Create initial model¶

TomoATT requires a 3D initial model to start the inversion. The initial model is a h5 file that contains the velocity and anisotropy information. The velocity and anisotropy are stored in Three datasets, vel, xi, and eta respectively. The shape of the datasets is (nr, nt, nt), where nr, nt, and np are the number of grid points along the depth, latitude, and longitude, respectively. These values are defined in the domain section of the parameter file with key n_rtp.

The range of the model is defined by the domain section of the parameter file. The domain section should contain the following keys:

min_max_dep: The minimum and maximum depth of the model in km.
min_max_lat: The minimum and maximum latitude of the model in degrees.
min_max_lon: The minimum and maximum longitude of the model in degrees.

PyTomoATT provides a simple command line interface pta create_model to create a 3D initial model. The help message of this command is as follows:

usage: pta create_model [-h] [-m 1|2] [-i fname] [-c ncol_lon/ncol_lat/ncol_dep/ncol_vel] [-o fname] [-s sigma] [-t vel_type] input_params

Create model for TomoATT from external models: CRUST1.0 or custom model
Ex1 (CRUST1.0): pta create_model -oatt_model.h5 -s5 -tvs input_params.yml
Ex2 (custom model): pta create_model -m2 -imodel.txt -oatt_model.h5 -s3 input_params.yml

positional arguments:
  input_params          The parameter file of TomoATT, The section "domain" will be read.

options:
  -h, --help            show this help message and exit
  -m 1|2                Background model type. 1 for CRUST1.0, 2 for custom ASCII file, defaults to 1
  -i fname              Path to input custom model with ASCII format, only valid for -m2
  -c ncol_lon/ncol_lat/ncol_dep/ncol_vel
                        Columns used in custom model file, order by lon/lat/dep/vel. defaults to 0/1/2/3
  -o fname              Path to output model, defaults to Sub_CRUST1.0_nr_nt_np.h5
  -s sigma              Smooth the 3D model with a Gaussian filter,Sigma is the standard division of the smoothing kernel in km, defaults to None
  -t vel_type           Type of velocity vp or vs are available, valid for -m1

Using internal CRUST1.0 model¶

PyTomoATT provide a internal CRUST1.0 model, which is a 3D model (Vp and Vs) based on the CRUST1.0 model. The model is stored in the data folder of the PyTomoATT package.

Using -m1 in pta create_model to create a 3D model based on the CRUST1.0 model, for example:

pta create_model -m1 -oatt_model.h5 -s15 -tvs input_params.yml

In this example, the command will create a 3D S-wave velocity model based on the CRUST1.0 model, smooth the model with a Gaussian filter with a standard division of 15 km, and save the model to att_model.h5. The size of the model is defined in the domain section of the parameter file.

Using custom model¶

PyTomoATT also supports creating a 3D model based on a custom ASCII file. The ASCII file should contain the velocity information in the format of lon lat dep vel. The columns used in the ASCII file can be specified by -c option. The order of the columns should be longitude, latitude, depth, and velocity. The default order is 0, 1, 2, and 3. The ASCII file can be specified by -i option. For example:

pta create_model -m2 -i model.txt -oatt_model.h5 -s20 input_params.yml

In this example, the command will create a 3D model based on the ASCII file model.txt, smooth the model with a Gaussian filter with a standard division of 20 km, and save the model to att_model.h5. The size of the model is defined in the domain section of the parameter file.