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111.
In this paper, known simplified methods for the assessment of soil liquefaction are summarized. Their discrepancies are examined. Using the Chi-Chi earthquake data as well as other reported data, a set of three critical cyclic strength curves were obtained by finding the minimum of misclassified points. The functional forms of these three curves are an exponential function, a hyperbola, and a cubic polynomial. A lower bound critical cyclic strength curve is then established. This curve may have important applications in practice for liquefaction-related designs. Through this case study, it was found that a minimum cyclic strength CSRlim may exist at a very low value of (N1)60. An upper limit (N1)60upp also exists beyond which liquefaction may not occur. Furthermore, current simplified methods seem suitable only for a limited range of N values and fines content, and may fail for general applications. The lower bound curve proposed in this paper may provide an alternative approach for improvement. Since the explicit functional form and the statistical indices are available, the statistically regressed curves seem to have a benefit in that it may be used directly to conduct hazard analysis, and evaluate the uncertainty within the critical cyclic strength curves. 相似文献
112.
Global mean sea surface heights (SSHs) and gravity anomalies on a 2′×2′ grid were determined from Seasat, Geosat (Exact Repeat Mission and Geodetic Mission), ERS-1 (1.5-year mean of 35-day, and
GM), TOPEX/POSEIDON (T/P) (5.6-year mean) and ERS-2 (2-year mean) altimeter data over the region 0∘–360∘ longitude and –80∘–80∘ latitude. To reduce ocean variabilities and data noises, SSHs from non-repeat missions were filtered by Gaussian filters
of various wavelengths. A Levitus oceanic dynamic topography was subtracted from the altimeter-derived SSHs, and the resulting
heights were used to compute along-track deflection of the vertical (DOV). Geoidal heights and gravity anomalies were then
computed from DOV using the deflection-geoid and inverse Vening Meinesz formulae. The Levitus oceanic dynamic topography was
added back to the geoidal heights to obtain a preliminary sea surface grid. The difference between the T/P mean sea surface
and the preliminary sea surface was computed on a grid by a minimum curvature method and then was added to the preliminary
grid. The comparison of the NCTU01 mean sea surface height (MSSH) with the T/P and the ERS-1 MSSH result in overall root-mean-square
(RMS) differences of 5.0 and 3.1 cm in SSH, respectively, and 7.1 and 3.2 μrad in SSH gradient, respectively. The RMS differences
between the predicted and shipborne gravity anomalies range from 3.0 to 13.4 mGal in 12 areas of the world's oceans.
Received: 26 September 2001 / Accepted: 3 April 2002
Correspondence to: C. Hwang
Acknowledgements. This research is partly supported by the National Science Council of ROC, under grants NSC89-2611-M-009-003-OP2 and NSC89-2211-E-009-095.
This is a contribution to the IAG Special Study Group 3.186. The Geosat and ERS1/2 data are from NOAA and CERSAT/France, respectively.
The T/P data were provided by AVISO. The CLS and GSFC00 MSS models were kindly provided by NASA/GSFC and CLS, respectively.
Drs. Levitus, Monterey, and Boyer are thanked for providing the SST model. Dr. T. Gruber and two anonymous reviewers provided
very detailed reviews that improved the quality of this paper. 相似文献
113.
Assessment of groundwater chemistry in a coastal region (Kunsan, Korea) having complex contaminant sources: a stoichiometric approach 总被引:1,自引:0,他引:1
Kangjoo Kim Natarajan Rajmohan Hyun Jung Kim Gab-Soo Hwang Min Joe Cho 《Environmental Geology》2004,46(6-7):763-774
Groundwater chemistry in a coastal region (Kunsan, Korea) having complex contaminant sources was investigated. Water analysis data for 197 groundwater samples collected from the uniformly distributed sixty-six wells were used. Chemical analysis results indicate that groundwaters show wide concentration ranges in major inorganic ions, reflecting complex hydrochemical processes. Due to the complexity of groundwater chemistry, the samples were classified into four groups based on Cl and NO3 concentrations and the processes controlling water chemistry were evaluated based on the reaction stoichiometry. The results explained the importance of mineral weathering, anthropogenic activities (nitrification and oxidation of organic matters), and Cl-salt inputs (seawater, deicer, NaCl, etc.) on groundwater chemistry. It was revealed that mineral dissolution is the major process controlling the water chemistry of the low Cl and NO3 group (Group 1). Groundwaters high in NO3 (Groups 2 and 4) are acidic in nature, and their chemistry is largely influenced by nitrification, oxidation of organic matters and mineral dissolution. In the case of chloride rich waters (Group 3), groundwater chemistry is highly influenced by mineral weathering and seawater intrusion associated with cation-exchange reactions. 相似文献
114.
