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1.
V. G. Bondur I. A. Garagash M. B. Gokhberg M. V. Rodkin 《Izvestiya Physics of the Solid Earth》2016,52(1):117-128
A three-dimensional geomechanical model of Southern California, which includes the mountain topography, fault tectonics, and main structural boundaries (the top of the lower crust and the Moho), is developed. The main stress state of the model is determined by the own weight of the rocks and by the horizontal tectonic motions identified from the GPS observations. The model enables tracking the changes which occur in the stress-strain state of the crust due to the evolution of the seismic process. As the input data, the model uses the current seismicity and treats each earthquake as a new defect in the Earth’s crust which brings about the redistribution of strains, elastic energy density, and yield stress of the crust. Monitoring the variations in the stress state of the crust and lithosphere arising in response to the seismic process shows that the model is suitable for forecasting the enhancement in seismic activity of the region and delineating the earthquake-prone areas with a reasonable probability on a given time interval. 相似文献
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利用山东及周边区域地震台网1975—2014年1月期间记录到的1369个地震的13781个P波到时数据对山东地区地壳结构进行了层析成像研究.结果表明,山东地区地壳速度结构存在明显的不均匀性.沂沭断裂带介质速度结构复杂,呈现明显的分段特征,两侧块体速度存在差异,具有块体边界的构造特征.鲁西断块20km以下深度处存在大规模的低速异常区,这与该地区始新世发生的大规模滑脱拆离构造有关,可能产生于太平洋板块的西向俯冲导致地幔热物质沿沂沭断裂带向上并向西涌动.历史大震及ML4.0以上中强震大部分为走滑型地震,主要发生于高低速异常过渡带且有深大断裂穿过的地区.震群主要发生于低速体上部或周边,且震源深度优势分布在中上地壳,这与地下介质富含流体并导致应力集中有关. 相似文献
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《Earth and Planetary Science Letters》2006,241(1-2):2-10
Surface heat flows are calculated from elastic lithosphere thicknesses for the heavy cratered highlands of Mars, in terms of the fraction of the surface heat flow derived from crustal heat sources. Previous heat flow estimations for Mars used linear thermal gradients, which is equivalent to ignoring the existence of heat sources within the crust. We compute surface heat flows following a methodology that relates effective thickness and curvature of an elastic plate with the strength envelope of the lithosphere, and assuming crustal heat sources homogeneously distributed in a radioactive element-rich layer 20 or 60 km thick. The obtained results show that the surface heat flow increases with the proportion of heat sources within the crust, and with the decrease of both radioactive element-rich layer thickness and surface temperature. Also, the results permit us to calculate representative temperatures for the crust base, rock strength for the upper mantle, and lower and upper limits to the crustal magnetization depth and intensity, respectively. For Terra Cimmeria, an effective elastic thickness of 12 km implies between 30% and 80% of heat sources located within the crust. In this case the uppermost mantle would be weak at the time of loading, and temperatures in the lower crust cold enough to favor unrelaxed crustal thickness variations and to permit deep Curie depths in the highlands, as suggested by the observational evidence. 相似文献
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大地震发生之后通常会诱发一系列的余震序列,对比1976年MS7.8唐山大地震和2001年MS8.1昆仑山大地震周边区域的地震事件可以看出,唐山大地震余震活动时间要明显长于昆仑山大地震余震活动时间.余震序列往往与震后形变密切相关,而影响震后形变的因素不仅与地震发震断层和震级有关,同时与岩石圈的结构有关.考虑到唐山大地震的发震区华北地块和昆仑山大地震的发震区青藏高原有着较大的岩石圈结构差异,本文采用PSGRN/PSCMP软件计算了岩石圈分层模型的大地震同震和震后形变,分析了地壳弹性模量、弹性厚度以及黏滞性系数对同震和震后形变的影响,进而讨论了影响唐山地震和昆仑山地震余震序列差异的原因.计算结果显示,震后形变会在黏弹性效应的作用下逐渐调整,震后形变的持续时间与地壳弹性模量、地壳弹性厚度和下地壳黏滞性系数有关.上地壳和下地壳弹性模量越大,震后形变达到稳定值的时间越短,弹性模量对震后形变稳定值影响很小.地壳弹性厚度越大,震后形变达到稳定值的时间越短,当断层面底端深度小于地壳弹性厚度时,地壳弹性厚度的增加会引起震后形变稳定值的减小;下地壳厚度对震后形变达到稳定值的时间和稳定值基本无影响.下地壳黏滞性系数越大,震后形变达到稳定值的时间越长,反之亦然.结合唐山地震区的华北地块和昆仑山地震的青藏高原深部结构发现,两者之间的上地壳弹性模型差别不大,唐山地震区地壳弹性厚度略大于昆仑山地震区,但昆仑山地震区下地壳黏滞性系数明显低于唐山地震区.这些因素均决定了昆仑山地震的震后形变持续时间短（余震时间序列短）而唐山地震的震后形变持续时间长（余震时间序列长）.由此可见,岩石圈结构差异可能是导致唐山地震和昆仑山地震余震序列差异的主要因素之一. 相似文献
