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Frequency domain corrections of earthquake accelerograms with experimental verifications

Khemici, Omar; Shah, Haresh C.

BLUME-055, The John A. Blume Earthquake Engineering Center Stanford, California, 1982-06, PDF (2 MB) (415/K55/1982)

In this report, an attempt is made to improve the current data processing method used to correct and filter uncorrected accelerograms. The first part of the report presents a comparative study of the time-domain correction method suggested in the Standard Data Processing of Accelerograms developed at the California Inst. of Technology (Caltech) about ten years ago and its frequency domain equivalent. This equivalent method uses the frequency response functions obtained digitally from the Caltech routine. A new and efficient procedure called the Stanford Accelerogram Correction Procedure (SACP) is formulated in the second part. This method uses the fast convolution technique to perform the digital filtering of earthquake accelerograms. The several advantages to this method are discussed. The processing of four earthquake records with the SACP permitted a saving of 37% of the CPU time with respect to the Caltech method. The Fourier amplitude spectra are directly calculated with the SACP. The corrected acceleration obtained with the SACP is higher than that obtained with the Caltech program. A discrepancy of 10% in the corrected acceleration was observed in one of the four earthquake records that has higher frequency content. However, the corrected velocity and displacement obtained with both methods are very close to each other. finally, the last part describes an experimental study using a shaking table. Two different motions were simulated on the table and recorded simultaneously with a standard accelerograph and a high-precision displacement laser beam interferometer. The integrated displacement from both methods showed excellent agreement with the measured displacement when an appropriate low cutoff frequency was applied to the filtering.

Available online: https://stacks.stanford.edu/file/druid:jg579pd4923/TR55_Khemici.pdf