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1.
粗糙床面风廓线的转折特征及其物理意义 总被引：4，自引：3，他引：1
为了进一步认识粗糙床面空气动力学粗糙度的物理意义,理解空气动力学粗糙度对动量传递和跃移起动的影响机制,从风洞试验测定的粗糙床面风廓线转折特征入手,分析了粗糙床面的空气动力学性质并提出了内边界层动量传递及近壁区沙粒起动的可能机制。结果表明,细高粗糙元（方向比率在4~20之间）和孔隙粗糙元（孔隙度在0.15~0.75）风廓线呈现4个转折段,对应的湍流垂直分层为近壁区-尾涡层（Z≤0.15H~0.5H）、内边界层-尾涡层过渡层（0.15H≤Z≤0.75H）、内边界层（0.3H~0.75H≤Z≤1.2H~6H）和内边界层与外边界层过渡层等。粗矮粗糙元（粗糙元的方向比率在0.4~1.25之间）风廓线存在几个转折段,对应气流垂直分层为近壁区-尾涡层（Z≤1H~1.5H）和内边界层（1H~1.5H≤Z≤7H~35H）等。细高粗糙元和孔隙粗糙元覆盖21组床面（侧影盖度在0.007~0.50,粗糙元的高度在10~100 mm）的内边界层内空气动力学粗糙度在0.07~30.74 mm之间,比内边界层以上或以下过渡层的空气动力学粗糙度高几个数量级到数倍;内边界层摩阻风速的0.50~1.66 m\5s-1之间,是内边界层以下过渡层的1.5~10倍、内边界层以上过渡层的摩阻风速的1.1~2.8倍。内边界层的空气动力学粗糙度和摩阻风速分别代表了粗糙床面对气流阻力特征和湍流切应力。内边界层以下过渡层湍流切应力与粗糙元之间光滑地表所受切应力关系不大,而近壁层切应力与光滑地表所受切应力直接相关。近壁层猝发过程上抛运动和内边界层湍流猝发过程下扫运动耦合关系是内边界层的一部分动量传递到近壁区并导致沙粒起动的可能机制。 相似文献
2.
砾石覆盖对边界层风速梯度的影响 总被引：3，自引：3，他引：0
通过莫高窟窟顶野外风洞实验对不同覆盖度砾石床面风速梯度的变化规律进行了研究。结果表明,床面砾石平均高度以下风速梯度随砾石覆盖度变化比较杂乱,而砾石平均高度以上风速梯度随覆盖度增加呈现出有规律的变化。从覆盖度5%到35%风速逐渐减小, 40%~80%趋于稳定,35%最小。据此,大气边界层可明显分为两层,约以砾石平均高度为界,下层定义为粗糙亚层,上层定义为惯性亚层。粗糙亚层风速梯度随砾石间距高度比D/H值的变化同样比较杂乱;惯性亚层风速梯度随砾石间距高度比D/H值的变化规律比较一致:风速在D/H值0.3~1.5段趋于稳定,2.0~4.0段风速逐渐增大,1.5处风速最小。另外,对砾石床面不同高度阻风效应的计算表明,砾石床面的阻风作用在砾石床面表面附近最强(0.75 H~1.1 H),粗糙亚层阻风作用随高度增大而增大,惯性亚层阻风作用随高度增大逐渐减小。该粒径砾石阻风效应最优间距高度比D/H值为1.5,最优间距为3 cm,最优覆盖度为35%,为砾石防沙工程的铺设提供了一定的参考作用。 相似文献
3.
本文在水槽实验的基础上,根据最小能量耗散原理,考虑诸如水流脉动、床沙组成、河床糙率、粗细颗粒间相互作用、河床粗化程度等因素的影响,建立了宽级配床沙起动的三种模式以及相应的非均匀沙起动流速公式,经实验资料检验,符合较好。 相似文献
4.
