Code and data accompanying a paper entitled "Broad Resonance of Fault Slip under Oscillatory Normal Stress: Insights from a Microphysical Friction Model"
Description
Earthquakes and slow-slip events can sometimes be triggered or modulated by small stress changes produced by passing seismic waves, solid-Earth tides, or seasonal variations in groundwater and surface-water loading. Precisely how these weak environmental forces influence fault behavior, however, remains poorly understood. In this study, I use a physics-based numerical model to investigate how faults respond to repeated fluctuations in the normal stress that clamps the two sides of a fault together. I perform numerical simulations using a spring–slider fault analog and a solver embedded in the commercial finite-element software COMSOL, to quantify how the shear-stress response varies with spring stiffness, perturbation period, perturbation amplitude, and the material properties of fault-filling rocks (fault gouge). The results show that these small periodic stress changes can, under favorable conditions, produce resonant fault slip—a process in which repeated forcing greatly amplifies fault motion, much like pushing a swing at the right rhythm. The enclosed code and data include: 1. CNS model with variable normal stress_COMSOL.mph — A COMSOL source file that solves the two coupled ordinary differential equations (ODEs) with time-dependent normal stress as input. 2. All Simulation Results.rar — Numerical simulation results from 109 runs. Each run contains the evolution of apparent friction coefficient (shear stress / background normal stress), normal stress, and log₁₀(slip velocity) as functions of load-point displacement. Selected runs additionally include the evolution of gouge state variable [tan(dilatancy angle)] with load-point displacement. 3. Six MATLAB source code files, "Processing, a–f…" — Used to process the simulation results sequentially. 4. Six MATLAB source code files, "Plot, stressdrop_Weakening_vs_…" — Used to extract key diagnostic parameters from the time-series results, including normalized shear-stress oscillation amplitude, peak slip velocity, phase lag, and slip recurrence period. 5. Data for Original graphs.rar — Compiled numerical results containing all intermediate processing outputs (9 files in format of .csv). 6. Data_extracted for Original graphs.rar — Compiled, cleaned numerical results ready for plotting (9 files in format of .csv). 7. Original graphs.rar — All figures generated by the MATLAB code and data, saved in PDF format, totally 18. 8. Extracted results for saturated velocity, v_max_1s.xlsx — An Excel table containing extracted saturated slip velocity under short-period forcing (T_ext = 1 s) as a function of normalized stiffness and relative modulation amplitude.
Files
Institutions
- Institute of Geology, China Earthquake AdministrationBeijing, Beijing