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191.
— In this paper, the site characteristics of the Dahan downhole array are studied by analyzing the September 21, 1999 M 7.3 Chi-Chi earthquake sequence including the main shock and some aftershocks. The four-level array (0 m, 50 m, 100 m and 200 m) is located to the north of Hualien City in eastern Taiwan. Polarization analysis is used to check the orientation errors of the seismometers at different levels of depth. If the surface instrument is chosen as reference, the angle between the major polarization axes of the surface and any downhole records is the orientation error that must be corrected for the downhole accelerographs. The orientation errors at depths of 50 m, 100 m and 200 m are 32°, 120° and –84°. After the corrections, the coherency between the surface and downhole records is substantially improved. Spectral ratio analysis shows that the predominant frequency of the Chi-Chi main shock shifts to a lower frequency. We also simulate ground motions at different depths by using the Haskell method with a linear velocity structure model. The record at surface is chosen as the input motion. Compared with the observed data, ground acceleration can be well reproduced for the aftershocks (weak-motion events) of the September 21, 1999 M 7.3 Chi-Chi earthquake. However, for the Chi-Chi main shock, the synthetic waveform cannot match well with the observation neither in amplitude nor in phase. This indicates that large ground shaking probably induced the nonlinear site effect at that time, and the model used cannot support it.Acknowledgement. The authors would like to express their thanks to Dr. L.F. Bonilla and one anonymous reviewer for their valuable suggestions. This research was supported by the National Science Council under grant number NSC 89-2921-M-194-007. The Institute of Earth Sciences, Academia Sinica supplied the strong-motion data. The support of these organizations is gratefully acknowledged. 相似文献
192.
Laura Gaggero Laura Buzzi Ivan Haydoutov Luciano Cortesogno 《International Journal of Earth Sciences》2009,98(8):1853-1877
Eclogitic rocks were sampled from two zones in the basement of the Sredna Gora terrane (central western Bulgaria): (1) partially
retrogressed eclogites and amphibolites embedded in sillimanite-bearing garnet-micaschists with kyanite relics and migmatites
and (2) banded amphibolites associated with muscovite-bearing metagranites within two-mica paragneisses. Rutile relics and
oligoclase + green hornblende + epidote ± biotite pseudomorphs after garnet suggest an eclogite facies event. A tholeiitic,
transitional affinity was determined for the protoliths, suggesting a continental rift environment, consistent with several
eclogite-bearing complexes in the eastern segments of the Variscan belt that arose from the Cambro-Ordovician Gondwana break-up.
Decreasing pressure after the eclogite overprint was demonstrated by (a) diopside-albite symplectite, and (b) plagioclase
+ red–brown to green amphibole kelyphite. The early static re-equilibration, dated to 398 ± 5.2 Ma by 40Ar–39Ar technique, was followed by an amphibolite facies foliation, which was pervasive in amphibolites, gneisses and micaschists,
and poorly developed in eclogites. The lithospheric PT paths corresponding to higher and lower metamorphic gradients reflect
the juxtaposition of crustal and lithospheric mantle units, respectively. In the build-up of the basement of the Balkan orogen,
the physical properties of the lithological complexes might have influenced the collisional pattern of involved microplates. 相似文献
193.
Caledonian high-pressure metamorphism in the Strona-Ceneri Zone (Southern Alps of southern Switzerland and northern Italy) 总被引:3,自引:0,他引:3
The Strona-Ceneri Zone comprises a succession of polymetamorphic, pre-Alpidic basement rocks including ortho- and paragneisses,
metasedimentary schists, amphibolites, and eclogites. The rock pile represents a Late Proterozoic or Palaeozoic subduction
accretion complex that was intruded by Ordovician granitoids. Eclogites, which occur as lenses within the ortho-paragneiss
succession and as xenoliths within the granitoids record a subduction related high-pressure event (D1) with peak metamorphic
conditions of 710 ± 30 °C at 21.0 ± 2.5 kbar. After isothermal uplift, the eclogites experienced a Barrowtype (D2) tectonometamorphic
overprint under amphibolite facies conditions (570-630 °C, 7-9 kbar). U-Pb dating on zircon of the eclogites gives a metamorphic
age of 457 ± 5 Ma, and syn-eclogite facies rutile gives a 206Pb/238U age of 443 ± 19 Ma classifying the subduction as a Caledonian event. These data show that the main tectonometamorphic evolution
of the Strona-Ceneri Zone most probably took place in a convergent margin scenario, in which accretion, eclogitization of
MOR-basalt, polyphase (D1 and D2) deformation, anatexis and magmatism all occurred during the Ordovician. Caledonian high-pressure
metamorphism, subsequent magmatism and Barrow-type metamorphism are believed to be related to subduction and collision within
the northern margin of Gondwana.