Yongen Cai Chi-yuen Wang Win-tsuang Hwang Guy R. Cochrane 《Pure and Applied Geophysics》1995,145(3-4):637-646
Fluid venting in accretionary prisms, which feeds chemosynthetic biological communities, occurs mostly on the marginal thrust ridge. New seismic data for the marginal ridge of the Cascadia prism show significantly lower velocity than that in the adjacent oceanic basin and place important constraints on the interpretations of why fluid venting occurs mostly on the marginal ridge. We employed a finite-element method to analyze a typical fault-bend folding model to explain the phenomenon. The fault in the model is simulated by contact elements. The elements are characterized not only by finite sliding along a slide line, but also by elastoplastic deformation.We present the results of a stress analysis which show that the marginal ridge is under subhorizontal extension and the frontal thrust is under compression. This state of stress favors the growth of tensile cracks in the marginal ridge, facilitates fluid flow and reduces seismic velocities therein; on the other hand, it may close fluid pathways along the frontal thrust and divert fluid flow to the marginal ridge.On leave from Peking University, Beijing, 100871, China 相似文献
115.
A large quantity of by-product lime wastes with high water content produced from chemicals manufacturing processes has been stacked in an open area in Incheon, Korea. Highly alkaline leachate and fine dust emanating from the stacked lime wastes caused an environmental concern in the city. So evaporative drying and stabilization of the fine-grained wastes and use of the on site marine clay as a natural geomembrane liner using drying hardening were considered as a part of a landfill construction plan. Treatment of the lime wastes and marine clay was focused on maximizing the evaporative drying and the density. Evaporation experiments were conducted in field condition to understand evaporation characteristics and to evaluate actual evaporation rate of the lime wastes and marine clay. Local Class A pan evaporation data from a nearby weather station for last 30 years indicated that mean annual and monthly evaporations were 1,178.5 and 98.2 mm, respectively. Relative evaporations of the sludge lime, cake lime, and marine clay compared with the pan evaporation were 114.9, 61.9, and 119.0%, respectively. Estimates of annual evaporations from storage surfaces in the field based on the relative evaporation data were 1,353.6, 729.1, and 1,402.2 mm for the sludge lime, cake lime, and the marine clay, respectively. And annual net evaporations considering rainfall effect were estimated as between 879.9 and 1,082.9 mm for the lime sludge, between 473.9 and 583.3 mm for the lime cake, and between 981.5 and 1,191.9 mm for the marine clay. It was expected that the actual field evaporation rate would be varied with the moisture contents of the lime and the clay. Results of these experiments will provide useful implications for the drying behavior of the by-product lime and the marine clay and landfill or management plan of the storages. 相似文献
116.
Electrostatic waves excited by a field-aligned electron current sheet of finite thickness are investigated. The finite width of the current sheet gives rise to boundary conditions to be satisfied at the sheet edge. This results in a restriction to the number of modes which may be driven unstable. Ducted and evanescent mode solutions are obtained. It is shown that the finite thickness of the current sheet partially stabilizes the system and contributes to the coherence of the excited waves. 相似文献
117.
Cheinway Hwang Tzu-Pang Tseng Ting-Jung Lin Dražen Švehla Urs Hugentobler Benjamin Fong Chao 《GPS Solutions》2010,14(1):121-131
The precise orbit determination antennas of F3/C and GRACE-A satellites are from the same manufacturer, but are installed
in different configurations. The current orbit accuracy of F3/C is 3 cm at arcs with good GPS data, compared to 1 cm of GRACE,
which has a larger ratio of usable GPS data. This paper compares the qualities of GPS observables from F3/C and GRACE. Using
selected satellites and time spans, the following average values for the satellite F3/C and satellite A of GRACE are obtained:
multipath effect on the pseudorange P1, 0.78 and 0.38 m; multipath effect on the pseudorange P2, 1.03 and 0.69 m; occurrence
frequency of cycle slip, 1/29 and 1/84; standard error of unit weight, 4 and 1 cm; dynamic–kinematic orbit difference, 10
and 2 cm. For gravity determination using F3/C GPS data, a careful selection of GPS data is critical. With six satellites
in orbit, F3/C’s large amount of GPS data will make up the deficiency in data quality. 相似文献
118.
