HR: 16:30h
AN: S34A-03    [Abstracts]
TI: Unexpected Mode Observations in the Low Frequency Seismic Spectrum
AU: * Vernon, F L
EM: flvernon@ucsd.edu
AF: UCSD, IGPP 0225 UCSD, La Jolla, CA 92093-0225,
AU: Thomson, D J
EM: djt@mast.queensu.ca
AF: Queens University, 411 Jeffrey Hall Queen's University, Kingston, ON K7L 3N6, Canada
AB: The initial observations of the continuous excitation of Earth's normal modes were first presented a decade ago. While significant research by multiple groups has been directed at the source of the continuous excitation since these discovery papers, one set of interesting observations in the discovery papers has not been pursued. These observations are of modes or lines in the seismic spectrum which do not correspond to Earth normal modes. We present more detailed multitaper power spectral density observations of these modes in seismic data recorded by the IRIS Global Seismic Network during seismically quiet times. In addition to the generally accepted continuously forced Earth normal modes, we find the following observations: 1) Modes in seismic spectrum not associated with Earth normal modes. 2) Q (quality factor) of these observed modes have values 1000 and higher. 3) Amplitudes of these modes observed on horizontal seismometers is significantly larger than observed on vertical seismometers. 4) The frequencies and Q of these modes in the seismic spectrum are consistent with Solar normal modes We suggest that the ultimate source of these modes observed in the seismic spectrum are solar modes coupling into the terrestrial system.
DE: 3205 Fourier analysis (3255)
DE: 3280 Wavelet transform (3255, 4455)
DE: 7299 General or miscellaneous
DE: 7524 Magnetic fields
SC: Seismology [S]
MN: 2007 Fall Meeting