北部湾6．1、6．2级地震的烈度分布与发震构造

调查了北部湾６．１、６．２级地震的烈度分布，陆地最高达六度，六度区的长轴呈ＮＷ向。研究了海底地形、重力资料、断裂产状、震中空间分布以及震源机制解，结果表明，该地震序列是在南北向的区域应力场作用下产生的共轭剪切错动，ＮＷ向的涠洲－斜阳断裂为主要发震构造，一系列较小的余震则是ＮＥ向断裂活动引发的。     

大同盆地现今构造活动及地壳应力场特征

大量震源机制结果推断出大同分轩现代地壳应力场和主压应力方向为ＮＥ－ＮＥＥ，仰角变化不定，主张应力方向为ＮＷ－ＮＮＷ，仰角很小的结论。这与区域构造应力场ＮＥ－ＮＥＥ向挤压作用的结果相符，另据大同一阳高６．１级、５．８级地震的震源机制结果得出，大同一阳高地震的孕震应力场与华北区域应力场相一致，而不是受本地局部小区域应力场的控制的结论。     

大同─阳高2次地震前后震源应力场的变化过程

利用１９８９、１９９１年大同－阳高两次地震前后几年的地震记录资料，详细分析了其震源应力场的变化，结果表明，６．１级地震前震源应力场中两个主应力轴的方向曾发生逆转，主压应力袖逆转时间约１０个月，主张应力轴逆转时间为２个月。６．１级主震前４个月，两个主应力轴的方向、仰角都恢复到正常状态，且与华北区域应力场的特征某本一致，而１９９１年５．８级地震前却没有出现上述现象。说明大同－阳高２次地震是在同一震源应力场作用之下孕育、发展的，亦说明５．８级地震是６．１级地震的晚期强余震。指出山西地震带６级以上地震的孕育发生似是在华北区域应力场的作用之下完成的。     

台湾海峡的活动断裂与地震活动

根据地质、地貌、地球物理资料以及晚第四纪地层的分析对比，探讨了台湾海峡ＮＥ、ＮＷ向断裂的活动性及其与地震的关系。研究表明，以晚更新世晚期以来，上述断裂具有明显的活动性，海峡中５级以上地震大多发生在这些断裂附近或其交汇处。     

北部湾6．1、6．2级地震发震构造探讨

北部湾６．１、６．２级地震震源位于北部湾盆地的东部，构造上处于盆地内部ＮＥＥ向的次一级企西凸起与乌石断陷的交界地带，发震断裂主破裂是ＮＥＥ向的北部湾－珠江口外断裂，ＮＷ向的临高断裂可能也参加了活动。     

1996年3月19日新疆阿图什6.9级地震震源破坏特征的研究

通过对１９９６年３月１９日新疆阿图什６．９级地震余震分布特征的研究，分析了这次地震震源破裂过程，并结合柯坪断裂带的构造运动、区域应力场的分布特征以及１９７２年以来该带的另外３次６级地震的余震分布方向。探讨了柯坪断裂带附近地区不同构造部位震源破裂扩展方向与强震活动的迁移方向。结果表明，本次地震震源破坏为明显的单侧破裂；震源断错以逆断层为主，区内主要受ＮＷ向压应力。不同地段强震震源破裂扩展具有明显的区     

菏泽5.9级地震的发震构造及其前兆构造活动

在分析了地震地质、物探、卫片等新的资料的基础上，认为在菏泽地震区地下隐伏着一条北东向深大断裂带。地震区内的解元集－小留集断裂与北西向的成武－定陶断裂构成共轭破裂导致藻泽５．９级地震发生，北东向断裂是其主要的发震构造。由菏泽５．９级地震前沿发震断层的ＭＬ≥３．０级地震震中迁移、震源深度的变化及跨断层形变测量资料表明，发震断层在区域构造应力场的作用下逐步克服障碍，使断层贯通，与此同时在发震构造断层面上     

2012年2月16日河源M4.8级地震

通过地震序列特征分析初步判断认为,河源ML4.8级地震与库水位变化的对应关系不明显,短期内震中区发生更大地震的可能性很小。现场宏观调查结果显示,极震区Ⅵ度等震线长轴为北北西向,震源机制解所反映的震源应力场主压应力方向为北西西向,与区域构造应力场方向一致;地震的发震构造应为北北西向,但震中区附近并无此组断裂出露地表,因此河源ML4.8级地震的成因,仍然值得深入研究。     

