震前应变固体潮畸变的物理模式   总被引：1，自引：0，他引：1  

吴子泉  张昭栋 《高原地震》1994,(1)

本文根据岩石力学及固体潮理论，建立了孕震期弹性物体应变固体潮的物理模式，给出了其数学公式。通过分析潮汐应力与寻震应力的合力随潮汐力相位的变化，从物理本质上讨论了不同应力阶段应变固体潮曲线的形态特征；讨论了震前不同异常时期，应变固体潮畸变的不同特．点；并对震例进行了分析，同时，对应变固体潮畸变与地震三要素预报作了初步探讨。  相似文献   

Regional significance of kilometric-scale north-east vergent recumbent folds associated with east to south-east directed shear on the southern border of the Central Iberian Zone (Hornachos-Oliva region,Variscan belt,Iberian Peninsula)     

A. Azor  F. González Lodeiro  D. Martínez Poyatos  J. F. Simancas 《International Journal of Earth Sciences》1994,83(2):377-387

On the southern border of the Central Iberian Zone there are two sectors with different styles of deformation. To the south-west, in the Hornachos sector, large-scale recumbent folds associated with ductile shearing can be seen. This shearing is characterized by a direction of movement parallel to the fold axes and can be correlated for 150 km along strike. The K-values of the strain ellipsoid range from 0.8 to 2.0. Stretching in the X direction, parallel to the recumbent fold axes, is more than 100%. To the north-east, in the Oliva sector, first-phase folds are upright and the strain intensity is lower than in the Hornachos sector. Metamorphic, geometric and kinematic considerations lead us to conclude that the shearing in the Hornachos sector is better explained as conjugate to a main shear zone along which the southern border of the Central Iberian Zone is moved onto the Ossa-Morena Zone. This main thrust is at present obliterated by a left-lateral extensional shear zone that affects a high pressure exotic unit located between the Central Iberian and the Ossa-Morena Zones. This high pressure unit constitutes a suture of the Variscan belt in the Iberian Peninsula.  相似文献   

Ground stress determinations in Canada     

G. Herget 《Rock Mechanics and Rock Engineering》1974,6(1):53-64

SummaryGround Stress Determinations in Canada Stress determinations with the biaxial (Doorstopper) and the triaxial strain cell of the C. S. I. R., South Africa, are discussed and show that the triaxial cell is the more desirable instrument if good rock conditions exist. Vertical and average horizontal stresses in Canada are similar in magnitude to those from other parts of the earth's crust and show that vertical stresses are related to weight of overburden and average horizontal stresses increase in most of the cases with 0.407 kg/cm² per metre of depth. More data are necessary to make any prediction for the average horizontal stress beyond a depth of 800 m.Stress determinations and a tectonic analysis show that the unravelling of the geological stress-strain history allows some prediction of principal stress directions, but the attached uncertainties due to gaps in documentation require proof by stress determinations.With 8 Figures  相似文献   

Numerical modeling of the propagation and morphological changes of turbidity currents using a cost-saving strategy of solution updating     

《国际泥沙研究》2020,35(6):587-599

Existing layer-averaged numerical models for turbidity currents have mostly adopted the global minimum time step (GMiTS) for solution updating, which confines their computational efficiency and limits their attractiveness for field applications. This paper presents a highly efficient layer-averaged numerical model for turbidity currents by implementing the combined approach of the local graded-time-step (LGTS) and the global maximum-time-step (GMaTS). The governing equations are solved for unstructured triangular meshes by the shock-capturing finite volume method along with a set of well-balanced evaluations of the numerical flux and geometrical slope source terms. The quantitative accuracy of the model, given reasonably estimated empirical and model parameters (e.g., bed friction, water entrainment, sediment deposition and erosion coefficients), is demonstrated by comparing the numerical solutions against laboratory data of the current front positions and deposition profiles, as well as field data of the current front positions. The improved computational efficiency is demonstrated by comparing the computational cost of the present model against that of a traditional model that uses a GMiTS. For the present simulated cases, the maximum reduction of the computational cost is approximately 80% (e.g., a simulation that cost 1 h before will only require 12 min with the new model).  相似文献   

