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1.
Based on the 1︰50000 active fault geological mapping, combining with high-precision remote imaging, field geological investigation and dating technique, the paper investigates the stratum, topography and faulted landforms of the Huashan Piedmont Fault. Research shows that the Huashan Piedmont Fault can be divided into Lantian to Huaxian section (the west section), Huaxian to Huayin section (the middle section) and Huayin to Lingbao section (the east section) according to the respective different fault activity.
The fault in Lantian to Huaxian section is mainly contacted by loess and bedrock. Bedrock fault plane has already become unsmooth and mirror surfaces or striations can not be seen due to the erosion of running water and wind. 10~20m high fault scarps can be seen ahead of mountain in the north section near Mayu gully and Qiaoyu gully, and we can see Malan loess faulted profiles in some gully walls. In this section terraces are mainly composed of T1 and T2 which formed in the early stage of Holocene and late Pleistocene respectively. Field investigation shows that T1 is continuous and T2 is dislocated across the fault. These indicate that in this section the fault has been active in the late Pleistocene and its activity becomes weaker or no longer active after that.
In the section between Huaxian and Huayin, neotectonics is very obvious, fault triangular facets are clearly visible and fault scarps are in linear distribution. Terrace T1, T2 and T3 develop well on both sides of most gullies. Dating data shows that T1 forms in 2~3ka BP, T2 forms in 6~7ka BP, and T3 forms in 60~70ka BP. All terraces are faulted in this section, combing with average ages and scarp heights of terraces, we calculate the average vertical slip rates during the period of T3 to T2, T2 to T1 and since the formation of T1, which are 0.4mm/a, 1.1mm/a and 1.6mm/a, and among them, 1.1mm/a can roughly represent as the average vertical slip rate since the middle stage of Holocene. Fault has been active several times since the late period of late Pleistocene according to fault profiles, in addition, Tanyu west trench also reveals the dislocation of the culture layer of(0.31~0.27)a BP. 1~2m high scarps of floodplains which formed in(400~600)a BP can be seen at Shidiyu gully and Gouyu gully. In contrast with historical earthquake data, we consider that the faulted culture layer exposed by Tanyu west trench and the scarps of floodplains are the remains of Huanxian MS8½ earthquake.
The fault in Huayin to Lingbao section is also mainly contacted by loess and mountain bedrock. Malan loess faulted profiles can be seen at many river outlets of mountains. Terrace geomorphic feature is similar with that in the west section, T1 is covered by thin incompact Holocene sand loam, and T2 is covered by Malan loess. OSL dating shows that T2 formed in the early to middle stage of late Pleistocene. Field investigation shows that T1 is continuous and T2 is dislocated across the fault. These also indicate that in this section fault was active in the late Pleistocene and its activity becomes weaker or no longer active since Holocene.
According to this study combined with former researches, we incline to the view that the seismogenic structure of Huanxian MS8½ earthquake is the Huashan Piedmont Fault and the Northern Margin Fault of Weinan Loess, as for whether there are other faults or not awaits further study. 相似文献
2.
GEOMORPHOLOGICAL CHARACTERISTICS OF DAQINGSHAN DRAINAGE AREA IN THE NORTHERN MARGIN OF HETAO BASIN 
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下载免费PDF全文 The Daqingshan Fault located in the northern margin of the Hetao Basin has experienced intensive activity since late Quaternary, which is of great significance to the molding of the present geomorphology. Since basin geomorphological factors can be used to reflect regional geomorphological type and development characteristics, the use of typical geomorphology characteristics indexes may reveal the main factors that control the formation of topography. In recent years, more successful research experience has been accumulated by using hypsometric integral(HI) values and channel steepness index(ksn)to quantitatively obtain geomorphic parameters to reveal regional tectonic uplift information. The rate of bedrock uplifting can be reflected by channel steepness index, the region with steep gradient has high rate of bedrock uplifting, while the region with slower slope has low rate of bedrock uplifting. The tectonic uplift can shape the geomorphic characteristics by changing the elevation fluctuation of mountains in study area, and then affect the hypsometric integral values distribution trend, thus, the HI value can be used to reflect the intensity of regional tectonic activity, with obvious indicating effect.
