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1.
1995年日本新泻北部M6.0地震发生在新泻地震空区的东部边缘.由于此次地震震源较浅(10
km),造成了55栋房屋倒塌、165栋房屋半倒.通过计算倾倒墓碑的地震矩,对本区地震烈度进行了分析,发现烈度6度区(据日本JMA度)为一覆盖面积6.1×1
km2,呈NNE-SSW向分布的条带,表明震中区的冲积平原下存在一条隐伏断层.震中区地下水的温度、电导率和Cl-浓度等异常区与呈线性分布的6度烈度区大致吻合,也有力地证明了震中区下面存在一条隐伏断层.这次地震可能是由高压型热水系沿隐伏活动断层喷溢引起.带着高温的高压热水降低了岩石的断裂强度,从而触发了地震. 相似文献
2.
The 1995 Northern Niigata Earthquake (M 6.0) occurred at a shallow depth in the Niigata seismic gap. The anomaly areas in temperature, electrical conductivity and Cl- concentration of groundwater trend northeast as linear distribution in the epicentral area and are approximately coincident with the area of the seismic intensity 6 (JMA scale). The distributions of seismic intensity 6 and groundwater anomalies convincingly imaged the presence of a buried active fault beneath the epicentral area. The occurrence of this earthquake and the anomalies of groundwater were related to the expulsion of geopressured hydrothermal system (GHS). All epicenters of the destructive earthquakes along the Shinanogawa seismic belt are actually located in the buried active fault zones characterized by the areas of temperature and geochemical anomalies of groundwater. These earthquakes might have been triggered by the activity of GHS. The expulsion of GHS along an active fault in combination with the thermal softening of fault 相似文献
3.
信浓川地震带位于日本大地沟北部,地壳运动十分强烈,区内地震主要沿信浓川流域发生,并密集成带,大地构造上处于日本海板块向本州板块俯冲的边界线上。该地震带大多数地震为中强震,且均为浅源地震,地震发生伴随着明显的地下水前兆异常,震中区有强烈的超压热水系的喷溢活动。震中区地下水的温度、电导率以及主要地球化学成分呈线性异常分布,并与地震强弱或地震断裂规模有关,地震断层的规模控制了超压热水系喷溢活动的强度和规模。地震发生与超压热水系喷溢活动有着密切的成生关系,超压热水系喷溢活动使断层发生活动所需应力条件降低,诱发地震发生,同时断层活动为超压热水系向上喷溢提供通道。 相似文献
4.
Abstract The Shinanogawa Seismic Belt in the Northern Fossa Magna, Honshu Island, Japan, extends along the Shinano River, bounding the Eurasian Plate and the Okhotsk Plate. The geopressured hydrothermal system occurs widely in the Northern Fossa Magna region. Many destructive earthquakes are related to the activity of this system in the Shinanogawa Seismic Belt. Expulsion of a geopressured hydrothermal system and rising from depth along an active fault triggers the occurrence of an earthquake and opens the fault as a pathway. Anomalous areas in temperature, electrical conductivity and Cl– concentration of groundwater trend north–east in a linear distribution, and convincingly demonstrate the presence of a buried active fault at the epicentral area of the destructive earthquake in the Shinanogawa Seismic Belt. The distribution of the major axis of the anomalous area in groundwater temperature shows a strong positive relationship with earthquake magnitude, which means that the distribution of this area may indicate the scale of earthquake fault. The linearly anomalous areas in groundwater temperature, resulting from the percolation of a geopressured hydrothermal system, that have no record of previous destructive earthquake are predicted to be areas where destructive earthquakes could occur in the future. Four potential earthquake areas are proposed and discussed in this paper, based on re-examination of active faults and seismicity in the Shinanogawa Seismic Belt. 相似文献
5.
