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1.
Ordos block was squeezed by the Qinghai-Tibetan block and North China block, and the tectonic activity was intense. In the periphery of Ordos block, there was a series of folds zones and compressed faults with complicate structures. This paper used three-phase data of 1980,1990 and 2014 to calculate vertical velocity of Northwestern margin of Ordos and the analytical results indicated that ① the Hetao basin between the rise of Yinshan fault block and Ordos fault block showed relatively subsidence, in which Linhe basin was the most evident and the subsidence rate was about 2-4mm/a. The subsidence rate of Jartai -Yinchuan rift zone on the western margin of Ordos block was about 2mm/a; ② the whole testing zone exhibited the evident inherited movement characterized by mountain rise and basin subsidence; ③the two leveling section through the northern margin fault and Dengkou-Benjing fault showed that the difference between vertical velocities on two sides of the fault was less than 0.5mm/a. 相似文献
2.
位于青藏块体和华北块体之间的鄂尔多斯块体及其周缘地区是中国大陆构造活动最活跃的地区之一,从1300年至今,在块体周边断陷盆地和西南缘断裂带上发生了五次8级以上的地震.为了了解该地区现今地壳运动、应变状态以及断裂滑动分布,我们收集了中国大陆构造环境监测网络2009—2013年、国家GPS控制网、跨断陷盆地的8个GPS剖面等共527个流动站和32个连续站GPS观测数据,获得了高空间分辨率的地壳水平运动速度场,进一步用均匀弹性模型计算了应变率分布.结果表明,块体内部GPS站点向NEE方向运动,速度变化较小,应变率大多在(-1.0~1.0)×10~(-8)/a之间;山西断陷带构造运动与变形最为强烈,盆地相对于鄂尔多斯块体为拉张变形,应变率为(1.0~3.0)×10~(-8)/a,相对于东部山地则为挤压变形,应变率为(-2.0~-3.0)×10~(-8)/a,盆地西侧断裂(如罗云山断裂、交城断裂)以拉张运动为主,拉张速率为2~3mm·a-1,盆地东侧断裂主要以右旋缩短运动为主,速率为1~3mm·a-1;河套断陷带西部的临河凹陷处于较强的张性应变状态,应变率为(2.0~3.0)×10~(-8)/a;块体西南边缘处于压缩应变状态,应变率为(-1.0~-2.0)×10~(-8)/a,六盘山断裂存在明显的地壳缩短运动,速率约为2.1mm·a-1,速率在断裂附近逐渐减小,反映了断裂处于闭锁状态;相对于鄂尔多斯块体内部渭河断裂带为左旋运动,速率为1.0mm·a-1,盆地处在弱拉张变形状态. 相似文献
3.
鄂尔多斯块体受青藏块体和华北块体的挤压,在其周缘形成一系列褶皱和压性断层,构造较为复杂。本文利用1980、1990和2014这3期精密水准资料计算了鄂尔多斯块体西北缘的垂直运动速率,分析结果表明:① 位于阴山断块隆起与鄂尔多斯断块隆起之间的河套盆地相对下沉,其中临河盆地最为明显,下沉速率为2-4mm/a,位于鄂尔多斯块体西缘的吉兰泰-银川断陷带沉降速率有所减缓,目前沉降速率约为2mm/a;② 整个测区表现为明显的山区上升、盆地下沉的继承性运动;③ 穿过乌拉山北缘断裂和磴口-本井断裂的2条水准剖面显示断裂两侧的垂直运动速率差异小于0.5mm/a。 相似文献
4.
利用双平面波干涉面波层析成像方法研究山西断陷盆地及鄂尔多斯地台三维速度结构 总被引：4，自引：1，他引：3
本文利用了北京大学在山西地堑的34个台站以及中国地震局台网中心在鄂尔多斯地区46个台站的远震波形数据,运用双平面波干涉的面波层析成像方法,提取瑞利面波相速度频散曲线,开展台阵覆盖区三维速度结构反演,据此分析了研究区地壳和上地幔的结构特征。结果表明,瑞利面波相速度分区特征显著,山西断陷盆地和渭河断陷盆地的相速度整体偏低。鄂尔多斯块体在莫霍面以下有明显高速异常,表明该地块为构造稳定的克拉通块体,鄂尔多斯块体的岩石圈下界面在120～140km的深度左右。与此相反,山西断陷盆地和渭河断陷盆地地下70～120km左右均有低速异常,显示这两个地区构造活动活跃,这也与该区域历史上多次发生强震是相符的。 相似文献
5.