农田休闲期不同保护性耕作措施的防风效应研究 总被引：5，自引：2，他引：3
保护性耕作是旱作农田土壤风蚀防治的必要措施\.通过野外试验,对深松、浅耕、翻耕覆盖、免耕油菜低茬和高茬、免耕小麦低茬和高茬等7种保护性耕作措施和传统翻耕、草地两种对照下0～4 m的风流场进行了观测,对各种下垫面上空气动力学粗糙度、摩阻速度、风速绝对脉动强度和相对脉动强度进行对比分析。结果显示,不同保护性耕作措施降低风的侵蚀力,防治土壤风蚀的机制不同。留茬主要通过增加地表空气动力学粗糙度和摩阻速度,利用作物残茬和秸秆等粗糙元分解风对地表的剪切应力,降低风蚀强度。而深松、浅耕、翻耕覆盖等措施在增加地表粗糙度和摩阻速度上效果不如留茬,但近地表0\^05 m处风速脉动较弱,相同风速下对地表的剪切应力较小,土壤风蚀速率降低。此外,作物残茬、秸秆和牧草等粗糙元的高度、密度及直立性均对下垫面的空气动力学粗糙度、摩阻速度及风速脉动有一定影响。 相似文献
5.
粗糙床面风廓线统一对数区的空气动力学粗糙度及其空间变异特征 总被引：1，自引：1，他引：0
为了进一步理解粗糙床面阻力效应,减小空气动力学粗糙度测试中的不确定性,依据风沙风洞测试的3类粗糙元（细高粗糙元、孔隙粗糙元和粗矮粗糙元）覆盖的39个粗糙床面在不同自由风速下的风廓线数据,提出了风廓线统一对数区的概念并得出以下结论：粗糙床面风廓线统一对数区范围约在0.1～0.3 h至边界层顶部,空气动力学粗糙度是变应力层内床面对气流阻力效应的垂向平均;在统一对数区内拟合的空气动力学粗糙度的垂向变异分为先增后减型（概率为71%）、减小型（20%）和增加型（9%）等类型,而采用统一对数区的空气动力学粗糙度可以避免垂向变异带来的不确定性;统一对数区的无量纲空气动力学粗糙度随粗糙元密度以幂函数形式增加的特征,进一步表明该指标能更好地表征粗糙床面对气流阻力效应;尾涡流风廓线统一对数区的空气动力学粗糙度约为街流区1~5倍,表明街流区风廓线统一对数区的空气动力学粗糙度是模拟跃移起动更合适的参数。 相似文献
6.
流拖曳系数是海冰动力学模型中的重要参数,实际海冰运动时受到水流的底面剪切作用和侧面正压力作用,相应的拖曳系数分别为摩拖曳系数和形拖曳系数。利用实验室波流水槽设备,对长方平底、长方粗糙底和圆饼型淡水冰试样进行拖曳运动试验,获得26组冰样运动数据。根据这些试验数据,利用动量法原理和数学优化方法构造了摩拖曳系数和形拖曳系数的辨识模型,将摩拖曳系数和形拖曳系数两项分开。在此基础上,分析了冰样粗糙度指标(支承长度率和冰厚均方根偏差)对这两个系数的影响；发现了摩拖曳系数同冰样水平尺寸和垂直尺寸之比的关系,该关系能将冰山和浮冰的摩拖曳系数归结到同一条曲线上。 相似文献
7.
风沙流和净风场中瞬时水平风速廓线特征比较 总被引：1，自引：1，他引：0
为进一步认识风沙流和净风场中瞬时水平风速廓线特征的异同,在风洞中分别对风沙流和净风场中瞬时水平风速廓线进行了测量,风速采集时间间隔缩短至0.01s,分析了风沙流和净风场中瞬时水平风速、瞬时摩阻风速和瞬时空气动力学粗糙度的变化特征。结果表明：相同来流条件下,风沙流中水平风速脉动强度高于净风场,风沙流中瞬时摩阻风速、瞬时空气动力学粗糙度以及它们的脉动幅度均大于净风场;风沙流和净风场中瞬时摩阻风速概率密度分布均可以表示为正态分布,但其正态分布的特征值却存在一定差别;净风场中瞬时空气动力学粗糙度的概率密度分布表现出单调递减分布,而风沙流中瞬时空气动力学粗糙度的概率密度分布呈现出单峰分布。因此,在相同主流风速下风沙流和净风场中瞬时水平风速廓线特征有明显差别。 相似文献
8.
9.
固定沙质床面的空气动力学粗糙度 总被引：17，自引：7，他引：10
通过固定沙质床面的空气动力学粗糙度z0的风洞实验研究,结果表明,z0与沙粒粒径的关系为:z0=a1+b1D2ln(D),并非Bagnold的1/30定律,也不是其他研究者的z0与沙粒粒径D的固定关系。Bagnold的1/30定律仅对有限风速情况和非常狭窄的颗粒粒径范围有效。风也是影响空气动力学粗糙度的活跃因子。z0与沙粒粒径,z0与摩阻速度,z0与摩阻雷诺数之间的关系都与风速有关。类似于水利学粗糙度,将空气动力学粗糙度划分为空气动力学完全光滑区、过渡区和完全粗糙区三个区域。 相似文献
10.