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由试验均衡的理论出发,得到了该区的均衡响应函数并建立了复合补偿模式。地形高度对重力场的影响很复杂,波长小于300km的地形起伏具有偏高的均衡响应值。 局部补偿是华北地区的主要补偿机制,所占比例达90%。区域补偿的等效弹性板厚度偏小,仅18km, 表明了华北地壳破裂程度严重和下地壳流变性突出。 均衡重力异常具有块体分布和均衡调整方向同新生代构造运动方向不完全符合等特点,其中一些成分是由于表浅层地质体的非均匀载荷所造成,不能简单地归因于欠补偿或过补偿。均衡异常的垂直导数分布清晰地揭示了华北地区几条重要的断块分界线。从深部构造上看,均衡补偿过程发生在下地壳特别是上地幔中。本文从均衡的角度探讨了地震危险性。 相似文献
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本文介绍利用地震转换波测深法研究1976年7.8级唐山大震区深部构造的某些结果,得出了沿两条测线的深部构造剖面图。发现在极震区的数十公里的范围内,地壳和上地幔具有异常结构,在地壳中部比震区外围多出一个中间层位,埋深约12-20km,地壳上部界面向上挠曲,而莫霍面和上地幔顶部界面却强烈地向下挠曲,引起了震区岩石圈厚度的加大,在震区存在深浅不等的深部断裂。深部构造与震源分布的对比表明,唐山主震和绝大多数余震均分布在壳内中间层之上,有的甚至就分布在壳内中间层的上、下界面附近。转换波测深结果表明,本区地壳上地幔中强烈的升降差异运动可能是唐山大震的重要促发因素。 相似文献
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The interpretation of deep seismic sounding (DSS) data has been made on the basis of a two-dimensional inhomogeneous model. The refracted first arrivals as well as reflected and diffracted waves on the seismic records have been utilized. The seismic section was modeled in the iso-veolcity lines v(x, y) = const, taking into account the zones of diffraction associated with deep faults. Gravity observations have been used to construct a block model of the Earth's crust with vertical boundaries. It is suggested to define the base of the crust as the zone with velocities between 7.8 and 8.2 km/s. The reflecting boundaries of different length occurring in this zone can be conformal or unconformal with the iso-velocity lines near the base of the crust. As an example of our approach to the interpretation of DSS data the folded-blocky structure of the crust with horizontal inhomogeneities of velocity and density is shown in the Kzyl-Orda-Dzheskazgan profile in Central Kazakhstan. 相似文献
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基于Ｍａｘｗｅｌｌ和Ｋｅｌｖｉｎ流变模型，以延续时间与松弛期的比值，即松弛数，作为衡量指标，对地壳、上地幔不同层次的变形属性进行了判别。结果表明，除软流圈地幔主要为粘性流动外，其上各层的情况是：在漫长的地质过程中，不仅岩石圈地幔和下地壳属于粘性，上地壳也有可能处于粘性流动状态；在延续数十年的情况下，上地壳以及岩石圈地幔都可能呈弹性状态；延续时间介乎二者，通常上地壳为弹性，下地壳和岩石圈地幔为粘性或滞弹粘性。此外，还结合变形属性的判别，就岩石圈地幔的流动和板内的驱动力远程传递等问题进行了讨论 相似文献
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大同—阳高震区深部构造背景 总被引：6，自引：0，他引：6
利用通过本区的宽角反射／折射剖面资料对大同－阳高震区及邻区地壳上地幔速度结构与构造进行了详细的研究,结果表明,地壳上地幔速度结构与构造在纵向和横向上具有明显的不均一性,浅部基底断裂发育,对应其深部,根据波组特征,壳内界面及速度等值线起伏变化和低速异常体的边界等推测了地壳深断裂带,区内最明显的上地壳低速体位于大同－阳原附近,其南界存在地壳断裂,大同－阳高地震群与该低速异常体和深断裂有关。 相似文献
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A three-layer elastic-gravitational fault displacement model using dislocation theory has been developed and used to examine the effect of layering of earth elastic moduli on surface and subsurface displacement fields for a vertical strike-slip fault. The model has been used to examine the effect of depth variation of elastic properties at coseismic and postseismic time scales. For pure strike-slip motion the effect of gravity on coseismic and postseismic horizontal deformation is negligible. For coseismic deformation the model predicts that (for constant Poisson's ratio) an increase in elastic moduli with depth attenuates the displacements within the upper layers with respect to displacement distribution for a uniform half-space, while an inclusion of a soft layer between the top layer and lower half-space amplifies upper layer displacements. The effect of variation in Poisson's ratio on surface and subsurface displacements has also been examined.The effect of postseismic stress relaxation on surface and subsurface displacements for a three-layer model has been calculated and compared with that of a uniformly relaxed half-space model. Layer 1 is assumed to correspond to the upper crust, layer 2 the lower crust and layer 3 the upper mantle. The effect of