基于华北中西部和青藏高原东北缘3个流动台阵共480个台站新得到的远震XKS(SKS、SKKS和PKS)波分裂结果,并结合研究区已得到的987个台站的分裂结果,获得了高分辨率的上地幔各向异性图像.分析表明,鄂尔多斯块体的时间延迟较小,反映了其稳定性和弱的各向异性变形特征,可能保留了古老克拉通根的"化石"各向异性,但其靠近边缘的局部区域表现出与相邻边缘相一致的各向异性特征,反映了其局部区域受到了与其相邻边缘的构造活动影响.青藏高原东北缘、阿拉善块体和鄂尔多斯块体西缘快波方向主要为NW-SE方向,鄂尔多斯块体北缘主要为NNW-SSE方向,反映了青藏高原沿NE方向推挤过程中岩石圈沿NW-SE方向和NNW-SSE方向发生了伸展变形;位于四川盆地和鄂尔多斯块体两个刚性块体间的秦岭造山带的快波方向为近E-W方向或NWW-SEE方向,时间延迟较大,推测岩石圈东向挤出和软流圈东流共同促进了观测的各向异性;在鄂尔多斯块体南部边缘,快波方向自西向东逆时针沿西南缘六盘山的NW-SE方向转到南缘渭河地堑的近E-W方向再到东南缘太行山的NEE-SWW方向,推断该区域可能存在一个绕刚性块体的逆时针软流圈绕流,与上覆岩石圈左旋简单剪切变形产生了观测的各向异性,并一起驱动了鄂尔多斯块体的逆时针旋转.作为华北克拉通东西部的过渡带,华北中部的各向异性相对复杂,其东部快波方向为近E-W方向或NWW-SEE方向,时间延迟较大,其各向异性主要反映了太平洋板块西向俯冲作用引起的地幔流;其西北部吕梁山的各向异性主要由岩石圈沿NNW-SSE到NW-SE的拉张变形导致,而西南部太行山的各向异性还反映了软流圈绕流作用.鄂尔多斯块体东北缘大同火山区存在一个快波方向顺时针快速旋转且时间延迟较小的区域,可能与火山群下地幔岩浆上涌形成的局部地幔对流相关.紧邻华北北部的中亚造山带中南部快波方向为近E-W方向,其各向异性不仅受到与构造走向一致的岩石圈变形作用,而且也受到太平洋板块西向俯冲引起的地幔流影响. 相似文献
6.
L ateral Variation of Pn velocity beneath northeastern marginal region of Qinghai—Xizang plateau 总被引：1，自引：0，他引：1
Pn arrival time data are collected from the bulletins of both national and regional seismological network in China-These data are tomographically inverted to map the lateral variation and anisotropy of Pn velocity in the northeast-ern marginal region of Qinghai-Xizang plateau.The average Pn velocity in this region is 8.09km/s,being a little higher than the average for whole China,Higher velocity is found in tectonically stable Qaidam basin,while lower velocity is seen in and around tectonically active Shanxi graben.The region where the 1920 Haiyuan great earth-quake occurred shows a slightly low Pn velocity.A noticeable result is that,differing from the tectonically com-pressive Tianshan region.where Pn velocity is low,the Qilianshan region,where the Neotectonic deformation is also primarily compressive,shows high Pn velocity,In the uppermost mantle beneath the Ordos plateau Pn veloc-ity is inhomogeneous,varying from higher velocity in southwestern part to lower one in northeastern part.This may be attributed to possible movement of the Ordos block,as there are strong earthquakes all around the block. 相似文献
7.
