HFQsim

Description

HFQsim is an earthquake simulator to study the partitioning of seismic/aseismic slip and dynamics of earthquakes on a Heterogeneous strike-slip Fault (HFQsim) using a generalized model of a discrete strike-slip fault governed by static/dynamic friction and creep in an elastic half-space. The simulator includes feedback between frictional heat generated by earthquake slip and subsequent creep slip on the fault. HFQsim generates multiple realistic features of earthquakes (e.g., frequency-size statistics, spatio-temporal clustering including aftershock sequences, heterogeneous slip patterns).

References

Zhou, X., and Y. Ben-Zion (2025), A simulator of earthquakes and aseismic slip on a heterogeneous fault (HFQsim) with static/kinetic friction and temperature dependent creep, J. Geophys. Res., in review.

Outputs

A. Synthetic catalog:

Earthquake catalog generated by the model is recorded in test_model_eqcat.out. The synthetic catalog has 8 columns, including:

• 1. Earthquake time
• 2. Hypocenter location along strike
• 3. Hypocenter location along depth
• 4. Local magnitude following scaling relation of (Trugman and Ben-Zion, 2024)
• 5. Potency magnitude following quadratic form of (Ben-Zion and Zhu, 2002)
• 6. Moment magnitude following Hanks and Kanamori scaling relation
• 7. Rupture area
• 8. Average stress drop

B. Files generated when you start the model:

• 1. Initial temperature on the fault, which is the same as background temperature profile - test_model_faultBkgdT.txt
• 2. Distribution of Arrhenius amplitude - test_model_Arrheamp.txt
• 3. Initial distribution of activation energy - test_model_activE.txt
• 4. Distribution of strength change parameter - test_model_SCP.txt
• 5. Distribution of healing time - test_model_tau_heal.txt
• 6. Distribution of strength profile - test_model_strengthProfile.txt

C. Files record time evolutions of model parameters, which will slow down the simulation. The time interval of recording is defined by running parameters 17 and 18. If you do not want to save those files, set parameters 17 and 18 larger than the simulation time (parameter 16).

• 1. Model time step. (X denotes time sequence of those files) - test_modelX_timeStep.txt
• 2. Type of slip at each time step. 1 means aseismic slip; 2 means seismic slip - test_modelX_slip_type.txt

The following files have a format of 1D array with nL*nD*nTimeStep data points. Index of point (i,j) at time step k is: (k-1)*nL*nD+(i-1)*nD+j

• 3. Slip values at each time step - test_modelX_faultSlip.txt
• 4. Time evolution of slip deficit - test_modelX_hist_slipdef.txt
• 5. Time evolution of stress on the fault - test_modelX_hist_tau.txt
• 6. Time evolution of temperature change on the fault - test_modelX_hist_dT.txt
• 7. Time evolution of activation energy on the fault - test_modelX_hist_actE.txt
• 8. Time evolution of creep velocity on the fault - test_modelX_hist_vc.txt

D. Files generated when the simulation is finished.

• 1. Cumulative aseismic slip - test_model_creepslip.txt
• 2. Cumulative seismic slip - test_model_eqkslip.txt
• 3. Final stress on the fault - test_model_finalstress.txt
• 4. Final slip deficit on the fault - test_model_finalslipdef.txt