粘滑失稳及其物理场时空分布的实验研究

摩擦滑动的物理场实验研究表明：（１）能量空间分布的差异是失稳的重要条件，单发型大事件常发生于高能量向低能量的突变带或高能量背景区内的相对低能量区；（２）单发型大事件的孕育过程常常经历若干个能量输入输出循环，产生多个前兆阶段，并在失稳前源区常有一个弱化过程。小震或群发型事件失稳前常常只有一个能量积累与强化的过程，失稳前兆阶段性反映较差；（３）粘滑失稳时断层的位错与声发射的大小未见明显关系     

拐折断层黏滑过程的实验研究

采用位移、应变和声发射等测量手段,研究了预置5°拐折断层的房山花岗岩样品的黏滑过程,分析了不同加载速率下5°拐折断层失稳的黏滑特征及相关物理场的演化过程。实验结果表明: 1)5°拐折断层的黏滑周期与加载速率在数值上呈负对数相关关系; 2)在不同的加载速率下,大多数的5°拐折断层失稳是双震事件, 2次子事件的间隔时间大多在100～200ms之间; 3)采用不同的观测手段,即使采样速率一致,其临震响应也存在差异性,如断层失稳前沿断层的应变测量结果呈现明显的应变弱化,断层位移则未见明显的变化; 4)断层黏滑过程中的声发射事件呈现明显的沿断层迁移的特征。认识强震的发生机理和余震特征需要进一步研究断层失稳过程的动力学信息。     

区域加载过程与发震断层变形演化的实验研究

使用双剪粘滑模型模拟自发地震和诱发地震的区域加载过程,利用应变观测系统多点连续观测发震断层附近的局部应变变化。在应力与应变空间上描述了地震过程的区域应力路径和局部应变路径。结果表明,局部应变路径与应力宏观路径的形态差异较大,但两者的转换阶段对应,存在一定映射关系。断层局部变形路径的走向标明了断层所处在的变形阶段。自发地震的应变路径可以划分为3个部分:应变积累阶段、剪应变的线性偏离阶段和失稳滑动阶段。诱发地震的应变路径包括4个阶段:正斜率的应变积累阶段、负斜率的稳态滑动阶段、亚稳态应变僵持阶段、扰动失稳滑动阶段。自发地震与诱发地震有各自的路径模式,可以从应变路径上判别断层稳定性与可能的地震类型。     

阶区对走滑型地震地表破裂带传播与终止行为的影响

系统收集了国内外28个走滑地震破裂带上阶区与地震破裂行迹的资料,利用数理统计的方法分析了阶区的类型、尺度与地震破裂的关系。结果表明,不同震级档的走滑地震阶区限制破裂传播的止裂尺度是不同的,震级MS为6.5~6.9,阶区的最小止裂宽度约为3km;震级MS为7.0~7.5,阶区的最小止裂宽度约为4km;震级MS为7.5~8.0,阶区的最小止裂宽度约为6km;震级MS为8.0~8.5,阶区的最小止裂宽度约为8km;且拉分阶区比挤压阶区更容易被破裂所贯通。上述给出的阶区的最小止裂宽度可作为判定地震破裂止裂尺度的重要标志,是进行破裂分段的前提和基础,对地震危险性分析具有重大的实用价值。     

