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1.
通过阐述北京西北的活动构造定量数据及其精度，用确定性方法、概率方法和综合评分方法，通过排队，比较出北京西北及邻近地区未来强震可能发生的地点，讨论预测结果中存在的一些问题．结果显示，未来强震最危险的断裂段为:阳原盆地南缘断裂B段和A段、延矾盆地的燕水段、宣化盆地南缘断裂、怀安镇南缘断裂东段和阳高——天镇北缘断裂东段等段落．亦即阳原-深井盆地为最危险区；天镇-怀安镇-宣化盆地为次危险区；万全-张家口和蔚县东北-矾山西南为更次危险区． 相似文献
2.
地震事件中,断层破裂面的倾角大小直接影响到地表强地震动的分布状态,尤其在断陷盆地中,强地面运动特征还可能受到盆地结构及盆地内多条围限断层的影响.本文模拟了银川断陷盆地内的活动断层--银川隐伏断层南段发生Mw6.5特征地震时,断层破裂面倾角在30°~85°范围内变化时引起的强地面运动,探讨了断层破裂面倾角变化对盆地内强地面运动分布特征和强度的影响.结果表明:破裂面倾角较缓时,银川盆地内的强地面运动分布区域不仅仅决定于发震断层的产状,同时还受到断层上盘距离最近的芦花台断层的影响,致使强地面运动集中于两条断层所围限的区域;随着发震断层破裂面的倾角逐渐增大,强地面运动以发震断层产状的影响为主,强震集中区向发震断层靠近并分布于发震断层上盘,且沿断层走向方向出现了强度不同的地震动反射区;尤其是发震断层破裂面倾角接近垂直时,受银川盆地"西陡东缓"结构和盆地西边界贺兰山东麓断裂反射作用的影响,竖向地震动反射区强度在远离发震断层的西北方向明显增大,致使芦花台断层附近区域与银川断层南段上盘区域成为地震发生时可能遭受震害最严重的地区.本文探讨结果提醒我们在类似区域的活动断层附近进行建(构)筑规划和地震工程设计时,有必要考虑发震断层破裂面倾角大小和盆地内其它断层构造的共同影响,综合评价潜在地震对盆地内近断层地表及各类建(构)筑物的危害性. 相似文献
3.
本研究基于分层黏弹介质模型,考虑强震或大地震同震位错、震后黏滞松弛及主断层段震间构造应力加载三方面效应,给出1480年以来,川滇菱形块体东边界鲜水河断裂带、安宁河断裂带、则木河断裂带和小江断裂带共20个断层段由三方面效应引起的累积库仑应力变化随时间的演化,分析强震间相互作用和强震发生的应力累积背景,定性分析各断层段的地震危险性.同时,分别采用现今台网地震目录和川滇菱形块体东边界各断层段强震复发间隔两种资料,定量计算2030年各断层段的强震发生概率;并基于摩擦本构理论,将周边强震引起的库仑应力变化量作为应力扰动,修正强震发生概率的计算结果.各断层段累积库仑应力演化的结果表明,鲜水河断裂带中部八美段、色拉哈段及南部磨西段、安宁河断裂带冕宁-西昌段、小江断裂带北部巧家-东川段和南部建水段的累积库仑应力显著增加.修正的强震发生概率计算结果显示,鲜水河断裂带中部八美-色拉哈-康定一带、安宁河断裂带冕宁-西昌段、小江断裂带南部华宁-建水一带强震发生概率较高,地震危险性值得关注.本研究基于库仑应力演化计算定性分析强震危险性的同时,基于摩擦本构律理论,结合地震引起的应力扰动和强震发生背景,定量计算修正的强震发生概率,为川滇菱形块体东边界强震危险地点及中长期发震紧迫程度判定提供方法和依据. 相似文献
4.
Based on seismic data from the regional network for the last 34 years,we analyzed the present fault behavior of major fault zones around the Mabian area,southern Sichuan,and identified the risky fault-segments for potential strong and large earthquakes in the future.The method of analysis is a combination of spatial distribution of b-values with activity background of historical strong earthquakes and current seismicity.Our results mainly show:(1) The spatial distribution of b-values indicates significant heterogeneity in the studied area,which reflects the spatial difference of cumulative stress levels along various fault zones and segments.(2) Three anomalously low b-value areas with different dimensions were identified along the Mabian-Yanjin fault zone.These anomalies can be asperities under relatively high cumulated stress levels.Two asperities are located in the north of Mabian county,in Lidian town in western Muchuan county,and near Yanjin at the south end of the fault zone.These two areas represent potential large earthquake seismogenic sites around the Mabian area in the near future.Besides them,the third relatively smaller asperity is identified at southern Suijiang,as another potential strongearthquake source.(3) An asperity along the southwestern segment of the Longquanshan fault zone indicates the site of potential moderate-to-strong earthquakes.(4) The asperity along the segment between Huangmu town in Hanyuan county and Longchi town in Emeishan city on Jinkouhe-Meigu fault has potential for a moderate-strong earthquake. 相似文献
5.
