FORMOSAT-3/COSMIC observations of the ionospheric auroral oval development     

Ho-Fang Tsai  Jann-Yenq Liu  Chien-Hung Lin  Mei-Lan Hsu 《GPS Solutions》2010,14(1):91-97

The ionospheric radiance and electron density observed by the tiny ionospheric photometer (TIP) and GPS occultation experiment (GOX) payloads on FORMOSAT-3/COSMIC satellites are applied to determine the boundaries of the auroral oval and its width in the winter nighttime ionosphere for both hemispheres. The TIP collects ionospheric emission at 135.6 nm due to electron impact excitation, while the GOX offers ionospheric electron density profiles with radio occultation (RO) technique. Comparison between them shows similar patterns of the plasma structure in the polar caps. The mean width of the auroral bands ranges between about 2 and 11° latitude in the winter nighttime and it varies with longitudes. The comparison by month suggests that the mean radius of the auroral ovals varies with the intensity of the auroral radiance.  相似文献   

Marine 3D seismic volumes from 2D seismic survey with large streamer feathering     

Lin  Liang-Fu  Hsu  Ho-Han  Liu  Char-Shine  Chao  Kuo-Han  Ko  Chia-Chun  Chiu  Shye-Dong  Hsieh  Hsin-Sung  Ma  Yu-Fang  Chen  Song-Chuen 《Marine Geophysical Researches》2019,40(4):619-633

Marine Geophysical Research - Strong ocean current influences a marine seismic survey and forces the streamer off-course from the survey line. The sideway drift of the streamer results in that the...  相似文献   

The hydrodynamic coefficients for an oscillating rectangular structure on a free surface with sidewall     

Hu-Hsiao Hsu  Yung-Chao Wu 《Ocean Engineering》1997,24(2):177-199

Based on a two dimensional linear water wave theory, the boundary element method (BEM) is developed and applied to study the heave and the sway problem of a floating rectangular structure in water to finite depth with one side of the boundary is a vertical sidewall and the other boundary is an open boundary. Numerical results for the added mass and radiation damping coefficients are presented. These coefficients are not only depend on the submergence and the width of the structure, but also depend on the clearance between structure and sidewall. Negative added mass and sharp peaks in the damping and added mass coefficients have been found when the clearance with a value close to integral times of half wave length of wave generated by oscillation structure. The important effect of the clearance on the added mass and radiation damping coefficients are discussed in detail. An analytical solution method is also presented. The BEM solution is compared with the analytical solution, and the comparison shows good agreement.  相似文献   

Observations and modeling of flat subduction and its geological effects     

Yan  Zhiyong  Chen  Lin  Xiong  Xiong  Wang  Kai  Xie  Renxian  Hsu  Hou Tze 《中国科学:地球科学(英文版)》2020,63(8):1069-1091

Flat subduction refers to low-angle(10°) or sub-horizontal subduction of oceanic slabs. Flat subduction is only recognized in ～10% of present-day subduction zones, but its impact on the behavior of the overriding plate is particularly strong.For example, flat subduction zones are typically associated with stronger earthquakes. The deformation caused by typical flat subduction will transfer from the trench to the overriding continental interior and form a broad magma belt. The formation mechanism of flat subduction has been linked to the relative buoyancy of subducted oceanic plateaus, overthrusting of the overriding plate, hydrodynamic suction, and trench retreat. However, these mechanisms remain debated. This paper systematically analyzes and summarizes previous studies on flat subduction, and outlines the possible geological effects of flat subduction, such as intracontinental orogeny and magmatism. Using examples from numerical modeling, we discuss the possible formation mechanisms. The most important factors that control the formation of flat subduction are associated with overthrusting of the overriding plate and the arrival of an oceanic plateau at the subduction zone. In addition, trench retreat is necessary to enable flat subduction. Hydrodynamic suction contributes to the reduction of the slab dip angle, but is insufficient to form flat subduction. Future numerical modeling of flat subduction should carry out three-dimensional high-resolution thermo-mechanical simulation, considering the influence of crustal eclogitization(negative buoyancy) and mantle serpentinization(positive buoyancy) of oceanic lithosphere, in combination with geological and geophysical data.  相似文献   

An integrated earthquake early warning system and its performance at schools in Taiwan     

Bing-Ru Wu  Nai-Chi Hsiao  Pei-Yang Lin  Ting-Yu Hsu  Chiou-Yun Chen  Shieh-Kung Huang  Hung-Wei Chiang 《Journal of Seismology》2017,21(1):165-180

An earthquake early warning (EEW) system with integration of regional and onsite approaches was installed at nine demonstration stations in several districts of Taiwan for taking advantages of both approaches. The system performance was evaluated by a 3-year experiment at schools, which experienced five major earthquakes during this period. The blind zone of warning was effectively reduced by the integrated EEW system. The predicted intensities from EEW demonstration stations showed acceptable accuracy compared to field observations. The operation experience from an earthquake event proved that students could calmly carry out correct action before the seismic wave arrived using some warning time provided by the EEW system. Through successful operation in practice, the integrated EEW system was verified as an effective tool for disaster prevention at schools.  相似文献   

