PythonFastCycles

This is a Python package to interact with the the Fortran code FastCycles.
FastCycles has been developped by Pierre Romanet during his PhD thesis under the direction of R. Madariaga and H. Bhat.
See Romanet et al. (2018). [1]

Install

You can install the lastest version of PythonFastCycles using pip.
Run in a terminal:
pip install PythonFastCycles

How to use

Create files for a simulation

Defines path to a simulation folder

path = 'path/to/fastcycles/problems/'

Defines parameters

fric_law = 'RateStateAgeing_R'
frac_mode = 'ModeIII'

mu = 3e10 
Dc = 1e-3
sigma_N = -1e8
a = 0.0075
b = 0.01

The lenght of the fault L is defined with the ratio L/L_nuc (L_nuc is computed automatically).

L_over_Lnuc = 2

Defines σ

s11 = 0.0
s22 = 0.0
s33 = 0.0
s12 = 0.0
s13 = 0.0
s23 = 0.1

sigma_dot = np.array([[s11, s12, s13], [s12, s22, s23], [s13, s23, s33]])

Create a simulation 'test'

First initialise the simulation

test = Simulation(path, 'Test', mu, a, b, fric_law=fric_law, frac_mode=frac_mode, sigma_N=sigma_N, Dc=Dc)

You can thus create all files (i.e. config.in, geometry.in, GPS.in and tides.in) using :

test.create_all_files(L_over_Lnuc, sigma_dot, geom_type='1fault')

Parameters that can be parse to this function:

• geom_type specifies the geometry of your fault system. For now you can only choose from:

  • "1fault", a geometry with a single fault of length L defines with L/L_nuc

  • "2faults_overlapping", the geometry of Romanet et al. (2018), GRL. You can then specify:

    • D/L_nuc with D_over_Lnuc
    • the overlap (L/(2L_nuc in the figure below) the parameter overlap

    

  • "multiple", a geometry with multiple faults defined with a length, an angle and the distance in x and y of one edge from the first fault

    • lengths is a vector with the lengths of the faults normalised by Lnuc (L/L_nuc). It has size n, with n the number of fault.
    • angles is a vector with the orientation of the faults. The angle is positive in the trigonometric direction. It has size n.
    • xs is the distance in x normalized by L_nuc between the edge defining the fault and the first fault. Hence it has size n-1.
    • ys is the distance in y normalized by L_nuc between the edge defining the fault and the first fault. Hence it has size n-1.

    

• stop_crit can be 0, 1 or 2.

• stop_crit = 0: simulation will stop after the first event
• stop_crit = 1: simulation will stop after max_it iterations
• stop_crit = 2: simulation will stop at final_time

• GPSx and GPSy, two lists with the GPS stations coordinates. By default there is only one GPS station at (10, 10).
• Tampli, Tperiod, Tphase, three lists uses to impose tides. By default there is no tides.
• Vval_x1 and Vval_x2, x coordinates delimiting the portion on the fault on which the initial perturbation is imposed
• Vval_pourc, the amplitude of the perturbation

Instead of creating all files at once, you can choose to create just one file.
The following code lines are doing exactly the same thing as:

test.create_all_files(L_over_Lnuc, sigma_dot, geom_type='1fault', stop_crit=1, max_it=10000)

# Creates tides.in with default values of tides (i.e. no tides)
test.create_tides_file()
# Creates GPS.in with default values (one GPS station at (10, 10))
test.create_GPS_file()
# Creates geometry.in for a single fault 
test.create_geom_1fault(0, test.Lnuc * test.L_over_Lnuc)
# Creates config.in file with default values 
test.create_config_file(sigma_dot)

When you create a geometry, you can add the argument show=True to the function to plot the geometry.

Reading and processing simulation data

First we need to read output files:

Test = ReadData(path/to/simulation/folder)

Plot the geometry of the fault system:

Test.plot_geometry()

By default axis are normalised by L_nuc but you can add the argument scale='X' to have coordinates in meters.

Plot the maximum velocity for all faults:

Test.plot_max_vel()

You can choose the location of horizontal earthquake and SSE limits with eql and ssel arguments. Default is eql=1e-3, ssel=1e-8.

Plot slip rate evolution

Test.plot_slip_rate()

With vmask you can specify a value under which all data will be display as white.

Plot moment rate evolution

Test.plot_moment_rate()

Plot GPS rate evolution

Test.plot_GPS_rate()

Plot GPS displacements

Test.plot_GPS_disp()

By default all GPS stations are plot in the save graph. With the argument plot_type='each' each GPS station will be displayed in a subplot.

Aditional arguments

• For all this functions, to plot data between a and b indices you can specify a start=a and/or a stop=b argument(s).
• By default figures are saved in the simulation directory. You can specify savefig=False is you don't want to save them.

Fixing simulations' problems

Sometimes, the maximum slip rate in 'MomentRate.out' is '-Infinity' and the moment rate is 'nan'. It is due to a wrong tolerance criteria for the adaptive time step. For the moment there is no way to know it before running the simulation, and it has to be manually modified afterwards. The tolerance criteria is denoted as tol_solver and can be set in 'config.in'.
The class FixSimulations check if simulations have '-Infinity' maximum slip rate and can modify the tolerance criteria.
All you have to do is:

fix = FixSimulations(path, simunames)

with path the path to the simulations directory and simunames a list with the names of the simulations to check.
For example:

simunames= ['simu1', 'simu2', 'simu3']

You will then be asked if you want to automatically change tol_solver. Press y to do so and press y again to relaunch simulations.
tol_solver will be decreased by an order of magnitude but it might not be sufficient. You can thus redo the manipulation to decrease it further down.

If you press n you will exit the function but you can still find the simulations that need to be changed using:

fix.simu_affected

Miscellaneous functions

find_simunames

find_simunames(path, regex) finds all simulations in the directory path matching the expression regex. For example:

find_simunames(path, '^simu3\d')

will search all simulations with name starting by 'simu3' and a digit (simu30, simu31, ..., simu39).
You can type help(find_simunames) to see common regex syntax.

References

[1] Romanet et al. (2018). ast and slow slip events emerge due to fault geometrical complexity. Geophysical Research Letters, 45(10), pp.4809-4819 https://doi.org/10.1029/2018GL077579