Physically Based Phase Spectrum and Simulation of Strong Earthquake Ground Motions

Abstract eng:
A physical method m of moddeling phase spectrum s (i.e. Fourier phasee spectrum) is derived throuugh defining tthe relationshiips between the relative arrivval time of w wave groups and a the Fourieer amplitude. The conceptt of the relatiive arrival tim me highlights thee phase properrties of strong earthquake grround motionss, i.e. the enveelope delay. Inn this method, two parameteers with clear phyysical meaninngs are introduuced, say, the m median arrivall time and stroong shock duraation, which provide p a logiccal basis for thee modeling of phase specttrum in physsical sense. F For illustrativee purposes, thhe time seriees of horizonttal acceleration rrecords of eartthquake grounnd motions aree investigated.. Two techniquues based on the t discrete Foourier transforrm (DFT) and thhe continuous Fourier transfform (CFT) arre used to calcculate the scattter diagram between the Foourier amplitude and relative arrival time. It is shown tthat using thee DFT, the raange of relativve arrival tim me correspondiing to the peak amplitudes hiinges upon thee time range oof strong shockk of ground m motions, whichh is not held bby the CFT. Nuumerical results reveal that thhe understandiing of relativee arrival time and its relevaance to the Foourier amplituude of wave grroup providess a feasible meanns for the simuulation of stronng earthquakee ground motioons in engineeering practice.

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