Knick point can be formed by fault activity, and the information of knick point and its continuous migration to upstream can be recorded along the longitudinal profile of stream. Therefore, it is possible and feasible to obtain the information of tectonic activity from the geomorphic characteristics of Daqinshan area. The research on the quantitative analysis of regional large-scale tectonic activities in the Daqingshan area of the Yellow River in the Hetao Basin is still deficient so far. Taking this area as an example, based on the method of hypsometric integral(HI) and channel steepness index(ksn), we use the DEM data with 30m resolution and GIS spatial analysis technology to extract the networks of drainage system and seven sub-basins. Then, we calculate the hypsometric integral(HI) values of each sub-basin and fit its spatial distribution characteristics. Finally, we obtain the values of channel steepness index and its fitting spatial distribution characteristics based on the improved Chi-plot bedrock analysis method. Combining the extraction results of geomorphic parameters with the characteristics of fault activity, we attempt to explore the characteristics of drainage system development and the response of stream profile and geomorphology to tectonic activities in the Daqingshan section of the Yellow River Basin.
The results show that the values of the hypsometric integral in the Daqingshan drainage area are medium, between 0.5~0.6, and the Strahler curve of each tributary is S-shaped, suggesting that the geomorphological development of the Daqingshan area is in its prime, and the tectonic activity and erosion is strong. Continuous low HI value is found in the tectonic subsidence area on the hanging wall of the Daqingshan Fault. The distribution characteristics of the HI value reveal that the Daqingshan Fault controls the geomorphic difference between basin and mountain. Longitudinal profiles of the river reveal the existence of many knick points. The steepness index of river distributes in high value along the trend of mountain which lies in the tectonic uplift area on the footwall of the Daqingshan Fault. It reflects that the bedrock uplift rate of Daqingshan area is faster. The distribution characteristics of the channel steepness index show that the uplift amplitude of Daqingshan area is strong and the bedrock is rapidly uplifted, which is significantly different from the subsidence amplitude in the depression basin at the south margin of the fault, indicating that the main power source controlling the basin mountain differential movement comes from Daqingshan Fault. Based on the comparison and analysis on tectonic, lithology and climate, there is no obvious corresponding relationship between the difference of rock erosion resistance and the change of geomorphic parameters, and the precipitation has little effect on the geomorphic transformation of Daqingshan area, and its contribution to the geomorphic development is limited. Thus, we think the lithology and rainfall conditions have limited impact on the hypsometric integral, longitudinal profiles of the river and channel steepness index. Lithology maybe has some influences on the channel knick points, while tectonic activity of piedmont faults is the main controlling factor that causes the unbalanced characteristics of the longitudinal profile of the channel and plays a crucial role in the development of the channel knick points. So, tectonic activity of the Daqingshan Fault is the main factor controlling the uplift and geomorphic evolution of the Daqingshan area. 相似文献
3.
DISTRIBUTION CHARACTERISTICS OF THE AD 1556 HUAXIAN EARTHQUAKE TRIGGERED DISASTERS AND ITS IMPLICATIONS 下载免费PDF全文
下载免费PDF全文 A complete understanding to the disasters triggered by giant earthquakes is not only crucial to effectively evaluating the reliability of existing earthquake magnitude, but also supporting the seismic hazard assessment. The great historical earthquake with estimated magnitude of M8.5 in Huaxian County on the 23rd January 1556, which caused a death toll of more than 830 000, is the most serious earthquake on the global record. But for a long time, the knowledge about the hazards of this earthquake has been limited to areas along the causative Huashan piedmont fault(HSPF) and within the Weihe Basin. In this paper, we made a study on earthquake triggered landslides of the 1556 event along but not limited to the HSPF.
Using the high-resolution satellite imagery of Google Earth for earthquake-triggered landslide interpretation, we obtained two dense loess landslides areas generated by the 1556 earthquake, which are located at the east end and west end of the HSPF. The number of the interpreted landslides is 1 515 in the west area(WA), which is near to the macro-epicentre, and 2 049 in the east area(EA), respectively. Based on the empirical relationship between the landslide volume and area, we get the estimated landslide volume of 2.85~6.40km3 of WA and EA, which is equivalent or bigger than the value of ~2.8km3 caused by Wenchuan earthquake of MW7.9 on 12th May 2008. These earthquake triggered landslides are the main cause for the death of inhabitants living in houses or loess house caves located outside of the basin, such as Weinan, Lintong, Lantian(affected by WA) and Lingbao(affected by EA). Our results can help deeply understand the distribution characteristics of coseismic disaster of the 1556 Huaxian earthquake to the south of Weihe Basin, and also provide important reference for the modification of the isoseismals. 相似文献
4.
