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1.
交城断裂带位于山西断陷系中部,是晋中盆地西界的控制性断裂。该断裂北端起自阳曲县泥屯镇,南到汾阳西侧,长约125km,总体走向NE,倾向SE。文中通过对山西交城断裂带41条冲沟124个裂点的实测和研究,论述了交城断裂带冲沟裂点的展布特征:1)冲沟上游裂点级数的数目与冲沟上游的长度呈正比关系;2)在各级裂点中,裂点距离与冲沟的长度呈正比关系;3)约1/3冲沟不同级别裂点距离接近,这种冲沟裂点的等间距反映了断层垂直位移事件活动的时间等间隔性;4)基岩裂点和松散沉积物中的裂点具有共性,两者之间不存在明显差异;5)在测区124个裂点中,1～5m高的裂点占裂点总数的72%,这种主体裂点高度反映了断裂位移事件的垂直活动量;6)与该断裂带沿线开挖探槽揭示的古地震事件进行对比,调查区内最新的一、二、三级裂点分别对应距今3.06～3.74ka、5.91ka和8.53～8.56ka发生的断层活动事件;7)以古地震事件的时间为参照,得到a～d级冲沟第一级裂点后退速率分别为0.6～0.7cm/a、2.7～3.3cm/a、5.6～6.8cm/a和8.4～10.2cm/a,b～d级冲沟第二级裂点后退速率分别为2.6cm/a、4.6cm/a和8.4cm/a;8)这3次事件的平均高度分别为2.8m、3.0m、2.6m,与前人通过探槽揭示的3次古地震事件位错吻合。最后讨论了可能影响裂点级数及裂点距离的部分因素。 相似文献
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1654年7月21日甘肃省礼县8级地震发生在南北地震带的中北段,该地区的构造变形和构造活动与青藏高原向北东方向的扩展密切相关,复杂的构造几何特征主要受控于东昆仑断裂、西秦岭北缘断裂和一系列北东向断裂.礼县—罗家堡断裂为一条北东东向的左旋走滑活动断裂,错断了含有仰韶文化红色陶瓷片的一级阶地堆积物,阶地面上断层陡坎高约1.5m.沿断裂带发现冲沟的左旋位错量为3~10m,晚更新世黄土中残留的断层陡坎高4.5~8m.其中两条冲沟中发现裂点,高3.5~3.9m,距断层陡坎的距离为16m.礼县—盐关—罗家堡—天水镇一带发育大量的滑坡,长轴走向与礼县—罗家堡断裂一致,滑坡体后缘、侧壁陡峭,出露晚第四纪黄土,鲜有植被覆盖.礼县—罗家堡断裂为1654年8级地震的发震断裂.综合分析认为,受青藏高原向北东方向的扩展,被西秦岭北缘断裂、礼县—罗家堡断裂和岷县—宕昌断裂围限的礼县次级地块向南东滑动可能导致了1654年礼县8级地震的发生.断裂北、南两侧地壳电性结构的差异为强震的孕育提供了深部构造条件. 相似文献
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用地貌学方法研究贺兰山山前断层全新世活动状况 总被引：10，自引：5，他引：10
本文根据穿过断层的45条冲沟中的裂点和阶地测量资料,论述贺兰山山前断层全新世以来的活动状况。我们认为全新世以来该断层至少有8次活动。最后一次断层活动错断了距今400年的长城,并在冲沟中形成一个裂点,该裂点现今已距断层陡坎约5米远。假定这次断层活动和1739年平罗大地震有关,求出裂点的溯源侵蚀平均速度为2.0—2.5厘米/年.根据两裂点间的距离和裂点的溯源侵蚀平均速度,并考虑到我国近5000年的气候有逐渐变干的趋势,求出断层活动的周期(表3)。从断层陡坎附近的各级阶地面之间的高差,求出断层各次活动的幅度(表4)。 相似文献
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华山山前断裂中段晚第四纪活动的地貌表现及响应 总被引：2，自引：1，他引：1
调查了华山山前断裂中段（石堤峪-杜峪）晚更新世以来,尤其是全新世以来的断层构造地貌,讨论了它们的成因、特点及对断裂活动的响应关系。断层构造地貌主要包括：断层三角面、断层陡坎、洪积阶地、埋藏型洪积扇以及冲沟裂点。对各大沟峪峪口的洪积阶地进行了大比例尺微地貌测量,并在部分沟峪两侧沿断层崖陡坎及冲沟沟床布置了测线。结合T1、T2级洪积阶地位错测量结果及其14C年龄计算得到,华山山前断裂中段6000a-2000aB.P.的垂直滑动速率为1.485mm/a;2000aB.P.以来的垂直滑动速率为3.73mm/a。最后结合野外调查与理论认识,建立了正断层作用下洪积阶地与埋藏型洪积扇的演化模式。本研究结果支持华山山前断裂是1556年华县814级地震发震构造的观点。 相似文献
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热水 -日月山断裂带是发育在青藏高原东北缘柴达木 -祁连活动地块内部的 1条重要的NNW向逆 -右旋走滑活动断裂带 ,长约 183km。断裂由 4条不连续的次级断裂段右阶羽列而成 ,阶距 2～ 3km左右 ,在不连续部位形成拉分区。主断裂两端则形成帚状分叉。断裂活动形成了一系列山脊、冲沟和阶地等右旋断错微地貌 ,其中Ⅰ级阶地右旋断错约 8～ 11m ,Ⅱ级阶地右旋断错约 35m。同时沿断裂带还形成了许多断层陡坎 ,Ⅰ级阶地或洪积台地上断层陡坎高约 0 .5～ 1m ,最高达 2 .8m ,Ⅱ级阶地或台地上的断层陡坎高约 2 .5～ 3m ,最高达 4～ 5m。根据相应的阶地年代 ,计算得到断裂带全新世以来的平均水平滑动速率为 3 16mm/a ,垂直滑动速率为 0 .83mm/a 相似文献
