共查询到20条相似文献，搜索用时 15 毫秒
1.
利用GIS技术对2000年的SRTM和2009年的ASTERGDEM数据进行处理,得到两个时期之间洞庭盆地东部及其周边区域的地表垂直形变分布图,然后从整体到局部分析洞庭盆地东部的地表垂直形变分布状况及其原因。结果表明,东洞庭盆地受构造沉降影响,大部分地区处于沉降状态,而局部地区受到泥沙淤积或人类活动的影响较严重,导致地表抬升;盆地外的地区,临湘市、岳阳县和汨罗市东部呈南北向的抬升带,处于幕阜一九岭隆起之上,受构造抬升影响,大部分地区处于抬升状态,而临湘市和岳阳市西北地区未处于隆起之上,大部分则处于沉降状态。这对掌握洞庭盆地演变趋势和洞庭盆地的工农业规划建设具有重要的理论意义。 相似文献
2.
Holocene acceleration of deformation and postseismic relaxation are two hypotheses to explain the present-day deformation in the Central Nevada Seismic Belt (CNSB). Discriminating between these two mechanisms is critical for understanding the dynamics and seismic potential of the Basin and Range province. Interferometric synthetic aperture radar detected a broad area of uplift (2 to 3 millimeters per year) that can be explained by postseismic mantle relaxation after a sequence of large crustal earthquakes from 1915 to 1954. The results lead to a broad agreement between geologic and geodetic strain indicators and support a model of a rigid Basin and Range between the CNSB and the Wasatch fault. 相似文献
3.
为分析立式浮放储罐在三维地震动作用下的结构反应,进行了1000m3储罐模型地震动模拟试验,通过输入水平、竖向、三维地震激励,测试立式浮放储罐的地震响应。结果表明:储罐在三维地震动激励下的地震反应与一维激励相比具有较明显的放大效应。加速度反应放大1.76%~79.08%,平均放大幅度42.86%;三维激励下位移主要表现为放大趋势,平均放大幅度为31.83%;三维激励条件下储罐发生提离的概率及提离高度明显增大,增幅在20.47%~79.54%。建议立式浮放储罐应考虑三维地震动进行地震反应分析。 相似文献
4.
Migration of fluids beneath yellowstone caldera inferred from satellite radar interferometry 总被引：1，自引：0，他引：1
Satellite interferometric synthetic aperture radar is uniquely suited to monitoring year-to-year deformation of the entire Yellowstone caldera (about 3000 square kilometers). Sequential interferograms indicate that subsidence within the caldera migrated from one resurgent dome to the other between August 1992 and August 1995. Between August 1995 and September 1996, the caldera region near the northeast dome began to inflate, and accompanying surface uplift migrated to the southwest dome between September 1996 and June 1997. These deformation data are consistent with hydrothermal or magmatic fluid migration into and out of two sill-like bodies that are about 8 kilometers directly beneath the caldera. 相似文献
5.
Geophysical investigations of the tectonic boundary between East and west antarctica 总被引：1，自引：0，他引：1
The Transantarctic Mountains (TAM), which separate the West Antarctic rift system from the stable shield of East Antarctica, are the largest mountains developed adjacent to a rift. The cause of uplift of mountains bordering rifts is poorly understood. One notion based on observations of troughs next to many uplifted blocks is that isostatic rebound produces a coeval uplift and subsidence. The results of an over-snow seismic experiment in Antarctica do not show evidence for a trough next to the TAM but indicate the extension of rifted mantle lithosphere under the TAM. Furthermore, stretching preceded the initiation of uplift, which suggests thermal buoyancy as the cause for uplift. 相似文献
6.
Borehole data from young sediments folded above the Puente Hills blind thrust fault beneath Los Angeles reveal that the folding extends to the surface as a discrete zone (相似文献
7.
Coastal uplift and mortality of intertidal organisms caused by the september 1985 Mexico earthquakes
Coastal uplift associated with the great Mexican earthquake of 19 September 1985 and its principal aftershock produced widespread mortality of intertidal organisms along the coast of the states of Michoacán and Guerrero, Mexico. Measurements of the vertical extent of mortality at ten sites provided estimates of the magnitude of the vertical component of deformation along the coast. Within the affected area, uplift ranged from about 12 centimeters to about 1 meter, and no subsidence was observed. The observations are consistent with models of the tectonic deformation that results from buried slip on a shallow-dipping underthrust fault. 相似文献
8.