敦煌莫高窟顶几种典型床面蚀积量变化过程的初步观测 总被引：8，自引：7，他引：1
通过对莫高窟窟顶自然和人工床面的风蚀、输导及堆积沙量变化的野外监测,初步观测结果表明：在偏西风作用下,自然状况下的戈壁床面阻截了来自鸣沙山40％的沙量,其余60%的沙量进入窟区;而偏东风又可将偏西风、偏南风作用下沉积于窟顶90％的沙量吹回到鸣沙山边缘。床面阻、输性质与沙源供给状况密切相关。沙源丰富时,风沙流以较饱和形式输送,易形成输沙床面性质;沙源匮乏时,风沙流多以不饱和形式输送,形成阻沙-输沙床面性质。砾石直径较大（＞4 cm）的床面主要呈现堆积性质,对偏西的风沙流阻滞功效比较明显,每100 m阻沙率可达45％;偏东风作用下,每100 m阻沙率可达19％; 而砾石直径较小（1 cm）的床面,主要以风沙输沙功能为主,是一个非堆积搬运床面。 相似文献
11.
A coarse surface layer can help to limit bedload transport rates in channels with cobble and gravel beds. In these systems, periodic boulder-sized clasts often exist with small deposits of fine material in the lee of these large bed elements. A combined field and flume study was conducted to investigate the potential impact of lee deposits with distinctly finer sediment-sizes behind boulders on bedload transport rates. Detailed sediment characterizations were performed on surface, subsurface, and lee sediments in two coarse-bedded Connecticut channels. Bedload measurements also were conducted in a series of flows that approached the bankfull level in these two systems to determine transport rates and the size distribution of bedload material. A 6-m long, 0.5-m wide flume was used to model these systems with fine sediment passing over a fixed bed of sediment particles with uniform-sized, large bed elements. Sediment distributions of the lee deposits in the two Connecticut channels indicate that lee deposits may be produced from winnowing of sediments from the surface layer. Lee deposits also exhibit sediment distributions similar to bedload sediment distributions from low to near-bankfull flow in one of the two channels. Bedload sediments in the second channel were finer than lee deposits, presumably from selective entrainment of fines. Flume experiments demonstrate that bedload transport rates are lower for periods of steady flow relative to periods that include either an increase or decrease in discharge. The results show that lee sediments establish a metastable deposit behind each obstruction for a given discharge. Either increases or decreases in discharge disrupt this temporary stability and increase sediment delivery to the main flow. The study suggests that the influence of the rate of change in discharge may be as important as the absolute magnitude of discharge on sediment transport rates at moderate and low discharges in sediment-limited systems with large bed elements. 相似文献
12.
Channel responses to varying sediment input: A flume experiment modeled after Redwood Creek, California 总被引：1，自引：0，他引：1
At the reach scale, a channel adjusts to sediment supply and flow through mutual interactions among channel form, bed particle size, and flow dynamics that govern river bed mobility. Sediment can impair the beneficial uses of a river, but the timescales for studying recovery following high sediment loading in the field setting make flume experiments appealing. We use a flume experiment, coupled with field measurements in a gravel-bed river, to explore sediment transport, storage, and mobility relations under various sediment supply conditions. Our flume experiment modeled adjustments of channel morphology, slope, and armoring in a gravel-bed channel. Under moderate sediment increases, channel bed elevation increased and sediment output increased, but channel planform remained similar to pre-feed conditions. During the following degradational cycle, most of the excess sediment was evacuated from the flume and the bed became armored. Under high sediment feed, channel bed elevation increased, the bed became smoother, mid-channel bars and bedload sheets formed, and water surface slope increased. Concurrently, output increased and became more poorly sorted. During the last degradational cycle, the channel became armored and channel incision ceased before all excess sediment was removed. Selective transport of finer material was evident throughout the aggradational cycles and became more pronounced during degradational cycles as the bed became armored. Our flume results of changes in bed elevation, sediment storage, channel morphology, and bed texture parallel those from field surveys of Redwood Creek, northern California, which has exhibited channel bed degradation for 30 years following a large aggradation event in the 1970s. The flume experiment suggested that channel recovery in terms of reestablishing a specific morphology may not occur, but the channel may return to a state of balancing sediment supply and transport capacity. 相似文献
13.
