HR: 0800h
AN: S41C-1011    [Abstracts]
TI: Structural Sensitivities of Finite-Frequency ``Onset Times''
AU: * Zhao, L
EM: zhaol@earth.sinica.edu.tw
AF: Institute of Earth Sciences Academia Sinica, 128 Sec.2 Academia Road Nankang District, Taipei, 115 Taiwan
AB: Recently, finite-frequency effect on the traveltimes of seismic waves has been recognized and finite-frequency Fréchet kernels (``banana-doughnut kernels'') have been gaining popularity in traveltime tomography inversions. A striking feature of the banana-doughnut kernels is the lack of sensitivity of traveltimes to the structural perturbations along the ray paths the seismic waves are supposed to travel. The reason for this is that the ``traveltime anomaly'' defined for the banana-doughnut kernel is measured by the synthetic-record cross-correlation of the entire waveform of a given seismic phase. This is almost completely opposite to the traditional traveltime tomography approach in which the residuals of the onset times of seismic phases are inverted by sensitivity functions distributed only along the ray paths. Here, we explore an alternative approach in which the traveltime anomalies are measured from the early portions of the waveforms rather than the entire waveforms or the onset times of the arrivals. By avoiding the use of the entire waveforms, this type of measurements reduces the contamination from interfering spurious signals, thus increasing the quality and/or quantity of the measurements. It also accounts for the intrinsic finite-frequency nature of the seismic signals ignored in the traditional traveltime tomography. We apply this measurement approach to different seismic phases such as direct P and S waves, surface reflected PP and SS waves, CMB diffracted P_diff and S_diff waves, and Love and Rayleigh waves. We investigate the behavior of this type of measurements at different frequencies and for different seismic phases and also examine the characteristics in their structural sensitivities.
DE: 7260 Theory
DE: 7270 Tomography (6982, 8180)
SC: Seismology [S]
MN: Fall Meeting 2005