Displacement above the hypocenter of the 2011 Tohoku-Oki earthquake

The moment magnitude (M(w)) = 9.0 2011 Tohoku-Oki mega-thrust earthquake occurred off the coast of northeastern Japan. Combining Global Positioning System (GPS) and acoustic data, we detected very large sea-floor movements associated with this event directly above the focal region. An area with more than 20 meters of horizontal displacement, that is, four times larger than those detected on land, stretches several tens of kilometers long along the trench; the largest amount reaches about 24 meters toward east-southeast just above the hypocenter. Furthermore, nearly 3 meters of vertical uplift occurred, contrary to observed terrestrial subsidence.     

基于遥感数据的洞庭盆地东部地表垂直形变研究

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。     

Mantle uplifted block in the Western Indian ocean

An anomalous topographic high located close to the intersection of the Owen Fracture Zone with the Mid-Indian Ridge exposes exclusively ultramafic rocks for a thickness of more than 2 kilometers. The rocks, consisting of partly serpentinized spinel lherzolites, with minor harzburgites and dunites, display protogranular to porphyroclastic fabrics, but no cumulate textures. The chemistry of olivine, ortho-and clinopyroxene, and spinel crystals suggests that the rocks originated at a depth of at least 25 kilometers in the oceanic lithosphere and were partially reequilibrated and recrystallized during subsequent upwelling. Thus, field, textural, and mineral chemistry data indicate the presence of an uplifted block of upper mantle. The considerable vertical uplift can be explained by a two-stage process: mantle upwelling in the axial zone of plate accretion, followed by vertical tectonic uplift along the fracture zone. The rate of uplift in the fracture zone was of the order of 1 millimeter per year.     

Aseismic uplift in southern california

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.     

Migration of fluids beneath yellowstone caldera inferred from satellite radar interferometry

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.     

Modes of tilting during extensional core complex development

Crustal extension and formation of the Mineral Mountains core complex, Utah, involved tilting of the Mineral Mountains batholith and associated faults during hanging wall and footwall deformation. The batholith was folded in the hanging wall of the Beaver Valley fault between 11 and 9 million years ago yielding about 45 degrees of tilt. Subsequently, the batholith was unroofed along the Cave Canyon detachment fault, and the batholith and fault were tilted approximately 40 degrees during footwall uplift. Recognition of deformed dikes beneath the detachment fault establishes the importance of footwall tilt during formation of extensional core complexes and demonstrates that footwall rebound can be an important process during extension.     

Episodic strain accumulation in southern california

Reexamination of horizontal geodetic data in the region of recently discovered aseismic uplift has demonstrated that equally unusual horizontal crustal deformation accompanied the development of the uplift. During this time interval compressive strains were oriented roughly normal to the San Andreas fault, suggesting that the uplift produced little shear strain accumulation across this fault. On the other hand, the orientation of the anomalous shear straining is consistent with strain accumulation across northdipping range-front thrusts like the San Fernando fault. Accordingly, the horizontal and vertical crustal deformation disclosed by geodetic observation is interpreted as a short epoch of rapid strain accumulation on these frontal faults. If this interpretation is correct, thrust-type earthquakes will eventually release the accumulated strains, but the geodetic data examined here cannot be used to estimate when these events might occur. However, observation of an unusual sequence of tilts prior to 1971 on a level line lying to the north of the magnitude 6.4 San Fernando earthquake offers some promise for precursor monitoring. The data are adequately explained by a simple model of up-dip aseismic slip propagation toward the 1971 epicentral region. These observations and the simple model that accounts for them suggest a conceptually straightforward monitoring scheme to search for similar uplift and tilt precursors within the uplifted region. Such premonitory effects could be detected by a combination of frequenlty repeated short (30 to 70 km in length) level line measurements, precise gravity traverses, and continuously recording gravimeters sited to the north of the active frontal thrust faults. Once identified, such precursors could be closely followed in space and time, and might then provide effective warnings of impending potentially destructive earth-quakes.     