postseismic stress relaxation within a uniform half-space and within just the lower crust and upper mantle has been examined. Stress relaxation within the whole half-space decreases the amplitude and shortens the wavelength of displacements, while stress relaxation within the lower two layers increases the amplitude and broadens the wavelength of displacements. The difference between uniform and layered postseismic relaxation is particularly pronounced at the base of the crust.Coseismic and postseismic normal and volumetric strains for a vertical strike-slip fault have also been examined. For a uniformly relaxed half-space model, an increase in normal strains is shown with respect to the coseismic elastic solution, whereas the postseismic volumetric strain is effectively zero. For a three-layer model with stress relaxation in the lower layers only, the normal and volumetric strains within the top elastic layer resemble coseismic strains, while in the lower layers which suffer a rigidity decrease, the postseismic volumetric strain is effectively zero. 相似文献
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A. R. Zhdanovich 《Izvestiya Physics of the Solid Earth》2013,49(1):93-104
The gravitational potential energy of the Earth’s crust in southeastern Kazakhstan relative to the subcrustal level is assessed. Neotectonic geological-geophysical control of variations in the gravitational potential is demonstrated. The seismic parameters are shown to be correlated with the gravitational potential energy and boundaries separating the layers of the Earth’s crust. 相似文献
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冈底斯成矿带为我国著名的成矿区域,其东段存在一系列规模较大的矿床.为了研究冈底斯成矿带东段的电性结构特征,对覆盖主要矿集区的大地电磁测深数据进行全面的处理分析,通过二维与三维反演的综合对比得到了可靠的电性结构模型.结合其他地质与地球物理资料,对电性结构模型进行分析得到冈底斯成矿带东段的矿床分布规律:矿床主要分布在地壳浅表的电性分界面附近;中地壳高导体可能通过上地壳隐伏的南-北向断裂控制着与地壳伸展作用有关的矿床;南-北向张性构造与东-西向逆冲-推覆构造的交汇部位可能是冈底斯成矿带东段重要的成矿区域;下地壳可能受到软流圈物质上涌的影响发生部分熔融,从而与中地壳的高导体共同影响地壳浅部的成矿作用. 相似文献
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The traditional view of the rheology of the continental lithosphere, sometimes known as the “jelly sandwich model”, consists of a strong upper crust, a weak lower crust, and a strong upper lithospheric mantle. Some authors argue, however, that the lithospheric mantle is weak and contributes little to the total strength and the effective elastic thickness of the lithosphere; this weakness is claimed to be due to the mantle being wet or subjected to temperatures higher than usually believed. This paper uses the relationship between rheology of the lithosphere and heat flow to calculate theoretical effective elastic thicknesses for three regions of the central Iberian Peninsula (the Duero Basin, the Spanish Central System and the Tajo Basin), taking into account the contribution of the crust and the lithospheric mantle, for dry and wet rheologies. We found that a wet peridotite rheology for the lithospheric mantle is generally consistent with independent (based on Bouguer coherence or flexural modeling) estimates of the effective elastic thickness for the study area, whereas a dry peridotite rheology cannot be reconciled with them. Moreover, the contribution of the mantle to the bending moment of the lithosphere, and therefore to both the effective elastic thickness and the total strength of the lithosphere, is important, and it may even be the dominant contribution. Therefore, the jelly sandwich model may be considered valid for the central Iberian Peninsula. 相似文献
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提出了几个难以用断层弹性回跳模型解释的地震实例，指出必须重视地壳上地幔结构的探测和深部流体的研究。然后用简单型说明，没有流体在存在，则不可能发生岩体间快速的错动。重点探讨发生在地壳内10-25km深处的强震孕育和发生机理，分析了深部流体的迁移和岩体的错动。最后结合实例，给出了在发生深部流体迁移的条件下，一次强震释放的能量和岩体错动的最大加速度。 相似文献
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《Journal of Volcanology and Geothermal Research》1999,91(1):65-78
