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1.
This study presents the dynamic behaviour of a rigid block which rests on a footing supported by a spring and a dashpot on a rigid base. The response of the rigid body is examined carefully when the base is excited by a harmonic force. It is found that a periodic motion appears in three different modes: stick-stick, stick-slip and slip-slip. The conditions that initiate the stick-stick and slip-slip modes are derived in explicit forms and the maximum sliding displacement is also obtained analytically. Useful dimensionless parameters are proposed for the presentation of the dynamic behaviour. The accuracy of results is confirmed by the response history computed by the Nigam-Jennings method. 相似文献
2.
Recent structural, tephrochronologic and magnetostratigraphic studies conducted along the northernmost border of the Philippine Sea (PHS) plate enable us to reconstruct the precise tectonic evolution along the convergent boundary between the PHS plate and the Northeast Japan (NEJ) plate or the North American (NAM) plate since about 1 Ma. The authors of the present study split the tectonic evolution into five stages and present the characteristics of each stage. A plate tectonic interpretation is proposed, based upon the tectonic evolution, with special reference to the mode of convergent motion. In brief, our interpretations are as follows: the relative motion between the PHS and the NEJ plates was not recognized geologically within the area studied from about 1.0 to 0.9 Ma (Stage 1), suggesting either none or small influence from the coupling between the two plates during that period of time. Convergence between the PHS and the NEJ plates was possibly in N-S direction from 0.9 to 0.5 Ma (Stage II), and probably north-northwestward since 0.5 Ma (Stages III to V). The mode of the convergent motion was that of buoyant subduction in Stages II and III. The mode changed gradually from buoyant subduction during Stage IV to collision in Stage V (0.07 Ma to the present). 相似文献
3.
Hikaru Komatsu Narimasa Yoshida Hideki Takizawa Izumi Kosaka Chatchai Tantasirin Masakazu Suzuki 《Boundary-Layer Meteorology》2003,106(3):573-592
Using data for one year, we examined the vertical wind speed profileson a mountain slope covered with forest in northern Thailand undera tropical monsoon climate. We defined two profile patterns: higherwind speeds at greater heights (Pattern 1) and lower wind speeds atgreater heights (Pattern 2). We classified 9.4% of the data as Pattern 2;this pattern tended to occur during the night, at low wind speeds, and with high outgoing longwave radiation. In addition, stable stratification anddecoupling between the canopy surface air and the overlying layers wereobserved when Pattern 2 occurred frequently. These facts suggested thatPattern 2 was caused by a nocturnal drainage flow. The occurrence ofPattern 2 showed a clear seasonal trend, indicating that there is a seasonaltrend in the occurrence of nocturnal drainage flows. Pattern 2 was observedmore frequently between August and February and less frequently betweenMarch and July. This corresponded to the seasonal trend in wind speed, butdid not correspond to the seasonal trend in the outgoing longwave radiation. 相似文献
4.
5.
Hidemi Tanaka Shin-Ichiro Hinoki Kazuo Kosaka Aiming Lin Keiji Takemura Akihiro Murata Takao Miyata 《Island Arc》2001,10(3-4):381-391
Abstract This paper describes the results of petrographical and meso- to microstructural observations of brittle fault rocks in cores obtained by drilling through the Nojima Fault at a drilling depth of 389.52 m. The zonation of deformation and alteration in the central zone of the fault is clearly seen in cores of granite from the hanging wall, in the following order: (i) host rock, which is characterized by some intragranular microcracks and in situ alteration of mafic minerals and feldspars; (ii) weakly deformed and altered rocks, which are characterized by transgranular cracks and the dissolution of mafic minerals, and by the precipitation of zeolites and iron hydroxide materials; (iii) random fabric fault breccia, which is characterized by fragmentation, by anastomosing networks of transgranular cracks, and by the precipitation of zeolites and iron hydroxide materials; and (iv) fault gouge, which is characterized by the precipitation of smectite and localized cataclastic flow. This zonation implies that the fault has been weakened gradually by fluid-related fracturing over time. In the footwall, a gouge layer measuring only 15 mm thick is present just below the surface of the Nojima Fault. These observations are the basis for a model of fluid behavior along the Nojima Fault. The model invokes the percolation of meteoric fluids through cracks in the hanging wall fault zone during interseismic periods, resulting in chemical reactions in the fault gouge layer to form smectite. The low permeability clay-rich gouge layer sealed the footwall. The fault gouge was brecciated during coseismic or postseismic periods, breaking the seal and allowing fluids to readily flow into the footwall, thus causing a slight alteration. Chemical reactions between fluids and the fault breccia and gouge generated new fault gouge, which resealed the footwall, resulting in a low fluid condition in the footwall during interseismic periods. 相似文献
6.