Abstract Geothermal waters in the Niigata Sedimentary Basin, central Japan, are divided into four groups based on their chemical composition (i.e. Na-SO4 -type, Na-SO4 -Cl-type, Na-Cl-type and Na-Cl-HCO3 -type). The Na-SO4 -type geothermal water forms as a consequence of water–rock interaction and generally occurs in the outer part of the basin. The Na-Cl-type geothermal water is further subdivided into the original Na-Cl-type geopressured thermal water and the mixed Na-Cl-type geothermal water, in terms of its geochemical and isotopic composition. The original Na-Cl-type geopressured thermal water originates from a geopressured hydrothermal system containing the altered fossil formation waters that are sealed at depth. It moves up to the upper part of the depositional succession or the ground, and generally does not mix with groundwater that is of meteoric origin. This type of water is cooled by heat conduction. The concentration of Cl– in this type of thermal water is very similar to that in seawater. The δD and δ18 O values are approximately constant and independent of temperature. The original Na-Cl-type geopressured thermal water is distributed mainly along anticlinal axes in folded Neogene formations. The mixed Na-Cl-type geothermal water is related to the expulsion activity of the geopressured hydrothermal system and occurs mostly along active faults. It is formed by shallow groundwater of meteoric origin being mixed with geopressured hydrothermal water when the geopressured hydrothermal system was expulsed along active faults by paroxysmal tectonic events. 相似文献
6.
简述了最近20年来国内外岩石高速摩擦实验研究领域的进展和动态:岩石高速摩擦实验技术的发展实现了对高滑动速率、大位移的地震过程的实验模拟;其结果揭示了岩石和断层泥在地震滑动速率下的力学性状,深化了对断层滑动弱化机制、临界滑动距离、以及地震发生过程的认识和理解;实验在假玄武玻璃成因方面取得了重要进展,并提出了断层发生地震滑动可能留下的其它地质证据,可望为研究断层滑动性状与地震物理过程提供新的思路和信息.岩石高速摩擦实验今后的发展方向主要包括:发展具有加温系统和孔隙压系统的岩石高速摩擦实验装置,研究水热作用下岩石和断层泥的高速摩擦性状;室内实验和地震资料分析相结合研究断层滑动和地震机制;室内实验和野外地质调查相结合探索断层发生地震错动的地质证据等等. 相似文献
7.
地震的等震线不仅反映了地震的大小,而且也反映了地震断层过程的类型和破裂速度.单侧破裂的断层过程呈现出蛋型的等震线,而双侧破裂的断层过程呈现出椭圆的等震线,等震线的长轴与短轴之比对于破裂传播速度十分敏感.本研究利用理论等震线与观测结果相比较的方法,确定了1964年日本新地震、1983年日本海中部地震、1975年中国海城地震和1976年中国唐山地震的破裂传播速度、断层类型以及断层走向.得到的断层破裂速度是剪切波的0.7——0.9倍.这些值比用长周期地震波所确定的要稍大.产生这种差异的原因是:对烈度起主要影响的短周期地震波强烈地依赖于小尺度的断层不均匀破裂过程,以及局部的破裂传播的开始和终止;而由长周期波所得到的破裂速度却反映了在整个断层上破裂传播的平均过程.根据等震线图所得出的断层类型及断层走向与其它独立方法的结果相一致.这意味着本方法可以应用于推断某些历史地震的断层类型、破裂传播速度及破裂传播方向. 相似文献
8.
Isoseismals of seismic intensity distributions are represented by earthquake source size, faulting mode, and rupture velocity of fault propagation. Unilateral faulting forms egg—shaped isoseimals, while bilateral faulting forms elliptical ones. It is found that the ratio of major to minor axes of isoseismals is sensitive to rupture velocity. Rupture velocity, faulting mode, and fault trend have been determined from the seismic intensity maps of the 1964 Niigata and the 1983 Japan Sea earthquakes in China by matching theoretical isoseismals. Rupture velocities thus estimated are mostly 70% to 90% of shear wave velocity. The difference would be considered as follows: short—waves which determine the seismic intensity are strongly dependent on the rupture of small—scale fault heterogeneities and on the jerky—onsets and abrupt terminations of local rupture propagations. On the other hand, rupture velocity from long—waves represents an average rupture propagation along the whole fault length. Faulting mode and fault trend estimated from seismic intensity maps match with each earthquake faulting independently determined. This suggests that the present method would be applicable to some historical earthquakes with known seismic intensity distribution to obtain detailed information on the faulting process. 相似文献
9.
