Correction and processing of earthquake accelerograms

Acceleration of ground motion in earthquake is recorded by accelerographs. For analogue accelerographs (SMA-1), human and instrumental errors and in the case of digital ones (SSA-2), low and high frequency noises would be included in accelerograms. In order to use the accelerograph recorded data in practical applications both, errors and noises, should be omitted. The main purpose of this paper is to find different types of errors and noises which appear in the accelerograms and then to introduce appropriate methods to remove them as to maintain characteristics of the recorded earthquake. Correction methods are based on mean removal, base line correction, and high and low frequency removal by the use of low-pass and high-pass filters. Acceleration, velocity and displacement time history were used in processing earthquake signals in the time domain and frequency 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-off frequencies in order not to lose earthquake frequency content is not the same for various records and the filtration process would be better done using the frequency amplitude spectrum related to the particular accelerogram.