利用鄂尔多斯地块北部及其邻区2008—2018年期间固定台网的地震波形记录,手动拾取出高质量的Pn波到时资料,反演获得了研究区上地幔顶部的Pn波速度结构及各向异性。结果表明:鄂尔多斯地块北部及其邻区上地幔顶部的Pn波速度存在明显的横向不均匀性,与区域地质构造和地震活动相关;研究区内平均Pn波速为8.18 km/s,鄂尔多斯地块内部表现出大范围的高速异常,阿拉善地块的高速异常体中存在低速异常现象,河套断陷带、阴山—燕山造山带、银川—吉兰泰断陷带和海原—六盘山弧形断裂带区域均表现为显著的低速异常,河套断陷带下方存在向鄂尔多斯地块内部延伸的明显低速异常条带,大同火山群下方存在强低速异常;多数历史强震均发生在低速异常区或高低速异常过渡带上;鄂尔多斯地块内部Pn波各向异性快波方向西部为近NE?SW向,而东部为近NW?SE向,河套断陷带和鄂尔多斯地块西缘、青藏高原东北缘与阿拉善地块的交界带以及阴山—燕山造山带的各向异性快波方向总体均呈现为NW?SE向,而阴山—燕山造山带东部则呈NE?SW向。 相似文献
8.
Yongcai Tang Yongshun John Chen Yuanyuan V. Fu Haiyang Wang Shiyong Zhou Eric Sandvol Jieyuan Ning Yongge Feng Mian Liu 《地震科学（英文版）》2010,23(6):549-553
Located at the northeastern margin of the Tibetan plateau,the Ordos block is a stable tectonic unit in North China.With its active boundary fault zones,the Ordos block played an important role in the eastward extrusion mechanism of the Tibetan plateau.Peking University deployed a linear array of 15 portable broadband seismometers across the western Weihe graben during September 2005 to August 2006 and later a 2-D seismic array(Southwest Ordos Array) of 14 portable broadband seismometers during 2007-2008 at its southwestern boundary.Analyses of shear wave splitting of SKS and SKKS phases at these stations show that the fast directions trend ～110° with an average delay time of 0.9 s in the southwestern margin of the Ordos block.The agreement between the lithosphere deformation indicated by GPS data and Quaternary fault slip-rate observations and the mantle flow represented by shear wave splitting implies that accordant deformation patterns from lithosphere to asthenosphere in relation to the eastward extrusion of the Tibetan plateau could extend at least to 200 km depth.Spatial distribution of splitting polarization directions indicates that the mantle flow driven by the Tibetan plateau is blocked by the Ordos block and locally restricted in a narrow channel along the Qinling-Dabie fault zones between the Ordos block and Sichuan basin. 相似文献
9.
搜集整理了中国国家地震台网和区域地震台网记录的Pn波到时资料，利用层析成像方法分析了青藏高原东北地区上地幔顶部P波速度及其各向异性的横向变化．结果表明，该地区Pn波的平均速度偏高，为8.09 km/s；构造上稳定的柴达木盆地下面，上地幔顶部Ｐ波速度较高，而构造上比较活跃的山西地堑地区波速则较低．1920年发生海原大地震的地区，上地幔顶部是Ｐ波速度偏低的地区．一个值得注意的结果是，与天山挤压带上地幔顶部Ｐ波速度偏低的情况不同，在青藏高原东北缘的祁连山现代挤压变形带地区，上地幔顶部是Ｐ波速度偏高的地区．鄂尔多斯地块下面，波速度不均一，存在高低速的变化．这与该地块四周皆有强地震活动、地块本身可能有整体的构造运动有关． 相似文献
10.
