HR: 0800h
AN: T51B-1344    [Abstracts]
TI: Observations of residual ULF signals from the Parkfield magnetometer surrounding large Earthquakes
AU: * Bortnik, J
EM: jbortnik@gmail.com
AF: QuakeFindedr, LLC., 250 Cambridge Ave., Suite 204, Palo Alto, CA 94306 United States
AU: Cutler, J W
EM: jcutler@quakefinder.com
AF: QuakeFindedr, LLC., 250 Cambridge Ave., Suite 204, Palo Alto, CA 94306 United States
AU: Dunson, C
EM: cdunson@quakefinder,com
AF: QuakeFindedr, LLC., 250 Cambridge Ave., Suite 204, Palo Alto, CA 94306 United States
AU: Bleier, T
EM: tbleier@quakefinder.com
AF: QuakeFindedr, LLC., 250 Cambridge Ave., Suite 204, Palo Alto, CA 94306 United States
AB: We use long-term (1999-2004) ULF data (<10 Hz) from a triaxial search-coil magnetometer located in Parkfield, California, to construct signal statistical quantities parametrized according to time of day, frequency range, coil orientation, season, and geomagnetic activity (Kp index). For each such parameter bin, we compute statistical quantities such as mean, variance, median and quartiles of the magnetic signal, and use these quantities as the baseline values from which signals are assumed to deviate. We then examine time periods surrounding those of large, nearby Earthquakes, and subtract the average and median signal values from the absolute signal values to obtain signal `residues'. Results show that this technique can be effective in reducing large background variations and thereby increasing the signal to noise ratio (SNR), allowing much lower amplitude signals of local origin to be detected. To further increase the SNR, we superpose a number of large earthquake periods and discuss the results in light of possible seismogenic ULF signal sources.
DE: 0925 Magnetic and electrical methods (5109)
DE: 3270 Time series analysis (1872, 4277, 4475)
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
DE: 8178 Tectonics and magmatism
SC: Tectonophysics [T]
MN: Fall Meeting 2005