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排序方式: 共有726条查询结果,搜索用时 218 毫秒
41.
Yoshinobu Tsuji Fumihiko Imamura Hideo Matsutomi Costas E. Synolakis Puspito T. Nanang Jumadi Satoshi Harada Se Sub Han Ken'ichi Arai Benjamin Cook 《Pure and Applied Geophysics》1995,144(3-4):839-854
A field survey of the June 3, 1994 East Java earthquake tsunami was conducted within three weeks, and the distributions of the seismic intensities, tsunami heights, and human and house damages were surveyed. The seismic intensities on the south coasts of Java and Bali Islands were small for an earthquake with magnitudeM 7.6. The earthquake caused no land damage. About 40 minutes after the main shock, a huge tsunami attacked the coasts, several villages in East Java Province were damaged severely, and 223 persons perished. At Pancer Village about 70 percent of the houses were swept away and 121 persons were killed by the tsunami. The relationship between tsunami heights and distances from the source shows that the Hatori's tsunami magnitude wasm=3, which seems to be larger for the earthquake magnitude. But we should not consider this an extraordinary event because it was pointed out byHatori (1994) that the magnitudes of tsunamis in the Indonesia-Philippine region generally exceed 1–2 grade larger than those of other regions. 相似文献
42.
Very soft organic harbour mud is increasingly used as a filling and construction material in harbour construction and reorganization.
The undrained shear strength of such soft sediments is the critical geotechnical soil parameter with regard to any specific
construction design. Field and laboratory vane shear testing is a standard method to quickly determine this important parameter.
So far, the effect of rod friction on vane shear tests in very soft organic soils is unclear. In this study we present results
from laboratory experiments on harbour mud from a construction site in northern Germany. Relations among vane and rod geometry,
penetration depth, water content, rod friction and undrained shear strength are derived. Based on these relations the influence
of rod friction on vane shear test results is investigated. The results indicate that field and laboratory vane shear test
measurements may be significantly influenced by rod friction. Methods are proposed to correct for the rod influence, which
is shown to increase with rising water contents. 相似文献
43.
44.
In the work reported here the comprehensive physics‐based Integrated Hydrology Model (InHM) was employed to conduct both three‐ and two‐dimensional (3D and 2D) hydrologic‐response simulations for the small upland catchment known as C3 (located within the H. J. Andrews Experimental Forest in Oregon). Results from the 3D simulations for the steep unchannelled C3 (i) identify subsurface stormflow as the dominant hydrologic‐response mechanism and (ii) show the effect of the down‐gradient forest road on both the surface and subsurface flow systems. Comparison of the 3D results with the 2D results clearly illustrates the importance of convergent subsurface flow (e.g. greater pore‐water pressures in the hollow of the catchment for the 3D scenario). A simple infinite‐slope model, driven by subsurface pore‐water pressures generated from the 3D and 2D hydrologic‐response simulations, was employed to estimate slope stability along the long‐profile of the C3 hollow axis. As expected, the likelihood of slope failure is underestimated for the lower pore pressures from the 2D hydrologic‐response simulation compared, in a relative sense, to the higher pore pressures from the 3D hydrologic response simulation. The effort reported herein provides a firm quantitative foundation for generalizing the effects that forest roads can have on near‐surface hydrologic response and slope stability at the catchment scale. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
45.
Benjamin Ross Gunnar Johannson Gregory D. Foster William P. Eckel 《Hydrogeology Journal》1992,1(1):66-76
Ether derivatives of dihydroxy alcohols, which are formed from ethylene or propylene, comprise an important group of groundwater contaminants known as glycol ethers. Compounds in this group are used as solvents, cleaning agents, and emulsifiers in many chemical products and manufacturing operations. Glycol ethers have been associated with a variety of toxic effects, and some compounds in the group are relatively potent teratogens. The limited information available suggests that glycol ethers are contaminants in groundwater, especially in anaerobic plumes emanating from disposal of mixed industrial and household waste. Most methods used to analyze groundwater samples cannot adequately detect 7g/ (ppb) concentrations of glycol ethers, and the existing methods perform worst for the most widely used and toxic species. A new method capable of analyzing 7g/ concentrations of glycol ethers was recently developed, and its use is recommended for groundwater samples where glycol ethers are likely to be present. Résumé. Les éthers glycol, polluants des eaux souterraines. Les dérivés d'éther de dihydroxy-alcool, formés à partir de l'éthylène ou du propylène, constituent un important groupe de polluants des eaux souterraines connus sous le nom d'éthers glycol. Les composés de ce groupe sont utilisés comme solvants, comme agents de nettoyage et comme émulsifiants dans de nombreux produits chimiques et dans de nombreux processus de fabrication. Des effets toxiques variés ont été attribués aux éthers glycol et certains des composés sont des agents tératogènes relativement puissants. Les données disponibles, qui sont limitées, indiquent que les éthers glycol sont des polluants communs dans les eaux souterraines, particulièrement dans les panaches anaéorobies émis par les décharges mixtes de déchets industriels et domestiques. La plupart des méthodes d'analyse d'échantillons d'eau souterraine ne sont pas capables de détecter convenablement des concentrations en éthers glycol de l'ordre du 7g/l (ppb); les méthodes actuelles sont médiocres pour doser les espèces toxiques les plus courantes. Une nouvelle méthode permettant de doser des concentrations en éthers glycol de l'ordre du 7 g/l a été récemment mise au point; son utilisation est préconisée pour les échantillons d'eau souterraine contenant des éthers glycol. 相似文献
46.
