Abstract    Pulse period of earthquake records has been known as a key parameter in seismology and earthquake engineering. This paper presents a detailed characterization of this parameter for a special class of earthquake records called pulse-like ground motions. This type of motions often resulting from directivity effects is characterized by a strong pulse in the velocity time history of motion, in normal-fault component. Wavelet analysis was used as a powerful and useful technique in the analysis of non-stationary signals in this study. The period of velocity pulses is basically determined by using the pseudo-period of the mother wavelets. The effects of three different mother wavelets on results were investigated and new empirical predictive equations for pulse period have been derived.

Keywords    Pulse-like ground motions; pulse period; wavelet analysis; directivity effect; magnitude scaling; mother wavelet

چکیده    پریود پالس به عنوان پارامتری مهم در زلزله شناسی و مهندسی زلزله به شمار می رود. این مقاله به بررسی مشحصه های کامل این پارامتر درگروه خاصی از زلزله ها بنام حرکت های پالس-گونه می پردازد. این حرکت ها معمولا به دلیل اثرات جهت داری در حوزه نزدیک گسل و در راستای عمود بر گسل بوجود می آید. در این مطالعه تحلیل موجک ها به عنوان ابزاری قوی در تحلیل سیگنالهای نامانا مورد استفاده قرار می گیرد. پریود پالس با استفاده از مفهوم شبه پریود متناظر با موجک مادر محاسبه می شود. اثرات سه موجک مادر مختلف در تخمین پریود پالس بررسی و در انتها رابطه تجربی جدیدی ارائه خواهد شد.

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