阐述张家口市尚义M_S 4.0地震构造背景、地震活动特征,总结地震应急调查成果,介绍极震区震感现象和分布范围。通过对地震现场调查点和电话调查点的烈度评定,确定极震区的影响烈度为Ⅴ度,圈定地震等烈度分布区域,同时修正观测仪器震中位置。结合本次地震的宏观烈度分布、震源机制和震区卫星影像的线性构造解释等资料,讨论本次地震的孕震构造和发震断层。 相似文献
10.
断层活动方式与地震地表变形分布特征研究 总被引：2，自引：0，他引：2
基于断层弹性位错理论及断层滑动非均匀模型,用三维有限元方法计算了发震断层逆断、正断和水平走滑三种不同活动方式下的地表变形,探讨了断层不同活动方式下的地震应变与位移的分布规律及震级、断层倾角对地震地表变形分布的影响。研究结果表明,地震地表变形影响因素很多,如地质构造条件、岩性介质特征、断层活动强度、断层产状和区域构造应力场等,但分布形态最终决定于断层活动方式,变形大小则决定于断层活动强度,其它均为局地因素,只影响分布形态的局部扭曲。断层不同活动方式下的地震地表变形分布各有其自身的规律和特点,这些分布特征可作为地震研究及近活动断层建筑工程抗震设计或加固防护参考。 相似文献
11.
TWO DIMENSIONAL MODEL ON RELATION BETWEEN THERMAL ANOMALY BEFORE WENCHUAN EARTHQUAKE AND TECTONIC STRESS 
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下载免费PDF全文 ZHU Chuan-hua SHAN Xin-jian ZHANG Guo-hong JIAO Zhong-hu ZHANG Ying-feng LI Yan-chuan QIAO Xin 《地震地质》2019,41(6):1497-1510
It has been reported that there is thermal anomaly within a certain time and space preceding an earthquake, and previous research has indicated potential associations between the thermal anomaly and earthquake faults, but it is still controversial whether physical processes associated with seismic faults can produce observable heat.Based on rock experiments, some scholars believe that the convective and stress-induced heat associated with fault stress changes may be the cause of those anomalies. Then, did the thermal anomaly before the Wenchuan earthquake induced by the fault stress change?It remains to be tested by numerical simulations on the distribution and intensity of thermal anomalies. For example, is the area of thermal anomaly caused by the fault stress changes before the earthquake the same as the observation?Is the intensity the same?To clarify the above questions, a two-dimensional thermo-hydro-mechanical(THM)finite element model was conducted in this study to simulate the spatial and temporal variations of thermal anomalies caused by the underground fluid convection and rock stress change due to the tectonic stress release on fault before earthquake. Results showed that the simulated thermal anomalies could be consistent with the observed in magnitude and spatio-temporal distribution. Before the Wenchuan earthquake, deformation-related thermal anomalies occurred mainly in the fault zone and its adjacent hanging wall, which are usually abnormal temperature rise, and occasionally abnormal cooling, occurring in the fault zone after the peak temperature rise. In the fault zone, the thermal anomaly is usually greater than the order of 1K of the equivalent air temperature and is controlled by the combined effect of fluid convection and stress change. The temperature increases first and then decreases before the earthquake. In the hanging wall, it's weaker than that of the fault zone, mainly depending on the convection of the fluid. The temperature gradually increases before the earthquake and is dramatically affected by the permeability. Usually, only when the permeability is larger than 10-13m2, can the air temperature rise higher than 1K occur. The results of this study support the view that fluid convection and stress change caused by fault slip before the earthquake can produce observable air temperature anomalies. 相似文献
12.