The tectonic stresses can significantly affect the propagation of a magma-filled crack. It has been pointed out that the rheological boundaries control the emplacement of magmas through the effect of stress. However, it has not been clarified how the role of rheological boundaries depends on the regional tectonic and thermal states. We have evaluated the role of rheological boundaries under various tectonic and thermal conditions and found that the level of magma emplacement may jump according to the changes in the tectonic force or the surface heat flow. The stress profiles were estimated by a simple model of lithospheric deformation. We employed a three-layer model of the lithosphere; the upper crust, the lower crust and the upper mantle have different rheological properties. A constant horizontal force is applied to the lithosphere, and the horizontal strain is assumed to be independent of depth. When realistic tectonic forces (>1011 N/m) are applied, the rheological boundaries mainly control the emplacement of magma. The emplacement is expected at the MOHO, the upper–lower crust boundary, and the brittle–ductile boundary. For lower tectonic forces (<1011 N/m), the tectonic stress no longer plays an important role in the emplacement of magmas. When the tectonic stress controls the emplacement, the roles of rheological boundaries strongly depend on the surface heat flow. When the surface heat flow is relatively high (>80 mW/m2), the stress in the mantle is quite low and the MOHO cannot trap ascending magmas. For relatively low heat flow (<80 mW/m2), on the other hand, the MOHO acts as a magma trap, and the upper–lower crust boundary acts as a magma trap only when the magma supply rate is sufficiently high. Our results suggest that the emplacement depth can change responding to the change in the tectonic force and/or that in the surface heat flow. This may provide us a key to understand the relation between the evolution of a volcanic region and its tectonic and/or thermal history. 相似文献
19.
The subduction of the Indian plate underneath Eurasian plate results not only in deformation and movement of the elastic upper crust, but also flow of the ductile lower crust in the high temperature and high pressure which drags the brittle upper crust to move at the same time. These two actions work together producing the present movement and deformation field in Tibetan plateau. The dynamics progress has been verified by GPS observation data. Therefore, in a two-dimension plain model, only the elastic deformation with the boundary action at the upper crust cannot explain the deformation well, the drag force acted on the base of upper crust by the drag of ductile flow of the lower crust also need to be considered. However, it's hard to figure out the magnitude and direction of the drag force. Thus, we established a two-dimension plain elastic finite element model, with the equivalent-body force approach to simulate the drag force. With the internal GPS observation data of Tibetan plateau as constraint condition, we calculated inversely the drag force of key nodes in the model with trial method, and the other nodes in the model with bilinear interpolation method. Finally, we got the drag forces(nodal forces, unit:N) caused by the difference flow of ductile lower crust dragging the brittle upper crust, which are distributed mainly in the region of 86°~100°E and 26°~32°N, the direction is east and south, and the maximum reaches to 1e8N; in some areas in the western part of the study region at 31°~36°N and 76°~80°E, the direction is west, and the maximum reaches to 1e7N. All these work provides a new thought for further research on long-term dynamic mechanism of surface deformation in Tibetan plateau and its surrounding area. 相似文献