失稳前断层加速协同化的实验室证据和地震实例

地震是断层的快速错动,它有2个主要条件:一是断层协同化程度较高,一旦应力条件达到,能够迅速连接造成较长断层段的快速错动;二是断层上一些部位积累了足够高的应变,能够克服局部高强部位的错动阻力。地震短临前兆和必震信息识别是地震预报研究的焦点问题之一,为此开展了实验室平直断层失稳模拟研究。从应力变化曲线上可以判定标本所处的应力状态和识别亚失稳应力阶段。利用在实验室便于对压机信息和场上物理量的观测信息进行对比的优势,捕捉和比较应力偏离线性阶段和亚失稳阶段平行断层应变的时空演化过程中的差别。研究表明,由于断层上不同部位相互作用,断层各部位由独立活动逐渐转变为协同化活动,而断层活动协同化程度是判定断层所处应力状态的一个标志。断层活动协同化过程一般包括应变释放点产生、释放点的扩展和增多以及释放段之间相互连接3个阶段:第1阶段发生在偏离线性阶段,断层上不同部位的应变变化开始分化,出现孤立的应变释放区和积累区;第2阶段应变释放区的平稳扩展与亚失稳前期准静态失稳有关,断层上孤立应变释放区增多,并出现稳态扩展;第3阶段相当于亚失稳的后期,即准动态失稳阶段,断层上的应变释放区加速扩展,积累区应变水平加速提高。加速协同化开始于由准静态扩展向准动态扩展的转化,加速的机制是断层段间出现强相互作用。转化的本质在于扩展机制发生了变化,即由孤立断层段的扩展转变为断层段间在相互作用下的连接,这时断层进入发生地震的临界状态。根据实验结果,结合海原断裂带西侧的老虎山-毛毛山断裂地震活动的时空演化,分析了2000年6月6日ML6.2地震前该断层的协同化过程。     

红河断裂热红外高温条带的成因及其与地震活动性关系的探讨

针对2003年发生在云南大姚的两次6级以上地震,利用1999年、2003年和2004年的NOAA卫星资料,对川滇地区（22deg;～33deg;N,97deg;～107deg;E）的热红外影像进行了对比分析解译,对红河断裂高温条带的亮温年变特征作了分段和分区统计分析. 结果表明,红河断裂高温条带的成因与水系和地形等地表环境因素有关,是由下垫面热辐射差异造成的红外影像特征. 但在地震年份,高温条带内的亮温年均值明显高于非地震年份,这说明地震年份断裂的热活动性增强,能够引起高温年变异常. 利用卫星热红外遥感资料,通过监测不同年份之间高温条带的相对活动水平, 可以对这种地震前的断裂热活动性进行监测和异常判断.     

亚失稳准动态及同震过程变形场时空演化特征 ——实验与分析

断层亚失稳模型指出,在临震亚失稳阶段中各种物理量存在规律性的时空演化特征,控制这些物理参数变化的根本原因是震源的力学过程.为深入观测和分析该过程,文中介绍了一套自主研发的64通道、16位分辨率、4MHz采样频率、可并行连续采集的超动态变形场观测系统(Ultra-HiDAM),首次实现了在4MHz频率下对应变信号和声发射...     

识别断层活动和失稳的热场标志——实验室的证据

利用一套双向伺服系统对含压性和张性雁列断层的标本进行变形实验,实验中应用红外热像仪和接触式测温仪同步记录岩石变形过程中热红外辐射的亮度温度场和温度场的变化;使用数字CCD相机同步采集标本表面的数字图像,并利用数字散斑方法对采集到的图像进行分析得到位移场和应变场的演化过程。实验结果表明:1)在断层贯通前压性雁列岩桥区温度最高,而张性雁列岩桥区温度最低;数字散斑结果显示压性岩桥区平均应变最高,而张性岩桥区平均应变最低。温度场对两类雁列断层在岩桥区相反的受力状态有清晰的响应,可以为判断断层应力状态提供标志。2)雁列断层经历了从岩桥区应力积累、破坏到断层失稳错动两个变形阶段,升温机制也由应变升温变为摩擦升温;伴随升温机制的转变,在岩桥区观测到断层失稳错动前的破坏降温、温度快速起伏以及升温脉冲等现象,是观测失稳前兆的最佳部位。3)在雁列岩桥区裂纹端点附近观测到升温脉冲,表现为温度快升快降,随后即出现断层带的快速升温。升温脉冲现象可能与裂纹端部的应力奇异集中和破裂扩展引起的应力释放有关。裂纹端部的扩展是断层失稳错动的条件,随后断层带的升温正是断层失稳错动造成的。断层带开始升温发生在失稳前2～3s内,岩桥区的降温发生在失稳     