本文采用天然地震近震走时反演地壳三维速度结构的方法获得了郯庐断裂带鲁苏皖段及附近地壳(30°N—37°N,113°E—122°E)三维速度结构.对地壳内分层速度结构的分析发现,郯庐断裂带鲁苏皖段存在速度的分段特征.郯庐断裂带鲁苏皖段浅层35.3°N以北,34.5°N—35.3°N间,33°N—34.5°N间呈现的速度分段和地表出露地层有关,与地质上安丘段、莒县—郯城段,新沂—泗洪段三个破裂单元相对应,且和各段的地震活动相呼应,表明郯庐带新沂到泗洪段可能是断裂的闭锁段.郯庐断裂带鲁苏皖段地壳速度结构自浅至深分为三段,大体位置是:南段(32.5°N—33°N以南),中段(32.5°N—33°N至35°N—35.3°N),北段(35°N—35.3°N以北).上地壳分段与苏鲁超高压变质岩带的插入有关,中、下地壳速度分段则可能和火山岩滞留有关.地壳各层速度结构不同段的速度差异反映了构造块体的速度差异,表明各构造块体在地壳下部仍有差异,郯庐带西侧速度总体高于东侧,反映了不同构造块体的形成和组成差别,也说明了该断裂带可能延伸到莫霍面.而不同深度的分段性可能反映了不同地质演化过程. 相似文献
6.
郯庐断裂带中段全新世活断层的特征滑动行为与特征地震 总被引：16，自引：0，他引：16
郯庐断裂带中段全新世活断层由３个独立的破裂段组成。从各破裂段的运动性质、位移分布看，断层的运动属特征地震型滑动。地震活动以强震活动为主，强震具有周期性原地重复发生的特点，且其强度基本相同；中强地震缺失或很少发生；ｂ值在高震级范围内具低ｂ值的非线性关系。这些特点正是特征地震的典型表现．根据郯庐断裂带中段活断层全新世以来的活动特点看，未来该区仍然以特征地震方式活动．按郯庐带的强震复发间隔和各段的最新一次活动时代推算，未来一段时期内新沂－宿迁段复发大震的可能性较大，安丘段次之，莒县－郯城段复发大震的可能性则很小。 相似文献
7.
2017年4月12日浙江临安发生了4.2级地震,在震中附近范围(35～50 km)内,主要发育3条断裂,分别为马金—乌镇断裂、湖州—临安断裂和昌化—普陀断裂,通过对这3条断裂开展野外地质调查、断层泥年龄样品测试等手段得出:北东向的马金—乌镇断裂、湖州—临安断裂均被近东西向的昌化—普陀为界分南北为两段,其中,马金—乌镇断裂北段以正断为主,南段以逆断为主,两段活动时代均为中更新世早期;湖州—临安断裂南北两段均以逆断为主,北段活动时代为中更新世早期,南段活动时代为前第四纪。昌化—普陀断裂以走滑活动为主,自西向东分为西、中、东三段,活动时代自西向东逐渐减弱,东段为前第四纪断裂,中西段为中更新世断裂。 相似文献
8.
《中国科学D辑(英文版)》2008,(9)
The authors processed the seismic refraction Pg-wave travel time data with finite difference tomography method and revealed velocity structure of the upper crust on active block boundaries and deep features of the active faults in western Sichuan Province. The following are the results of our investigation. The upper crust of Yanyuan basin and the Houlong Mountains consists of the superficial low-velocity layer and the deep uniform high-velocity layer, and between the two layers, there is a distinct, and gently west-dipping structural plane. Between model coordinates 180-240 km, P-wave velocity distribution features steeply inclined strip-like structure with strongly non-uniform high and low velocities alternately. Xichang Mesozoic basin between 240 and 300 km consists of a thick low-velocity upper layer and a high-velocity lower layer, where lateral and vertical velocity variations are very strong and the interface between the two layers fluctuates a lot. The Daliang Mountains to the east of the 300 km coordinate is a non-uniform high-velocity zone, with a superficial velocity of approximately 5 km/s. From 130 to 150 km and from 280 to 310 km, there are extremely distinct deep anomalous high-velocity bodies, which are supposed to be related with Permian magmatic activity. The Yanyuan nappe structure is composed of the superficial low-velocity nappe, the gently west-dipping detachment surface and the deep high-velocity basement, with Jinhe-Qinghe fault zone as the nappe front. Mopanshan fault is a west-dipping low-velocity zone, which extends to the top surface of the basement. Anninghe fault and Zemuhe fault are east-dipping, tabular-like, and low-velocity zones, which extend deep into the base-ment. At a great depth, Daliangshan fault separates into two segments, which are represented by drastic variation of velocity structures in a narrow strip: the west segment dips westward and the east segment dips eastward, both stretching into the basement. The east margin fault of Xichang Mesozoic basin features a strong velocity gradient zone, dipping southwestward and stretching to the top surface of the basement. The west-dipping, tabular-like, and low-velocity zone at the easternmost segment of the profile is a branch of Mabian fault, but the reliability of the supposition still needs to be confirmed by further study. Anninghe, Zemuhe and Daliangshan faults are large active faults stretching deep into the basement, which dominate strong seismic activities of the area. 相似文献
9.