武都形变对岷县Ms5.2级地震的前兆异常反映     

蒲小武  高原  苏永刚  韩英 《高原地震》2004,16(2):66-71

2003年11月13日岷县Ms5 2级地震前,武都应变、倾斜资料均出现了明显的前兆短临异常变化。应变在震前2个多月出现了加速变化,震前20多天受力状态发生变化;倾斜资料在震前3个多月出现NW方向的加速倾斜变化,震前数天模拟曲线、数字化资料都出现了明显的固体潮汐畸变。  相似文献   

Plate kinematics, origin and tectonic emplacement of supra-subduction ophiolites in SE Asia   总被引：2，自引：0，他引：2  

Manuel Pubellier  Christophe Monnier  Ren Maury  R. Tamayo 《Tectonophysics》2004,392(1-4):9

A unique feature of the Circum Pacific orogenic belts is the occurrence of ophiolitic bodies of various sizes, most of which display petrological and geochemical characteristics typical of supra-subduction zone oceanic crust. In SE Asia, a majority of the ophiolites appear to have originated at convergent margins, and specifically in backarc or island arc settings, which evolved either along the edge of the Sunda (Eurasia) and Australian cratons, or within the Philippine Sea Plate. These ophiolites were later accreted to continental margins during the Tertiary. Because of fast relative plate velocities, tectonic regimes at the active margins of these three plates also changed rapidly. Strain partitioning associated with oblique convergence caused arc-trench systems to move further away from the locus of their accretion. We distinguish “relatively autochthonous ophiolites” resulting from the shortening of marginal basins such as the present-day South China Sea or the Coral Sea, and “highly displaced ophiolites” developed in oblique convergent margins, where they were dismantled, transported and locally severely sheared during final docking. In peri-cratonic mobile belts (i.e. the Philippine Mobile Belt) we find a series of oceanic basins which have been slightly deformed and uplifted. Varying lithologies and geochemical compositions of tectonic units in these basins, as well as their age discrepancies, suggest important displacements along major wrench faults.We have used plate tectonic reconstructions to restore the former backarc basins and island arcs characterized by known petro-geochemical data to their original location and their former tectonic settings. Some of the ophiolites occurring in front of the Sunda plate represent supra-subduction zone basins formed along the Australian Craton margin during the Mesozoic. The Philippine Sea Basin, the Huatung basin south of Taiwan, and composite ophiolitic basements of the Philippines and Halmahera may represent remnants of such marginal basins. The portion of the Philippine Sea Plate carrying the Taiwan–Philippine arc and its composite ophiolitic/continental crustal basement might have actually originated in a different setting, closer to that of the Papua New Guinea Ophiolite, and then have been displaced rapidly as a result of shearing associated with fast oblique convergence.  相似文献   

Longitudinal velocity patterns and bed morphology interaction in a rill   总被引：2，自引：0，他引：2  

Rafael Gimnez  Olivier Planchon  Norbert Silvera  Gerard Govers 《地球表面变化过程与地形》2004,29(1):105-114

Present‐day understanding of rill dynamics is hampered by a lack of detailed data on velocity distributions in rills. The latter are dif?cult to collect with traditional techniques due to the very low water depths and the relatively high ?ow velocities in rills. The objectives of this paper were to investigate the feasibility of miniaturized acoustic Doppler velocimeter (mADV) measurements in rill ?ow and to explore longitudinal variations in ?ow velocities and their relationship with rill bed morphology. Detailed data on longitudinal ?ow velocity were required to achieve these objectives. A 1·8 m long rill was formed freely in a ?ume at 5° slope and 0·001 m³ s^?1 discharge. Rill topography was characterized by an alternation of steps and pools. The ?ume surface was then ?xed to preserve rill roughness. A topographical scanning of the entire ?ume surface was made. Velocity was measured with a mADV along the rill, and at different depths. Flow depth in a longitudinal direction was also measured using an elevation gauge. A strong relationship exists between rill topography and ?ow hydraulics. Over steps, ?ow was unidirectional and rapidly accelerating until a threshold Froude number (Fn) value between 1·3 and 1·7 was reached and a hydraulic jump occurred leading to the formation of a pool. In the pool, the ?ow pattern was multidirectional and complex. The ?ow was subcritical when leaving the pool and accelerated over the next step until the threshold Froude number value was again reached. Energy loss in the rill was concentrated in the pools, mainly due to the action of a hydraulic jump. This mechanism of energy dissipation appeared to be an essential factor in rill formation and bedform evolution. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

