Groundwater Level Changes in Taiwan Caused by The Wenchuan Earthquake on 12 May 2008     

Tsai-Ping Lee  Yeeping Chia  Hsin-Ying Yang  Ching-Yi Liu  Yung-Chia Chiu 《Pure and Applied Geophysics》2012,169(11):1947-1962

Widespread persistent coseismic groundwater level changes induced by the M _w 7.9 Wenchuan earthquake were recorded in 80 wells in Taiwan, located approximately 2,000?km from the epicenter. The timing and magnitude of these changes, ranging from ?40 to +23?cm, have been examined by statistical evaluation. The coseismic fall dominated in the plain area, but in the mountainous area most changes are coseismic rises. Both the coseismic rise and the coseismic fall were observed in wells of different depths at two monitoring stations. The processes of the coseismic changes can be shown by the high-frequency well water level data. Analysis of the 1?Hz water level data and the broadband seismogram revealed that a temporary water level change, ranging from 0.2 to 2.3?cm, occurred at the arrival of high-energy Love waves and Rayleigh waves. However, a water level change of 0.3–6.4?cm occurred in 7–20?min after the passing of high-energy surface waves. It is doubtful that such a change could be induced directly by ground shaking. The cross-formational flow due to fracturing or unclogging of sediment pores was possibly too slow to cause the coseismic change. Further studies are required to understand the mechanism of coseismic groundwater level changes induced by a distant earthquake.  相似文献   

Interactive effects of hypoxia and polybrominated diphenyl ethers (PBDEs) on microbial community assembly in surface marine sediments     

Yuki Chan  Amy Li  Singaram Gopalakrishnan  Paul K.S. Shin  Rudolf S.S. Wu  Stephen B. Pointing  Jill M.Y. Chiu 《Marine pollution bulletin》2014

Hypoxia alters the oxidation–reduction balance and the biogeochemical processes in sediments, but little is known about its impacts on the microbial community that is responsible for such processes. In this study, we investigated the effects of hypoxia and the ubiquitously dispersed flame-retardant BDE47 on the bacterial communities in marine surface sediments during a 28-days microcosm experiment. Both hypoxia and BDE47 alone significantly altered the bacterial community and reduced the species and genetic diversity. UniFrac analysis revealed that BDE47 selected certain bacterial species and resulted in major community shifts, whereas hypoxia changed the relative abundances of taxa, suggesting slower but nonetheless significant community shifts. These two stressors targeted mostly different taxa, but they both favored Bacteroidetes and suppressed Gammaproteobacteria. Importantly, the impacts of BDE47 on bacterial communities were different under hypoxic and normoxic conditions, highlighting the need to consider risk assessments for BDE47 in a broader context of interaction with hypoxia.  相似文献   

Influences of ambient air pollutants and meteorological conditions on ozone variations in Kaohsiung,Taiwan     

Kuo  Yi-Ming  Chiu  Chuan-Hung  Yu  Hwa-Lung 《Stochastic Environmental Research and Risk Assessment (SERRA)》2015,29(3):1037-1050

Stochastic Environmental Research and Risk Assessment - The complex process of ozone formation, its precursor compounds (volatile organic compounds (VOCs) and nitrogen oxides (NOx)) emissions,...  相似文献   

Canyon topography effects on ground motion at Feitsui damsite     

Huey-Chu Huang  Hung-Chie Chiu 《Soil Dynamics and Earthquake Engineering》1999,18(2):213

The free-field accelerograms along Feitsui Canyon are analyzed and modeled by a numerical scheme to study the effect of canyon topography. Since six strong-motion accelerometers (SC1–SC6) were deployed along the Feitsui Canyon in 1991; there are 14 earthquakes (4.9≤M_L≤6.6) recorded by these stations until June 1996, but only five triggered all six stations. The maximum PGA value is 68.6 cm s⁻² recorded at station SC1. According to the present data, the effect of the dam on the ground motions at canyon stations can be negligible. The amplitude of ground motion on the slopes of the canyon is bigger than that at its trough. The integral equation method is applied to a two dimensional model of Feitsui Canyon to study the effects of the canyon topography. We choose the ground motion of SC3 or SC4 station at the trough of the canyon as the input motion for the model, which is then used to predict the ground motion at the other five stations. Apart from the earthquake close to the damsite, the simple model can reproduce the observed accelerations at all frequencies below 4 Hz. Overall, the numerical method can well predict the ground motion along the canyon, although the high-frequency simulation is underestimated.  相似文献   

Respiration rate and swimming activity of larvae of two sub-tidal nassariid gastropods under reduced oxygen levels: implications for their distributions in Hong Kong waters     

Liu CC  Chiu JM  Li L  Shin PK  Cheung SG 《Marine pollution bulletin》2011,63(5-12):230-236

The effects of hypoxia on the larvae of two sub-tidal nassariid gastropods, Nassarius siquijorensis and N. conoidalis were compared so as to understand how the species-specific tolerance to hypoxia might have resulted in changes in the abundance and distribution of these two species in the hypoxic Tolo Harbour, Hong Kong, since the 1980s. Respiration rates of N. siquijorensis and N. conoidalis larvae were reduced at 4.5 mg O2 l(-1), or below, as compared with the normoxic control. Significant reduction in swimming velocity was also observed for 10-day old larvae which were exposed to <2.0 mg O2 l(-1) for N. siquijorensis and <1.0 mg O2 l(-1) for N. conoidalis. The 48 h LC50 values of N. siquijorensis and N. conoidalis larvae were 0.7 and 1.7 mg O2 l(-1), respectively. The results suggested that N. siquijorensis are more tolerant to hypoxia than N. conoidalis.  相似文献   

