Near-Surface Shear-Wave Velocity Structure of the Chiayi Area, Taiwan

Wu, Cheng Feng; Huang, Huey Chu

doi:10.1785/0120110245

Cited by 18 publications

(8 citation statements)

References 18 publications

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“…8. Several crustal models have been presented for Taiwan (e.g., Hwang et al 2003;Lin et al 2009;Wu and Huang 2013;Huang et al 2013Huang et al , 2014Kuo et al 2015). To represent the soft basin structure for the station W21B, we refer to the S wave structure in the shallow crust shown in Lin et al (2009) for a profile near Jiali (Lat.…”

Section: Crustal Structurementioning

confidence: 99%

A strong-motion hot spot of the 2016 Meinong, Taiwan, earthquake (Mw = 6.4)

Kanamori¹,

Ye²,

Huang³

et al. 2017

Terr. Atmos. Ocean. Sci.

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Despite a moderate magnitude, M w = 6.4, the 5 February 2016 Meinong, Taiwan, earthquake caused significant damage in Tainan City and the surrounding areas. Several seismograms display an impulsive S-wave velocity pulse with an amplitude of about 1 m s -1 , which is similar to large S-wave pulses recorded for the past several larger damaging earthquakes, such as the 1995 Kobe, Japan, earthquake (M w = 6.9) and the 1994 Northridge, California, earthquake (M w = 6.7). The observed PGV in the Tainan area is about 10 times larger than the median PGV of M w = 6.4 crustal earthquakes in Taiwan. We investigate the cause of the localized strong ground motions. The peak-to-peak ground-motion displacement at the basin sites near Tainan is about 35 times larger than that at a mountain site with a similar epicentral distance. At some frequency bands (0.9 -1.1 Hz), the amplitude ratio is as large as 200. Using the focal mechanism of this earthquake, typical "soft" and "hard" crustal structures, and directivity inferred from the observed waveforms and the slip distribution, we show that the combined effect yields an amplitude ratio of 17 to 34. The larger amplitude ratios at higher frequency bands can be probably due to the effects of complex 3-D basin structures. The result indicates that even from a moderate event, if these effects simultaneously work together toward amplifying ground motions, the extremely large ground motions as observed in Tainan can occur. Such occurrences should be taken into consideration in hazard mitigation measures in the place with frequent moderate earthquakes.

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Section: Crustal Structurementioning

confidence: 99%

A strong-motion hot spot of the 2016 Meinong, Taiwan, earthquake (Mw = 6.4)

Kanamori¹,

Ye²,

Huang³

et al. 2017

Terr. Atmos. Ocean. Sci.

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“…The MacRay is an open software from the USGS web-site (https://earthquake.usgs.gov/ research/software/), which is being able to model the full range of simple to complex ray-paths such as the directed, reflected, refracted and converted wave. Since the Chia-Yi area is largely covered by thick sedimentary rocks (Ho 1988;Lin et al 2009;Wu and Huang 2013), the P wave velocity was 4.5 km s -1 on the surface and gradually increased to 5.4 km s -1 at depths of ~7 km (Fig. 6).…”

Section: Travel-time Simulationmentioning

confidence: 99%

A west-dipping seismogenic boundary beneath the Chia-Yi area of western Taiwan

Shih¹,

Lin²,

Pu³

et al. 2018

Terr. Atmos. Ocean. Sci.

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Taiwan is one of the most typical arc-continental collision systems in the world. The Taiwan orogeny is often explained by the thin-skin model, where a shallow decollement, with depths of less than 10 km, is considered as the crustal deformation boundary for generating significant mountains on the island of Taiwan. In this study, the seismic data generated by crustal earthquakes, recorded by seismic stations in the Chia-Yi area of western Taiwan was examined to find the crustal structures beneath the Taiwan orogeny. A significant velocity boundary below the decollement was found from unambiguous multiple secondary waves and phases of primary waves converted to secondary waves. Careful comparison between the observations and calculated results of the travel-time and ray-path indicates that this boundary is dipping to the west at ~10 degrees, which, surprisingly, is dipping to the opposite direction of the proposed decollement. It is also interesting to note that this boundary is not only a velocity boundary but also consistent with a seismicity boundary. This westdipping boundary is the major seismogenic boundary in the upper crust, while the east-dipping decollement proposed earlier is a geological boundary. As a result, the westward dipping boundary observed in this study is more suitable, than the eastward dipping decollement, to be the seismogenic boundary in the Chia-Yi area.

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“…The 1-D distribution of shear wave velocity is subsequently computed via inversion of the dispersion curve. The SPAC method was assessed and adopted in various studies [4][5][6][7][8] and was collectively found to show reliability.…”

Section: Introductionmentioning

confidence: 99%

Estimation of Ground Structure at USM using Microtremor Observation Technique

2018

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Determination of ground structure is important for seismic hazard analysis and earthquake design of structures. Different types of ground structure at site, depending on its profile of shear-wave velocity, will amplify seismic wave at different extents. Therefore, structures should be designed accordingly to withstand the expected surface ground motion considering seismic site amplification. Microtremor observations were conducted in this study due to its simplicity, less field effort and economy. Field measurement was carried out at two sites at Universiti Sains Malaysia Engineering Campus where the actual soil profiles were known from the existing borelog data. Two sizes of circular array formed by three three-component velocity sensors along the circumference of circle and a three-component velocity sensor at the center for each array were performed. The recorded data were analysed using Spatial Autocorrelation (SPAC) method. Shear wave velocity profile for the site was then estimated through inversion of phase velocity. To produce convincing estimation of ground structure, the horizontal to vertical (H/V) spectra at the center of the circular array was compared with the computed ellipticity of the fundamental mode of Rayleigh wave. The obtained results were also compared with the borelog data. The accuracy for the estimation of ground structure based on various microtremor array sizes and analysis techniques was assessed.

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Near-Surface Shear-Wave Velocity Structure of the Chiayi Area, Taiwan

Cited by 18 publications

References 18 publications

A strong-motion hot spot of the 2016 Meinong, Taiwan, earthquake (Mw = 6.4)

A strong-motion hot spot of the 2016 Meinong, Taiwan, earthquake (Mw = 6.4)

A west-dipping seismogenic boundary beneath the Chia-Yi area of western Taiwan

Estimation of Ground Structure at USM using Microtremor Observation Technique

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