The IRIS/IDA Data Collection Center is a facility funded through the IRIS Data Management System to process data from the IDA portion of the IRIS Global Seismic Network and make them available to the research community at large. To this end, IDA DCC personnel routinely perform tasks that include, but are not limited to, maintaining contact with, and reviewing instructions for, station operators; documenting and reporting data problems; maintaining records of instrument response and equipment modifications; receiving, logging, and unpacking data; performing quality control and reviewing of that data to assess station performance; and reformatting and distributing data in a timely manner via the IRIS Data Management System.
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IRIS/IDA Travel Times Dataset
The IRIS/IDA Data Collection Center (DCC) is responsible for processing field tapes from IRIS/IDA GSN stations and performing routine quality control review of the data collected. After initial processing to check the accuracy of timing and quality of data, an analyst reviews the waveforms for significant events.
Data are processed using the Antelope software package, developed by Boulder Real Time Technologies, Inc. (www.brtt.com). The Antelope software package provides a wide variety of tools for managing and working with seismic data. Two of the more important programs for processing are DBDETECT and DBLOC2. DBDETECT is an automated arrival picker with an onset estimation; it adds arrival picks to the arrival table. DBLOC2 allows interactively picking, grouping, and associating arrivals, finding locations and displaying waveforms and residuals.
ARRIVAL DETECTION: Raw arrival picks are created by running the DBDETECT program on waveform files in a database. Theoretical travel times are computed based on a predetermined list of events, currently events of mb>=5.0 from the International Data Center's Reviewed Event Bulletin (IDC REB).
ANALYST PROCESSING: An analyst reviews and modifies the raw picks based upon visual analysis of the waveforms in a graphic display window; the DBLOC2 program is used for this purpose. DBLOC2 displays seismic waveforms, bandpassed through a 0.8-3.0 BF filter, and temporary predicted arrivals. Actual arrival times are determined by adjusting pick placement to correspond to the onset of phase arrivals, judging by waveform amplitude differentials. Processed arrivals are then associated with bulletins of predetermined events. We currently associate with the IDC REB and the National Earthquake Information Center Quick Epicenter Determination (NEIC QED) list.
TRAVEL TIMES DATASET: The travel times dataset currently contains first arriving P phases and S phases recorded by the IRIS/IDA network of GSN broadband stations. Included in the dataset are station, channel, phase, DCC phase pick time, associated origin time, standard deviation of the detection time (delta time), latitude, longitude, focal depth, magnitude, and the catalog referenced for association.
TRAVEL TIME RESIDUALS: The travel time residual (measured in seconds) is found by taking the observed arrival time of a seismic phase and subtracting the expected arrival time. The expected arrival time is calculated by a formula based on the iasp91 travel time model, an event location and origin time, the distance to the station, and the particular seismic phase.
IDA travel times dataset (tabular form)
Travel Time Residuals. The travel time residual (measured in seconds) is found by taking the
observed arrival time of a seismic phase and subtracting the expected arrival time. The
expected arrival time is calculated by a formula based on the iasp91 travel time model, an event location and origin time, the distance to the station, and the particular seismic phase.
IRIS/IDA Data Collection Center
Field Data Status for Entire Network
Full Arrival Time Data