In this study, we reevaluate, based on our investigation, the ground deformation caused around the area of the Great Wall by the ca. M 8 Pingluo earthquake of 1739 along an active fault zone in the Yinchuan graben, on the western margin of the Ordos Block in northern central China. Previous studies have shown that the Great Wall of China was damaged and right-laterally offset by the 1739 M 8 Pingluo earthquake up to ～1.6–2 m, with a 0.1–1.9-m vertical component, at three locations. However, our recent fieldwork and in-situ measurements have shown that the Great Wall was not affected by the ca. M 8 Pingluo earthquake of 1739, as reported previously, but was actually built on preexisting active fault scarps. This study reinterprets the offset of the Great Wall based on these new field observations and attempts to identify the seismogenic source fault that triggered the 1739 Pingluo earthquake. More work is required if we are to better understand the deformation characteristics of the seismogenic source fault and also improve our ongoing assessments of the seismic hazard within the densely populated area of the Yinchuan graben, central China. 相似文献
11.
Asymmetric rifting of the northern Mariana Trough 总被引：3，自引：0，他引：3
The evolution of rifting in the northern Mariana Trough was studied, based on single-channel seismic reflection profiles and heat flow. The rift showed structural asymmetry. The northernmost part of the Mariana Trough at 24°N, just south of Minami-Iwojima Island, is now in an incipient rifting stage and shows a half-graben structure. The arc crust just behind the volcanic front is cut by a few major east-dipping normal faults. The major faults extend southward behind the Hiyoshi seamounts around 23°30'N. The rift develops to a full-graben stage at ∼ 23°N, where the width of the trough increases to 80 km. The trough is comprised of several faulted and tilted blocks of island-arc crust. Maximum subsidence occurs along a row of small grabens on the eastern margin of the trough. These grabens are separated by arc volcanoes, and their depths increase southward from 2500 m at 23°20'N to 4500 m at 22°N. The strike of each graben is north-northwest–south-southeast, which is close to the trend of the remnant West Mariana Ridge, but oblique to the active Mariana arc. Crustal extension becomes concentrated along the eastern margin of the trough as rifting progresses. The transition from rifting to sea floor spreading may occur at ∼ 22°N, where the width of the trough is ∼ 120 km. The possible spreading center lies along the southern extension of the grabens on the eastern margin. The period of back-arc rifting before spreading begins is estimated to be less than 3 million years. Heat flow is asymmetric in the rift. High heat flow was observed only in or close to the row of grabens along the eastern margin of the trough. The asymmetric pure shear extension model fits the observed heat flow distribution better than the simple shear extension model. 相似文献
12.
M. Teresa Ram��rez-Herrera Vladimir Kostoglodov Jaime Urrutia-Fucugauchi 《Pure and Applied Geophysics》2011,168(8-9):1415-1433
Holocene and Pleistocene tectonic deformation of the coast in the Mexico subudction margin is recorded by geomorphic and stratigraphic markers. We document the spatial and temporal variability of active deformation on the coastal Mexican subduction margin. Pleistocene uplift rates are estimated using wave-cut platforms at ca. 0.7?C0.9?m/ka on the Jalisco block coast, Rivera-North America tectonic plate boundary. We examine reported measurements from marine notches and shoreline angle elevations in conjunction with their radiocarbon ages that indicate surface uplift rates increasing during the Holocene up to ca. 3?±?0.5?m/ka. In contrast, steady rates of uplift (ca. 0.5?C1.0?m/ka) in the Pleistocene and Holocene characterize the Michoacan coastal sector, south of El Gordo graben and north of the Orozco Fracture Zone (OFZ), incorporated within the Cocos-North America plate boundary. Significantly higher rates of surface uplift (ca. 7?m/ka) across the OFZ subduction may reflect the roughness of subducting plate. Absence of preserved marine terraces on the coastal sector across El Gordo graben likely reflects slow uplift or coastal subsidence. Stratigraphic markers and their radiocarbon ages show late Holocene (ca. last 6?ka bp) coastal subsidence on the Guerrero gap sector in agreement with a landscape barren of marine terraces and with archeological evidence of coastal subsidence. Temporal and spatial variability in recent deformation rates on the Mexican Pacific coast may be due to differences in tectonic regimes and to localized processes related to subduction, such as crustal faults, subduction erosion and underplating of subducted materials under the southern Mexico continental margin. 相似文献
13.