L.R. Lyons D.-Y. Lee H.-J. Kim J.A. Hwang R.M. Thorne R.B. Horne A.J. Smith 《Journal of Atmospheric and Solar》2009,71(10-11):1059-1072
High geomagnetic activity occurs continuously during high-speed solar wind streams, and fluxes of relativistic electrons observed at geosynchronous orbit enhance significantly. High-speed streams are preceded by solar wind compression regions, during which time there are large losses of relativistic electrons from geosynchronous orbit. Weak to moderate geomagnetic storms often occur during the passage of these compression regions; however, we find that the phenomena that occur during the ensuing high-speed streams do not depend on whether or not a preceding storm develops. Large-amplitude Alfvén waves occur within the high-speed solar wind streams, which are expected to lead to intermittent intervals of significantly enhanced magnetospheric convection and to thus also lead to repetitive substorms due to repetitively occurring reductions in the strength of convection. We find that such repetitive substorms are clearly discernible in the LANL geosynchronous energetic particle data during high-speed stream intervals. Global auroral images are found to show unambiguously that these events are indeed classical substorms, leading us to conclude that substorms are an important contributor to the enhanced geomagnetic activity during high-speed streams. We used the onsets of these substorms as indicators of preceding periods of enhanced convection and of reductions in convection, and we have used ground-based chorus observations from the VELOX instrument at Halley station as an indicator of magnetospheric chorus intensities. These data show evidence that it is the periods of enhanced convection that precede substorm expansions, and not the expansions themselves, that lead to the enhanced dawn-side chorus wave intensity that has been postulated to cause the energization of relativistic electrons. If this inference is correct, and if it is chorus that energizes the relativistic electrons, then high-speed solar wind streams lead to relativistic electron flux enhancements because the embedded large-amplitude Alfvén waves give multi-day periods of intermittent significantly enhanced convection. 相似文献
119.
Groundwater Impacts from the M5.8 Earthquake in Korea as Determined by Integrated Monitoring Systems
Soo-Hyoung Lee Jae Min Lee Heesung Yoon Yongcheol Kim Seho Hwang Kyoochul Ha Yongje Kim 《Ground water》2020,58(6):951-961
This paper describes the impacts of the M5.8(5.1) Gyeongju earthquakes on groundwater levels using data obtained from a unique coastal monitoring well. The monitoring strategy integrates conventional water level monitoring with periodic, continuous measurements of temperature and electrical conductivity (EC) within the water column of the well. Another important component of the monitoring system is a new instrument, the InterfacEGG, which is capable of dynamically tracking the freshwater-saltwater interface. Although the system was set up to monitor seawater intrusion related to over-pumping, as well as rainfall and tidal effects, it recorded impacts associated with a large earthquake and aftershocks approximately 241 km away. Seismic energies associated with the M5.8(5.1) Gyeongju earthquakes induced groundwater flows to the monitoring well through fractures and joints in the crystalline basement rocks. Temperature and EC logging data showed that the EC vertical profile declined from an average of approximately 5300 to 4800 μS/cm following the earthquakes. The temperature profile showed a trend toward lower temperatures as the depth increased, a feature not commonly observed in previous studies. Data from the InterfacEGG suggested that the rise in EC was not due to the saltwater intrusion, but from the tendency for brackish water entering the borehole to induce convective mixing at deeper depths as the seismic waves travel through the well-aquifer system. The increase in groundwater levels was caused by pulse of colder, less brackish water flowing into the well because of the earthquake. This behavior reflects an enhancement in rock permeability by removing precipitates and colloidal particles from clogged fractures, which improve the hydraulic connection with a nearby unit with a higher hydraulic head. This study suggests there is value added with a more aggressive monitoring strategy. 相似文献
120.
Steven J. Berg Nancy R. Grosso Michael P. Sherrier Kevin Mudrick Matthias Ohr Hyoun-Tae Hwang Young-Jin Park Michael V. Callaghan Steven K. Frey Edward A. Sudicky 《Ground water》2019,57(1):21-35
The interaction between surface water and groundwater during flood events is a complex process that has traditionally been described using simplified analytical solutions, or abstracted numerical models. To make the problem tractable, it is common to idealize the flood event, simplify river channel geometry, and ignore bank soil heterogeneity, often resulting in a model that only loosely represents the site, thus limiting its applicability to any specific river cross-section. In this study, we calibrate a site-specific fully-integrated surface and subsurface HydroGeoSphere model using flood events for a cross-section along the South River near Waynesboro, VA. The calibration approach presented in this study demonstrates the incorporation of fining direction regularization with a highly parameterized inversion driven by natural stimuli, to develop several realistic realizations of hydraulic conductivity fields that reflect the depositional history of the system. Specifically, we calibrate a model with 365 unique material zones to multiple flood events recorded in a dense well network while incorporating possible fining sequences consistent with the depositional history of the riverbank. Over 25,000 individual simulations were completed using calibration software and a cloud platform specifically designed for highly parallelized computing environments. The results of this study demonstrate the use of fining direction regularization during model calibration to generate multiple calibrated model realizations that account for the depositional environment of the system. 相似文献