汤郎-易门断裂位于青藏高原东南缘,走向近南北,按地貌特征及区域构造背景可将其划分为北段（营盘村-插甸断裂）、中段（插甸-碧城断裂）及南段（碧城-易门断裂）。针对汤郎-易门断裂构造地貌差异,利用30 m分辨率的DEM数据,基于GIS技术提取与断裂活动相关的水系,并计算其陡峭指数,结合野外考察及遥感影像讨论断裂在不同分段的活动习性与地貌特征。研究发现,区域内降水及基岩抗风化能力对亚流域陡峭指数的影响较小,认为陡峭指数能够较好地反映汤郎-易门断裂的垂直构造运动。陡峭指数显示,断裂走向呈两端高、中间低的特点,其分段性与前人划分结果具有较好一致性,所表征的基岩垂直活动性差异可作为断裂带活动分段的依据。断裂带东西侧陡峭指数在不同分段上表现出差异性,北段断裂东西侧陡峭指数显示出东、西向差异性抬升不显著,其与地貌上断裂北段表现的左旋走滑运动一致,以水平运动为主;断裂中段及南段陡峭指数在东西侧表现出东高西低的特点,显示东侧较西侧基岩抬升更快,可能以垂直差异运动为主。 相似文献
5.
ACTIVITY CHARACTERISTICS OF THE HUASHAN PIEDMONT NORMAL FAULT: INSIGHTS FROM FLUVIAL GEOMORPHIC PARAMETERS 下载免费PDF全文
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
6.
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
7.
色尔腾山山前断裂得令山以东段属全新世活动断裂。距今约 30ka以来 ,断裂上升盘的平均抬升速率为 :大佘太段 0 19mm/a ,乌兰忽洞段 0 2 0mm/a。探槽揭露 ,大佘太段 ,约 32kaBP以来 ,发生过 4次古地震事件 ,事件发生时间依次为 (316 90± 1770 ) ,(2 30 0 0± 132 0 ) ,(15 42 0± 870 ) ,(74 40± 4 40 )aBP ,相应的位移量分别为 2 6 ,1 6 ,2 2 ,1 4m ;乌兰忽洞段 ,约 2 5kaBP以来 ,也发生过4次古地震事件 ,事件发生时间依次为 (2 5 130± 14 30 ) ,(14 5 70± 82 0 ) ,(116 6 0± 6 5 0 ) ,(72 2 0± 4 0 0 )aBP ,相应的位移量分别为 2 6 ,1 8,1 3,1 2m。根据位移量限定法 ,两个活动段落的古地震活动历史是完整的 相似文献
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9.
通过航卫片解译和野外实地调查,对六盘山断裂带新活动特征开展详细研究。调查发现六盘山东麓断裂为一条全新世活动的逆左旋走滑断裂,而六盘山西麓断裂为晚更新世活动的挤压逆冲断裂,二者的构造活动控制和影响了本区的地貌发育和地震活动。同时利用SRTM数据提取六盘山东西两侧泾河和水洛河上游流域盆地水系,得到流域盆地面积-高程积分值(HI值)分布图,探讨本区活动构造和地貌的响应关系。分析结果表明,在相同的岩性条件下六盘山东侧的HI值要低于西侧,反映了活动断裂对本地区地貌演化特征的不同影响。上述地貌分析研究为认识和理解六盘山地区地貌演化以及控制因素提供了基础数据和思路。 相似文献
10.
HOLOCENE SLIP RATE AND EARTHQUAKE HAZARD OF THE NORTH-EDGE FAULT OF THE YANQI BASIN,SOUTHEASTERN TIAN SHAN,CHINA 下载免费PDF全文
下载免费PDF全文 The Tian Shan Mountains is an active orogen in the continent. Previous studies on its tectonic deformation focus on the expanding fronts to basins on either side, while little work has been done on its interiors. This work studied the north-edge fault of the Yanqi Basin on the southeastern flank of Tian Shan. Typical offset landforms, and lineaments of scarps on the eastern segment of this fault were used to constrain the vertical displacement and shortening rates. Geological and geomorphic mapping in conjunction with high-resolution GPS differential measurement reveals that the vertical offsets can be divided into three groups of 1.9m, 2.4m and 3.0m, and the coseismic vertical offset was estimated as 0.5~0.6m. In situ 10Be terrestrial cosmogenic nuclide dating of three big boulders capping the regional geomorphic surface that preserved 3.0m vertical offset suggests that the surfaces were exposed at~5ka. Meanwhile, the lacustrine sediments from Bosten Lake within the Yanqi Basin suggest climate change during cooling-warming transitions was also at~5ka. The climate, therefore, controlled creation and abandonment of geomorphic surfaces in southern piedmont of Tian Shan. Combining the exposure ages and vertical offsets, we inferred that the east section of the north-edge fault in the Yanqi Basin has a dip slip rate 0.6~0.7mm/a,~0.5mm/a of vertical slip and~0.4mm/a of shortening since 5ka. Based on calculation of earthquake moment, we estimated that this fault is capable of generating M7.5 earthquakes in the future. This study provides new data for further understanding tectonic deformation of Tian Shan and is useful in seismic hazard assessment of this area. 相似文献
11.