Velocity structure and active fault of Yanyuan-Mabian seismic zone—The result of high-resolution seismic refraction experiment 总被引：3，自引：0，他引：3
FuYun Wang YongHong Duan ZhuoXin Yang ChengKe Zhang JinRen Zhao JianShi Zhang XianKang Zhang QiYuan Liu AiLan Zhu XiWei Xu BaoFeng Liu 《中国科学D辑(英文版)》2008,51(9):1284-1296
The authors processed the seismic refraction Pg-wave travel time data with finite difference tomography method and revealed
velocity structure of the upper crust on active block boundaries and deep features of the active faults in western Sichuan
Province. The following are the results of our investigation. The upper crust of Yanyuan basin and the Houlong Mountains consists
of the superficial low-velocity layer and the deep uniform high-velocity layer, and between the two layers, there is a distinct,
and gently west-dipping structural plane. Between model coordinates 180–240 km, P-wave velocity distribution features steeply
inclined strip-like structure with strongly non-uniform high and low velocities alternately. Xichang Mesozoic basin between
240 and 300 km consists of a thick low-velocity upper layer and a high-velocity lower layer, where lateral and vertical velocity
variations are very strong and the interface between the two layers fluctuates a lot. The Daliang Mountains to the east of
the 300 km coordinate is a non-uniform high-velocity zone, with a superficial velocity of approximately 5 km/s. From 130 to
150 km and from 280 to 310 km, there are extremely distinct deep anomalous high-velocity bodies, which are supposed to be
related with Permian magmatic activity. The Yanyuan nappe structure is composed of the superficial low-velocity nappe, the
gently west-dipping detachment surface and the deep high-velocity basement, with Jinhe-Qinghe fault zone as the nappe front.
Mopanshan fault is a west-dipping low-velocity zone, which extends to the top surface of the basement. Anninghe fault and
Zemuhe fault are east-dipping, tabular-like, and low-velocity zones, which extend deep into the basement. At a great depth,
Daliangshan fault separates into two segments, which are represented by drastic variation of velocity structures in a narrow
strip: the west segment dips westward and the east segment dips eastward, both stretching into the basement. The east margin
fault of Xichang Mesozoic basin features a strong velocity gradient zone, dipping southwestward and stretching to the top
surface of the basement. The west-dipping, tabular-like, and low-velocity zone at the easternmost segment of the profile is
a branch of Mabian fault, but the reliability of the supposition still needs to be confirmed by further study. Anninghe, Zemuhe
and Daliangshan faults are large active faults stretching deep into the basement, which dominate strong seismic activities
of the area.
Supported by the National Basic Research Program of China (Grant No. 2004CB428400) 相似文献
10.
龙门山断裂带可分为南段、中段和北段,2008年汶川M8.0级地震发生在该断裂带中-北段. 龙门山断裂带南段是否存在发生强震的危险性倍受关注. 利用1977-2012年四川区域地震台网资料,获得了龙门山断裂带南段的地震活动性参数b值图像以及汶川地震前、后b值的差值Δb图像. 同时,根据宽频带数字地震波形资料,计算了2007年以来南段及附近区域ML≥3.8级地震的视应力. 结果表明,2008年汶川地震后,龙门山断裂带南段天全-芦山、泸定和宝兴北部等区域应力增强,而靠近汶川余震区南端的大邑地区应力水平降低. 天全至宝兴段应力水平相对较高,具有发生中-强地震的条件. 鲜水河断裂带康定以南段应力水平低,短期内发生强震的可能性较小. 相似文献
11.
