmetric interseismic ground surface deformation rate.

Zhai, P., F. Li, and J. Huang (2023), Influences of across-strike heterogeneous viscosity on the earthquake cycle in a three-dimensional strike-slip fault model, Earthquake Research Advances, 100218, doi:https://doi.org/10.1016/j.eqrea.2023.100218.

Project 2

Effects of Characteristic Weakening Distance (DRS) on Earthquake Initiation

The characteristic weakening distance influences earthquake nucleation styles significantly.

Fixed length nucleation styles are more common than expanding crack nucleation styles for a wide range of a/b and DRS.

Nucleation sites can also affect the nucleation style and a twin-like nucleation style has been recognized for small a/b.

Zhai, P., and Y. Huang (2024), The Effects of Characteristic Weakening Distance on Earthquake Nucleation Styles in Fully Dynamic Seismic Cycle Simulations, Journal of Geophysical Research: Solid Earth, 129(12), e2024JB029719, doi:https://doi.org/10.1029/2024JB029719.

Project 3

2D seismic cycle model controlled by damage rheology

A novel 2D modeling framework that simultaneously simulates dynamic earthquake cycles and the evolving damage in fault zones, accounting for both seismic (coseismic) events and long-term interseismic processes.

Off-fault damage—characterized by both rigidity reduction and inelastic deformation—primarily accumulates during earthquakes, especially near the surface in a distinct “flower structure,” and does not fully heal between events due to a logarithmic healing law.

Over multiple seismic cycles, the width and rigidity of the fault zone increase and eventually stabilize, resulting in a mature fault zone that reflects the long-term accumulation and saturation of off-fault damage.

Zhai, P., Y. Huang, C. Liang, J-P. Ampuero (2025), Fully dynamic seismic cycle simulations in co-evolving fault damage zones controlled by damage rheology, Geophysical Journal International, 242, doi:https://doi.org/10.1093/gji/ggaf274.

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