潜在震源区的划分主要包括潜在震源区范围的划定以及震级上限的确定,目前遵循地震构造类比和地震活动重复等原则。而活断层的分段特性也是潜在震源区划分时必须考虑的一个重要因素。大青山山前断裂带至今有3种不同的分段方案,文中比较分析了前人对大青山山前断裂带的分段,并在此基础上对大青山及山前盆地的潜在震源区作了新的划分。鄂尔多斯块体周缘被拉张性断陷盆地围绕,这些断裂系地震构造相似,且除呼包盆地外均有历史8级以上地震记录。文中将大青山山前断裂带与鄂尔多斯块体周缘断裂系进行了构造对比,特别是与华山山前断裂进行了断裂活动性定量对比,得出雪海沟到土左旗段的震级上限为8级,断裂两端潜源震级上限均为7.5级 相似文献
12.
The regional geologic and geomorphic observations show that an active arcuate normal fault constitutes the main boundary fault of the Haba-Yulong Snow Mountains (HYSM). This fault is called eastern piedmont fault of Haba-Yulong Snow Mountains (HYPF). The fault consists of two segments with differential trend; the northern segment is NW-trending and NE-dipping and the southern section is S-N trending and E-dipping. Three sets of fault scarps cutting late Quaternary landforms and their dating results indicate... 相似文献
13.
The geomorphologic structure in the southeastern Tibetan Plateau is one of the important indexes for the expansion and deep dynamic process of Tibet. There are two different understandings for the geomorphologic structure in the southeastern Tibetan Plateau, i.e. gradual change and abrupt change. The gradient model suggests a gradual topographic reduction towards southeast which is an important evidence for the lower crust channel flow. The abrupt model considers that the southeast boundary of the plateau shows an abrupt change of topography in a zone of 50~200km wide which is controlled by the Yarlung-Yulong fault system. Here, we describe the morphotectonic feature in detail of the Sichuan-Yunnan block on the southeast edge of the plateau through the digital elevation model(DEM)analysis, further review the structural controls on the geomorphologic structure by combining the tectono-thermochronology analysis, and evaluate the southeastward spreading mode of the plateau.
The topographic arithmetic progression ranking by using the DEM of the Sichuan-Yunnan block reveals three geomorphologic steps gradually lowering from the northwest to southeast. The switching of hypsometric integral(HI)value and the anomaly of SL/K value(where SL is stream length-gradient index and K is altitude of the profile)of river systems all occur on the edge of terraces. The high terrace is located on the north of Muli-Yulong with average elevation~4 200m; the secondary level of terrace extends to the Yanyuan-Lijiang area with average elevation~3 000m; and the third level is the region between the Jinhe-Qinghe and Anninghe with average elevation~1 800m.
Structure investigation reveals that all the topographic boundaries between different terraces are consistent with regional major faults. The Muli thrust fault and Yulong thrust fault control the southeast edge of the high terrace, the Jinhe-Qinghe thrust fault separates the second and third level of terrace. The coincidence between topography boundaries and faults suggests that the formation of the stepped geomorphology on the southeast edge of the plateau were induced by the fault activities, reflecting the fault-controlled southeastward stepped-expanding mode of the plateau.
The fission-track(FT)dating of the granites at the hanging wall of the Yuling-Muli Fault reveals fast uplift during~27~22Ma BP, reflecting the major thrusting along the Yulong-Muli Fault, which is consistent with the early-stage activity (~30~25Ma BP) of the Longmenshan Fault. Therefore, the high terrace was formed during the Oligocene to early Miocene with the thrusting of the Yulong-Muli Fault. Tectono-thermochronology analysis also reveals the major thrusting of the Jinhe-Qinghe Fault occurred during~18~11Ma BP, indicating the middle terrace was formed in the middle Miocene, which also could correspond to the middle Miocene(~15~10Ma BP) activity of the Longmenshan Fault.
