Table of Contents
- Part I: Setting up SPECFEM3D_GLOBE
- Part II: Continental-scale Simulations
- Part III: Visualization
- Part IV: Adjoint Simulations (Bonus)
- Further Work
Part II: Continental-scale Simulations
This second part of the tutorial will take you through the steps that are needed to run a continental-scale simulation with SPECFEM3D_GLOBE. The steps we need to take are the following:
- Prepare the Data and Parameters
- Generate a Mesh for the Continental Model
- Run the Solver
Prepare the Data and Parameters
As we talked about in the previous part of the tutorial, the parameter files
for the SPECFEM3D_GLOBE package are found in the
DATA/ folder. In order to
set up the simulation, we need to:
- Provide the source characteristics for the event we want to simulate
- Provide names and locations for the stations we want to use
- Set the relevant simulation parameters in the
Step 1: Provide the source characteristics for the event we want to simulate
The format for the source should follow that of the Global CMT Catalog. For the South Napa earthquake, the source
CMTSOLUTIONis given as follows:
CMT 2014 08 24 10 20 49.36 38.3100 -122.3800 12.0000 6.1 6.1 C201408241020A event name: C201408241020A time shift: 0.0000 half duration: 0.0000 latitude: 38.3100 longitude: -122.3800 depth: 12.0000 Mrr: -4.760000E+23 Mtt: -1.090000E+25 Mpp: 1.140000E+25 Mrt: -1.360000E+24 Mrp: -2.500000E+24 Mtp: 1.120000E+25
Step 2: Provide the names and locations for the stations we want to use
The recording stations are given in the
STATIONSfile, using the following format:
Station Network Latitude(degrees) Longitude(degrees) Elevation(m) Burial(m)
For the South Napa earthquake, the
STATIONSfile has 167 stations from the Global Seismographic Network (GSN):
AAE IU 9.0292 38.7656 2442.0 0.0 AAK II 42.6390 74.4940 1645.0 30.0 ABKT II 37.9304 58.1189 678.0 7.0 ABPO II -19.0180 47.2290 1528.0 5.3 ADK IU 51.8823 -176.6842 130.0 0.0 ... XMAS IU 2.0448 -157.4457 19.0 1.0 XPF II 33.6092 -116.4533 1280.0 100.0 XPFO II 33.6107 -116.4555 1280.0 0.0 YAK IU 62.0310 129.6805 110.0 14.0 YSS IU 46.9587 142.7604 148.0 2.0
More station information can be found on the FDSN webpage.
Step 3: Set the relevant simulation parameters in the
Par_fileis the file where most of the simulation parameters are set. In this tutorial, we will only work with the subset of parameters that is shown below. For a full description of all the parameters in the
Par_file, please consult the SPECFEM3D_GLOBE manual.
# forward or adjoint simulation SIMULATION_TYPE = 1 # set to 1 for forward simulations, 2 for adjoint simulations for sources, and 3 for kernel simulations NOISE_TOMOGRAPHY = 0 # flag of noise tomography, three steps (1,2,3). If earthquake simulation, set it to 0. SAVE_FORWARD = .false. # save last frame of forward simulation or not # number of chunks (1,2,3 or 6) NCHUNKS = 1 # angular width of the first chunk (not used if full sphere with six chunks) ANGULAR_WIDTH_XI_IN_DEGREES = 45.d0 # angular size of a chunk ANGULAR_WIDTH_ETA_IN_DEGREES = 45.d0 CENTER_LATITUDE_IN_DEGREES = 40.d0 CENTER_LONGITUDE_IN_DEGREES = -120.d0 GAMMA_ROTATION_AZIMUTH = 0.d0 # number of elements at the surface along the two sides of the first chunk # (must be multiple of 16 and 8 * multiple of NPROC below) NEX_XI = 192 NEX_ETA = 192 # number of MPI processors along the two sides of the first chunk NPROC_XI = 12 NPROC_ETA = 12 ... # 3D model MODEL = s362ani # parameters describing the Earth model OCEANS = .true. ELLIPTICITY = .true. TOPOGRAPHY = .true. GRAVITY = .true. ROTATION = .true. ATTENUATION = .true. # absorbing boundary conditions for a regional simulation ABSORBING_CONDITIONS = .true. # record length in minutes RECORD_LENGTH_IN_MINUTES = 10.0d0 ... # path to store the local database files on each node LOCAL_PATH = ./DATABASES_MPI ... # output format for the seismograms (one can use either or all of the three formats) OUTPUT_SEISMOS_ASCII_TEXT = .false. OUTPUT_SEISMOS_SAC_BINARY = .true. ...
We will leave the
Par_fileas it is for now, and use this setup to generate the model mesh and run a simulation of the South Napa earthquake.
NOTE: As mentioned in the previous section, if you make any changes to the
Par_file after compiling SPECFEM3D_GLOBE, you need to recompile the package by
make clean and
make all in the root folder.
In this section, we have looked at how to provide the input data that is necessary to run a continental-scale simulation with SPECFEM3D_GLOBE.
In the next section, we will look at how to generate a mesh for the continental-scale model.