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41.
Jianliang Deng Hiroshi Kameya Yukika Miyashita Jiro Kuwano Reiko Kuwano Junichi Koseki 《Engineering Geology》2011,123(4):302
Among the extensive failed slopes in the 2004 Niigata-ken Chuetsu Earthquake, Japan, a dip slope at Yokowatashi, Ojiya, was investigated intensively. The sliding plane was along a weak thin tuff sandy layer which had been deeply weathered. Triaxial compression tests and plane strain compression tests were performed on undisturbed specimens obtained by block sampling and boring sampling to evaluate the strength that was mobilized on the sliding plane. Stability analysis based on the test results reveals that, at normal time, without earthquake and without an extremely high groundwater level, the slope is stable. Furthermore, the calculation of earthquake-induced displacement provides a reasonable simulation of the failure of this slope. 相似文献
42.
Martin Michálek Marián Putiš Christoph A. Hauzenberger 《Central European Journal of Geosciences》2011,3(2):197-206
This study focuses on metapelites of the Polinik complex in the Kreuzeck Mts. southeast of the Tauern Window, Eastern Alps, where kyanite — staurolite — garnet gneisses host eclogites and high pressure (HP) amphibolites of the Austroalpine basement. The stable mineral assemblage is garnet — staurolite — biotite — kyanite — quartz. Estimated metamorphic conditions from conventional geothermobarometry are 654±30 °C and 0.9±0.08 GPa, and Average P-T values calculated by THERMOCALC, are 665±15 °C at 0.77±0.09 GPa. Formation of the present mineral association in gneisses is related to the exhumation (D2) stage of hosted eclogites/HP amphibolites within a lateral strike-slip zone. 相似文献
43.
Spectral ratios of teleseismic P waves for 15 deep (>200 km) earthquakes recorded at 146 High-Sensitivity Seismographic Network stations in the Kanto district and its surrounding area, eastern Japan, were inverted for attenuation parameter $ t_P^{ * } $ . The dataset consisted of good-quality vertical-component seismograms, whose P phases were handpicked. The P wave spectral ratios with high signal-to-noise ratios were calculated up to 1 Hz for all the station pairs, linear regressed, and then inverted for $ t_P^{ * } $ using the technique of least squares . The result showed that the active volcanic areas were clearly characterized by high $ t_P^{ * } $ . In contrast, $ t_P^{ * } $ varied in the nonvolcanic areas. The present result on the $ t_P^{ * } $ distribution was roughly consistent with the shallow part (<30 km) of an attenuation structure, which has been previously obtained based on 3-D tomography by using records of high-frequency (around 5 Hz) P waves from local earthquakes. This suggested that the present method of $ t_P^{ * } $ estimation is valid. The advantage and possible application to other areas were also discussed. 相似文献
44.
U–Pb ages of detrital zircons and white mica K–Ar ages are obtained from two psammitic schists from the western and eastern units of the Sanbagawa Metamorphic Belt located in the Sakuma–Tenryu area. The detrital zircons in the sample from the western unit (T1) show an age cluster around 95 Ma, and the youngest age in the detrital zircons is 94.0 ± 0.6 Ma. The detrital zircons in the sample from the eastern unit (T5) show a main age cluster in the Late Cretaceous with some older ages, and the youngest age in the detrital zircons is 72.8 ± 0.9 Ma. The youngest zircon ages restrict the older limit of the depositional ages of each sample. White mica K–Ar ages of T1 and T5 are 69.8 ± 1.5 Ma and 56.1 ± 1.2 Ma, respectively, which indicate the age of exhumation and restrict the younger limit on the depositional age of each sample. The results show that the western and eastern units were different in their depositional and exhumation ages, suggesting the episodic subduction and exhumation of the Sanbagawa Belt in the Sakuma–Tenryu area. These results also suggest simultaneous existence of subduction and exhumation paths of metamorphic rocks in the high‐P/T Sanbagawa Metamorphic Belt. 相似文献
45.
46.