47.
Adam Carter Benjamin van Wyk de Vries Karim Kelfoun Patrick Bachèlery Pierre Briole 《Bulletin of Volcanology》2007,69(7):741-756
A clear model of structures and associated stress fields of a volcano can provide a framework in which to study and monitor
activity. We propose a volcano-tectonic model for the dynamics of the summit of Piton de la Fournaise (La Reunion Island,
Indian Ocean). The summit contains two main pit crater structures (Dolomieu and Bory), two active rift zones, and a slumping
eastern sector, all of which contribute to the actual fracture system. Dolomieu has developed over 100 years by sudden large
collapse events and subsequent smaller drops that include terrace formation. Small intra-pit collapse scars and eruptive fissures
are located along the southern floor of Dolomieu. The western pit wall of Dolomieu has a superficial inward dipping normal
fault boundary connected to a deeper ring fault system. Outside Dolomieu, an oval extension zone containing sub-parallel pit-related
fractures extends to a maximum distance of 225 m from the pit. At the summit the main trend for eruptive fissures is N80°,
normal to the north–south rift zone. The terraced structure of Dolomieu has been reproduced by analogue models with a roof
to width ratio of approximately 1, suggesting an original magma chamber depth of about 1 km. Such a chamber may continue to
act as a storage location today. The east flank has a convex–concave profile and is bounded by strike-slip fractures that
define a gravity slump. This zone is bound to the north by strike-slip fractures that may delineate a shear zone. The southern
reciprocal shear zone is probably marked by an alignment of large scoria cones and is hidden by recent aa lavas. The slump
head intersects Dolomieu pit and may slide on a hydrothermally altered layer known to be located at a depth of around 300 m.
Our model has the summit activity controlled by the pit crater collapse structure, not the rifts. The rifts become important
on the mid-flanks of the cone, away from pit-related fractures. On the east flank the superficial structures are controlled
by the slump. We suggest that during pit subsidence intra-pit eruptions may occur. During tumescence, however, the pit system
may become blocked and a flank eruption is more likely. Intrusions along the rift may cause deformation that subsequently
increases the slump’s potential to deform. Conversely, slumping may influence the east flank stress distribution and locally
control intrusion direction. These predictions can be tested with monitoring data to validate the model and, eventually, improve
monitoring. 相似文献
48.
Pit crater structure and processes governing persistent activity at Masaya Volcano, Nicaragua 总被引:1,自引:1,他引:0
Hazel Rymer Benjamin van Wyk de Vries John Stix Glyn Williams-Jones 《Bulletin of Volcanology》1998,59(5):345-355
Persistent activity at Masaya Volcano, Nicaragua, is characterised by cycles of intense degassing, lava lake development
and pit crater formation. It provides a useful site to study the processes which govern such activity, because of its easy
accessibility and relatively short cycles (years to decades). An understanding of the present activity is important because
Masaya is visited by large numbers of tourists, is located close to major cities and has produced voluminous lavas, plinian
eruptions and ignimbrites in the recent past. We provide structural and geophysical data that characterise the "normal" present
state of activity. These indicate that the ongoing degassing phase (1993 to present) was not caused by fresh magma intrusion.
It was associated with shallow density changes within the active Santiago pit crater. The activity appears to be associated
predominantly with shallow changes in the pit crater structure. More hazardous activity will occur only if there are significant
departures from the present gravity, deformation and seismic signatures.
Received: 16 May 1997 / Accepted: 29 October 1997 相似文献
49.
Benjamin N. Powell 《Tectonophysics》1975,27(3):295-297
50.
Tracing variability of run‐off generation in mountainous permafrost of semi‐arid north‐eastern Mongolia 下载免费PDF全文
The headwaters of mountainous, discontinuous permafrost regions in north‐eastern Mongolia are important water resources for the semi‐arid country, but little is known about hydrological processes there. Run‐off generation on south‐facing slopes, which are devoid of permafrost, has so far been neglected and is totally unknown for areas that have been affected by recent forest fires. To fill this knowledge gap, the present study applied artificial tracers on a steppe‐vegetated south‐facing and on two north‐facing slopes, burned and unburned. Combined sprinkling and dye tracer experiments were used to visualize processes of infiltration and water fluxes in the unsaturated zone. On the unburned north‐facing slope, rapid and widespread infiltration through a wet organic layer was observed down to the permafrost. On the burned profile, rapid infiltration occurred through a combusted organic and underlying mineral layer. Stained water seeped out at the bottom of both profiles suggesting a general tendency to subsurface stormflow (SSF). Ongoing SSF could directly be studied 24 h after a high‐intensity rainfall event on a 55‐m hillslope section in the burned forest. Measurements of water temperature proved the role of the permafrost layer as a base horizon for SSF. Repeated tracer injections allowed direct insights into SSF dynamics: A first injection suggested rather slow dispersive subsurface flow paths; whereas 18 h later, a second injection traced a more preferential flow system with 20 times quicker flow velocities. We speculate that these pronounced SSF dynamics are limited to burned slopes where a thermally insulating organic layer is absent. On three south‐facing soil profiles, the applied tracer remained in the uppermost 5 cm of a silt‐rich mineral soil horizon. No signs of preferential infiltration could be found, which suggested reduced biological activity under a harsh, dry and cold climate. Instead, direct observations, distributed tracers and charcoal samples provided evidence for the occurrence of overland flow. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献