Farla RJ Jackson I Fitz Gerald JD Faul UH Zimmerman ME 《Science (New York, N.Y.)》2012,336(6079):332-335
Crystal defects form during tectonic deformation and are reactivated by the shear stress associated with passing seismic waves. Although these defects, known as dislocations, potentially contribute to the attenuation of seismic waves in Earth's upper mantle, evidence for dislocation damping from laboratory studies has been circumstantial. We experimentally determined the shear modulus and associated strain-energy dissipation in pre-deformed synthetic olivine aggregates under high pressures and temperatures. Enhanced high-temperature background dissipation occurred in specimens pre-deformed by dislocation creep in either compression or torsion, the enhancement being greater for prior deformation in torsion. These observations suggest the possibility of anisotropic attenuation in relatively coarse-grained rocks where olivine is or was deformed at relatively high stress by dislocation creep in Earth's upper mantle. 相似文献
9.
Analysis of seismograms from a magnitude 3.9 seismic event on 6 August 2007 in central Utah reveals an anomalous radiation pattern that is contrary to that expected for a tectonic earthquake and which is dominated by an implosive component. The results show that the seismic event is best modeled as a shallow underground collapse. Interestingly, large transverse surface waves require a smaller additional noncollapse source component that might represent either faulting in the rocks above the mine workings or deformation of the medium surrounding the mine. Seismic moment tensor results for nuclear explosions, explosion and other mining cavity collapses, and tectonic earthquakes are compared, and the separation of the different populations indicates that the seismic moment tensor may be used for source-type discrimination. 相似文献
10.
Comparison of precise leveling measurements made in 1923 with those made in 1975, 1976, and 1977 reveals that the 600,000-year-old Yellowstone caldera is being uplifted relative to its surroundings. Maximum relative uplift since 1923 is in excess of 700 millimeters-about 14 millimeters vertically per year. The most likely cause of this rapid and unusually large surface deformation is a recent influx of molten or partially molten materials to a location within the crust beneath Yellowstone National Park. 相似文献
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12.
Preliminary examination of the historic geodetic record has disclosed crustal uplift of 0.15 to 0.25 meter that apparently began around 1960 and has since grown to include at least 12,000 square kilometers of southern California. This uplift extends at least 150 kilometers west-northwestward along the San Andreas Fault from Cajon to Maricopa, southward from the San Andreas into the northern Transverse Ranges, and eastward from Lebec into and including much of western Mojave block. It seems to have grown spasmodically eastward from a center near the junction of the San Andreas and Garlock faults and has occurred largely within an area that has remained virtually aseismic since at least 1932. Although much of this area has been characterized by crustal mobility since at least the turn the century, the described uplift seems to be an unusually large and probably unique event superimposed the existing pattern of continuing deformation. 相似文献
13.
Seismic anisotropy: tracing plate dynamics in the mantle 总被引：2，自引：0，他引：2
Elastic anisotropy is present where the speed of a seismic wave depends on its direction. In Earth's mantle, elastic anisotropy is induced by minerals that are preferentially oriented in a directional flow or deformation. Earthquakes generate two seismic wave types: compressional (P) and shear (S) waves, whose coupling in anisotropic rocks leads to scattering, birefringence, and waves with hybrid polarizations. This varied behavior is helping geophysicists explore rock textures within Earth's mantle and crust, map present-day upper-mantle convection, and study the formation of lithospheric plates and the accretion of continents in Earth history. 相似文献
14.
The geological evolution of the Tibetan Plateau 总被引：15，自引：0，他引：15
The geological evolution of the Tibetan plateau is best viewed in a context broader than the India-Eurasia collision zone. After collision about 50 million years ago, crust was shortened in western and central Tibet, while large fragments of lithosphere moved from the collision zone toward areas of trench rollback in the western Pacific and Indonesia. Cessation of rapid Pacific trench migration ( approximately 15 to 20 million years ago) coincided with a slowing of fragment extrusion beyond the plateau and probably contributed to the onset of rapid surface uplift and crustal thickening in eastern Tibet. The latter appear to result from rapid eastward flow of the deep crust, probably within crustal channels imaged seismically beneath eastern Tibet. These events mark a transition to the modern structural system that currently accommodates deformation within Tibet. 相似文献
15.