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祁连山北缘佛洞庙-红崖子断裂古地震特征初步研究 总被引：4，自引：1，他引：3
佛洞庙-红崖子断裂位于祁连山北缘断裂带中部,是祁连山与河西走廊之间的一条重要边界断裂,断裂全长约110km,总体走向北西西,该断裂为一条全新世活动的逆-左旋走滑断裂,断裂活动形成了一系列陡坎、断层崖以及冲沟和阶地左旋等断错地貌.本文通过3个探槽剖面对发生在该断裂上的古地震事件进行了分析,可确定地震事件2次,事件Ⅰ为历史地震,发生在距今400年前,为1609年红崖堡71/4级地震;事件Ⅱ的年代为距今（6.3±0.6）ka B.P.和（7.4±0.4）ka B.P.之间.同时结合前人的一些研究资料,对古地震的复发模式和间隔进行了初步讨论. 相似文献
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云南建水-蒙自一带位于川滇菱形块体向SE145°平移的前锋,受其影响,该地区的蒙自东山断裂、田山断裂和黑泥地断裂等表现出一定程度的晚第四纪活动性,跨过断裂的冲沟被走滑断错。攀枝花以东的蒙自东山断裂右旋错断冲沟和其间的山脊约40m,并在山前洪积扇上形成偏离上游约30m的废弃古河道,古河道中堆积物的年龄为44kaBP,断裂右旋滑动速率约为0.7mma。大红地北一条冲沟在跨过田山断裂时发生右旋拐弯。冲沟在山前形成了年龄分别为31kaBP和39kaBP的2级洪积阶地,呈现出年轻阶地位错量大于老阶地的反常现象。田山断裂的平均右旋滑动速率约0.9mma。发育于黑泥地断裂南侧的多条冲沟在流过断裂时发生一致性的右旋位错,其中一条冲沟位错量达14m,断裂的右旋滑动速率为0.4mma。这一地区自30～40kaBP开始发生了一次明显的构造运动,表现为这一时代的洪积扇上的地貌过程由加积转变为切割,并被断裂错断。断裂的走滑速率明显低于小江断裂带、曲江断裂带和石屏-建水断裂带等。川滇菱形地块向SSE方向的平移及其构造活动不仅仅局限在小江断裂带以西的地块内部,而是引起了外围地块上的断裂活动,但断裂活动强度不及内部断裂的13。冲沟对走滑断错的响应分为3种类型,分别为同步弯曲型、加剧弯曲型和不对称谷地型,其中加剧弯曲型的地貌过程较为复杂。每种类型都记录了断裂的走滑活动,在估算断错量和滑动速率时应甄别不同的响应类型,以免人为的“加大”或“减小”甚至“忽略”断裂的活动幅度。 相似文献
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Gully erosion of cultural sites in Grand Canyon National Park is an urgent management problem that has intensified in recent decades, potentially related to the effects of Glen Canyon Dam. We studied 25 gullies at nine sites in Grand Canyon over the 2002 monsoon–erosion season to better understand the geomorphology of the gully erosion and the effectiveness of erosion‐control structures (ECS) installed by the park under the direction of the Zuni Conservation Program. Field results indicate that Hortonian overland flow leads to concentrated flow in gullies and erosion focused at knickpoints along channels as well as at gully heads. Though groundcover type, soil shear strength and permeability vary systemat‐ically across catchments, gradient and, to a lesser degree, contributing drainage area seem to be the first‐order controls on gully extent, location of new