An open-source script bundle that contains a series of Python scripts to:
- request waveforms and response data for given station/channels using the ObsPy FDSN client
OR read user’s waveform data files (in SAC, MSEED, CSS, etc. format) and only request response information
- compute and populate an hourly file-based polarization attributes database
- extract hourly and daily polarization PDFs from the polarization database
Polarization attributes of 3-component seismograms are calculated as function of frequency from eigen-decomposition of the spectra covariance matrix of a sliding time window, as described by Koper and Hawley (2010). The derived frequency dependent polarization attributes are:
- degree of polarization (β^2) – a measure of the extent to which noise is organized
- polarization azimuth (θH) – a horizontal direction parameter representing azimuth of the polarization ellipsoid
- polarization inclination (θV) – a vertical direction parameter representing inclination of the polarization ellipsoid
- phase difference between components:
- phase difference between the vertical and principal horizontal components (Φ VH)
- phase difference between the horizontal components (Φ HH)
The Python scripts contained in the Polarization Toolkit bundle generate and display polarization attributes of the waveforms based on user-defined parameters. The following image is generated by the ntk_computePolarization.py script showing power and polarization attributes obtained by processing one hour of BHZ, BHN, BHE data of the NM.SLM station (St. Louis, MO station, Cooperative New Madrid Seismic Network, NM) between 2009-01-01 01:00:00.0 and 2009-01-01 02:00:00.0 UTC.
The Noise Toolkit Polarization Attributes bundle contains 3 Python scripts:
- ntk_computePolarization.py – an ObsPy script to calculate polarization attributes for a given station and time window
- ntk_extractPolarHour.py – a Python script to extract polarization attributes for the given channels and bounding parameters
- ntk_binPolarDay.py – a Python script to bin polarization attributes to daily files for a given channel tag and bounding parameters
visit Polarization Attribute’s SeisCode page for more information on the content of this bundle.
To cite the IRIS DMC Data Products effort:
- Hutko, A. R., M. Bahavar, C. Trabant, R. T. Weekly, M. Van Fossen, T. Ahern (2017), Data Products at the IRIS‐DMC: Growth and Usage, Seismological Research Letters, 88, no. 3, https://doi.org/10.1785/0220160190.
To cite the IRIS DMC The IRIS DMC Noise Toolkit or reference use of its bundles:
- IRIS DMC (2014), Data Services Products: The IRIS DMC Noise Toolkit, https://doi.org/10.17611/DP/NTK.1.
To cite the source of the Noise Toolkit Polarization Attributes bundle:
- Koper K.D. and V.L. Hawley, “Frequency dependent polarization analysis of ambient seismic noise recorded at a broadband seismometer in the Central United States”, Earthquake Science, 23, 439-447, 2010.
To reference the use of the Noise Toolkit Polarization Attributes bundle:
- IRIS DMC (2015), Data Services Products: Polarization Attributes bundle, https://doi.org/10.17611/DP/NTK.4.
- IRIS DMC Products Team
- Keith Koper University of Utah