多层砌体1/4比例模型墙体顶部裂缝试验研究

为了研究多层砌体结构房屋顶端裂缝问题, 根据简单相似性原理构建了一1∶4比例、每层均布有构造柱和圈梁的H型六层混凝土小型空心砌块砌体结构墙体模型.通过对墙体模型进行竖向加载的拟静力试验，模拟了纵横墙荷载差，深入研究了在竖向荷载差作用下砌体房屋顶端裂缝的产生行为和发展规律.研究结果表明：随着承重墙上竖向荷载的增加，承重墙与非承重墙之间的荷载差所引起墙体的竖向变形差增大，同时承重墙中部变形相对承重墙和非承重墙交界处变形较大.当荷载增加到一定值时，由于承重墙对非承重墙产生的拉应力进一步加大，承重墙上靠近非承重墙一端顶部出现裂缝.随着荷载的继续增加，承重墙上裂缝宽度增大并扩展，并有新的裂缝出现.由于构造柱-圈梁体系的约束作用，有效地控制了承重墙与 非承重墙之间的竖向变形差的增大.     

Stream networks and long-term surface uplift in the new madrid seismic zone

Stream networks are sensitive to low rates of surface uplift and can be used to decipher the history of large earthquakes even where faults do not rupture the surface, as in intraplate seismic zones. Statistical analysis of alluvial network data from topographic maps in the New Madrid seismic zone, in the central United States, shows that stream-segment gradients deviate the most from an estimated natural stream profile where surface uplift is greatest. Evidence of cumulative deformation distilled from stream network patterns represents at least several meters of differential surface uplift during Holocene time, which suggests that more than one cycle of surface deformation occurred.     

Late cenozoic uplift of denali and its relation to relative plate motion and fault morphology

Apatite fission-track analysis of samples that cover a 4-kilometer vertical section from the western flank of Denali (Mount McKinley), North America's highest mountain, suggests that the mountain massif was formed by rapid uplift (> 1 kilometer per million years) beginning approximately 6 million years ago (Ma). Uplift was a result of the morphology of the Denali fault and a change in motion of the Pacific plate with respect to North America at approximately 5 Ma, which created opposing tangential vectors of relative movement along the fault and forced the intervening crustal blocks upward.     

Hot-spot evolution and the global tectonics of venus

The global tectonics of Venus may be dominated by plumes rising from the mantle and impinging on the lithosphere, giving rise to hot spots. Global sea-floor spreading does not take place, but direct convective coupling of mantle flow fields to the lithosphere leads to regional-scale deformation and may allow lithospheric transport on a limited scale. A hot-spot evolutionary sequence comprises (i) a broad domal uplift resulting from a rising mantle plume, (ii) massive partial melting in the plume head and generation of a thickened crust or crustal plateau, (iii) collapse of dynamic topography, and (iv) creep spreading of the crustal plateau. Crust on Venus is produced by gradual vertical differentiation with little recycling rather than by the rapid horizontal creation and consumption characteristic of terrestrial sea-floor spreading.     

Magmatic resurgence in long valley caldera, california: possible cause of the 1980 mammoth lakes earthquakes

Changes in elevation between 1975 and October 1980 along a leveling line across the Long Valley caldera indicate a broad (half-width, 15 kilometers) uplift (maximum, 0.25 meter) centered on the old resurgent dome. This uplift is consistent with reinflation of a magma reservoir at a depth of about 10 kilometers. Stresses generated by this magmatic resurgence may have caused the sequence of four magnitude 6 earthquakes near Mammoth Lakes in May 1980.     

