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GPS detection of ionospheric perturbations following the January 17, 1994, northridge earthquakeSources such as atmospheric or buried explosions and shallow earthquakes producing strong vertical ground displacements produce pressure waves that propagate at infrasonic speeds in the atmosphere. At ionospheric altitudes low frequency acoustic waves are coupled to ionispheric gravity waves and induce variations in the ionoispheric electron density. Global Positioning System (GPS) data recorded in Southern California were used to compute ionospheric electron content time series for several days preceding and following the January 17, 1994, M(sub w) = 6.7 Northridge earthquake. An anomalous signal beginning several minutes after the earthquake with time delays that increase with distance from the epicenter was observed. The signal frequency and phase velocity are consistent with results from numerical models of atmospheric-ionospheric acoustic-gravity waves excited by seismic sources as well as previous electromagnetic sounding results. It is believed that these perturbations are caused by the ionospheric response to the strong ground displacement associated with the Northridge earthquake.
Document ID
19950063667
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Calais, Eric
(Scripps Institution of Oceanography, La Jolla, CA United States)
Minster, J. Bernard
(Scripps Institution of Oceanography, La Jolla, CA United States)
Date Acquired
August 17, 2013
Publication Date
May 1, 1995
Publication Information
Publication: Geophysical Research Letters
Volume: 22
Issue: 9
ISSN: 0094-8276
Subject Category
Geophysics
Accession Number
95A95266
Funding Number(s)
CONTRACT_GRANT: NAG5-1910
Distribution Limits
Public
Copyright
Other

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