Research
Induced Earthquake Mitigation
This study is motivated by the Ridgecrest aftershock sequence, which appears to be strongly suppressed within the Coso geothermal area. I conducted a simulation to estimate the stress change during geothermal operation and found that the 30 years of accumulated thermal stress results in considerable shear stress depletion, which is sufficiently large to suppress the Ridgecrest aftershock in the area.
(Im et al., 2021 Nature; 2021 Geothermics).
3D Earthquake Simulation (Quake-DFN)
Forecasting induced earthquakes requires a comprehensive understanding of friction, fault geometry, and local stress field. Numerical simulation, therefore, is a useful tool as it can incorporate complex fault systems with heterogeneous frictional properties. My earthquake simulator can incorporate a complex 3-D Discrete Fault Network with rate and state friction applicable to actual injection sites that have complex fault geometry heterogeneous friction
https://github.com/limkjae/Quake-DFN
(Im and Avouac, in-prep).
Earthquake nucleation in Complex Fault system
Earthquakes come in clusters formed mostly of mainshock-aftershock sequences, including occasional foreshocks. This clustering is thought to result primarily from stress transfer among faults. In there work, we analyze how the characteristics of foreshock and aftershock cascades can be explained by fault interactions, taking into account the spatial distribution of faults and the fact that earthquake nucleation is not instantaneous. We resort to analytical approximations and numerical simulations with a discrete network of faults governed by rate and state friction. A fault network including a high-density fault zone favorable to stress transfer produces realistic foreshocks and aftershocks.
(Im and Avouac, 2023 GJI).
2D Discrete Fault Simulation Code: https://github.com/limkjae/MDFNRSF2D
ETAS and MLE Inversion Code: https://github.com/limkjae/ETAS_and_Inversion
Mode of Frictional Slip
Frictional sliding exhibits different modes. I investigate those slip modes with modern friction formulation with numerical simulation with full consideration of inertia. Simulation results can demonstrate the entire spectrum of deformation response - steady sliding, stick-slip, slow slip, and inertia-dominated vibration. My model explains slow earthquakes and associated tremors.
(Im et al., 2020 Nature Geoscience; 2018 JMPS; 2021 EPSL; 2022 JMPS)
This work is based on the rate and state friction spring slider simulation code:
https://github.com/limkjae/MDFNRSF2D (Im et al., 2017 GJR)
Fracture Permeability Evolution
It is challenging to develop realistic yet tractable physics-based permeability models since the transport properties of rocks are strongly influenced by various chemo-mechanical effects such as pressure solution, subcritical crack growth, shear comminution, elastic and inelastic dilation, and clogging/unclogging. I experimentally investigated the combined evolution of friction and permeability during dynamic and static motion.
(Im et al., 2018 GRL; 2019 JGR)