基于绝对和相对重力观测获得的区域重力场时、空动态变化,结合区域GPS测量资料与活动构造分析,本文研究了华北中部地区2009-2011年的重力场变化特征,讨论了该区域重力场动态变化的强震危险含义.结果主要表明:(1)华北中部的活动地块边界及部分重要活动断裂带两侧存在较大差异的重力场空间变化;其中,以山西断陷带北东段所在的晋冀蒙交界地区为中心,形成较大面积的重力负值变化区,且沿该区西北缘的NE向岱海-黄旗海断裂带以及东南缘的NNE向太行山山前断裂带附近分别形成重力变化的高梯度带,可能反映这些部位近年的构造或断裂活动显著.(2)不同时段的重力场差分动态演化图像可能反映了近年山西断陷带北东段(京西北盆-岭构造区)及其附近的重力场整体经历了"准均匀→非均匀→断陷带北段侧向显著变化→局部"硬化"的演化过程.(3)研究区重力场的时间累积变化图像可用"区域应力场增强→区域断裂与断块差异运动及变形增强→局部运动受阻"的过程进行解释.(4)研究区的一些重力异常部位存在中-长期强震危险背景. 相似文献
14.
鄂尔多斯地块紧邻青藏高原东北缘,位于华北克拉通的西部,在我国中生代、新生代以来东部地区的构造活动中起到了重要作用.对鄂尔多斯及其周缘地区的研究可以提供有关华北克拉通的形成、演化和破坏过程的重要信息.本文选取了纵贯鄂尔多斯的107.6°E附近南北剖面上的44个流动地震台站进行分析,采用接收函数方法,进行Kirchhoff偏移成像,并且结合在该区域内前人的地震面波频散进行联合反演,获得剖面下方的地壳内部精细结构.研究结果显示:(1)莫霍面在鄂尔多斯北部较平缓,约45km深;在鄂尔多斯南部有所加深,达到50km;其北边的河套盆地的地壳厚度约为50km;南边的渭河盆地到秦岭地区及四川盆地的地壳厚度从约为40km增厚到47～50km.(2)河套盆地下方存在大规模的低速异常,最深可达25km,反映了其显著的拉张构造和沉积历史.(3)秦岭造山带下方的低速异常对应于其主要为长英质的地壳组分,可能是由于中生代的拆沉作用导致的地壳下部基性岩石层的缺失.(4)以38°N为界的鄂尔多斯地块,南北部地壳速度结构存在差异,可能表明了这两部分经历的构造历史不同. 相似文献
15.
LI Zhang-jun CHAI Xu-chao GAN Wei-jun HAO Ming WANG Qing-liang ZHUANG Wen-quan YANG Fan 《地震地质》1979,42(2):316-332
Located among the South China block, Tibetan plateau, Alxa block and Yinshan orogenic belt, the Ordos block is famous for its significant kinematic features with stable tectonics of its interior but frequent large earthquakes surrounding it. After the destruction of the North China Craton, the integrity, rotation movement and kinematic relations with its margins are hotly debated. With the accumulation of active tectonics data, and paleomagnetic and GPS observations, some kinematic models have emerged to describe rotation movement of the Ordos block since the 1970's, including clockwise rotation, anticlockwise rotation, clockwise-anticlockwise-alternate rotation, and sub-block rotation, etc. All of these models are not enough to reflect the whole movement of the Ordos block, because the data used are limited to local areas.