青藏高原中北部的巴颜喀喇地块是近年来强震最为活跃的地区,自1997年以来在地块周围发生了一系列7级以上地震.2014年于田MS7.3级地震就发生在该地块西边界附近的硝尔库勒盆地南缘,该区是阿尔金断裂、康西瓦断裂和东昆仑断裂等多组不同走向大型走滑活动断裂带的交汇部位,不同断裂走向的突然转变及滑动速率差异使该地区形成局部的拉张应力状态,发育了多条NE和近SN向的左旋正断裂. 通过余震分布、震源机制解结果等资料分析,认为此次地震的发震构造为阿尔金断裂西南端的一条次级断裂——硝尔库勒断裂,地震破裂特征为左旋走滑兼正断性质. 在巴颜喀喇地块这一轮的强震活动中,其北边界和东边界都显示块体向东挤出约7 m的位移量,但块体西边界产生的伸展量明显与整个块体向东的位移量不协调,2014年于田MS7.3级地震是巴颜喀喇地块向东挤出的构造响应和应变调整.模拟结果显示阿尔金主断裂上的库仑应力有所增加,东昆仑—柴达木地块可能为下一个强震活跃区,特别是阿尔金断裂的中西段,是今后应该重点关注和监视的地区. 相似文献
12.
本文利用CAP波形反演方法,获取了汶川MS8.0地震序列中312个具有较高信噪比波形资料的4级以上余震的震源机制解和震源深度. 基于震源深度空间分布与震源机制时空分布,分析了主震后余震区断层行为特征与应力场时空变化,并对龙门山断裂带中北段的发震断层面几何形态进行了初步探讨. 获得的主要认识如下:(1)余震震源深度分布存在显著的空间分段差异. 绵竹以西的余震区南段与平武以东的北段余震深度范围大于中段(绵竹-平武段),但深度小于5 km的5级以上超浅源地震主要分布在明显偏离龙门山断裂带走向的理县NW向分支与余震区北端NNE向分支,而中段余震主要分布在7~19 km深度. (2)余震机制类型存在明显的时空差异. 余震区中段逆冲型地震占绝对优势,理县NW向分支余震则以走滑型为主,机制类型随时间变化不显著. 沿龙门山断裂带走向的余震区南段,早期(2008年8月底前)逆冲型地震比例高于走滑型、晚期走滑型地震比例显著升高并超过逆冲型;而余震区北段早期走滑型地震占绝对优势、晚期逆冲型地震比例大幅上升且超过走滑型. 南、北两段余震机制类型比例的显著变化,可能是余震区两端断层调整性运动的表现. (3)节面走向及P轴方位优势方向均存在显著的空间差异. 南段NWW向P轴方位与区域应力场一致,中段及理县NW向分支P轴优势方向NEE,而北段具NWW和NEE两个优势方向,这种差异反映了余震活动除了受区域应力场控制外,还受到主震引发的局部应力场的控制. 节面走向的多方位分布则反映不同走向的构造参与了主震后的余震活动. (4)沿龙门山断裂带走向,余震区南段具深部缓倾角、浅部高倾角的铲形断面特征;中段深部倾角均值较稳定、浅部倾角均值随深度减小而增大;北段倾角均值相对稳定,显示其断面几何形态相对简单. 上述不同区段倾角均值随深度的变化揭示龙门山断裂带中北段断层面几何形态复杂. 相似文献
13.
