DBPapers
DOI: 10.5593/sgem2011/s06.118

PROPOSITION OF A NEW BASELINE CORRECTION METHOD AND COMPARISON WITH DIFFERENT CONVENTIONAL SCHEMES

AUTHOR/S: F. MEHRABI, N. MIRZAEI, M. REZAPOUR , A. BEITOLLAHI
Monday 1 August 2011 by Libadmin2011

11th International Multidisciplinary Scientific GeoConference SGEM2011, www.sgem.org, SGEM2011 Conference Proceedings/ ISSN 1314-2704, June 20-25, 2011, Vol. 2, 123-130 pp

ABSTRACT

It is shown by experience that direct double integration of strong motion data with the
aim of generating earthquake displacement records usually leads to unrealistic values of
residual displacements even for earthquakes with moderate magnitudes or at far
epicentral distances. The appearance of velocity and displacement records suggests that
changes in the zero level of acceleration are responsible for these drifts. Therefore, in
order to calculate real displacements, baseline correction seems consequential. This
article illustrates the effect of different conventional baseline correction schemes on
amplitude spectra for a couple of earthquakes of Iran. In addition, a new scheme is
proposed in which the velocity data are first baseline corrected in the time domain using
a sliding window and fitting technique, and the derived acceleration is processed in the
frequency domain using a fourth order band pass Butterworth filter. The acceleration
data are then integrated to obtain the real velocity and displacement. Affecting the
synthetic parameters of accelerograms (PGA, PGV, etc.), the ability to attenuate the
artificially produced long period oscillations before the onset of the earthquakes and
independency on record length are among the features of the new scheme. The feasibility of the proposed approach is assessed using several examples. Finally, comparisons are made between the results of the proposed scheme and conventional procedures.

Keywords: baseline correction, velocity drift, residual displacement, strong motion, sliding window, regression

PAPER 2011/s06.118: PROPOSITION OF A NEW BASELINE CORRECTION METHOD AND COMPARISON WITH DIFFERENT CONVENTIONAL SCHEMES

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