Spatial variation of abundant picoeukaryotes in the subtropical Kuroshio Current in winter     

Ya-Fan Chan  Chih-Ching Chung  Gwo-Ching Gong  Ching-Wei Hsu 《Marine Ecology》2020,41(1):e12579

To understand the importance of picoeukaryotes in the biogeochemical cycle in the subtropical Kuroshio Current, a year-round survey of the hydrography and the distribution of picoeukaryotes were conducted in four oceanographic cruises from October 2012 to July 2013. In comparison with other seasons, the highest abundancy of photosynthetic picoeukaryotes, with concentrations >10⁴ cells/ml, was observed around the eastern boundary of the Kuroshio in the winter. Accordingly, the composition of picoeukaryotes in this cold season was further studied by a metabarcoding analysis of the 18S rRNA gene. The majority of picoeukaryotes comprised Alveolata, followed by Haptophyta and Stramenopiles. Their composition was diverse in the waters affected by the Kuroshio and in the offshore province. For Haptophyta, in contrast to clade A prevailing in the Kuroshio waters, clade B1, which was considered the host of uncultivated diazotrophic cyanobacterium group A (UCYN-A), appeared only in the offshore area. Similarly, in Stramenopiles, Pseudo-nitzschia spp. and MAST-1D, respectively, dominated in the Kuroshio-influenced and offshore areas. While Alveolata was the most abundant group, the distributions of all lineages were similar. The association between picoeukaryote succession and hydrographic change is yet to be fully understood. Our results will assist future studies on the community composition of picoplankton and their relationship with marine ecology in the region.  相似文献   

The effect of bathymetric filtering on nearshore process model results     

Nathaniel G. Plant  Kacey L. Edwards  James M. Kaihatu  Jayaram Veeramony  Larry Hsu  K. Todd Holland 《Coastal Engineering》2009

Nearshore wave and flow model results are shown to exhibit a strong sensitivity to the resolution of the input bathymetry. In this analysis, bathymetric resolution was varied by applying smoothing filters to high-resolution survey data to produce a number of bathymetric grid surfaces. We demonstrate that the sensitivity of model-predicted wave height and flow to variations in bathymetric resolution had different characteristics. Wave height predictions were most sensitive to resolution of cross-shore variability associated with the structure of nearshore sandbars. Flow predictions were most sensitive to the resolution of intermediate scale alongshore variability associated with the prominent sandbar rhythmicity. Flow sensitivity increased in cases where a sandbar was closer to shore and shallower. Perhaps the most surprising implication of these results is that the interpolation and smoothing of bathymetric data could be optimized differently for the wave and flow models. We show that errors between observed and modeled flow and wave heights are well predicted by comparing model simulation results using progressively filtered bathymetry to results from the highest resolution simulation. The damage done by over smoothing or inadequate sampling can therefore be estimated using model simulations. We conclude that the ability to quantify prediction errors will be useful for supporting future data assimilation efforts that require this information.  相似文献   

Reply to “Discussion of wave setup and setdown generated by obliquely incident waves” by F. Shi and J.T. Kirby     

Tai-Wen Hsu  Yuan-Jyh Lan 《Coastal Engineering》2009

The authors are grateful to the derivation and correction addressed by Shi and Kirby (2008) for the calculation of the wave setup and setdown induced by obliquely incident waves. The mathematical equations for the expression of setup and setdown are rederived in which the velocity potential is expanded to the second-order on the still water lever. The correct form of setdown presented by Shi and Kirby is confirmed in the present paper.  相似文献   

Temporal and spatial variations of post-seismic deformation following the 1999 Chi-Chi, Taiwan earthquake     

Ya-Ju Hsu  Paul Segall  Shui-Beih Yu  Long-Chen Kuo  Charles A. Williams 《Geophysical Journal International》2007,169(2):367-379

