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2. Near-Surface Shear-Wave Velocity Structure of the Chiayi Area, Taiwan.
- Author
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Cheng-Feng Wu and Huey-Chu Huang
- Subjects
SHEAR waves ,VELOCITY ,SURFACE waves (Fluids) - Abstract
This paper uses microtremor-array measurements to obtain an overall view of S-wave velocity structure in the Chiayi area, Taiwan. The Rayleigh-wave dispersion curves are calculated using the frequency-wavenumber (f-k) spectrum method and then the S-wave velocity structure of the area is estimated by surface-wave inversion. According to the inversion results, the S-wave velocities decrease from east to west. If the S-wave velocity of the bedrock is assumed to be 1500 m/s, the depths of the alluvium are between 560 and 1400 m gradually increasing from east to west. In order to understand the variations of the shallow S-wave velocity in the area, we sketch 2D and 3D maps using the imaging techniques based on interpolation algorithms. From the 3D results, the thickness of the sediments having an S-wave velocity in the range 270-1500 m/s increases from east to west; whereas the thickness of the layers having an S-wave velocity in the range 1500-2370 m/s decreases from east to west. The results are also in good agreement with the geological and geophysical information of the Chiayi area. Therefore, microtremor-array measurement provides a good alternate to estimate shallow S-wave velocity structure. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
3. Evolution of the temporal multifractal scaling properties of the Chiayi earthquake (ML =6.4), Taiwan
- Author
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Tang, Yi-Jiun, Chang, Young-Fo, Liou, Tai-Sheng, Chen, Chien-Chih, and Wu, Yih-Min
- Subjects
- *
MULTIFRACTALS , *EARTHQUAKES , *FAULT zones , *EARTHQUAKE aftershocks , *SEISMOLOGY - Abstract
Abstract: Variations in the fractal dimension of earthquakes have been suggested to be a precursor of a large earthquake. However, the physical characteristics and seismicity are always different along a large fault system, and it is difficult to segment a large fault for further investigating. Therefore, the fractal dimension of earthquakes on a given fault only reflects the average seismic characteristics of the area and may be unrelated to precursory activity. In this paper, the evolution of the temporal generalized fractal dimension (Dq) of a seismic cluster within a small fault system associated with the Chiayi earthquake (ML =6.4), Taiwan, is investigated. The earthquakes of this sequence are confined in small source volume and reflect the behavior of the local fault system. Our results show that the Dq curve of the background stage is smooth with a low multifractal degree (0.36) and the seismicity is nearly monofractal in the Chiayi region. During the foreshock stage, the seismicity becomes active such that not only the Dq curve exhibits greater variability especially for the steep slope of Dq curve at q=0 but also the temporal fractal dimension changes from nearly monofractal to multifractal. In the aftershock stage, the fluctuation of Dq is large and the multifractal degree is up to 1.0. The temporal multifractal property becomes more pronounced as well. Finally, when the seismicity returns to the background stage, the Dq curve becomes smooth and nearly monofractal again. Therefore, the fluctuations in the Dq spectrum of an earthquake cluster associated with a large earthquake not only give a clear picture of the temporal alterations in the seismogenic regimes but also illustrate their variability through time for a large earthquake. In addition, the variation of the slope of Dq curve at q=0 in the foreshocks may be used as a precursor of a large earthquake. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
- View/download PDF
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