Ocean warming and sea level rise along the southwest u.s. Coast

Hydrographic time-series data recorded during the past 42 years in the upper 500 meters off the coast of southern California indicate that temperatures have increased by 0.8 degrees C uniformly in the upper 100 meters and that temperatures have risen significantly to depths of about 300 meters. The effect of warming the surface layer of the ocean and there by expanding the water column has been to raise sea level by 0.9 +/- 0.2 millimeter per year. Tide gauge records along the coast are coherent with steric height and show upward trends in sea level that vary from about 1 to 3 millimeters per year.     

Earthquake Swarm Along the San Andreas Fault near Palmdale, Southern California, 1976 to 1977

Between November 1976 and November 1977 a swarm of small earthquakes (local magnitude 相似文献   

New evidence on the state of stress of the san andreas fault system

Contemporary in situ tectonic stress indicators along the San Andreas fault system in central California show northeast-directed horizontal compression that is nearly perpendicular to the strike of the fault. Such compression explains recent uplift of the Coast Ranges and the numerous active reverse faults and folds that trend nearly parallel to the San Andreas and that are otherwise unexplainable in terms of strike-slip deformation. Fault-normal crustal compression in central California is proposed to result from the extremely low shear strength of the San Andreas and the slightly convergent relative motion between the Pacific and North American plates. Preliminary in situ stress data from the Cajon Pass scientific drill hole (located 3.6 kilometers northeast of the San Andreas in southern California near San Bernardino, California) are also consistent with a weak fault, as they show no right-lateral shear stress at approximately 2-kilometer depth on planes parallel to the San Andreas fault.     

Evolution of the northern santa cruz mountains by advection of crust past a san andreas fault bend

The late Quaternary marine terraces near Santa Cruz, California, reflect uplift associated with the nearby restraining bend on the San Andreas fault. Excellent correspondence of the coseismic vertical displacement field caused by the 17 October 1989 magnitude 7.1 Loma Prieta earthquake and the present elevations of these terraces allows calculation of maximum long-term uplift rates 1 to 2 kilometers west of the San Andreas fault of 0.8 millimeters per year. Over several million years, this uplift, in concert with the right lateral translation of the resulting topography, and with continual attack by geomorphic processes, can account for the general topography of the northern Santa Cruz Mountains.     

The geological evolution of the Tibetan Plateau

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.     

Late holocene tectonics and paleoseismicity, southern cascadia subduction zone

Holocene deformation indicative of large subduction-zone earthquakes has occurred on two large thrust fault systems in the Humboldt Bay region of northern California. Displaced stratigraphic markers record three offsets of 5 to 7 meters each on the Little Salmon fault during the past 1700 years. Smaller and less frequent Holocene displacements have occurred in the Mad River fault zone. Elsewhere, as many as five episodes of sudden subsidence of marsh peats and fossil forests and uplift of marine terraces are recorded. Carbon-14 dates suggest that the faulting, subsidence, and uplift events were synchronous. Relations between magnitude and various fault-offset parameters indicate that earthquakes accompanying displacements on the Little Salmon fault had magnitudes of at least 7.6 to 7.8. More likely this faulting accompanied rupture of the boundary between the Gorda and North American plates, and magnitudes were about 8.4 or greater.     

立式浮放储罐三维地震动台模型试验分析

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。     

长江口水域水体结构的季节变化

通过对比不同季节长江口水域温度和盐度的观测数据,深入分析了该水域温、盐跃层的季节分布特征和变化规律后发现：长江口水域的温度（热）层化现象一般形成于春季,并在夏季最为显著,进入秋季后逐渐减弱,而在冬季该水域的温度在垂直方向基本是均匀分布,显示出较强的垂向热混合过程。另一方面,该水域的盐度分布特征主要受长江冲淡水的影响,因此在长江径流量最大的夏秋季节盐度层化现象最为显著,春季较弱,而冬季在东北季风作用下,长江冲淡水的影响主要局限于沿岸一带,长江口外的盐度垂向混合较为充分。在此基础上对引起水体结构季节变化的动力机制进行了探讨,对于进一步了解主要营养盐和污染物在该海域的分布特征和输运规律具有重要的指导意义。