Houston C. Saunderson 《自然地理学》2013,34(2):125-145
Two series of experiments were run to ascertain the nature of the transformation of antidunes when suppressed by a tunnel roof. One series was performed in a recirculating flume 30cm in width and 6 meters in length using well sorted sand, 0.35 mm in mean diameter. The second series was conducted in a flume 76cm wide and 18 meters long using very well to very poorly sorted gravel and sandy gravel. In the first series, standing waves, antidunes, and breaking antidunes were generated in the open channel section of the flume; in the second series, standing waves and downstream-migrating antidunes were generated. In both series, these bedforms were replaced in the tunnel section by a plane bed, often with a rheological front. In the smaller flume, antidunes contained backset and foreset (lee-side) laminae, poorly sorted and less than about 10° in maximum dip. In the larger flume, although backsets formed, they were temporary only, and were soon eroded by the downstream migration of the antidunes. Sand was deposited on the downstream sides of bed waves, but although clearly visible in plan, it did not show up clearly as lamination in section: well sorted gravel was just as abundant as poorly sorted. The open channel data from the gravel experiments showed that in-phase waves form at about the same Froude numbers for both coarse sand and granule-pebble gravel. 相似文献
14.
The mass balance distribution over a 0.5 km2 area of the lower part of South Cascade Glacier is obtained from remotely sensed measurements of its geometry and velocity field over two periods, 1992–93 and 1993–94. Vertical aerial photography from late summer 1992, 1993, and 1994 is analyzed photogrammetrically to get surface topography of South Cascade Glacier on a 100-meter square grid. The known bed topography is subtracted from the surface topography to get the ice thickness, and the surface topographies are subtracted from each other to get the thickness change. Annual displacement vectors, determined at points where natural features could be tracked from one year to the next, are contoured by hand and interpolated to the grid. Assuming that the ice follows Glen's flow law with exponent n = 3, and that 10% of the ice flow is due to sliding at the bed, the surface velocity is scaled by 0.82 to get the average velocity in the vertical ice column. The average velocities are combined with the thicknesses to calculate the flux divergence at each of 46 gridpoints on a 100-m square grid, where it is subtracted from the thickness change to get the mass balance.
Use of the same control points from year to year makes any systematic error in photogrammetric coordinates temporally constant, so such error has no effect on the mass balance estimate. Random error in coordinates is assumed to be uncorrelated from coordinate to coordinate, from point to point, from year to year; the standard error is estimated to be 1 m, resulting in a standard error in coordinate differences of about 1.5 m. A 1 m error in a vertical coordinate has nearly twice the effect on the estimated balance that one in a horizontal coordinate has and more than ten times the effect that one in ice thickness has. Compared with measurements at a stake, the estimated balances are about 1 m too negative. 相似文献
Use of the same control points from year to year makes any systematic error in photogrammetric coordinates temporally constant, so such error has no effect on the mass balance estimate. Random error in coordinates is assumed to be uncorrelated from coordinate to coordinate, from point to point, from year to year; the standard error is estimated to be 1 m, resulting in a standard error in coordinate differences of about 1.5 m. A 1 m error in a vertical coordinate has nearly twice the effect on the estimated balance that one in a horizontal coordinate has and more than ten times the effect that one in ice thickness has. Compared with measurements at a stake, the estimated balances are about 1 m too negative. 相似文献
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16.