knickpoints, and ECS damage. The installed ECS do reduce erosion relative to reaches without them and initial data suggest woody checkdams are preferable to rock linings, but maintenance is essential because damaged structures can exacerbate erosion. Topographic data from intensive field surveys and detailed photogrammetry provide slope–contributing area data for gully heads that have a trend consistent with previous empirical and theoretical formulations from a variety of landscapes. The same scaling holds below gully heads for knickpoint and ECS topographic data, with threshold coefficients the lowest for gully heads, slightly higher for knickpoints, and notably higher for damaged ECS. These topographic thresholds were used with 10‐cm digital elevation models to create simple predictive models for gully extent and structure damage. The model predictions accounted for the observed gullies but there are also many false‐positives. Purely topographical models are probably inadequate at this scale and application, but models that also parameterize the variable soil properties across sites would be useful for predicting erosion problems and ECS failure. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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ACTIVITY CHARACTERISTICS OF THE HUASHAN PIEDMONT NORMAL FAULT: INSIGHTS FROM FLUVIAL GEOMORPHIC PARAMETERS 
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下载免费PDF全文 The Huashan piedmont fault, forming a part of the southern margin of the Weihe graben, is one of the important normal faults that control the subsidence of the intracontinental rift. Developing on the footwall of the fault, the Huashan block has experienced rapid cooling during the Cenozoic, especially since the early-middle Miocene. Mountain exhumation causes and transports a great amount of sediments to the adjacent hanging wall, setting a typical case of mountain-basin coupling system. Studies on active tectonics, historical and paleo earthquakes and field investigations reveal that the middle section(Huaxian-Huayin)of the fault is much more active than the west(Lantian-Huaxian)and east(Huayin-Lingbao)sections.
