Correction and processing of earthquake accelerograms
Subject Areas :
حجت اله Torkian
1
(
عضو هیات علمی دانشگاه آزاد اسلامی واحد اسلامشهر
)
Keywords: correction of accelerogram, frequency spectrum, low-pass filter, high-pass filter,
Abstract :
Acceleration of ground motion in earthquake is recorded by accelerographs. For analogueaccelerographs (SMA-1), human and instrumental errors and in the case of digital ones (SSA-2), lowand high frequency noises would be included in accelerograms. In order to use the accelerographrecorded data in practical applications both, errors and noises, should be omitted. The main purpose ofthis paper is to find different types of errors and noises which appear in the accelerograms and then tointroduce appropriate methods to remove them as to maintain characteristics of the recordedearthquake. Correction methods are based on mean removal, base line correction, and high and lowfrequency removal by the use of low-pass and high-pass filters. Acceleration, velocity anddisplacement time history were used in processing earthquake signals in the time domain andfrequency content of earthquake was shown using frequency spectrum in frequency domain. All of theabove-mentioned corrections and processings were also applied to a raw accelerogram. The studyindicates that correction of accelerograms before application is inevitable. Besides, selection of cut-offfrequencies in order not to lose earthquake frequency content is not the same for various records andthe filtration process would be better done using the frequency amplitude spectrum related to theparticular accelerogram.