The simulation parameters are implemented by modifying the parameter.txt file, rather than by changing
the source code. The input variable list is in :numref:`General Parameters Settings`. If InputHetoparamter in :numref:`General Parameters Settings` is True, heterogeneous stress and friction parameters are
imported from external files. The external filename is defined in parameter.txt and must remain in the
same directory as parameter.txt. In this case, you don't need to set the parameters of
:numref:`Stress and Friction Settings` and :numref:`Nucleation Settings`. Otherwise, you need to appropriately set the parameters of stress and frictional initial conditions shown
in :numref:`Stress and Friction Settings` and :numref:`Nucleation Settings`. :numref:`Fluid Parameters Settings` and :numref:`Thermal Pressurization Parameter Settings` must be set up if fluid-induced dilatancy and thermal pressurization are considered.
| Parameter | Default | Description |
|---|---|---|
| Corefunc directory | The storage path for the kernel function matrix composed of stress Green's functions. | |
| Node_order | False | If True, the node order of the triangular element is clockwise. |
| save Corefunc | False | If True, save the kernel function so that it does not need to be recalculated next time. |
| Scale_km | True | If True, coordinates are scaled up by 1000 (modeled in km, suitable for natural earthquakes); otherwise remain in meters (suitable for laboratory earthquakes). |
| Hmatrix_mpi_plot | False (MPI only) | Draw H-matrix structure diagram; different colors represent sub-matrices calculated by different processes. |
| Lattice Matrice | False (MPI only) | Using Lattice H-Matrice |
| Lattice Partitioning depth | 2 (MPI only) | The initial Lattice partitioning depth. |
| Using C++ green function | True (MPI only) | If True, use C++ to calculate stress Green's functions; otherwise use Python. |
| GPU | False (CPU/GPU only) | If True, enable GPU parallel acceleration (using cupy). |
| Max thread workers | 50 (CPU/GPU only) | Number of processors in ProcessPoolExecutor to parallelize Green's function calculations. |
| Batch_size | 1000 (CPU/GPU only) | Number of batches in ProcessPoolExecutor to parallelize Green's function calculations. |
| Input Hetoparamter | False | If True, import heterogeneous stress and friction parameters from external files. |
| Inputparamter file | File name of imported heterogeneous stress and friction parameters. | |
| Lame constants | 0.32 × 10¹¹ Pa | First Lamé constant. |
| Shear modulus | 0.32 × 10¹¹ Pa | Shear modulus. |
| Rock density | 2670 kg/m³ | Rock mass density. |
| Reference slip rate | 1 × 10⁻⁶ m/s | Reference slip rate. |
| Reference friction coefficient | 0.6 | Reference friction coefficient. |
| Plate loading rate | 1 × 10⁻⁹ m/s | Plate loading rate. |
Note
The initial Lattice partitioning depth, typically 2 corresponds to 4*4 grids, and 3 corresponds to 8*8 grids.A larger depth indicates a greater degree of parallelism, but also a greater memory cost. Please ensure that the number of cpus used is an integer multiple of pow(2, depth). For example, if Lattice Partitioning depth=2, then the number of cpus used must be 4, 8, 12, 16, etc.; if Lattice Partitioning depth=3, then the number of cpus used must be 8, 16, 24, 32, etc.
| Parameter | Default | Description |
|---|---|---|
| If Dilatancy | False | If True, implement shear-induced dilatation. |
| If Coupledthermal | True | If True, coupled implement shear-induced dilatation and thermal pressurization in earthquake cycle. |
| Dilatancy coefficient | 3 × 10⁻⁴ | Quantifies the volume change (dilation or contraction) in a porous medium due to shear deformation. |
| Hydraulic diffusivity | 1 × 10⁻⁵ m²/s | The rate at which pore fluid diffuses across the fault. |
| Shear zone width | 2 × 10⁻³ m | The thickness of the actively shearing zone represents the width of the region undergoing significant shear deformation. |
| Effective compressibility | 8 × 10⁻¹¹ Pa⁻¹ | The volumetric strain response of the porous medium to changes in pore pressure. |
| Constant background porepressure | 2 MPa | Constant pore pressure. |
| Initial porepressure | 2 MPa | Initial pore pressure. |
| Parameter | Default | Description |
|---|---|---|
| If thermal | False | If True, implement thermal pressurization. |
| Thermal diffusivity | 1 × 10⁻⁶ m²/s | Material property that describes how quickly heat spreads through a material. |
| Shear zone width | 2 × 10⁻³ m | The thickness of the actively shearing zone represents the width of the region undergoing significant shear deformation. |
| Ratio of thermal expansivity to compressibility | 1 × 10⁻⁵ | Ratio of thermal expansivity to compressibility. |
| Heat capacity | 3 × 10⁻⁶ J/K | A measure of how much heat energy is required to raise the temperature of a system. |
| Background temperature | 0 Celsius degree | Background temperature. |
| Initial temperature | 0 Celsius degree | Initial temperature. |
Note
The implementation of dilatation and thermal pressurization is controlled by the following parameters:
- No dilatation or thermal pressurization
Dilatancy = FalseCoupledthermal = TrueorFalsethermal = False
- Dilatation only
Dilatancy = TrueCoupledthermal = TrueorFalsethermal = False
- Thermal pressurization only
Dilatancy = TrueCoupledthermal = Falsethermal = True
- Coupled dilatation and thermal pressurization
Dilatancy = TrueCoupledthermal = Truethermal = True
- Limitation
- The GPU version does not currently include thermal pressurization.