Editorial handling: Edwin Gnos 相似文献
194.
The possibility of filling empty underground spaces, which exist owing to the extraction of mineral raw materials, with fly
ash and cement fly ash mixes has been studied for the purpose of reducing the impact of deep mining on the surface. The method
of physical modelling was used to study the behaviour of fly ash mixes deposited in extracted mine spaces. The models were
constructed for two different geometries of underground extracted mine spaces: into cavities of the type of large slits created
in the course of mining in steeply lode deposits without subsequently filling the empty space and in vertical shafts of rectangular
or circular cross-section with horizontal side headings that have partly caved in due to mine shocks or other seismic events. 相似文献
195.
W. Bae D. Han E. Kim R. A. de Toledo K. Kwon H. Shim 《International Journal of Environmental Science and Technology》2016,13(7):1675-1684
The upflow anaerobic sludge blanket process followed by the biological aerated filter process was employed to improve the removal of color and recalcitrant compounds from real dyeing wastewater. The highest removal efficiency for color was observed in the anaerobic process, at 8-h hydraulic retention time, seeded with the sludge granule. In the subsequent aerobic process packed with the microbe-immobilized polyethylene glycol media, the removal efficiency for chemical oxygen demand increased significantly to 75 %, regardless of the empty bed contact time. The average influent non-biodegradable soluble chemical oxygen demand was 517 mg/L, and the average concentration in effluent from the anaerobic reactor was 363 mg/L, suggesting the removal of some recalcitrant matters together with the degradable ones. The average non-biodegradable soluble chemical oxygen demand in effluent from the aerobic reactor was 87, 93, and 118 mg/L, with the removal efficiency of 76, 74, and 67 %, at 24-, 12-, and 8-h empty bed contact time, respectively. The combined anaerobic sludge blanket and aerobic cell-entrapped process was effective to remove the refractory compounds from real dyeing wastewater as well as in reducing organic loading to meet the effluent discharge limits. This integrated process is considered an effective and economical treatment technology for dyeing wastewater. 相似文献
196.
In the geological evolution of the Tarim Basin, many transgressions and relictions happened. So there have been plentiful sources of salt. Moreover, because of uttermost drought, a lot of salt has been deposited. It is possible to find potash salt in this area. In our fieldwork, we have found salt and brine in western Tarim Basin. Based on a geological survey and the characteristics of sedimentary facies and paleogeography, this paper deals with the geochemical parameters and discusses the possibility of formation of potash salt in terms of the chemical analyses of samples collected from western Tarim Basin. Results of brine analysis lead to some conclusions: most of these salt brines have eluviated from very thick halite beds, mainly chloridetype salt and this kind of halite does not reach the stage of potash deposition in all aspects; WKSL (Wukeshalu) occupies a noticeable place, and we should attach importance to this district because there have been some indicators of the occurrence of potash deposits as viewed from the contents of Br and K. Finally, low Br contents are recognized in the Tarim Basin as a result of salt aggradation, and this point of view has been proved by the results of this experiment and the data available. It cannot depend upon the index of Br to judge the evolution stage of halite. We must look for other facies of potash except marine facies. 相似文献
197.
The pre-Mesozoic, mainly Variscan metamorphic basement of the Col de Bérard area (Aiguilles Rouges Massif, External domain)
consists of paragneisses and micaschists together with various orthogneisses and metabasites. Monazite in metapelites was
analysed by the electron microprobe (EMPA-CHIME) age dating method. The monazites in garnet micaschists are dominantly of
Variscan age (330–300 Ma). Garnet in these rocks displays well developed growth zonations in Fe–Mg–Ca–Mn and crystallized
at maximal temperatures of 670°C/7 kbar to the west and 600°C/7–8 kbar to the east. In consequence the monazite is interpreted
to date a slightly pressure-dominated Variscan amphibolite-facies evolution. In mylonitic garnet gneisses, large metamorphic
monazite grains of Ordovician–Silurian (~440 Ma) age but also small monazite grains of Variscan (~300 Ma) age were discovered.
