EarthScope Data

USArray Quality Control Overview and Resources at the DMC

Overview

Quality control measurements and assessment are performed on USArray data arriving at the DMC in collaboration with other quality monitoring efforts being done upstream from the DMC. For data delivered to the DMC in real-time streams QC is applied as it arrives at the DMC. The DMC's QC effort involves a number of automated measurements along with analyst review of both raw data and the results of the automated measurements.

Quick links:

QC Resources

Station Info - A collection area for USArray station details, including field reports, PDF-based measurements, etc.

Signal to Synthetic comparisons

DMC QC Reports - Routinely generated (weekly) reports by USArray component

QUACK Query Interface - All automated quality control measurement results from the QUACK system are available via this web-based interface, including signal RMS (standard deviation), signal mean, data coverage, gaps and overlaps along with other measurements.

Data Problem Reports - DPRs are issued for significant issues with the primary seismic channels. This interface allows searching for all DPRs stored at the DMC, and is not limited to those for USArray stations.

TA Quality Assessment Results (2005-2008) - These are individual studies of various metrics useful to quantify the overall quality of the Transportable Array:

US-TA and PBO Quarterly Quality Metrics - Gap and Continuity Histograms (3rd Quarter 2009 - 3rd Quarter 2014 ):

  • Gap analysis - number of gaps per station-day in histogram plots
  • Continuity analysis - longest contiguous data segment per month per station in histogram plots

Analyst Review

The review process includes quality assessment of both metadata and waveform data. The primary objective of the assessment is to identify sensor or digitizer malfunction, bad vault conditions, environmental noise sources and that the metadata is correct.

Analysts at the DMC routinely review all 1 sample/second seismic data streams from the Transportable Array and Reference Network (including the Permanent Array) and a significant portion of the higher rate (usally 40 Hz) data. The analyst review is focussed on two objectives: 1) relatively quick identification and reporting of station issues and 2) documenting data issues for future data use and evaluation. For waveform review DMC analysts use the PQLX system.

Routine Review - The DMC performs observational review of waveform data every 1 to 2 days with a focus on the 1 sps. The review processing includes the following observations:

  • Raw data in 1+ day windows
  • Low-pass (30-300 seconds) filtered data 2+ day windows, to identify sensor-related problems
  • Inspection of smaller time-windows as needed using various filters and transformations
  • Inspection of spectra and PDFs to identify noise sources and channel characterstics
  • PDF-based measurements are reviewed for changes and indications of data problems
  • QUACK reports and calulations are reviewed for indications of data problems
  • As needed: coarse station location sanity checks and sensor orientation checks for Reference Network (via particle motion)

The routine review results in:

  • Issue specific reports are emailed to nework operators
  • Weekly reports - Transportable Array and Reference Network (including Permanent Array)
  • Data Problem Reports - DPRs are filed for significant issues with the primary seismic channels, meaning issues that will prohibit or adversely effect common reseach analyses. The DMC's Data Problem Report systems contains DPRs from numerous networks and stations and is not specifically for USArray stations. Link to file new DPR.

Automated QC Processes

QUACK - All USArray data arriving at the DMC via real-time channels is processed using the DMC's QUACK system which performs a variety of quality related measurements.

PDF based measurements - The following image products are routinely calculated from the PDF spectral analysis data and are available in the station specific sections of the Station Info area:

  • Classical PDFs: illustrating station background noise as a probability density function
  • Daily PDF Mode Color Grids: tracking background noise (relative to a noise model)
  • Daily PDF Mode Timelines: tracking background noise for specific frequencies
Examples:
PDF Mode Timeline PDF Mode Color Grid ClassicPDF

A convient way to access these images is through the "PDF Browser" page for each station in the Station Info area or by the PDF link on the _US-TA Station List. The Browser page includes small versions of each image for each BHE, BHN and BHZ channel of the station for the last 60 days of station operation. Clicking on the small versions will return PDF plots for the entire station history, colorgrid plots for 2 years of history, and timelines for 5 years of history. As an example see the PDF Browser for TA station 109C.