张北地震与大气增温异常

通过对大气总温度资料的分析,认为１９９８年１月１０日张北地震前几天,震区及其周围的增温异常是一种临震前兆。异常的空间由显示,震中区及其附近为强异常区,并且被弱异常区所包围;该次地震可能是ＮＷ向的张家口－北京－蓬莱断裂带向西扩展活动所致,同时也与尚义－多伦等ＮＥ向断裂的活动有关。总温度等值线的系列演变图概略的反映出了应变能的积聚－扩展－释放的全过程。     

STUDY ON THE SEISMOGENIC FAULT AND DYNAMICS PARAME-TERS OF THE 2014 MS6.6 JINGGU EARTHQUAKE IN YUNNAN

On October 17, 2014, a M_S6.6 earthquake occurred in Jinggu, Yunnan. The epicenter was located in the western branch of Wuliang Mountain, the northwest extension line of Puwen Fault. There are 2 faults in the surrounding area, one is a sinistral strike-slip and the other is the dextral. Two faults have mutual intersection with conjugate joints property to form a checkerboard faulting structure. The structure of the area of the focal region is complex. The present-day tectonic movement is strong, and the aftershock distribution indicates the faulting surface trending NNW. There is no obvious surface rupture related to the known fault in the epicenter, and there is a certain distance from the surface of the Puwen fault zone. Regional seismic activity is strong. In 1941, there were two over magnitude 7.0 earthquakes in the south of the epicenter of Jinggu County and Mengzhe Town. In 1988, two mainshock-aftershock type earthquakes occurred in Canglan-Gengma Counties, the principal stress axes of the whole seismic area is in the direction of NNE. Geological method can be adopted to clarify the distribution of surficial fracture caused by active faults, and high-precision seismic positioning and spatial distribution characteristics of seismic sequences can contribute to understand deep seismogenic faults and geometric features. Thus, we can better analyze the three-dimensional spatial distribution characteristics of seismotectonics and the deep and shallow tectonic relationship. The focal mechanism reveals the property and faulting process to a certain extent, which can help us understand not only the active property of faults, but also the important basis for deep tectonic stress and seismogenic mechanism. In order to study the fault characteristic of the Jinggu earthquake, the stress field characteristics of the source area and the geometric parameters of the fault plane, this paper firstly uses the 15 days aftershock data of the Jingsuo M_S6.6 earthquake, to precisely locate the main shock and aftershock sequences using double-difference location method. The results show that the aftershock sequences have clustering characteristics along the NW direction, with a depth mainly of 5~15km. Based on the precise location, calculations are made to the focal mechanisms of a total of 46 earthquakes including the main shock and aftershocks with M_L ≥ 3.0 of the Jinggu earthquake. The double-couple(DC)component of the focal mechanism of the main shock shows that nodal plane Ⅰ:The strike is 239°, the dip 81°, and the rake -22°; nodal plane Ⅱ, the strike is 333°, the dip 68°, and the rake -170.31°. According to focal mechanism solutions, there are 42 earthquakes with a focal mechanism of strike-slip type, accounting for 91.3%. According to the distribution of the aftershock sequence, it can be inferred that the nodal plane Ⅱ is the seismogenic fault. The obtained focal mechanism is used to invert the stress field in the source region. The distribution of horizontal maximum principal stress orienation is concentrated. The main features of the regional tectonic stress field are under the NNE-SSW compression(P axis)and the NW-SE extension(T axis)and are also affected by NNW direction stress fields in the central region of Yunnan, which indicates that Jinggu earthquake fault, like Gengma earthquake, is a new NW-trending fault which is under domination of large-scale tectonic stress and effected by local tectonic stress environment. In order to define more accurately the occurrence of the fault plane of the Jinggu earthquake, with the precise location results and the stress field in the source region, the global optimal solution of the fault plane parameters and its error are obtained by using both global searching simulated annealing algorithm and local searching Gauss-Newton method. Since the parameters of the fault plane fitting process use the stress parameters obtained by the focal mechanism inversion, the data obtained by the fault plane fitting is more representative of the rupture plane, that is, the strike 332.75°, the dip 89.53°, and the rake -167.12°. The buried depth of the rupture plane is 2.746km, indicating that the source fault has not cut through the surface. Based on the stress field characteristics and the inversion results of the fault plane, it is preliminarily believed that the seismogenic structure of the Jinggu earthquake is a newly generated nearly vertical right-lateral strike-slip fault with normal component. The rupture plane length is about 17.2km, which does not extend to the Puwen fault zone. Jinggu earthquake occurred in Simao-Puer seismic region in the south of Sichuan-Yunnan plate. Its focal mechanism solution is similar to that of the three sub-events of the Gengma earthquake in November 1988. The seismogenic structure of both of them is NW-trending and the principal stress is NE-SW. The rupture plane of the Jinggu main shock(NW direction)is significantly different from the known near NS direction Lancang Fault and the near NE direction Jinggu Fault in the study area. It is preliminarily inferred that the seismogenic structure of this earthquake has a neogenetic feature.     