| Parameter | Default | Description |
|---|---|---|
| Half space | False | If True, calculating half-space Green's functions. |
| Fix_Tn | True | If True, fixed the normal stress. |
| Vertical principal stress (ssv) | 1.0 | The vertical principal stress scale: the real vertical principal stress is obtained by multiplying the scale and the value. |
| Maximum horizontal principal stress (ssh1) | 1.6 | Maximum horizontal principal stress scale. |
| Minimum horizontal principal stress (ssh2) | 0.6 | Minimum horizontal principal stress scale. |
| Angle between ssh1 and X-axis | 30° | Angle between maximum horizontal principal stress and X-axis. |
| Vertical principal stress value | 50 MPa | Vertical principal stress value when Shear traction solved from stress tensor is True, or normal stress when it is False. |
| Vertical principal stress value varies with depth | True | If True, vertical principal stress value varies with depth, and the horizontal principal stress value also changes with depth simultaneously. |
| Turning depth | 5000 m | If Vertical principal stress value varies with depth is True, starting at this depth, the stress no longer changes with depth. |
| Shear traction solved from stress tensor | False | If True, the non-uniform shear stress is projected onto the non-planar fault surface by the stress tensor. |
| Rake solved from stress tensor | False | If True, the non-uniform rakes are solved from the stress tensor. |
| Fix_rake | 30° | If True, set fixed rakes when Rake solved from stress tensor is False. |
| Widths of VS region | 5000 m | The width of the velocity-strengthening (VS) region near boundary. |
| Widths of surface VS region | 2000 m | Widths of velocity-strengthening (VS) region near free surface. |
| Transition region from VS to VW region | 3000 m | Transition region width from velocity-strengthening (VS) to velocity-weakening (VW) region. |
| Parameter | Default | Description |
|---|---|---|
| Set_nucleation | False | If True, sets a patch whose shear stress and sliding rate are significantly greater than the surrounding area to meet the nucleation requirements. |
| Radius of nucleation | 8000 m | The radius of the nucleation region. |
| Nuclea_posx | 34000 m | X-coordinate of the nucleation center. |
| Nuclea_posy | 15000 m | Y-coordinate of the nucleation center. |
| Nuclea_posz | -15000 m | Z-coordinate of the nucleation center. |
| Rate-and-state parameters a in VS region | 0.04 | Rate-and-state friction parameter a in velocity-strengthening (VS) region. |
| Rate-and-state parameters b in VS region | 0.03 | Rate-and-state friction parameter b in velocity-strengthening (VS) region. |
| Characteristic slip distance in VS region | 0.13 m | Characteristic slip distance (L) in velocity-strengthening (VS) region. |
| Rate-and-state parameters a in VW region | 0.004 | Rate-and-state friction parameter a in velocity-weakening (VW) region. |
| Rate-and-state parameters b in VW region | 0.03 | Rate-and-state friction parameter b in velocity-weakening (VW) region. |
| Characteristic slip distance in VW region | 0.13 m | Characteristic slip distance (L) in velocity-weakening (VW) region. |
| Rate-and-state parameters a in nucleation region | 0.004 | Rate-and-state friction parameter a in nucleation region. |
| Rate-and-state parameters b in nucleation region | 0.03 | Rate-and-state friction parameter b in nucleation region. |
| Characteristic slip distance in nucleation region | 0.14 m | Characteristic slip distance (L) in nucleation region. |
| Initial slip rate in nucleation region | 3e-2 m/s | Initial slip rate imposed in the nucleation region. |
| ChangefriA | False | If True, the parameter a changes gradually while b remains unchanged (and vice versa if False). |
| Initlab | True | If True, apply random non-uniform normal stress distribution. |
| Parameter | Default | Description |
|---|---|---|
| totaloutputsteps | 2000 | The total number of calculation time steps. |
| outsteps | 50 | The time step interval for outputting VTU files. |
| outputSLIPV | False | If True, output slip rate data for each recorded step. |
| outputstu | True | If True, VTU files will be saved in the outvtk directory. |
In addition to parameter.txt, the program requires an external .msh file for the geometry, as well as input parameter files if Input Hetoparamter is set to True. The filename(s) for these input parameter files are defined within parameter.txt.
The .msh file contains the necessary mesh data (node coordinates, element connectivity, etc.) and must be exported from Gmsh software. Please ensure that you select the Version 2 / ASCII format, as this is the only format compatible with the current reader in the code.
When Input Hetoparamter == True, heterogeneous initial conditions and friction/stress parameters can be imported from external file(s). The format of each row in the input parameter file is:
rake(0) a(0) b(0) dc(0) f0(0) tau(0) sigma(0) vel(0) taudot(0) sigdot(0) InitP(0) hs(0)
rake(1) a(1) b(1) dc(1) f0(1) tau(1) sigma(1) vel(1) taudot(1) sigdot(1) InitP(1) hs(0)
…
The total number of rows equals the number of triangular elements (cells) in the mesh.
- Column 1: rake angle (in degrees). This value can vary during the simulation.
- Columns 2-5: rate-and-state friction law parameters
- Column 2:
a- Column 3:b- Column 4: characteristic slip distancedc(orL) - Column 5: reference friction coefficientf0 - Columns 6-7: initial traction
- Column 6: initial shear traction
tau- Column 7: initial normal tractionsigma(positive for compression) - Column 8: initial slip rate
vel - Columns 9-10: additional loading rates (beyond the tectonic plate loading)
- Column 9: shear traction loading rate
taudot- Column 10: normal traction loading ratesigdot(usually 0) - Column 11-12 (optional): initial pore pressure
InitPand shearing zone widthhs. If fluid flow is not enabled or these two columns are omitted, a uniform initial setting defined elsewhere will be used.