Jean-Pierre Lefebvre Sylvain Ouillon Vu Duy Vinh Robert Arfi Jean-Yves Panché Xavier Mari Chu Van Thuoc Jean-Pascal Torréton 《Geo-Marine Letters》2012,32(2):103-121
In the Bach Dang–Cam Estuary, northern Vietnam, mechanisms governing cohesive sediment aggregation were investigated in situ
in 2008–2009. As part of the Red River delta, this estuary exhibits a marked contrast in hydrological conditions between the
monsoon and dry seasons. The impact on flocculation processes was assessed by means of surveys of water discharge, suspended
particulate matter concentration and floc size distributions (FSDs) conducted during a tidal cycle at three selected sites
along the estuary. A method was developed for calculating the relative volume concentration for the modes of various size
classes from FSDs provided by the LISST 100X (Sequoia Scientific Inc.). It was found that all FSDs comprised four modes identified
as particles/flocculi, fine and coarse microflocs, and macroflocs. Under the influence of the instantaneous turbulent kinetic
energy, their proportions varied but without significant modification of their median diameters. In particular, when the turbulence
level corresponded to a Kolmogorov microscale of less than ∼235 μm, a major breakup of flocs resulted in the formation of
particles/flocculi and fine microflocs. Fluctuations in turbulence level were governed by seasonal variations in freshwater
discharge and by the tidal cycle. During the wet season, strong freshwater input induced a high turbulent energy level that
tended to generate sediment transfer from the coarser size classes (macroflocs, coarse microflocs) to finer ones (particles/flocculi
and fine microflocs), and to promote a transport of sediment seawards. During the dry season, the influence of tides predominated.
The turbulent energy level was then only episodically sufficiently high to generate transfer of sediment between floc size
classes. At low turbulent energy, modifications in the proportions of floc size classes were due to differential settling.
Tidal pumping produced a net upstream transport of sediment. Associated with the settling of sediment trapped in a near-bed
layer at low turbulent energy, this causes the silting up of the waterways leading to the harbour of Haiphong. 相似文献
47.
Michael Rowan-Robinson Tom Babbedge Seb Oliver Markos Trichas Stefano Berta Carol Lonsdale Gene Smith David Shupe Jason Surace Stephane Arnouts Olivier Ilbert Olivier Le Févre Alejandro Afonso-Luis Ismael Perez-Fournon Evanthia Hatziminaoglou Mari Polletta Duncan Farrah Mattia Vaccari 《Monthly notices of the Royal Astronomical Society》2008,386(2):697-714
48.
49.
Marijan Herak Ivo Allegretti Davorka Herak Krešimir Kuk Vlado Kuk Krešimir Marić Snježana Markušić Josip Stipčević 《Bulletin of Earthquake Engineering》2010,8(3):483-499
Horizontal-to-vertical spectral ratios (HVSR) of ambient vibrations measured in the ancient town of Ston (Croatia) on 99 locations, are shown to be well matched to the theoretical ones computed for body-waves as well as for the surface waves. This match is poorer for sites on the slopes of nearby hills. The ratios of measured peak horizontal ground acceleration during the damaging earthquake in 1996 (M L = 6.0) and the ones obtained using empirical attenuation laws is approximately equal to the mapped value of the dynamic amplification factor determined on the basis of observed HVSR in the vicinity of the accelerometric station. The HVSR of the accelerogram is very similar to the HVSR of the ambient noise. The damage to the building stock in the old town centre caused by the earthquake series of 1996 is closely related to the estimated soil amplification and its fundamental frequency. More measurements in buildings are needed to arrive at confident conclusions about possible soil-structure resonance. 相似文献
50.
Applying the iterative shooting/bisection technique for rapid forward modeling to the seismic explosion data, we could refine the crustal velocity structure model of the western part of the Hidaka collision zone, Hokkaido, Japan. We used only the precise P-wave first arrival data obtained by the Research Group for Explosion Seismology, which set up a 113.4-km-long profile in August 2000 along with 327 observation points and four shot points with TNT charges from 100 to 300 kg. We could estimate a two-dimensional inhomogeneous crustal velocity structure model with a velocity decrease in the eastern direction at a depth of 15.7 km, several portions of velocity reversals with depth and a low velocity anomaly proposed in previous studies. The root-mean-square of travel-time residuals was improved from 0.398 s for the previous structure model to 0.176 s for the present model with a reduction of 55.8%. 相似文献