Last update: 2016-03-07
As of March 7, 2016 the PDF/PSD Bulk Data Delivery System is INACTIVE and is no longer supports user requests. Station PDF/PSDs are now available via IRIS’s MUSTANG data quality metrics web service
Information on long-term noise levels at seismic stations is important for characterizing the current and past performance of seismic stations and detecting potential operational and/or instrumental station problems. Starting in 2004, data received by the IRIS DMC’s near-real time data collection systems (BUD and USArray) have been analyzed by its automated Quality Analysis Control Kit (QUACK) system. For its noise analysis, QUACK utilizes a version of the McNamara and Boaz software to gather noise information on every broadband station that transmits its data to the DMC in real time.
In their noise processing scheme, McNamara and Boaz calculate Power Spectral Density (PSD) for each 1-hour time series segment. Then the raw frequency distributions are constructed by gathering individual PSDs into frequency distribution bins. A histogram of PSD bins results in PDF (Power Density Function) plots in which transient noises map into a low-level background probability while ambient noise conditions appear as high probability occurrences. The web-based interface of QUACK enables users to customize and display PDFs for time interval of their choosing.
Access to the Power Spectral Density data
For those users interested in the raw PSD data (bin) files, IRIS DMC has implemented an automated system that accepts BREQ_FAST requests and provides user with the corresponding PSD data files (daily bin files). To obtain the PSD data files from this DMC service, users should email their BREQ_FAST requests to: email@example.com.
The following fields must be included in the BREQ_FAST request:
.NAME .EMAIL .LABEL .END request 1ine-1
.NAME dmc .EMAIL firstname.lastname@example.org .LABEL my_request .END LYUB TW 2010 11 08 22 49 46.0000 2010 11 08 23 13 46.0000 1 BH? KAKA AU 2010 11 08 22 53 28.0000 2010 11 08 23 17 28.0000 1 BH? LDF CI 2010 11 08 22 57 29.0000 2010 11 08 23 21 29.0000 1 BH? BTDF MS 2010 11 08 22 49 50.0000 2010 11 08 23 13 50.0000 1 BH?
In response, the PSD Bulk Data Delivery system will bundle the selected PSD files into a gzipped tar file and notifies the user via email of their availability for download.
The structure of the delivered bundle is as follows:
PDFPSF - is the root directory of the PSD data files network - is the network code station - is the station code location - is the location ID yyyy - is the year of the data file jjj - is the julian day of the data file
Djjj.bin File Format
Djjj.bin is a cumulative “bin” file containing the hour long PSD measurements for an entire day, where jjj is the julian day for any given file. The file type is ASCII with data presented in 3 columns. A MATLAB script is available (download) to plot PDF of these PSDs.
FREQUENCY POWER #HITS FREQUENCY POWER #HITS FREQUENCY POWER #HITS FREQUENCY POWER #HITS FREQUENCY POWER #HITS . . . .
- FREQUENCY is the frequency in Hertz
- POWER is the power bin in (dB)
- #HITS is the number of times
To cite the IRIS DMC Data Products effort:
- Trabant, C., A. R. Hutko, M. Bahavar, R. Karstens, T. Ahern, and R. Aster (2012), Data Products at the IRIS DMC: Stepping Stones for Research and Other Applications, Seismological Research Letters, 83(5), 846–854, doi:10.1785/0220120032.
To cite the IRIS DMC PDF-PSD PDF/PSD Bulk Data Delivery System:
- IRIS DMC (2012), Data Services Products: PDF-PSD PDF/PSD Bulk Data Delivery System, doi:10.17611/DP/PDFPSD.1.
- Manochehr Bahavar, IRIS DMC