We extracted channel profiles of rivers that originate from the main water divide of the northern flank of the Huashan Mountain. Based on the method of slope-area analysis and the integral approach, we identified knickpoints, calculated channel concavity and steepness indices, and constructed paleo river profiles. Of most rivers, the concavities are within a relatively narrow range of 0.3~0.6, with no obvious correlation with tectonics. However, channel steepness and knickpoint distribution vary spatially. In the east section, rivers are under steady-state with smooth, concave-up channels and lower steepness((104±30)m0.9). In the other two sections, rivers are mainly under transient state with slope-break knickpoints. For the channel segments below knickpoints, steepness indices are much higher in the middle section((230±92)m0.9)than in the west((152±53)m0.9). Thus, the variance of fault activity can be reflected by channel steepness pattern. Above the knickpoints, channel steepness indices are much lower(middle(103±23)m0.9, west(60±14)m0.9). What's more, we found a statistically significant power-law scaling between knickpoint retreat distance and catchment drainage area. Thus, we attributed these knickpoints to be the results of recent rapid uplift of the Huashan block. The relief of paleo channels(middle(1000±153)m, west(751±170)m)accounts for~60%~80% of the relief of modern rivers(middle(1323±249)m, west(1057±231)m), which means that ~20%~40% of modern channel relief was caused by the episode of the rapid uplift. Assuming a balance between the rates of rock uplift and downstream river incision, a power-law function between uplift rates and channel steepness can be derived. According to the fault throw rates of the middle section 1.5~3mm/a(since late Pleistocene), we constrained slope exponent n~0.5 and channel erodibility K~1.5×10-4m0.55/a. Combining the knickpoint age formula, we estimated that the rapid mountain uplift/fault throw began at ~(0.55±0.25)Ma BP. Therefore, the middle of the Huashan piedmont fault is more active than the west and east sections. The fast fault throw of the west and middle sections since the middle Pleistocene has caused rapid mountain uplift and high topographic relief. 相似文献
We extracted channel profiles of rivers that originate from the main water divide of the northern flank of the Huashan Mountain. Based on the method of slope-area analysis and the integral approach, we identified knickpoints, calculated channel concavity and steepness indices, and constructed paleo river profiles. Of most rivers, the concavities are within a relatively narrow range of 0.3~0.6, with no obvious correlation with tectonics. However, channel steepness and knickpoint distribution vary spatially. In the east section, rivers are under steady-state with smooth, concave-up channels and lower steepness((104±30)m0.9). In the other two sections, rivers are mainly under transient state with slope-break knickpoints. For the channel segments below knickpoints, steepness indices are much higher in the middle section((230±92)m0.9)than in the west((152±53)m0.9). Thus, the variance of fault activity can be reflected by channel steepness pattern. Above the knickpoints, channel steepness indices are much lower(middle(103±23)m0.9, west(60±14)m0.9). What's more, we found a statistically significant power-law scaling between knickpoint retreat distance and catchment drainage area. Thus, we attributed these knickpoints to be the results of recent rapid uplift of the Huashan block. The relief of paleo channels(middle(1000±153)m, west(751±170)m)accounts for~60%~80% of the relief of modern rivers(middle(1323±249)m, west(1057±231)m), which means that ~20%~40% of modern channel relief was caused by the episode of the rapid uplift. Assuming a balance between the rates of rock uplift and downstream river incision, a power-law function between uplift rates and channel steepness can be derived. According to the fault throw rates of the middle section 1.5~3mm/a(since late Pleistocene), we constrained slope exponent n~0.5 and channel erodibility K~1.5×10-4m0.55/a. Combining the knickpoint age formula, we estimated that the rapid mountain uplift/fault throw began at ~(0.55±0.25)Ma BP. Therefore, the middle of the Huashan piedmont fault is more active than the west and east sections. The fast fault throw of the west and middle sections since the middle Pleistocene has caused rapid mountain uplift and high topographic relief. 相似文献
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Knickpoints in bedrock streams are often interpreted as transient features generated by a change in boundary conditions. It is typically assumed that knickpoints propagate upstream with constant vertical velocities, though this relies on a stream being in erosional steady state (erosion rate equals rock uplift rate) prior to the knickpoint's formation. Recent modeling and field studies suggest that along-stream contrasts in rock erodibility perturb streams from erosional steady state. To evaluate how contrasts in rock erodibility might impact knickpoint interpretations, we test parameter space (rock erodibility, rock contact dip angle, change in rock uplift rate) in a one-dimensional (1D) bedrock stream model that has variable rock erodibility and produces a knickpoint with a sudden change in rock uplift rate. Upstream of a rock