PQLX: A Software Tool to Evaluate Seismic Station Performance

PQLX screenshot snippet

PQLX is open-source software system for evaluating seismic station performance and data quality. The software consists of a server and client but also includes data extraction and manipulation tools. Given waveform data and instrument response files, PQLX server calculates trace statistics, Power Spectral Densities (PSD), and Probability Density Functions (PDF) and writes the results to a MySQL database for quick access.

The PSD and PDF calculations are based on the algorithm by D.E. McNamara and R.P. Buland, Ambient Noise Levels in the Continental United States, Bull. Seism. Soc. Am., 94, 4, 1517-1527, 2004. PQLX is compatible with the Linux, Mac OSX, and Solaris operating systems. Waveform data are supported in Mini-SEED, SAC, SEGY, AH, nano, and DR100 data formats and response files must be in SEED RESP file format.

The PQLX client used to access these results includes a GUI which is comprised of three parts:

  1. Trace Viewer: The Trace Viewer has the same functionality as PQLII (PASSCAL Quick Look II). The user can view trace data, filter, and calculate spectra.
  2. PDF Viewer: Accessing PSD and PDF information in the database, the PDF Viewer displays PDF plots using predefined and/or user-defined time windows.
  3. Station Viewer: After connecting to the database, the Station Viewer displays trace statistics (e.g. max/min values and gap counts), PDF thumbnails, and available trace data. The trace data is not stored in the MySQL database, but must be available via either the filesystem or a supported webservice. Additional waveform analysis functionality is in development.

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