Laura Jugaru Tiron Jrme Le Coz Mireille Provansal Nicolae Panin Guillaume Raccasi Guillaume Dramais Philippe Dussouillez 《Geomorphology》2009,106(3-4):186-197
This article analyzes the water and suspended solid fluxes through a straightened meander of the southern branch of the Danube Delta (the St. George branch) during episodic flooding. The Mahmudia study site corresponds to a vast natural meander which was cut off in 1984–1988 by an artificial canal opened to shipping. The meander correction accelerated fluxes through the artificial canal and dramatically enhanced deposition in the former meander. After his formation, the cutoff meander acted as sediment storage locations, essentially removing channel and point bar sediments from the active sediment budget of the main channel. Increases in slope and stream power in reaches upstream and downstream have also occurred, but to a lesser degree. During the one-hundred-year recurrent flood in April 2006, bathymetry, flow velocity and discharge data were acquired across several sections of both natural and artificial channels with an acoustic Doppler current profiler (aDcp Workhorse Sentinel 600 kHz, Teledyne RDI) in order to investigate the distribution of the flow and sediment and his impact on sedimentation in a channelized reach and its adjacent cutoff. The contrasting hydro-sedimentary processes at work in both channels and bifurcation/confluence nodal points are analyzed from the measured flux distribution, morphological profiles and velocity and concentration patterns. In the cutoff, a diminishing of the intensity of the flow velocity (c. 50%) and of the SSC was observed correlated with the aggradation of the river bed. In the bifurcation/confluence nodal points and in the artificial canal were observed the most intensive hydrodynamic activity (high flow velocity, SSC concentration, degradation of the river bad). Both the event-scale and long-term morphological trends of the alluvial system are discussed analyzing the boundary shear stress and SSC variability. Excess boundary shear stress in the sub-reaches directly affected by cutoffs resulted in scour that increased downstream bed material load. These high sediment loads play a key role in driving morphological adjustments towards equilibrium in the cutoff channel.The approach followed in this paper combines detailed episodic in-situ aDcp measurements and robust numerical 1D modeling in order to provide a practical comprehension of the relevant morphodynamical processes. The 1D model reproduces robustly the continuity of hydrodynamical variables along the streamwise axes of the two-channel network. The simulated are used in the paper for highlighting reach-scale morphological processes, at both event and long-term scales. 相似文献
17.
Ejection of sand grains from a sand surface is assumed to result from cascade collision caused by the impact of a saltating particle. Allowing for only two-body cascade collision and introducing new quantities such as the cross-section for sand grain–grain collisions and sand surface binding energy, the theoretical model for the cascade collision of ion particles is applied to simulate sand grain/bed collision processes. The results of simulations indicate that the collision cascade events caused by impacting particles can eventually lead to the ejection of grains taking place from the sand surface. The number of ejected grains at any surface point is found to be proportional to the fractional energy deposited at that point and inversely proportional to the sand surface binding energy. This cascade collision model also confirms that the peak in the spatial distribution of ejected grains does not appear at the impact point but is located downwind, and that the speed distribution of ejected grains at a fixed angle exhibits a peak having a value directly related to the ratio of surface binding energy to the mass of the ejected grain. The angular distribution at a certain ejection speed also exhibits a maximum at an ejection angle near 90°. The model also offers a new interpretation for the observed variability in the number of ejected grains under constant impact velocity; this variability is directly related to the wide distribution of the energy deposition in the surface layer of the sand bed. 相似文献
18.
Summary The thermomechanical differential equations governing deformation in viscous shear zones have been solved for both constant velocity and constant stress boundary conditions. The solutions show that the inertial term in these equations can be neglected everywhere.
The starting condition of the constant velocity model has been shown to be a constant velocity gradient and not a Heaviside function. The temperature anomaly produced by shear heating at the centre of the shear zone is shown to increase gradually and continuously with time, not reaching an asymptotic value. Conclusions for the constant velocity boundary condition are otherwise generally similar to those presented by Yuen et al , and agree with Fleitout & Froidevaux. The temperatures reached by constant velocity shears are sufficient for partial melting.
Constant stress boundary condition shear zone models show an initially broad shear zone with uniform shear velocity gradient. Depending on the level of applied shear stress and ambient temperature, localized intense shear heating may develop followed by thermal runaway. At lower ambient temperatures relatively high stresses are required to produce thermal runaway.
The broadening of the constant velocity shear zone proceeds more rapidly with increased ambient temperature. This can be used to show that shear zones broaden with depth. The merging of parallel shear zone pairs has been investigated and shear zones separated by distances of less than 10km coalesce to form a single shear zone within 3 Myr. Only shear zones separated by 50km or more remain distinct over periods of tens of millions of years. 相似文献
The starting condition of the constant velocity model has been shown to be a constant velocity gradient and not a Heaviside function. The temperature anomaly produced by shear heating at the centre of the shear zone is shown to increase gradually and continuously with time, not reaching an asymptotic value. Conclusions for the constant velocity boundary condition are otherwise generally similar to those presented by Yuen et al , and agree with Fleitout & Froidevaux. The temperatures reached by constant velocity shears are sufficient for partial melting.