Observations and modeling of 3- to 6-hertz seismic shear waves trapped within the fault zone of the 1992 Landers earthquake series allow the fine structure and continuity of the zone to be evaluated. The fault, to a depth of at least 12 kilometers, is marked by a zone 100 to 200 meters wide where shear velocity is reduced by 30 to 50 percent. This zone forms a seismic waveguide that extends along the southern 30 kilometers of the Landers rupture surface and ends at the fault bend about 18 kilometers north of the main shock epicenter. Another fault plane waveguide, disconnected from the first, exists along the northern rupture surface. These observations, in conjunction with surface slip, detailed seismicity patterns, and the progression of rupture along the fault, suggest that several simple rupture planes were involved in the Landers earthquake and that the inferred rupture front hesitated or slowed at the location where the rupture jumped from one to the next plane. Reduction in rupture velocity can tentatively be attributed to fault plane complexity, and variations in moment release can be attributed to variations in available energy. 相似文献
16.
Miyagi L Kanitpanyacharoen W Kaercher P Lee KK Wenk HR 《Science (New York, N.Y.)》2010,329(5999):1639-1641
Understanding deformation of mineral phases in the lowermost mantle is important for interpreting seismic anisotropy in Earth's interior. Recently, there has been considerable controversy regarding deformation-induced slip in MgSiO(3) post-perovskite. Here, we observe that (001) lattice planes are oriented at high angles to the compression direction immediately after transformation and before deformation. Upon compression from 148 gigapascals (GPa) to 185 GPa, this preferred orientation more than doubles in strength, implying slip on (001) lattice planes. This contrasts with a previous experiment that recorded preferred orientation likely generated during the phase transformation rather than deformation. If we use our results to model deformation and anisotropy development in the D' region of the lower mantle, shear-wave splitting (characterized by fast horizontally polarized shear waves) is consistent with seismic observations. 相似文献
17.
Julian B 《Science (New York, N.Y.)》2002,296(5573):1625-1626
The occurrence of more or less continuous ground vibrations ("volcanic tremor") is an important indicator of volcanic activity. But results from the "Hi-net" seismic network in Japan reported by Obara show that continuous ground vibrations can occur far away from any volcanic activity. In his Perspective, Julian discusses the idea that this tremor is excited by flow of metamorphic fluids. He also identifies other possible locations where such a tremor may be detected and explains what may be learnt from measuring it. 相似文献
18.
Repeat geodetic surveys show uplift of the Monroe and Wiggins anticlines in Louisiana and Mississippi. There are deformed Quaternary terraces, which indicate long-term deformation in the valleys of the alluvial rivers that cross these structures, and there are floodplain and channel convexities that provide evidence of modern deformation. In addition, the channels show significant variations of morphology (sinuosity, gradient, and depth) and behavior appropriate to reaches of increased and decreased valley slope. These alluvial rivers are adjusting to modern deformation and their adjustment confirms two geodetic leveling anomalies. 相似文献
19.
Changes in the ground surface tilt and in the rate of seismicity indicate that an aseismic deformation event may have occurred between 1978 and 1980 along the plate boundary in the eastern Aleutians, Alaska, within the Shumagin seismic gap. Pavlof Volcano was unusually quiescent during this period. The proposed event would cause an increase of stress on the shallow locked portion of the plate boundary, bringing it closer to rupture in a great earthquake. 相似文献
20.
An inverted double seismic zone in chile: evidence of phase transformation in the subducted slab 总被引：1，自引：0，他引：1
Data from two microseismic field experiments in northern Chile revealed an elongated cluster of earthquakes in the subducted Nazca plate at a depth of about 100 kilometers in which down-dip tensional events were consistently shallower than a family of compressional earthquakes. This double seismic zone shows a distribution of stresses of opposite polarity relative to that observed in other double seismic zones in the world. The distribution of stresses in northern Chile supports the notion that at depths of between 90 to 150 kilometers, the basalt to eclogite transformation of the subducting oceanic crust induces tensional deformation in the upper part of the subducted slab and compressional deformation in the underlying mantle. 相似文献