延矾盆地北缘断裂深浅构造关系研究

在已有的地表地质构造、浅层探测与深部探测等资料基础上，利用高精度地震局域网的数字地震记录，分析了延庆矾山次级盆地北缘断裂上的微、小地震活动特征, 及其与地表活断层和深部地壳结构关系. 通过对地震局域网获得的微、小地震的精确位置、震源机制解及其特点的分析，厘定了地表活断层延庆矾山盆地北缘断裂属旋转平面状正断层，揭示了延怀盆地区浅表地质与深部构造的相互关系，以及地壳脆韧性变形随深度的转换特征.      

华东地区现代地壳应力场及地震断层错动性质

使用143组中、小地震单震震源机制解和17组小区域综合机制解资料,统计分析了华东地区的现代构造应力场特征。华东地区现今处在NEE向(80°左右)主压、NNW向(350°左右)主张应力场的控制下;主应力作用方式以水平和近水平为主。在应力场方向和作用方式基本一致的背景上,不同地震构造分区存在一些差异,这些差异可能与相应区域主要活动断裂的主体分布方向有关,可能表征了现存构造对地震错动特征的影响和控制作用。现代中、小地震震源机制解,历史中、强地震和现代有感地震最内等震线长轴方向等资料显示华东地区地震主要沿NE,NW2个方向破裂错动,兼有NNE,NEE,NWW或近EW方向。以走滑和近走滑方式为主,兼有少量斜向滑动。地震断层的错动方式存在某些分区差异。华东地区历史中、强地震以NE向破裂错动为主,而现代中强地震在陆域以NW-SE为主,海域NE,NW兼有     

STUDY ON DYNAMIC CHANGE OF GRAVITY FIELD IN XIANSHUIHE FAULT ZONE AND THEIR RELATION TO THE OCCURRENCE OF MS ≥ 5.0 EARTHQUAKES