Constant stress boundary condition shear zone models show an initially broad shear zone with uniform shear velocity gradient. Depending on the level of applied shear stress and ambient temperature, localized intense shear heating may develop followed by thermal runaway. At lower ambient temperatures relatively high stresses are required to produce thermal runaway.
The broadening of the constant velocity shear zone proceeds more rapidly with increased ambient temperature. This can be used to show that shear zones broaden with depth. The merging of parallel shear zone pairs has been investigated and shear zones separated by distances of less than 10km coalesce to form a single shear zone within 3 Myr. Only shear zones separated by 50km or more remain distinct over periods of tens of millions of years. 相似文献
19.
Scales of boundary resistance in coarse-grained channels: turbulent velocity profiles and implications 总被引：2，自引：0，他引：2
Gravel-bed surfaces are characterized by morphological features occurring at different roughness scales. The total shear stress generated by the flow above such surfaces is balanced by the sum of friction drag (grain stress) and form drag components (created by bed forms). To facilitate a better understanding of total resistance and bed load transport processes, there is a need to mathematically separate shear stress into its component parts. One way to do so is to examine the properties of vertical velocity profiles above such surfaces. These profiles are characterized by an inner layer that reflects grain resistance and an outer layer that reflects total resistance. A flume-based project was conducted to address these concerns through systematically comparing different roughness scales to ascertain how increased roughness affects the properties of vertical velocity profiles. Great care was taken to create natural roughness features and to obtain flow data at a high spatial and temporal resolution using an Acoustic Doppler Velocimeter.Average vertical velocity profiles above each roughness scale were clearly segmented. The vertical extent of the inner flow region was directly related to the scale of roughness present on the bed (and independent of flow depth), increasing with increased roughness. On a rough but rather uniform “plane” bed made of heterogeneous coarse sediments (with no bed forms), the shape of the velocity profile was clearly dominated by the local variations in grain characteristics. When pebble clusters were superimposed, the average shear stress in the outer flow region increased by 100% from the plane bed conditions. The ratio of inner grain shear stress to outer total shear stress for this pebble cluster experiment was 0.18 under shallow flow conditions and 0.3 under deep flow conditions. The grain stress component that should be used in bed load transport equations therefore appears to vary in these experiments between 15% and 30% of the total channel stress, increasing with decreased resistance. Roughness height (Ks/D50) values at the grain scale for the plane bed and pebble cluster experiments were 0.73 and 0.63, respectively. These are values that should be used in flow resistance equations to predict grain resistance and grain stress for bed load transport modeling. 相似文献
20.
Yun-Hao Wu En-Chao Yeh Jia-Jyun Dong Li-Wei Kuo Jui-Yu Hsu Jih-Hao Hung 《Geophysical Journal International》2008,174(3):949-965
Taiwan Chelungpu-fault Drilling Project (TCDP) was initiated to understand the physical mechanisms involved in the large displacements of the 1999 Taiwan Chi-Chi earthquake. Continuous measurements of cores (including laboratory work) and a suite of geophysical downhole logs, including P - and S -wave sonic velocity, gamma ray, electrical resistivity, density, temperature, electrical borehole images and dipole-shear sonic imager, were acquired in Hole-A over the depth of 500–2003 m. Integrated studies of cores and logs facilitate qualitative and quantitative comparison of subsurface structures and physical properties of rocks. A total of 10 subunits were divided on the basis of geophysical characteristics. Generally, formation velocity and temperature increase with depth as a result of the overburden and thermal gradient, respectively. Gamma ray, resistivity, formation density, shear velocity anisotropy and density-derived porosity are primarily dependent on the lithology. Zones with changes of percentage of shear wave anisotropy and the fast shear polarization azimuth deduced from Dipole Shear-Imager (DSI) are associated with the appearance of fractures, steep bedding and shear zones. The fast shear wave azimuth is in good agreement with overall dip of the bedding (approximately 30° towards SE) and maximum horizontal compressional direction, particularly in the Kueichulin Formation showing strong shear wave velocity anisotropy. Bedding-parallel fractures are prevalent within cores, whereas minor sets of high-angle, NNW–SSE trending with N- and S-dipping fractures are sporadically distributed. The fault zone at depth 1111 m (FZA1111) is the Chi-Chi earthquake slip zone and could be a fluid conduit after the earthquake. The drastic change in fast shear wave polarization direction across the underlying, non-active Sanyi thrust at depth 1710 m reflects changes in stratigraphy, physical properties and structural geometry. 相似文献