HR: 1340h
AN: S33A-0315    [Abstracts]
TI: On Drift Effects in Velocity and Displacement of Greek Uncorrected Digital Strong Motion Data
AU: * Skarlatoudis, A
EM: askarlat@gmail.com
AF: Skarlatoudis Andreas, ARISTOTLE UNIVERSITY OF THESSALONIKI, GEOPHYSICAL LABORATORY, P.O. BOX. 352-1, Thessaloniki, 54124 Greece
AU: Margaris, B
EM: margaris@itsak.gr
AF: Margaris Basil, Institute of Engineering Seismology and Earthquake Engineering, P.O. Box 53, Foinikas, Thessaloniki, 55102 Greece
AB: Fifty years after the first installation of analog accelerographs, digital instruments recording the strong-motion came in operation. Their advantages comparing to the analog ones are obvious and they have been described in detail in several works. Nevertheless it has been pointed out that velocity and displacement values derived from several accelerograms, recorded in various strong earthquakes worldwide (e.g. 1999 Chi-Chi, Taiwan, Hector Mine, 2002 Denali) by digital instruments, are plagued by drifts when only a simple baseline correction derived from the pre-event portion of the record is removed. In Greece a significant number of accelerographic networks and arrays have been deployed covering the whole area. Digital accelerographs now constitute a significant part of the National Strong Motion network of the country. Detailed analyses of the data processing of accelerograms recorded by digital instruments exhibited that the same drifts exist in the Greek strong motion database. In this work, a methodology proposed and described in various articles (Boore, 2001; 2003; 2005) for removing the aforementioned drifts of the accelerograms is applied. It is also attempted a careful look of the nature of the drifts for understanding the noise characteristics relative to the signal. The intrinsic behaviour of signal to noise ratio is crucial for the adequacy of baseline corrections applied on digital uncorrected accelerograms. Velocities and displacements of the uncorrected and corrected accelerograms are compared and the drift effects in the Fourier and response spectra are presented.
DE: 7212 Earthquake ground motions and engineering seismology
SC: Seismology [S]
MN: Fall Meeting 2005