contact, the vertical velocity of a knickpoint generated by a change in rock uplift rate is strongly correlated with how the rock contact has previously perturbed erosion rates. These knickpoints increase vertical velocity upon propagating upstream of a hard over soft contact and decrease vertical velocity upon propagating upstream of a soft over hard contact. However, interactions with other transient perturbations produced by rock contacts make for nuances in knickpoint behavior. Rock contacts also influence the geometry of knickpoints, which can become particularly difficult to identify upstream of soft over hard rock contacts. Using our simulations, we demonstrate how a contact's along-stream horizontal migration rate and cross-contact change in rock strength control how much an upstream reach is perturbed from erosional steady state. When simulations include multiple contacts, the knickpoint is particularly prone to colliding with other transient perturbations and can even disappear altogether if rock contact dips are sufficiently shallow. Caution should be taken when analyzing stream profiles in areas with significant changes in rock strength, especially when rock contact dip angles are near the stream's slope. 相似文献
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Normal fault growth and linkage in the Gediz (Alaşehir) Graben,Western Turkey,revealed by transient river long‐profiles and slope‐break knickpoints 下载免费PDF全文
下载免费PDF全文 Emiko Kent Sarah J. Boulton Alexander C. Whittaker Iain S. Stewart M. Cihat Alçiçek 《地球表面变化过程与地形》2017,42(5):836-852
The Gediz (Ala?ehir) Graben is located in the highly tectonically active and seismogenic region of Western Turkey. The rivers upstream of the normal fault‐bounded graben each contain a non‐lithologic knickpoint, including those that drain through inferred fault segment boundaries. Knickpoint heights measured vertically from the fault scale with footwall relief and documented fault throw (vertical displacement). Consequently, we deduce these knickpoints were initiated by an increase in slip rate on the basin‐bounding fault, driven by linkage of the three main fault segments of the high‐angle graben bounding fault array. Fault interaction theory and ratios of channel steepness suggest that the slip rate enhancement factor on linkage was a factor of 3. We combine this information with geomorphic and structural constraints to estimate that linkage took place between 0.6 Ma and 1 Ma. Calculated pre‐ and post‐linkage throw rates are 0.6 and 2 mm/yr respectively. Maximum knickpoint retreat rates upstream of the faults range from 4.5 to 28 mm/yr, faster than for similar catchments upstream of normal faults in the Central Apennines and the Hatay Graben of Turkey, and implying a fluvial landscape response time of 1.6 to 2.7 Myr. We explore the relative controls of drainage area and precipitation on these retreat rates, and conclude that while climate variation and fault throw rate partially explain the variations seen, lithology remains a potentially important but poorly characterised variable. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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NATURAL AND ANTHROPOGENIC FACTORS CONTROLLING GULLY EROSION IN THEBASALTIC UPLAND OF SOUTHERN BRAZIL
This paper describes an analysis of natural and anthropogenic factors controlling the evolution of gullies in a rural basin in the basaltic upland in the State of Rio Grande do Sul, Southern Brazil. In this region of deep ferrallitic soils with more than 60% clay, runoff and erosion are of increasing concern. In the TaboAo drainage basin （100 km^2）, gully erosion was studied in a field survey that measured rills and gullies. Eighty-four gullies were identified. They had an average length of 136 m, were 10 m wide, and 3 m deep and had a volume of 15.458 m3. Each gully was characterised in terms of factors that included slope, geological structure, presence of piping, drainage, soil use, and the presence of surface and subsurface flow. On average, the main channels had knickpoints varying from 2 m to 7 m, and their evolution in the vertical plane increased until bed-rock basalt material was reached, after which gullies increase in width and length. Gully development was also monitored from 1991 to 2003. Subsurface flow appears to be the principal agent controlling their development. Results show that both natural （slope, surface curvature, geological structure and rainfall） and anthropogenic （soil use, road construction） factors are important in gully development. The change in cultural practices throughout the drainage basin from conventional to direct seeding has led to increased subsurface flow, which was more important than surface runoff in causing erosion. However, the higher rainfall during E1 Nifio Southern Oscillation （ENSO） events and the consequently higher subsurface flow were the dominant factors. From 1991 to 2003 a total land loss of 1,013 m3 was observed in one gully, with 236 m^3 lost during the 1992 ENSO and 702 m3 during the 1997 ENSO; 95% of the total volume lost occurred during ENSO periods. 相似文献
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Sean F. Gallen Karl W. Wegmann Kurt L. Frankel Stephen Hughes Robert Q. Lewis Nathan Lyons Paul Paris Kristen Ross Jennifer B. Bauer Anne C. Witt 《地球表面变化过程与地形》2011,36(9):1254-1267