Geomagnetic anomaly at Lunping before the 1999 Chi-Chi earthquake (M w  = 7.6) in Taiwan     

Chen  Kuang-Jung  Chiu  Bonbbon  Wang  Jee-Shiang  Lee  Cheng-Yu  Lin  Cheng-Horng  Chao  Kevin 《Natural Hazards》2011,58(3):1233-1252

A strong earthquake with a magnitude of 7.6 (M _L  = 7.3) occurred on September 21, 1999, in central Taiwan. In order to discern any potential precursors before this earthquake, geomagnetic data at Lunping (LNP), Taiwan, Geomagnetic Observatory situated 100 km from the epicenter are examined using two methods, i.e., the traditional induction arrows and complex demodulation. Our results show that the remarkable temporal variation of real induction arrows appear to be strong prior to the great earthquake over the previous 24 months. After the great earthquake, the magnitudes of induction arrows decreased to the normal (mean of 8 years) levels. In other words, the direction of real induction arrows of the periods 30 and 20 min rotated 85° and 40° anticlockwise, respectively, before the Chi-Chi earthquake and returned to mean direction of last 10 years after the earthquake. A horizontal source field model using the finite difference method for 3-D shows that the variation of the real induction arrows might be ascribed to the conductivity variation body, which is 5 km buried at the epicenter area of the Chi-Chi earthquake, changing its conductivity from 0.002S/m to 0.06 S/m. The ratios of modulus (demodulated by using the complex demodulation method) over a period 12, and 8 h relative to the period of 24 h reveal a remarkable change that appeared 4–5 months prior to this strong earthquake. They increased gradually from the beginning of 1999 to August 1999 and decreased again to a (8 years) mean level after the strong earthquake occurrence. We consider that the variation of the induction arrow might be ascribed to the conductivity anomaly, which is buried 5 km at the south-east side of LNP with a conductivity change of 0.06 S/m. We propose that this elevation might be related to the preparation process of the great earthquake.  相似文献   

Consideration of fine-scale coastal oceanography and 3-D acoustics effects for the ESME sound exposure model     

Lynch  J.F. Colosi  J.A. Gawarkiewicz  G.G. Duda  T.F. Pierce  A.D. Badiey  M. Katsnelson  B.G. Miller  J.E. Siegmann  W. Ching-Sang Chiu Newhall  A. 《Oceanic Engineering, IEEE Journal of》2006,31(1):33-48

Results and recommendations for evaluating the effects of fine-scale oceanographic scattering and three-dimensional (3-D) acoustic propagation variability on the Effects of Sound on the Marine Environment (ESME) acoustic exposure model are presented. Pertinent acoustic scattering theory is briefly reviewed and ocean sound-speed fluctuation models are discussed. Particular attention is given to the nonlinear and linear components of the ocean internal wave field as a source of sound-speed inhomogeneities. Sound scattering through the mainly isotropic linear internal wave field is presented and new results relating to acoustic scattering by the nonlinear internal wave field in both along and across internal wave wavefront orientations are examined. In many cases, there are noteworthy fine-scale induced intensity biases and fluctuations of order 5-20 dB.  相似文献   

Real‐time recurrent learning neural network for stream‐flow forecasting     

F.‐John Chang  Li‐Chiu Chang  Hau‐Lung Huang 《水文研究》2002,16(13):2577-2588

Various types of neural networks have been proposed in previous papers for applications in hydrological events. However, most of these applied neural networks are classified as static neural networks, which are based on batch processes that update action only after the whole training data set has been presented. The time variate characteristics in hydrological processes have not been modelled well. In this paper, we present an alternative approach using an artificial neural network, termed real‐time recurrent learning (RTRL) for stream‐flow forecasting. To define the properties of the RTRL algorithm, we first compare the predictive ability of RTRL with least‐square estimated autoregressive integrated moving average models on several synthetic time‐series. Our results demonstrate that the RTRL network has a learning capacity with high efficiency and is an adequate model for time‐series prediction. We also investigated the RTRL network by using the rainfall–runoff data of the Da‐Chia River in Taiwan. The results show that RTRL can be applied with high accuracy to the study of real‐time stream‐flow forecasting networks. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

The shelf-edge frontal structure in the central East China Sea and its impact on low-frequency acoustic propagation     

Ramp  S.R. Ching-Sang Chiu Bahr  F.L. Yiquan Qi Dahl  P.H. Miller  J. Lynch  J.F. Renhe Zhang Jixun Zhou 《Oceanic Engineering, IEEE Journal of》2004,29(4):1011-1031

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Maritime safety for fishing boat operations and avoidable hijacking in Taiwan     

Yi-Che Shih  Chiu L. Chou  Wen-Yan Chiau   《Marine Policy》2010,34(2):349-351

Taiwanese fishing boats have been hijacked many times this year. Trouble at sea can usually be attributed to communication problems, inappropriate management and an unfair salary system. The majority of boats hijacked are high sea (long-line) fishing boats. Although fishery authorities ask the fishing boats to set up vessel monitoring systems (VMSs), this precaution has not been sufficient. There is a further need for improved management by the fishing boat owner and for an improved employment policy for seamen. The issue of maritime security is not new, but it remains a major concern and continues to be a threat to Taiwan and other countries. To date, there have been many cases of hijacking in the South China Sea. This paper analyzes the reasons for the hijackings and provides potential strategies to prevent future incidents.  相似文献