The Chi‐Chi earthquake (MW = 7.6) took place in central western Taiwan in 1999. The earthquake caused reactivation of the Chelungpu Fault and resulted in 100‐km‐long surface ruptures. The fault strikes mostly north–south to NNE–SSW; however, the northern tip of the southern segment of the surface ruptures rotates clockwise to define an east–west trend, then jumps to a shorter NNW‐trending rupture. The largest vertical displacement is recorded in the Shihkang area of the Shihkang–Shangchi Fault Zone, where vertical slips are up to 8–10 m. The Shihkang–Shangchi Fault Zone displays a complex fault pattern as a linkage damage zone between two fault segments with the greatest concentration of faults and fractures. Our new interpretation, based on recent published geometric, kinematic, and geophysical studies on the Chi‐Chi earthquake fault, suggests that the Shihkang–Shangchi Fault Zone is not a simple termination zone, but may be an ‘overstep zone’ or a ‘transfer zone’. Slip analysis along the surface ruptures indicates that they are composed of three fault segments and the amount of slip partly depends on the intersection angle between slip direction and fault strike. Our numerical modeling for the area indicates that Coulomb stress changes are mainly concentrated on tips and bends of the surface ruptures. Slip patterns indicate that the fault propagates toward the northeast. Therefore, this study suggests high potential for future earthquake activity along the unruptured Shangchi segment. Hence, future geohazard studies should focus on the Shangchi segment to evaluate potential earthquakes, determine recurrence intervals, and reduce future earthquake hazards. 相似文献
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综合活动构造与重要活动断裂带的历史及现今强震震源区或破裂分布等资料,南北地震带北段存在长期缺少MSge;7.0地震的破裂空段．为了考察这些空段的地震危险性,首先采用Burgers体黏弹介质模型,计算周围有记载以来的历史强震在空段引起的库仑应力动态演化;其次结合背景地震发生率,采用Dieterich模型分析历史强震对空段地震活动的影响,讨论了空段所在区域的地震发生概率．结果显示,南北地震带北段强震破裂空段的地震危险性程度自高到低依次是:东昆仑活动断裂带东段的若尔盖——九寨沟段、六盘山断裂带中南段空段、香山——天景山段裂中南段同心空段、天祝——大靖空段、西秦岭北缘断裂带中西段、西秦岭北缘断裂带东段．该结果可为南北地震带北段的地震危险性估计提供参考． 相似文献
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在山东半岛北部近海海域进行了多条剖面的声波探测,初步查明了蓬莱－威海断裂带的基本活动特征.该断裂带由一系列北西走向的次级断层组成,主体在长岛至大竹岛之间的海域,多数断层以正断兼有走滑运动为主,部分断层具有逆冲运动性质.断裂带在第四纪活动明显,以北东向桃村-东陡山断裂在海域的延伸段为界,蓬莱-威海断裂带可分为两段：长岛-烟台段和烟台-威海段.西段长岛-烟台段为晚更新世活动段,多数次级断层上断点埋深位于海底以下30m,明显错断了中更新世地层,部分断层明显错断了晚更新世早期地层,有些断层达到晚更新世地层中部,但没有发现全新世地层错动现象.东段烟台-威海段为中更新世活动段,没有发现晚更新世地层错断现象.蓬莱-威海断裂带对历史地震和现代小震活动具有明显控制作用,其中1548年7级地震发生于断裂带西段,1948年6级地震发生于断裂带东段.蓬莱-威海断裂带与北东向断裂交汇区是中强地震发生的有利部位. 相似文献
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由现今地震活动分析鲜水河断裂带中-南段活动习性与强震危险地段 总被引：14，自引：0，他引：14
利用最近25年的区域台网地震资料, 基于沿鲜水河断裂带中-南段的b值分布以及多个地震活动参数值的不同组合, 结合震源深度分布、 历史强震背景等, 分析了不同断裂段落的现今活动习性, 进而初步判别该断裂带潜在的强震危险地段。 结果表明, 鲜水河断裂带中-南段目前存在6个不同活动习性的段落。 其中, 道孚段自1981年强震后已再次趋于闭锁, 原因可能与断层面存在“凹凸体”有关, 但应变可能还会进一步积累; 八美段目前处于中偏高应力下的相对静止状态, 推测其断面正处于新的应力积累阶段; 塔公段已有255~300年的无强震期, 目前正处于高应力下的相对闭锁状态, 震源深度剖面上的小震空白区显示出闭锁断层面的轮廓, 应属于未来最可能发生强震的危险地段; 康定、 磨西二个段落表现出中偏低应力下的稀疏小震滑动及较频繁小震滑动的状态, 意味着最晚的一次大地震破裂后断层面尚未重新耦合; 石棉段表现出偏高应力下的频繁中-小地震活动与该段的多条断裂交汇有关。 相似文献
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由地震活动参数分析龙门山-岷山断裂带的现今活动习性与强震危险性 总被引：38，自引：0，他引：38
根据最近28年的区域台网地震资料,利用b值空间分布及断裂带分段的多地震活动参数值的组合方法,结合历史强震背景,分析了沿川北龙门山-岷山断裂带不同断裂段的现今活动习性,并初步判别出了潜在的强震危险段落。研究结果表明:龙门山断裂带中-南段存在6个具有不同现今活动习性的段落,其中,绵竹-茂县段处于相对高应力背景下的频繁中-小震活动状态,被认为是龙门山断裂带上未来最可能发生强震的地段;江油-平武段处于相对高应力背景下的稀疏中-小震活动状态,未来有可能发生中强地震。而岷山断裂带中的岷江断裂段和虎牙断裂段,以及叠溪隐伏逆断层地区均具有相对偏低的应力水平,可能与其不久前分别发生过大地震和强震有关,未来不太长的时期内复发大地震的可能性较小。 相似文献