In this study, based on denser geophysical observations, such as GPS and SKS splitting data, we analyzed present-day crustal and mantle deformation characteristics in the Ordos block and its surrounding areas. GPS baselines, strain rates, and strain time series are calculated to describe the intrablock deformation and kinematic relationship between Ordos block and its margins. SKS observations are used to study the kinematic relationship between crust and deeper mantle and their dynamic mechanisms, combined with the absolute plate motion(APM)and kinematic vorticity parameters. Our results show that the Ordos block behaves rigidly and rotates anticlockwise relative to the stable Eurasia plate(Euler pole: (50.942±1.935)°N, (115.692±0.303)°E, (0.195±0.006)°/Ma). The block interior sees a weak deformation of~5 nano/a and a velocity difference of smaller than 2mm/a, which can be totally covered by the uncertainties of GPS data. Therefore, the Ordos block is moving as a whole without clear differential movement under the effective range of resolution of the available GPS datasets. Its western and eastern margins are characterized by two strong right-lateral shearing belts, where 0.2°~0.4°/Ma of rotation is measured by the GPS baseline pairs. However, its northern and southern margins are weakly deformed with left-lateral shearing, where only 0.1°/Ma of rotation is measured. Kinematics in the northeastern Tibetan plateau and western margin of the Ordos block can be described with vertical coherence model with strong coupling between the crust and deeper mantle induced by the strong extrusion of the Tibetan plateau. The consistency between SKS fast wave direction and absolute plate motion suggests the existence of mantle flow along the Qinling orogenic belt, which may extend to the interior of the Ordos block. SKS fast wave directions are consistent with the direction of the asthenosphere flow in Shanxi Rift and Taihang Mountains, indicating that the crustal deformation of these areas is controlled by subduction of the Pacific plate to North China. The week anisotropy on SKS in the interior of Ordos block is from fossil anisotropy in the craton interior. After comparing with the absolute plate motion direction and deformation model, we deem that anisotropy in the interior of Ordos block comes from anisotropy of fossils frozen in the lithosphere. In conclusion, the Ordos block is rotating anticlockwise relative to its margins, which may comes from positive movement of its margins driven by lithospheric extrusion or mantle flow beneath, and its self-rotation is slight. This study can provide useful information for discussion of kinematics between the Ordos block and its surrounding tectonic units. 相似文献
In this study, based on denser geophysical observations, such as GPS and SKS splitting data, we analyzed present-day crustal and mantle deformation characteristics in the Ordos block and its surrounding areas. GPS baselines, strain rates, and strain time series are calculated to describe the intrablock deformation and kinematic relationship between Ordos block and its margins. SKS observations are used to study the kinematic relationship between crust and deeper mantle and their dynamic mechanisms, combined with the absolute plate motion(APM)and kinematic vorticity parameters. Our results show that the Ordos block behaves rigidly and rotates anticlockwise relative to the stable Eurasia plate(Euler pole: (50.942±1.935)°N, (115.692±0.303)°E, (0.195±0.006)°/Ma). The block interior sees a weak deformation of~5 nano/a and a velocity difference of smaller than 2mm/a, which can be totally covered by the uncertainties of GPS data. Therefore, the Ordos block is moving as a whole without clear differential movement under the effective range of resolution of the available GPS datasets. Its western and eastern margins are characterized by two strong right-lateral shearing belts, where 0.2°~0.4°/Ma of rotation is measured by the GPS baseline pairs. However, its northern and southern margins are weakly deformed with left-lateral shearing, where only 0.1°/Ma of rotation is measured. Kinematics in the northeastern Tibetan plateau and western margin of the Ordos block can be described with vertical coherence model with strong coupling between the crust and deeper mantle induced by the strong extrusion of the Tibetan plateau. The consistency between SKS fast wave direction and absolute plate motion suggests the existence of mantle flow along the Qinling orogenic belt, which may extend to the interior of the Ordos block. SKS fast wave directions are consistent with the direction of the asthenosphere flow in Shanxi Rift and Taihang Mountains, indicating that the crustal deformation of these areas is controlled by subduction of the Pacific plate to North China. The week anisotropy on SKS in the interior of Ordos block is from fossil anisotropy in the craton interior. After comparing with the absolute plate motion direction and deformation model, we deem that anisotropy in the interior of Ordos block comes from anisotropy of fossils frozen in the lithosphere. In conclusion, the Ordos block is rotating anticlockwise relative to its margins, which may comes from positive movement of its margins driven by lithospheric extrusion or mantle flow beneath, and its self-rotation is slight. This study can provide useful information for discussion of kinematics between the Ordos block and its surrounding tectonic units. 相似文献
16.
