A method has been developed which takes a seed earthquake time history and modifies it to produce a time-history with a given design response spectrum. It is a multistep process with an emphasis on maintaining phasing during the strong motion duration. Initially, the seed earthquake time history is broken into a series of separate time histories which added together produce the original time history. Each separate time history is drift corrected using modifications only outside the strong motion duration of the seed earthquake time history. This allows the separate time histories to be individually scaled to improve the response spectrum match while the phase of the motion during the strong motion duration remains unchanged. To further improve the design response spectrum match, low cycle, low energy waves are added. This is primarily to control the response at higher frequency. These waves are tuned to improve the response at existing peaks.

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