Xianshuihe Fault, a main strong earthquake activity belt in southwest China, begins from Ganzi in the northwest, passes through Luhuo, Daofu, and Kangding, and then extents along the Dadu River valley. The fault is divided into two parts at Shimian, one part turns to south and converses to Anninghe Fault extending further to south, the other part, continuing to extend to southeast, cutting through Xiaoxiangling and then changing to Daliangshan Faults in the north of the Yuexi Basin, has the length of about 400km. Since 1700AD, there have happened 22 earthquakes larger than magnitude 6.0 and 8 earthquakes larger than magnitude 7.0. In this paper, we systematically collated and computed the gravity repetition measurement data along the Xianshuihe fault zone since 1988, and by referring to the anomaly index of gravity field of the predecessor achievements, analyzed the spatial-temporal variation of the regional gravity field and the relation to the occurrence of ≥ M_S5.0 earthquakes. The mechanism of the regional gravity changes is further studied, and also the implication of strong earthquake risk because of the dynamic variation of gravity field in the near future is discussed.The results show that:1)The mobile gravity observation has the ability to detect crustal activity and M_S ≥ 5.0 earthquake events. 2)There is definite correspondence between interannual gravitational field change and the 8 earthquakes among the 13 M_S ≥ 5.0 earthquakes occurring in the surveying area since 1988, which can be determined according to the change of interannual gravitational field. Three M ≥ 6.0 earthquakes occurred 3~4 years after the abnormal image was developed, 4 earthquakes that occurred in the region of no data available were not determined. 3)A significant feature of the spatial-temporal variation of the regional gravity is a north-south run-through image before 2004, and characterized by the alternatively positive or negative variation in different year, the earthquakes of M_S ≥ 5.0 occurring in this period were not distributed along the fault. Gravity variation magnitude indicates that there were two similar crustal material movement waves before 2004, corresponding to the course of earthquake space-time distribution from strong to weak in the study area. After 2010, the variation image shows that the local positive and negative zones are concurrent within a year, different from the image before 2004, and earthquakes of M_S ≥ 5.0 basically occurred on the fault. It is believed that the variation of gravity field since 1988 and the seismic distribution fit with the geodynamic mode of strong and weak stages of the northeast motion of Indian plate. According to the conclusion we can try to optimize gravity anomaly index. After the Kangding earthquake in 2014, the north segment of Moxi Fault was still subject to negative high value changes till 2017 and then the gravity variation was further developed to a four quadrant distribution image. Based on the analysis of this paper and the previous variation trend of gravity field, we believe that the north segment of Moxi Fault has the background of medium-long term, strong or large earthquake risk.     

2013年1月29日中哈交界Ms6．1地震震源机制解与发震断层研究

针对2013年1月29日发生在中哈交界Ms6．1地震,基于新疆数字台网中心宽频带波形记录,采用CAP方法反演了其震源机制解。结果显示：该次地震震源深度为27km,其中一个节面走向161°,倾角76°,滑动角-164°,与哈佛大学计算结果一致;结合余震空间分布和GPS观测结果,判定该节面为破裂面,同时推断该处有一发震断层,其走向NWW、倾角较大、断错性质为右旋走滑型。     

天水地区地壳结构热分布与热应力特征初步研究

地壳内热活动及其产生的热应力作用是地震孕育发生的重要因素之一. 不同特征的地壳结构对热分布及其热应力有特殊的影响. 在含有莫霍面局部上隆、中下地壳的深大断裂、中地壳低速高导体和中上地壳断裂的典型孕震地壳结构模型中,深部热扰动作用下产生的热应力作用会明显上移至中上地壳,对上层脆性地壳的破裂——强地震的发生有直接影响. 这一结果对理解深部热流体在地震孕育和发生过程中的作用,以及浅层流体前兆的产生机理具有指导意义.      

地震前兆含义,科学问题与研究途径的研讨

地震前兆的研究已经取得了很大的进展,地震前兆的复杂性引起了广泛的关注,对地震预报、有关科学问题和探索途径的研究现状及其前景有各种评价。文章认为由于一些科学问题没有解决,尽管对中缅边境１９９５年７月连７．３级地震作出了成功预报,经验性预报有一定的局限性,文中讨论了广义地震前兆和狭义地震前兆,广义地震前兆包含二类前兆：场兆和源兆;而狭义前兆仅指后者。大陆震例前兆的系统研究证实了广义地震前兆的存在,然而     

EXPERIMENT STUDY ON ACOUSTIC EMISSION,MICROSEISM AND CHARGE INDUCTION DURING FRACTURE PROCESS OF GRANITE WITH FAULT ZONE UNDER UNIAXIAL COMPRESSION

