Automatic digitization and processing of strong motion accelerograms, 1979

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 (Trifunac and Lee, 1973), for completeness of the system, the entire mini-computer software package for the corresponding data handling and processing has also been developed (Part II). Though the principles of 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.