渭河盆地是环鄂尔多斯地块周缘大型断陷盆地之一。在环鄂尔多斯地块的4个边中,渭河盆地的现代地震活动属于最弱的一边,表现为环鄂尔多斯地块最大的地震空段。渭河盆地内部由多个次级断块组成,但它们对盆地内的现代地震活动控制却不明显。作为青藏高原东北缘紧邻的一个大型外侧盆地,盆地内的现代地震活动与青藏高原的大震活动存在着一定的响应,表现为伴随着青藏高原的大震活动,盆地内部的地震活动也明显增强。 相似文献
17.
Hailemariam Meaza Amaury Frankl Jean Poesen Amanuel Zenebe Veerle Van Eetvelde Biadgilgn Demissie 《水文科学杂志》2018,63(6):957-977
Marginal grabens are major development corridors in Ethiopia, and need to be understood for proper assessment of the hydrological budget. This study investigates the water balance of the Aba’ala graben (553 km2) in the period 2015–2016 under the challenge of data scarcity. We measured the rainfall and river discharge in order to analyse the runoff components of the graben. The rainfall volume in the Aba’ala graben showed erratic behaviour, which led to rapid flood runoff of the major river into the graben bottom. The average annual inflow and outflow of the graben bottom for the period 2015–2016 amounted to 364 and 254 hm3, respectively. However, flood runoff and evapotranspiration had a marked effect on water availability. Water storage took 36% of the water inflow into the graben bottom. Sustainable water management could reduce the temporal variation of the water storage in Aba’ala graben. 相似文献
18.
藏南错那-沃卡裂谷的第四纪正断层作用及其特征 总被引：7，自引：0，他引：7
地表调查发现,位于西藏南部的错那-沃卡裂谷带包含了3个相对独立的地堑-半地堑——沃卡、邛多江和错那-拿日雍错地堑(从北到南),并构成了该区重要的近SN向控震构造带。该裂谷带整体的展布方式及其中各地堑主边界断裂带的正断层活动指示了100°±2°的区域伸展方向。各边界断裂带的活动强度分析表明,断裂的平均垂直活动速率介于0·3~1·9mm/a。其中,末次盛冰以来合理的活动速率估算值为1·2~1·5mm/a,而末次间冰期以来的活动速率只有(0·6±0·3)mm/a,暗示该裂谷带的断裂活动行为可能类似于地震的丛集活动,存在间歇期与活跃期交替出现的特点。综合分析认为,中-下地壳物质的近EW向伸展或流动所导致的上地壳均匀拉张模式可能是该裂谷带的主要成因 相似文献
19.
Relationship between subsidence and volcanic load,Hawaii 总被引：1，自引：0，他引：1
J. G. Moore 《Bulletin of Volcanology》1970,34(2):562-576
A computer analysis of tide-gage records in the northeast Pacific indicates that the active volcanic islands of eastern Hawaii are subsiding at a rate considerably faster than the eustatic rise of sea level. The rate of absolute subsidence increases progressively toward the center of current activity on the Island of Hawaii. Honolulu, Oahu, appears to be stable; Kahului, Maui, is subsiding at 1.7 mm per year; and Hilo, Hawaii, is subsiding at 4.8 mm per year. This subsidence is apparently related to downbowing of the crust throughout a zone 400 km in diameter by the weight of volcanic material added to the crust by active volcanoes, principally Mauna Loa and Kilauea on the Island of Hawaii. The Hawaiian Arch encircles the subsiding zone and may be uplifted by material moving down and outward from the zone of subsidence. The annual volume of subsidence is about 270×106 m3, whereas the average annual volume of erupted basalt on the Island of Hawaii (based on historic records back to about 1820) is about 50×106 m3. The great excess of subsidence over volcanic addition cannot be reconciled by isostatic models, and is apparently the result of other processes operating in the volcano and its basement thet are poorly understood. Probably the more important of these processes are intrusions and submarine volcanism, both of which are providing additional unseen load on the volcanoes. Furthermore, the rate of eruption may be uplifted by material moving down and outward from the zone of subsidence may be overestimated due to localized downslope movement of the margins of the islands. 相似文献