Indo-western Pacific ocean capacitor and coherent climate anomalies in post-ENSO summer: A review 总被引:8,自引:0,他引:8
ENSO induces coherent climate anomalies over the Indo-western Pacific, but these anomalies outlast SST anomalies of the equatorial Pacific by a season, with major effects on the Asian summer monsoon. This review provides historical accounts of major milestones and synthesizes recent advances in the endeavor to understand summer variability over the Indo-Northwest Pacific region. Specifically, a large-scale anomalous anticyclone(AAC) is a recurrent pattern in post-El Ni ?no summers, spanning the tropical Northwest Pacific and North Indian oceans. Regarding the ocean memory that anchors the summer AAC, competing hypotheses emphasize either SST cooling in the easterly trade wind regime of the Northwest Pacific or SST warming in the westerly monsoon regime of the North Indian Ocean. Our synthesis reveals a coupled ocean–atmosphere mode that builds on both mechanisms in a two-stage evolution. In spring, when the northeast trades prevail, the AAC and Northwest Pacific cooling are coupled via wind–evaporation–SST feedback. The Northwest Pacific cooling persists to trigger a summer feedback that arises from the interaction of the AAC and North Indian Ocean warming, enabled by the westerly monsoon wind regime. This Indo-western Pacific ocean capacitor(IPOC) effect explains why El Ni ?no stages its last act over the monsoonal Indo-Northwest Pacific and casts the Indian Ocean warming and AAC in leading roles. The IPOC displays interdecadal modulations by the ENSO variance cycle, significantly correlated with ENSO at the turn of the 20 th century and after the 1970 s, but not in between. Outstanding issues, including future climate projections, are also discussed. 相似文献
7.
The problem of response of sliding structures subjected to harmonic support motions is considered. The periodic motions, consisting of the three different modes, stick-stick, stick-slip and slip-slip, are a significant part of the responses to harmonic excitations. Assuming the periodicity of the motion, the condition of the initiation of the slip-slip motion is derived. Then analytical expressions for the occurrence of the periodic motions are obtained without integrating the equations of motion. The accuracy of the analytical expressions is confirmed by comparison with numerical results herein obtained. It is observed that the numerical results are sensitive to the starting and ending times of slip motions. 相似文献
8.
Climate Dynamics - It is widely recognized that no two El Niño episodes are the same; hence the predictable variations of the climate impacts associated with El Niño remain an open... 相似文献
9.
This article is an analysis of observed changes in the level of fishing effort and the spatial distribution of fishing effort following implementation of a marine reserve off the California coast. The Rockfish Conservation Area (RCA) closes the area between depth contour based boundaries to commercial trawl fishing. In this analysis, commercial fishing vessels are grouped based on their level of fishing effort within the closed area prior to the closure in order to compare changes in effort levels between groups. The results suggest that the RCA may have had a small effect on the level of fishing effort in the California groundfish trawl fishery. Spatial distribution of fishing effort before and after implementation of the marine reserve is also compared. Some concentration of effort occurred along parts of the closed area boundaries. This pattern suggests the “fishing the line” behavior noted in the marine reserve literature, but other possible explanations exist including the effects of coincident changes in other regulations and changing bioeconomic conditions. 相似文献
10.
Masakazu?NiwaEmail author Hideki?Kurosawa Koji?Shimada Tsuneari?Ishimaru Hideki?Kosaka 《Pure and Applied Geophysics》2011,168(5):887-900
Previous studies have reported that high concentrations of H2 gas are released from active fault zones. Experimental studies suggest that the H2 gas is derived from the reaction of water with free radicals formed when silicate minerals are fractured at hypocenter depths
during fault activities. However, the pathways for migration of deep-seated fluids to surface are still unknown. In this study
we performed quick, multipoint H2 gas measurements across a fault zone using a portable gas monitor and a hand drill. The fault zone studied includes a smectite-rich
fault core dividing two clearly distinguishable damage zones: granite cataclasite and welded tuff fault breccia. The measurements
show that H2 gas emissions collected in 2–3 h sampling periods from start of measurement range from 320.3 to 446.2 ppm/min in the granite
cataclasite and 60.5 to 137.8 ppm/min in the welded tuff fault breccias. Negligible quantities of H2 gas could be collected from the fault core. Particle size distribution analyses of fault rocks indicate that the granite
cataclasite tends to be rich in particles that are finer, i.e., less cohesive and easy to disaggregate, which leads to the
inference that the granite cataclasite has high permeability. Based on the H2 gas measurements and the particle size distribution analyses, the H2 gas is considered to have migrated in permeable damage zones mostly by advection with groundwater. Multipoint H2 gas measurement will be effective in qualitative delineation of variations in permeability of regional structures. 相似文献