The southern Appalachians represent a landscape characterized by locally high topographic relief, steep slopes, and frequent mass movement in the absence of significant tectonic forcing for at least the last 200 Ma. The fundamental processes responsible for landscape evolution in a post‐orogenic landscape remain enigmatic. The non‐glaciated Cullasaja River basin of south‐western North Carolina, with uniform lithology, frequent debris flows, and the availability of high‐resolution airborne lidar DEMs, is an ideal natural setting to study landscape evolution in a post‐orogenic landscape through the lens of hillslope–channel coupling. This investigation is limited to channels with upslope contributing areas >2.7 km2, a conservative estimate of the transition from fluvial to debris‐flow dominated channel processes. Values of normalized hypsometry, hypsometric integral, and mean slope vs elevation are used for 14 tributary basins and the Cullasaja basin as a whole to characterize landscape evolution following upstream knickpoint migration. Results highlight the existence of a transient spatial relationship between knickpoints present along the fluvial network of the Cullasaja basin and adjacent hillslopes. Metrics of topography (relief, slope gradient) and hillslope activity (landslide frequency) exhibit significant downstream increases below the current position of major knickpoints. The transient effect of knickpoint‐driven channel incision on basin hillslopes is captured by measuring the relief, mean slope steepness, and mass movement frequency of tributary basins and comparing these results with the distance from major knickpoints along the Cullasaja River. A conceptual model of area–elevation and slope distributions is presented that may be representative of post‐orogenic landscape evolution in analogous geologic settings. Importantly, the model explains how knickpoint migration and channel–hillslope coupling is an important factor in tectonically‐inactive (i.e. post‐orogenic) orogens for the maintenance of significant relief, steep slopes, and weathering‐limited hillslopes. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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Performance of riffle structures on the stabilization of two successive knickpoints over a sandy bed
《国际泥沙研究》2020,35(4):377-385
Two successive knickpoints with a 10% slope were constructed 1 m apart on a sandy bed in a rectangular flume with a longitudinal slope of 0.003. Bed erosion and knickpoint migration were studied experimentally for different discharges. The performance of two grade-control structures–Newbury rock riffles (NRR) and cross-vane riffles (CVR)–were studied experimentally for the stabilization of each knickpoint. Both of the structures were successful in controlling the bed erosion; however, the NRR operated relatively better than the CVR for they could concentrate the flow at the middle part of the channel to produce more regular contours with less local erosion and bed settlement. The experiments demonstrated that the construction of a control structure was not only effective in the stabilization of a knickpoint but also retarded the migration of its neighboring counterpart. 相似文献
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Loess gullies are the most active and changeable landform unit on the Loess Plateau of China. Under the influence of inhomogeneous internal and external forces, various gully morphologies have been identified as specific forms of asymmetrical loess gullies in the northeastern Loess Plateau. Thus, the formation mechanisms of asymmetrical gullies should be examined to better understand the gully evolution processes in this area. In this study, a typical asymmetrical gully area and its geological background in the northeastern Loess Plateau are investigated. Then, the asymmetrical gullies are extracted and ordered under different watershed hierarchies using 5 m horizontal resolution digital elevation models. The asymmetrical gullies are characterized using the gully deviation index and gully asymmetrical coefficient to quantitatively and qualitatively describe the gully formation from the perspective of gully morphology. Subsequently, environmental factors, such as the bedrock, climate, vegetation and interactions with neighbouring watersheds, are combined to achieve an in-depth understanding of the mechanisms of asymmetrical gully formation. The results show that most watersheds shift to the right side of the watershed geometric centre line, thereby forming a specific asymmetrical gully morphology. The phenomenon in which the asymmetrical degree characteristics decrease with the increase in drainage area suggests evident morphological differences on both sides of the main channel on a small scale, and relatively weak morphological differences on both sides of the main channel on a large scale. The degree of loess gully asymmetry appears higher in the area where only the windward slope is covered by loess than in areas where all slopes are covered by loess. The interaction between adjacent watersheds also influences the formation of asymmetrical gullies. These results support the understanding of asymmetrical gully formation in relation to the underlying bedrock structure and gully reorganization, thereby contributing to the development of process-based gully evolution models. 相似文献