民乐-山丹地震的区域构造变形背景与中短期前兆   总被引：9，自引：1，他引：9  

张希  王双绪  崔笃信  张晓亮  薛富平  陈兵 《中国地震》2004,20(3):238-246

利用青藏块体北缘地区2001～2003年GPS水平运动资料和1988—2003年跨断层短水准流动观测资料，借助改进的负位错模型及断层形变应变强度比一时变曲线，研究了与2003年10月25日民乐-山丹Ms6．1，Ms5．8地震孕育有关的区域构造变形背景与中短期前兆异常。分析表明，在昆仑山Ms8．1大震引起的大区域形变调整-短期松弛-开始恢复的背景下，民乐-山丹地震震源位于可能反映应变能积累加速的块体边界压性锁定段之间的剪应力强度增强段北侧；距震中最近的石灰窑口跨断层短水准流动场地在震前3个月呈现显著应变强度比异常，而震前10余天至数月内整个监测区异常个数、震前3个月相对近源区异常集中与局部增强均是对这两次地震的某种预示。  相似文献   

昌平地震台体应变资料分析     

刘福生  张国红 《地震地磁观测与研究》2005,(Z1)

简要介绍了昌平地震台概况,用相关分析、信息合成等方法,对体应变仪1989年7月至2001年的资料进行了处理,发现对发生在距昌平地震台300～500km范围内、震级5级以上的地震,体应变资料趋势异常明显,异常时间与震级相关性较好,地震多发生在信息合成值变化较大的时段。昌平地震台体积式应变仪观测到的同震效应多以张性阶跃为主。  相似文献   

Influence of object concentration on finite strain and effective viscosity contrast: insights from naturally deformed packstones     

Stefano Vitale  Stefano Mazzoli 《Journal of Structural Geology》2005,27(12):2135-2149

Deformed conglomerates and ooidal/oncoidal packstones are commonly used to evaluate finite strain in deformed sedimentary successions. In order to obtain a correct estimate of finite strain, it is necessary to consider not only the different behaviour of matrix and objects, but also object concentration. The analysis of two-component rocks characterised by high values of packing commonly results in a substantial underestimate of bulk strain and of viscosity contrast between objects and matrix. In this study, the effects of the volumetric fraction of competent inclusions on both object and bulk measured finite strain, as well as on apparent viscosity contrast, have been investigated in naturally deformed packstones characterised by variable object concentration on the scale of the hand specimen (and hence for homogenous viscosity contrast). Object finite strain has been obtained by Rf/ analysis, whereas the Fry method provides a measure of whole-rock strain that is also a function of inclusion concentration. Therefore, the finite strain measured by the Fry method is better termed effective bulk strain. In order to investigate the role of object concentration, this parameter has been plotted against object and effective bulk strain, and also against viscosity contrast. These diagrams show that: (i) for high values of packing, measured object and effective bulk strain show values that are significantly lower with respect to the calculated maximum value (that would result in the ideal case of no particle interaction and represents therefore the real bulk strain of the samples); (ii) the viscosity contrast shows lower values with respect to the calculated maximum one (that is equal for the three principal sections of the finite strain ellipsoid), and as packing reaches the maximum value, the viscosity contrast approaches a unit value. Empirical equations have also been found that link object concentration with both object and effective bulk finite strain.  相似文献