Garnets in the mylonitic garnet gneisses display high-temperature homogenized Mg-rich profiles in their cores and crystallized
near to ~800°C/6 kbar. The Ordovician–Silurian-age monazites can be assigned to a pre-Variscan high-temperature event recorded
by the homogenised garnets. These monazite age data confirm Ordovician–Silurian and Devonian–Carboniferous metamorphic cycles
which were already reported from other Alpine domains and further regions in the internal Variscides. 相似文献
198.
Naguleswaran Niroshan Nagaratnam Sivakugan Ryan Llewellyn Veenstra 《Geotechnical and Geological Engineering》2018,36(4):2261-2272
Cemented paste backfill (CPB) is primarily used for backfilling underground voids at George Fisher Mine (Mount Isa, Australia). The objective of this paper is to summarise the geotechnical characterisation of the tailings and the rheological properties of the CPB as determined from a laboratory testing program undertaken at James Cook University. Two binders were examined [a General Purpose cement and a slag blend cement] over a range of dosages from 0 to 6% and CPB mix solids content in the range of 72–78%. The slump tests were carried out using the standard cone (ASTM C 143) used for concrete and a cylinder with 110 mm (diameter) × 110 mm (height), whereas the yield stress was measured using a shear vane (Brookfield vane spindle V-73). The index characteristics of the tailings including the grain size distribution, liquid limit, plastic limit, specific gravity were determined as per ASTM standards. This paper will then discuss the interrelationships among the solid content, slump, saturated density and the yield stress of the CPB. It is shown that there is strong correlation between the two different slump test devices used in this study. The smaller cylindrical device appears to have good potential for slurries like mine tailings or dredged mud that have high water content for slump test. There is also strong inter-relationship among solid content, slump, yield stress, and bulk density. Increasing the solid content increases the bulk density and yield stress, but reduces the slump. While there is hardly any difference between the two binder types used in this study in terms of flow parameters, namely the yield stress and slump, the binder dosage has an effect. At any specific solid content, higher binder dosages lead to a drop in the slump and increase in the yield stress. The difference is more pronounced in dense slurries. It is also strongly believed that the trends and relationships developed in this study may be valuable for the other mining operations using CPB. 相似文献
199.
200.
This study provided a picture of the spatial and temporal distributions of Cr, Co, Ni Cu, Zn, As, Cd and Pb in bottom sediments
of Tolo Harbour. The concentrations of the eight heavy metals differed significantly between sites due to the poor tidal flushing
in Tolo Harbour. The levels of Cu, Zn, Cd and Pb were generally enriched in sediments from inner Tolo Harbour, while sediments
from outer Tolo Harbour (Tolo Channel) had higher levels of Cr, Co and Ni. The redox sensitive element arsenic showed no distinct
spatial pattern in Tolo Harbour. The decreasing levels of Cu, Zn, Pb and Cd in sediments with increasing distance from land
demonstrated a typical diffusion pattern from land to the direction of sea. Two hot spots of Cu, Zn, Pb and Cd in sediments
were located near Tai Po and Sha Tin new town, indicating that Cu, Zn, Pb and Zn were from land-derived sources. The sites
with relatively high levels of Cr, Co and Ni in sediments were located in areas close to waste spoil in sea floor. The natural
and anthropogenic inputs from Sha Tin and Tai Po to Tolo Harbour were mostly responsible for Cu, Zn, Cd and Pb enrichment
in sediments from inner Tolo Harbour. The waste spoil in sea floor was believed to contribute to the Cr, Co and Ni in outer
Tolo Harbour. The results of correlation coefficient between the eight heavy metals showed that Cu, Zn, Cd and Pb were strongly
positively correlated, and Cr, Co and Ni were also significantly correlated with each other. The best explanation of strong
correlation was their similar source. As, however, is not well correlated with the other seven heavy metals. The average concentrations
of Cu and Zn displayed general increasing trends from 1978 to 2006 in Tolo Harbour, while the mean levels of Cr and Pb displayed
a substantial decrease from 1978 to 1987, then a slight increase after 1987. No distinct temporal trends of the concentrations
of Ni and As were observed from 1978 due to the inconsecutive data. On the other hand, the increasing trends of Cr, Cu, Zn,
Cd and Pb were observed since 1996. 相似文献