Identification of Far‐Field Long‐Period Ground Motions Using Phase Derivatives

Abstract

The characteristics of long-period ground motions are of significant concern to engineering communities largely due to resonance-induced responses of long-period structures to far-field long-period ground motions which are excited by the existence of distant sedimentary basins. Classifications of records enable applications of far-field long-period ground motions in seismology and engineering practices, such as attenuation models and dynamic analysis of structures. Accordingly, the study herein aims to develop an approach for identifying the far-field long-period ground motions in terms of the later-arriving long-period surface waves. Envelope delays derived from phase derivatives are employed to determine the later-arriving long-period components on the basis of phase dispersion. A quantitative calibration for long-period properties is defined in terms of the ratio of energy from later-arriving long-period components to the total energy of a ground motion. In order to increase the accuracy of candidate far-field long-period records caused by sediments, recording stations within basins or plains are collected from the K-NET and KiK-net strong-motion networks. Subsequently, the motions are manually classified into two categories in order to form a training dataset by visual examinations on their velocity waveform. The two predictive variables, including the corner frequency obtained from envelope delays and the corresponding energy ratio, are used for the establishment of the classification criterion. Furthermore, the analysis of classification results provides insight into the causes for discrepancy and verifies the effectiveness of the proposed method. Finally, comparisons of the mean normalized acceleration response spectrum with respect to the predictors, as well as the local site effects, are performed.

Seismic fragility analysis of human perception in high‐rise buildings subjected to far‐field long‐period earthquake ground motions: A case study for Shanghai tower

“…Thus, aligning with the recommendation proposed by Boore, 20 a two-piecewise frequency function is employed to capture the envelope delay of these earthquake ground motions, 4 writing…”

“…To calibrate Equation ( 2), the least-square approximation incorporating with a weight function is introduced to determine the coefficients of α, β, f corner and t(f corner ) by minimizing the integrated square difference between the actual envelope delays and the assigned model. 4 Noted that the fitted values should be adhere to the physical boundaries, the parameter constraints are imposed. Specifically, α is restricted to the range of (0, −71], β is defined with no constrain range, f corner is constrained within the range of (0, 15 Hz].…”

“…Over the past decades, numerous researchers have investigated structural seismic response of high-rise buildings under far-field long-period earthquake ground motion excitations. [1][2][3] However, there are few studies on human perception to seismic tremor for high-rise buildings with the height from 400 m to 800 m. [4][5][6] The study to establish the way for human perceiving seismic tremors was typically linked to macro seismic intensity scales, such as the Modified Mercalli Intensity (MMI) developed by Richter 7 and the intensity scale introduced by the Japan Meteorological Agency (JMA). 8 The macro seismic intensity scales provide a structured framework to assess, and categorize the human experience of earthquake ground motions.…”

Analysis of Acceleration Signal of Field-Structure Seismological Networks and Assessment of Far-field Earthquake Action in Shanghai

“…The attenuation rate of the long-period component of the acceleration response spectrum of the bedrock site remained unchanged with changes in epicenter distance or magnitude (Xie et al 1990). The far-field longperiod ground motion had the characteristics of low amplitude, long duration, large amplitude in the long period part of acceleration response spectrum, and obvious double peaks (Cheng and Bai 2017;Dai et al 2019).…”

Combination of Spectral Representation and Wavelet Packets for Generating Long‐Period Ground Motions

“…According to the seismological mechanism, long-period ground motions are characterized by LALP surface waves, which are converted from body waves at the margins of either basins or plains [12][13][14][15]. Because of these phenomena, the identification of long-period ground motions with broadband long-period characteristics is developed considering that energy from LALP components is predominantly relative to that of high frequencies [16]. However, it has been suggested that LALP surface waves in the form of velocity traces are equivalent to the summation of sinusoids with narrow-frequency components in special cases [17], as amplifications to the amplitudes of LALP surface waves occur at specific long periods.…”