Harmonic decomposition

Background

Harmonic decomposition is an effective technique to separate anisotropic and dipping components from radius and transverse RFs (Bianchi et al., 2010). This technique not only used to estimate azimuthal crustal anisotropy and crustal layer dipping , but used to extract isotropic component of RF for 1D RF inversion. In the Seispy, the command rfharmo is accessible for computing the harmonic decomposition, plotting different components after the decomposition, and save the isotropic component to a local SAC file.

usage: Harmonic decomposition for extracting anisotropic and isotropic features from the radial and transverse RFs [-h] [-t tb/te] [-s dt] [-o outpath] [-e enf] [-p figure_path] rfpath

positional arguments:
  rfpath          Path to PRFs

optional arguments:
  -h, --help      show this help message and exit
  -t tb/te        Time window from tb to te for trimming RFs, NOTE: do not insert space before this argument, defaults to -2/10
  -s dt           Resample RFs with sampling interval of dt
  -o outpath      Specify output path for saving constant component.
  -e enf          Enlarge factor, defaults to 2
  -p figure_path  Figure output path, defaults to ./

Download this example

Users can download the same file as ex-rfani.tar.gz:

• Unzip the file to any directory.

  wget https://osf.io/download/4hk6d/ -O ex-rfani.tar.gz
  tar -xzf ex-rfani.tar.gz
  

Run this example

Change directory to ex-rfani and just run following in the command line

rfharmo -o./

• The RFs are trimmed from -2s to 10s as default.

• Append -o./ to specify the output path to save the isotropic component as SAC format (SC.LTA_constant_R.sac).

• The result of SC.LTA_harmonic_trans.png is automatically saved to current directory as default.

Result of harmonic decomposition in SC.LTA