We use GPS displacements collected in the 15 months after the 1999 Chi-Chi, Taiwan earthquake  ( M _w 7.6)  to evaluate whether post-seismic deformation is better explained by afterslip or viscoelastic relaxation of the lower crust and upper mantle. We find that all viscoelastic models tested fail to fit the general features in the post-seismic GPS displacements, in contrast to the satisfactory fit obtained with afterslip models. We conclude that afterslip is the dominant mechanism in the 15-month period, and invert for the space–time distribution of afterslip, using the Extended Network Inversion Filter. Our results show high slip rates surrounding the region of greatest coseismic slip. The slip-rate distribution remains roughly stationary over the 15-month period. In contrast to the limited coseismic slip on the décollement, afterslip is prominent there. Maximum afterslip of 0.57 m occurs downdip and to the east of the hypocentral region. Afterslip at hypocentral depths is limited to the southern part of the main shock rupture, with little or no slip on the northern section where coseismic slip was greatest. Whether this results from along strike variations in frictional properties or dynamic conditions that locally favour stable sliding is not clear. In general, afterslip surrounds the area of greatest coseismic slip, consistent with post-seismic slip driven by the main shock stress change. The total accumulated geodetic afterslip moment is  3.8 × 10¹⁹ N m  , significantly more than the seismic moment released by aftershocks,  6.6 × 10¹⁸ N m  . Afterslip and aftershocks appear to have different temporal evolutions and some spatial correlations, suggesting that aftershock rates may not be completely controlled by the rate of afterslip.  相似文献   

Climate-induced hydrological impacts on the groundwater system of the Pingtung Plain,Taiwan     

Kuo-Chin Hsu  Chung-Ho Wang  Kuan-Chih Chen  Chien-Tai Chen  Kai-Wei Ma 《Hydrogeology Journal》2007,15(5):903-913

The Pingtung Plain is one of the most important groundwater-resource areas in southwestern Taiwan. The overexploitation of groundwater in the last two decades has led to serious deterioration in the quantity and quality of groundwater resources in this area. Furthermore, the manifestation of climate change tends to induce the instability of surface-water resources and strengthen the importance of the groundwater resources. Southwestern Taiwan in particular shows decreasing tendencies in both the annual amount of precipitation and annual precipitation days. To effectively manage the groundwater resources of the Pingtung Plain, a numerical modeling approach is adopted to investigate the response of the groundwater system to climate variability. A hydrogeological model is constructed based on the information from geology, hydrogeology, and geochemistry. Applying the linear regression model of precipitation to the next two decades, the modeling result shows that the lowering water level in the proximal fan raises an alarm regarding the decrease of available groundwater in the stress of climate change, and the enlargement of the low-groundwater-level area on the coast signals the deterioration of water quantity and quality in the future. Suitable strategies for water-resource management in response to hydrological impacts of future climatic change are imperative.

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Resumen La llanura Pingtung constituye uno de los recursos de aguas subterráneas más importantes en el Suroeste de Taiwan. La sobreexplotación de las aguas subterráneas en las dos últimas décadas ha dado lugar a un serio deterioro de la calidad y la cantidad de los recursos subterráneos en esta área. En particular el Suroeste de Taiwan muestra una tendencia decreciente en las cantidades de precipitación y en los días anuales de lluvia. Para gestionar de forma efectiva los recursos subterráneos en la Llanura Pingtung, se ha utilizado un modelo numérico aproximado para investigar la respuesta de las aguas subterráneas a la variabilidad climática. Un modelo hidrogeológico se construye a partir de la información geológica, hidrogeológica y geoquímica. Aplicando el modelo de regresión linear de la precipitación para las próximas dos décadas, el modelo resultante muestra que el descenso de los niveles de agua en el abanico proximal es alarmante, observándose el descenso del agua subterránea disponible en la presión del cambio climático, y el crecimiento del área de descensos de niveles de agua subterránea en la costa apunta a un deterioro de la cantidad y calidad del agua subterránea en el futuro. Se imponen pues, estrategias apropiadas para la gestión de los recursos hídricos en respuesta a los impactos hidrológicos del futuro cambio climático.

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Résumé La plaine de Pingtung est l’une des plus importantes zones de ressource en eau souterraine du Sud-Ouest de Taiwan. La surexploitation de l’eau souterraine durant les deux dernières décennies a conduit à une sérieuse détérioration de la quantité et de la qualité des ressources en eau souterraine dans cette zone. De plus, la manifestation des changements climatiques tend à induire une instabilité des ressources en eau souterraine et renforce l’importance des ressources en eau souterraine. Le Sud-Ouest de Taiwan montre, en particulier, des précipitations annuelles et des nombres annuels de jour de pluie à la baisse. Pour gérer efficacement les ressources en eau souterraine de la Plaine de Pingtung, une approche par modélisation numérique est adoptée pour étudier la réponse du système hydrogéologique aux variabilités climatiques. La construction du modèle hydrogéologique est basée sur les informations géologiques, hydrogéologiques et géochimiques. En appliquant le modèle de régression linéaire aux précipitations pour les deux prochaines décades, le résultat de la modélisation montre que la baisse du niveau d’eau atteint un état alarmant au regard de la décroissance des eaux souterraines disponibles et la contrainte du changement climatique, tandis que l’extension de la zone de niveau bas des eaux souterraines à la cote indique une détérioration de la quantité et de la qualité de l’eau dans le futur. Des stratégies convenables pour la gestion des ressources en eau souterraine en réponse aux impacts hydrologiques de futurs changements climatiques sont impératifs.

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