As the rock samples will produce abnormal signals of acoustic emission, microseismic and charge signals under external loading, the waveform comprehensive monitoring devices are used to synchronously monitor acoustic emission, microseismic and charge signals during the deformation and failure process of granite with fault zone under uniaxial compression. The results show that, the granite with fault zone has obvious synchronous precursory signals of acoustic emission, microseism and charge induction in the elastic deformation stage, and has high amplitude synchronous precursory signals in the instability destruction stage. The influence of fault zone on granite samples strength is remarkable, and the uniaxial compressive strength of samples with the fault zone is greatly reduced. With the angle of the fault zone decreasing, the uniaxial compressive strength of the specimens is reduced, the samples are more liable to instability and the energy of instability destruction is greater. With the fault zone angle of granite samples decreasing, the acoustic emission, microseismic and charge induction signals increase in the deformation and failure process of samples. The samples stress decreases when the acoustic emission, microseismic and charge induction precursory signals appear synchronously. The duration of acoustic emission, microseismic and charge induction precursory signals is increasing in the instability destruction stage. When the angle of the fault zone reaches 30°, the mutability of acoustic emission, microseismic and charge induction signal increases, the time to enter the dangerous stage is much earlier, and the acoustic emission events of large magnitude increase significantly, and the large angle faults of coal mine are more dangerous. The intensive and high amplitude synchronous precursory signals of acoustic emission, microseism and charge induction are produced before the instability destruction, and the signals duration is shorter. The intensive and strongest synchronous precursory signals of acoustic emission, microseism and charge induction are produced in the instability destruction, and the signals duration is longer. Acoustic emission monitoring data can better reflect the micro rupture of rock. And combined with the acoustic emission, microseismic and charge induction precursory signals, the precursory information of rock instability destruction can be obtained more accurately.     

低速体与深浅断裂共同孕震过程的数值模拟初步研究

利用含劈节点黏弹性三维有限单元计算方法 ,对由地球物理探测结果提出的华北地区强震孕育物理模型进行了数值模拟分析 ,进而 ,在利用GPS资料反演计算首都圈地区断裂活动性的基础上 ,对首都圈三维区域应力场和能量的演化进行了模拟计算 ,并提出了强震危险区和震级上限预测意见     

龙滩库区水库地震震源机制及应力场特征

文中使用龙滩水库地震监测台网记录的波形数据,采用P波初动、SH波和P渡位移振幅比数据计算震源机制解的FOCMEC方法,获取了龙滩库区2006年9月蓄水至2008年底发生的73次M_L2.0以上地震的震源机制解,并在此基础上反演了库区应力场。龙滩库区2006年10月蓄水以来发生的2级以上地震以逆断层型为主,由震源机制解获得的2个地震丛集区应力场的主压应力都近于水平,取向都为NWW-SEE。反映出蓄水后库区仍为以水平NWW-SEE向压应力为主的应力场结构,且最大主压应力倾角更为水平。而最大主张应力及中等应力轴的分布则不一致,显示出在近水平的主压应力背景下,龙滩库区局部应力场的非一致性。通过对龙滩水库地震机制解特征及应力场的认识和讨论,初步提出了龙滩水库诱发地震的发震机理,认为载荷作用所引起的剪应力增大不是龙滩水库蓄水诱发地震的主要因素,而蓄水所产生的孔隙压力作用和库水渗透的润滑弱化作用的耦合作用可能是主要的成因     

青海省河南M_S5.1和玛沁M_S5.0地震后库玛断裂带的地震活动趋势研究

根据地震活动特征、大武地震台尾波持续时间及长宁、湟源和西宁 3个台水氡异常变化 ,讨论了 1 999年河南MS5 .1和玛沁MS5 .0地震发生后库玛断裂带的地震活动趋势 .结果表明 ,河南—玛沁地区的中强地震活动与库玛断裂带上的强震活动有明显的对应关系 ;在库玛断裂带中东段存在一个由ML ≥ 3.0地震围成的空区 ;上述2次地震发生后大武地震台尾波持续时间异常依然存在 ,长宁、湟源和西宁台水氡趋势异常仍然持续 .据此认为库玛断裂带存在发生强震的背景