Automatic digitization and processing of strong-motion accelerograms. Part I. Automatic digitization. Report No. 79-15 I

This report presents the current data reduction and analysis procedures which are used in routine processing of strong-motion accelerograms at the University of Southern California. It presents recent developments and changes with respect to our first report in 1973 dealing with this subject (Trifunac and Lee, 1973). The first part of this report (Part I) describes the new hardware facility for automatic computer digitization of analog film accelerograms. This facility is now completed; it is operational and performs automatic digitization on a routine basis. Since it is capable of digitizing raw data an order of magnitude faster than the semi-automatic hand-controlled digitizers considered in our previous reports, the entire mini-computer software package for the corresponding data handling and processing has also been developed (Part II). Though the principles for baseline correction, instrument correction and spectral analysis of strong-motion accelerograms remain the same as in Trifunac and Lee (1973), it has been necessary to modify the old programs written for an IBM-type computer, to the form convenient for a mini-computer using disk operating systems.