岫岩—海城5.6级地震地震地质背景及其发震构造

讨论了１９９９年１１月２９日岫岩－海城５．６级地震的地震地质背景,并依据地震震中分布、等震线形态、地震与断裂的关系等分析了此次地震的发震构造。结果表明,官次地震仍然是海城地震区内的地震活动,其发震构造是ＮＷ向海城河断裂。     

台湾海峡南部7.3级地震的地质构造背景

在我国辽阔的渤海、黄海、东海和南海，只有渤海发生过７级以上地震，而面积狭小的台湾海峡却发生４次７－８级地震，数十次５－６．９级地震。是我国大陆近海地震活动强度最大，频度最高的地区。台湾海峡位于欧亚大陆板块和太平洋菲律宾海板块的结合地带，地壳运动强烈。海峡中北东、北西向断裂发育，第四纪以来，上述断裂均有强烈的活动。在这种地质构造背景下，发生了历史上一系列强烈地震和这次７．３级地震。     

APPARENT STRESS VARIATION CHARACTERISTICS BEFORE AND AFTER BADONG EARTHQUAKE IN THE THREE GORGES RESERVOIR AREA

The causes of earthquakes in the Three Gorges reservoir area are complex. In order to study the cause of earthquakes happening in the region, we calculated the source parameters of 394 M_L ≥ 2.0 earthquakes occurring in Three Gorges reservoir area based on waveform data observed by the regional seismic network of Hubei Province and Three Gorges, obtained the apparent stress spatial-temporal variation map of Three Gorges reservoir area, and analyzed apparent stress spatial-temporal variation characteristics before and after the main earthquakes in the Three Gorges reservoir area. The results show that:1)Before the Badong M_L5.5, Zigui M_L4.7 and Zigui M_L5.1 earthquake, high apparent stress of earthquakes with different magnitudes is concentrated in Xinhua-Shuitianba Fault and Gaoqiao Fault. The distribution of high value area shows the high degree of synergism before the earthquake and the scattering after the earthquake, which indicates that the area accumulated a high stress before the earthquake, and the fault was in a locked state; 2)In the study area, the apparent stress before and after the earthquake showed significant rise in the first and then decline, the earthquake occurred in the process of rising; 3)Apparent stress depth profiles show that apparent stress at different depths has a positive correlation with the size of magnitude of earthquake, and the phenomenon of "small magnitude and strong apparent stress" did not appear. The small earthquakes occurring after the major earthquakes in the study area belong to low strain release under the background of low stress release, and there are no new apparent stress anomaly concentration areas appearing, this indicates that the Badong-Gaoqiao Fault, Zhoujiashan-Niukou Fault and Zigui Xiannushan Fault have been effective in releasing after the Badong earthquake and Zigui earthquakes and the probability of destructive earthquake is small on these faults.     

新丰江水库诱发地震的构造条件

本文在地质考察的基础上,采用数学模拟方法,重演了本区的地震序列,论证了诱发地震的构造条件。指出,新丰江水库有两组发震构造,它们的活动强度和时间有所不同。诱发地震的发震构造与水库蓄水前构造地震的发震构造属于相同构造体系,唯发震部位更逼近水库。文章还指出,库基弹性变形引起的附加引张应变使部分地区的活动断裂更易于错动。水库荷载还使地震在剖面上有浅层和深层之分。它们的频度与水库水位有不同的相关性     