Therefore, the thrusting faults controlled stepped terrace geomorphologic structure and the stepwise expanding mode under combined movements of large-scale thrusts and strike-slip faults at the southeast edge of Tibetan Plateau during the late Cenozoic do not support the lower crust channel flow model. 相似文献
14.
秦岭北麓晚第四纪断层陡坎的初步研究 总被引：4，自引：1，他引：4
根据航片解译和野外调查,发现在秦岭北麓第四纪松散沉积物中发育有断层陡坎,本文依据对这些陡坎的地质地貌分析、地形剖面测制、探槽揭露及测年数据,讨论了断层陡坎的空间分布和形态学特征、生成时代和断距,评估了秦岭北麓断裂在晚第四纪的活动强度。由断层陡坎高度经过校核获得断距变化范围在1.1至7.9米之间,由此求得秦岭北麓断裂中段全新世中晚期以来平均滑动速率接近1mm/a,西段在眉县一带为0.5mm/a左右。晚更新世以来,发生过3—4次古地震事件 相似文献
15.
THE COSEISMIC VERTICAL DISPLACEMENTS OF SURFACE RUPTURE ZONE OF THE 1556 HUAXIAN EARTHQUAKE 下载免费PDF全文
下载免费PDF全文 Coseismic displacement plays a role in earthquake surface rupture, which not only reflects the magnitude scale but also has effect on estimates of fault slip rate and earthquake recurrence intervals. A great historical earthquake occurred in Huaxian County on the 23rd January 1556, however, there was lack of surface rupture records and precise coseismic vertical displacements. It's known that the 1556 Huaxian earthquake was caused by Huashan front fault and Weinan plateau front fault, which are large normal faults in the east part of the southern boundary faults in Weihe Basin controlling the development of the basin in Quaternary. Here, we made a study on three drilling sites in order to unveil the coseismic vertical displacements.
It is for the first time to get the accurate coseismic vertical displacements, which is 6m at Lijiapo site of Huashan front fault, 7m at Caiguocun site, and 6m at Guadicun site of Weinan plateau front fault. These coseismic displacements measured based on same layers of drilling profiles both at footwall and hanging wall are different from the results measured by former geomorphological fault scarps. It's estimated that some scarps are related with the nature reformation and the human beings' activities, for example, fluviation or terracing field, instead of earthquake acticity, which leads to some misjudgment on earthquake displacements. Moreover, the vertical displacements from the measurement of geomorphological scarps alone do not always agree with the virtual ones. Hence, we assume that the inconsistency between the results from drilling profiles and geomorphological scarps in this case demonstrates that the fault scarp surface may have been demolished and rebuilt by erosion or human activities. 相似文献
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通过跨银川断陷盆地,完成了一条长68.9 km的高分辨深地震反射探测剖面,首次获得了银川盆地地壳精细结构、地堑型断陷盆地深部断裂系（黄河断裂、银川断裂、贺兰山东麓断裂）特征及深浅构造关系.结果表明：银川断陷盆地上地壳为双程走时8 s（深度约20 km）反射面以上的区域,上地壳上部地层层位丰富,地层分段连续性较好,上地壳下部地层分层特征不明显,地质构造简单;下地壳(8～13 s)反射能量较弱,反射同相轴不明显;下地壳下部壳幔过渡带（13 s附近）由一组能量较强、持续时间较长（1.5 s）的反射波组组成,厚度约4.5 km.芦花台断裂、银川断裂分别于12～12.5 km、18～19 km深处交汇于贺兰山东麓断裂,贺兰山东麓断裂于28～29 km深处交汇于黄河断裂,黄河断裂为错断Moho面的深大断裂,银川地堑为以黄河断裂为主,其他断裂为辅组合而成的负花状构造.根据贺兰山东麓断裂和银川断裂的相互关系,认为贺兰山东麓断裂对1739年平罗—银川8级地震起主要控制作用. 相似文献
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南北地震带北段及其两侧断层现今活动性 总被引：6，自引：2，他引：6
分析了南北地震带北段及其两侧跨断层流动形变资料，研究了各断裂带的活动水平、动态过程及其与强震的关系。结果表明，南北地震带北段及其两侧现今断层平均垂直活动速率为0.19mm/a，断层活动处于第四纪以来较低水平；区域断层活动增强是强震发生的重要标志之一；强震前断层异常活动存在由外围向震中迁移的特征；南西华山-六盘山断裂带为近年可能发生强烈地震的地区。 相似文献
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