Abstract
Spectrum representation of strong motion duration has been proposed using total threshold intervals of velocity response envelope calculated for viscously-damped single-degree-of-freedom oscillator of various natural periods.In addition to uniform thresholds in terms of velocity response, frequency-dependent threshold functions defined for various performance limits under strong motion are also applied. Examples of spectral representation are shown using two strong motions representative of a shallow crustal earthquake and a mega-thrust interplate earthquake. Examples of map representation are shown using approximately 700 strong motion records obtained in the 2011 off the Pacific coast of Tohoku Earthquake. It has been shown that the proposed method provides a convenient measure of frequency-dependent duration and the influence of strong shaking on various phenomena including structural response and human behavior.