孕震过程中孔隙压及地下水位变化的数值模拟 总被引：2，自引：2，他引：2
地震孕育过程中孕震区内各点的应力应变都将发生变化，介质的物性参数也将改变，因此孔隙压和地下水位随之改变。本文在研究孕震过程中包括扩容和断层蠕变效应在内的应力应变场的基础上，根据应力场与孔隙压场的耦合方程，把孔隙压场随应力场的应力变化定量地计算出来。计算结果表明，孕震过程中孔隙压的变化与应力场变的化的强弱及南的渗透性能等因素相关。孕震过程后期，震源区表现为扩容区并且孔隙压强以负压为主，此结果显示着震 相似文献
13.
中低温对流型地热资源在华北地区广泛分布,是一种清洁的替代能源.与活动断裂带相关的水热型地热资源是中低温地热系统的重要组成部分.本文基于高精度重力测量、微动测深及钻孔温度测量等数据,从热源、通道、储层和盖层四个方面探讨了南口—孙河断裂带水热系统特征.低重力异常揭示的燕山期花岗二长岩、闪长岩岩体范围为23.8 km~2和14.3 km~2,放射性测井数据计算得到其生热率均值为3.14μW·m~(-3),侏罗系火山岩生热率均值为1.65μW·m~(-3),隐伏岩体和火山岩均难以构成地热系统的附加热源.重力异常显示南口—孙河断裂带宽度约500~800 m,断裂带切割蓟县系雾迷山组白云岩热储层.钻井温度曲线显示断裂带内水热活动强烈,说明该断裂带是导水、导热的重要通道.断裂带南西侧马池口一带第四系松散层与侏罗系火山岩形成了热储盖层,微动测深显示火山岩最大厚度约1500 m.综上源、通、储、盖四个要素分析,该地热系统为热传导一对流复合型,来自京西北山区的大气降水经远距离径流深循环吸收地层热量后沿南口—孙河断裂上移到达裂隙发育的白云岩地层中形成热水.总之,沿南口—孙河断裂带具备了良好的地热地质条件,可达到规模开采的条件. 相似文献
14.
系统研究了水胜地层前云南地区的各种前兆异常，发现：震前2个月水胜地区的断层面总面积、多分维、蠕变、地层活动频度熵、地层活动强度熵呈明显异常；层前1年滇西北为低温异常区和高雨量异常区；展前3年滇西北地区GPS测量存在明显的奇异水平运动异常和最大剪切应变异常；震前2．5年至数十天云南地区出现大量的定点前兆异常成团分布，尤以滇西北最为集中。经分析后认为，水胜6．0级地层的各种前兆异常是明显的，普通存在的；水胜6.0级地层的孕育时间为2．5年；目前云南地区仍存在3个孕震区(滇西北、小滇西、滇东南)，未来3年甚至更短时间内云南地区的6级地震可能发生在第3个孕展区——滇东南地区。 相似文献
15.
数值模拟在黑山峡两坝址构造稳定性评价中的应用 总被引：6，自引：1，他引：5
通过对黑山峡进行区域应力场三维有限元模拟,利用岩石破裂危险度KR及断层滑动危险系数KF两个判别指标,确定出中卫一同心活动断裂带弧形顶点部位红谷梁—石圈区段及海原活动断裂带上西华山以东区段两个未来地震危险区,震源均处于上、中地壳交接带,即深15km左右,可能发生的最大地震震级分别为Ms7．3级及Ms8．2级。地震对两坝址的影响表明,大柳树坝址所受影响烈度可达9度,且位于极震区内,构造稳定性差;小观音坝址所受影响烈度约为7度,构造稳定性相对较好。 相似文献
16.
