نوع مقاله : مقاله پژوهشی
نویسندگان
1 Department of Ptrolum and Mining Engineering, South Tehran Branch, Islamic Azad University, Tehran, Iran
2 aDepartment of Electrical Engineering, South Tehran Branch, Islamic Azad University, Tehran, Iran,
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
The phenomenon of resonance caused by the behavior of alluvium during an earthquake affects the occurrence of damage. This phenomenon occurs when the dominant period of alluvion is equal to the dominant period of structures (Kvasnička et al., 2011; Kanli et al., 2006; Mukhopadhyay et al., 2004). Therefore, determining the dominant frequency of the soil with high certainty is particularly important and is this article's primary goal. The method of using microtremors to determine the site's response to earthquakes and determine the dominant frequency of the soil is of interest, and by measuring them at the ground level, information about the vibration characteristics of the soil can be obtained. (Kerh & Chu, 2002; Kianoush et al., 2023; Jamshidi et al., 2024; Khoshmagham et al., 2024).
Adib (2015) conducted the site classification of Ardakan City in Yazd province based on the earth's natural frequency based on microtremor data. While identifying the dynamic characteristics of the earth in this area, the level of compatibility of the land classification is suitable for the studies of the site effect based on the geotechnical, geophysical, and microtremor data with the regulations of dynamic design of buildings.
Adib and others (Adib et al., 2015) classified the site effect using a fractal model based on the analysis of microtremor data, frequency amplification index, and vulnerability (k-g)) in the city of Meybod and classified Nogoshi and Igarashi (1970, 1971) improved, and four types of soil, including (1) hard soil and weak rock with a frequency of 6.2 to 8 Hz, (2) hard soil with a frequency of about 4.9 to 6.2 Hz, (3) relatively soft soil with a frequency of 2.4 to 4.9 Hz and (4) soil Soft with a frequency of less than 2.4 Hz was separated in this city (Wahba et al., 2024; Labuta et al., 2025).
The Quality of microtremor data and processing methods considerably affects the accuracy of estimating dynamic soil parameters. In this paper, an artificial sampling frequency reduction technique has been proposed for removing high-frequency perturbations from microtremor data, and a running variance method has been used to improve the automatic detection of data sections infected by local perturbations. In this method, the running variance of the signal was calculated using a sliding window. Then, the resulting variance signal was used to remove the portions of data affected by transient perturbations. The proposed methods have been applied to the data recorded for the Meybod city in the North of Yazd Province. By comparing the results of the proposed techniques and the standard methods on microtremor data in urban areas, it is clear that the proposed methods have successfully removed the effects of local transients and their redundant fluctuations such that there is no sharp amplitude variation in the residual signal. The results of the simulation investigations confirm this claim.
Additionally, the ease of parameter setting in the running variance approach makes it superior to the ratio method. Discarding the fewer amounts of contaminated data is an effective method, especially in regions with extensive noise. This paper shows that some variations in microtremor data processes could reduce the destructive effects of local transients on them and consequently improve fundamental site frequency estimation based on the spectral ratio of microtremors. Therefore, considering the low cost of this approach, microtremor analysis can be used as a primary method for initial geotechnical studies in various regions. As a result, it increases the accuracy and degree of confidence in estimating the dominant frequency based on the spectral ratio based on the microtremors data.
کلیدواژهها [English]
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