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Thiyagu, Ramaswany; Chanerley, Andrew A. (2010)
Languages: English
Types: Unknown
This paper begins with a brief introduction regarding the problems associated with instrument tilts and rotations when recording a seismic event. Most instruments are designed to respond to translational motion along the longitudinal and vertical axes. Tilts in a gravity field introduce a horizontal acceleration component, which is indistinguishable from horizontal acceleration. When the seismometer frame is tilted by a small angle, a torque will be exerted around the hinge and will cause pendulum motion relative to the frame. The effect of this torque is the same as that produced by a horizontal acceleration and leads to baseline shifts in the recorded data. The base line offset of the recorded seismic data makes it difficult to locate the origin. Therefore this base line error should be corrected in order to remove the tilt component embedded in the ground acceleration. Fourier amplitude spectra are applied to vertical and horizontal components of acceleration to measure the difference in high frequency range; the difference is due to the residual tilt present in the horizontal component in the N-S and E-W directions. In this paper we apply independent component analysis (ICA) on simulated tilt data. ICA is a separation technique used in order to recover and hence remove the tilt time series from the acceleration time histories of a near field earthquake source.
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