四川北部地区位于南北强震构造带的中北段,区内活动断裂众多、构造关系复杂、历史及现今地震活动频繁。其中,早期历史地震因时间久远、史料记载简略等原因,其地震基本参数确定和发震构造分析难度较大,存在较大的不确定性。通过对地震史料的系统梳理和实地考证,对该区1900年以前的3次中强破坏性地震(公元638年松潘地震、1738年南坪地震和1748年松潘北地震)进行补充考证,对其震中位置、震级和烈度等基本参数进行重新核定,并综合分析其发震构造特征。研究结果对分析该区地震活动特征及判定未来强震危险区等均具有重要参考意义。 相似文献
17.
本文运用分块均匀介质模型,研究了唐山地区从1954年以来的七期三角(边)测量资料,对于唐山地震前、后的水平形变得到一些新的认识,即在1964——1971年间,唐山菱形块体有向北北东方向的运动,块体內部则有某种程度的挤压应变积累。唐山地震断层在这一时期至少在浅部保持闭锁状态。由于测量精度的限制,未能得到可靠的震后形变信息,但根据震后一年内的两次测量得到的可靠性不高的结果推测,震后一年內的调整时期,唐山地震断层两侧的相对运动可能与震时相反,但量值很小。目前唐山地区没有明显的形变。 相似文献
18.
1654年甘肃天水南8级地震补充考证 总被引：9，自引：3，他引：6
简要回顾了1654年天水南8级地震的研究历史,结合原有史料和新补充调查所获得的资料,核定了各破坏点的地震烈度,进而改绘了地震等震线图,其长轴方向为NE向。此次地震除造成大范围的城垣毁坏、房屋倒塌和人员伤亡之外,滑坡、山崩和堰塞湖等地震地质灾害也非常严重。其极震区位于礼县以东的西汉水河谷永兴镇—罗家堡—天水镇一带。该区发育了全新世活动的礼县—罗家堡断裂,其性质为左旋走滑兼正断。根据最新调查结果,该断裂沿礼县—盐关—罗家堡一带保存了地震陡坎、纹沟左旋和地震沟槽等地震地表破裂带形迹,其地理位置与历史资料考证所确定的极震区范围一致,印证了二者结论的可靠性和合理性。 相似文献
19.
邢台地区设定地震事件烈度影响 总被引：1，自引：1，他引：0
通过邢台地区历史地震烈度资料分析,得到该地区烈度—频率灾害曲线及地震风险。以地震地质资料理论为基础,结合河北省城市活断层探测成果、地壳结构等资料,确定2个设定地震事件。采用复合震源模型,模拟合成强地面运动,并基于强地面运动模拟结果,分析邢台地区地震影响烈度,为今后该地区建筑物抗震设防、避难场所选址、震后救援以及地震保险风险评估提供参考依据。 相似文献
20.
福建地区地震活动空间分布及活动断裂特点研究 总被引：6，自引：0，他引：6
分析了1604年发生在泉州海外的8级大地震, 将所获结果结合其后400年间发生在该地区的地震活动作进一步的探讨。 在获取对该大地震的认识的基础上, 结合现代地震观测数据资料, 对福建地区的地震活动性进行再研究。 结果表明, 由于菲律宾板块向西挤压, 导致大陆东南沿海的应力积累, 从而诱发了当年泉州海外8级特大地震; 重要的是, 在震源区附近有一条近NE向活动断裂贯穿而过, 它在这400年间释放出的地震活动能量占福建地区(含近邻)所释放地震活动能量的绝大部分。 分析结果认为: 牛山岛-兄弟屿断裂这条基本平行于长乐-诏安主干断裂东约50 km海中的断裂才是福建地区近几百年来地震活动主要区域, 也是福建地区现今和今后一段时间易发生地震的构造部位, 是控制东南沿海近海地震带的主要活动断裂。 相似文献