IRIS/IDA Seismic Wave Travel Times Data Set

[Adapted from the IDA Web site,
"http://ida.ucsd.edu/AboutIDA/index.html"]

Project IDA (International Deployment of Accelerometers) is a global
network of broadband and very long period seismometers operated by the
Institute of Geophysics and Planetary Physics (IGPP), Scripps
Institution of Oceanography (SIO), University of California, San Diego
(UCSD). Project IDA is an element of the IRIS Global Seismographic
Network supported by the Cecil and Ida Green Foundation for the Earth
Sciences, the National Science Foundation, and the Air Force Office of
Scientific Research. There are currently 36 broadband stations
deployed worldwide. Data from an earlier network of 15 very long
period IDA instruments are also available. The Principal Investigator
of Project IDA is Dr. Jonathan Berger ([e-mail]), and the
Executive Director is Dr. Peter Davis ([e-mail]).

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.