右江断裂带晚更新世活动的若干地质地貌证据及位移速率

右江断裂带地处桂西断块区,有记载以来沿带曾发生40～50级地震15次,属中强地震带。笔者在室内卫片、航片、大比例尺地形图解译和分析的基础上,经野外实地调查,获得了断裂带晚更新世活动的若干地质地貌证据,实测了断裂的左旋位移数据。文中介绍了有关证据,并根据年龄数据,计算了断裂中、晚更新世以来的水平和垂直位移速率。断裂带在平面上分3大段,即百色以西段、百色—思林段、思林—坛洛段,各大段又可进一步分为若干个小段。断裂断错了距今(328±025)×104a～(1016±079)×104a的阶地堆积物和残坡积物,控制着百色—田东晚第四纪盆地的发育,地貌上形成断层谷和槽地、断层崖和陡坎,横穿断裂的水系发生同步左旋位移,其活动性质以左旋走滑为主,兼有张性差异运动。晚更新世不同时段以来断裂的水平位移速率为147～198mm/a,中更新世以来的垂直位移速率为074～076mm/a,晚更新世以来为01～035mm/a。该断裂的位移速率明显低于其西的川滇断块内部断裂,更低于川滇断块周边断裂     

秦岭—大别东段应力状态研究

本文首先通过Snoke发展的利用P波、 SV波和SH波的初动和振幅比方法计算秦岭—大别东段2008年以来83次M_L≥2.5地震的震源机制解, 然后通过FMSI方法反演得到平均应力场的方向特征: 近东西向的水平挤压和近南北向的水平拉张作用, 与参数统计结果一致; 进而通过震源机制的一致性参数分析应力场方向的变化信息。 分析表明震源机制解呈现了由变化紊乱、 偏离平均应力场到变化一致、 趋于平均应力场再到变化紊乱、 偏离平均应力场的变化过程, 在显著地震前, 研究区整体的震源机制一致性参数处于持续低值状态; 计算了2008年以来93次M_L≥2.5地震的视应力, 拟合视应力与震级的关系, 分析扣除震级影响的差视应力随时间变化特征, 近似反映研究区应力大小的变化。 分析表明显著地震前研究区的差视应力值呈现出明显的先上升后下降的变化过程, 在下降过程中发生地震; 最后利用震源机制一致性参数和差视应力综合分析研究区的应力状态, 均表明显著地震前震源区的构造应力场增强。 目前研究区的震源机制一致性参数较高、 差视应力较低, 研究区的应力水平较低。     

天山地震带主要活动断层现今的滑动速率及其地震矩亏损

文中收集了1999—2015年天山地震带及其周边地区的GNSS数据,计算得到了速度场结果,并利用弹性块体模型计算了研究区域内各块体的闭锁深度和主要断层的滑动速率。研究结果表明:南天山断裂带西段的迈丹断裂的缩短速率处于高值状态,达(-6.3±1.9) mm/a,高于南天山东段;北天山断裂带西段的缩短速率同样高于东段。利用主要断裂带的滑动速率计算出各地震带的地震矩积累变化及1900年以来的地震矩释放变化量,以分析地震矩亏损分布,结果显示北天山山前断裂、迈丹断裂、额尔齐斯断裂带北段和喀什河断裂西段存在较大的地震矩亏损,具有孕育7级以上地震的潜能,而北轮台断裂、柯坪断裂带中段则呈现地震矩盈余状态,在未来的一段时间内不具备发生强震的可能。     

Faulting Processes of Historic (1917–1962) M = 6.0 Earthquakes Along the North-central Caribbean Margin

—The plate boundary along the north-central Caribbean margin is geologically complex. Our understanding of this complexity is hampered by the fact that plate motions are relatively slow (1 to 2 cm/yr), so that recent seismicity often does not provide a complete picture of tectonic deformation. Studies of the faulting processes of instrumentally recorded earthquakes occurring prior to 1962 thus provide important information regarding the nature and rate of seismic deformation within the region, and are essential for a comprehensive assessment of seismic hazard. We have conducted body waveform modeling studies of eight earthquakes which occurred along the north-central Caribbean plate margin, extending from southeastern Cuba to the Swan Island fracture zone (75 to 83°W). None of these earthquakes has been previously studied and several occurred in regions where no recent (post-1962) seismicity has been recorded. The plate margin in the western portion of our study area is characterized by a transform fault-spreading center system. In the central and eastern portions of our study area the plate margin is a complex, diffuse region of deformation that couples transform motion in the Cayman trough to subduction along the Lesser Antilles arc. Our results show that the western portion of the study area has only experienced large strike-slip earthquakes. Off southeastern Cuba two earthquakes appear to have occurred on high angle, northward dipping, reverse faults with south to southeastward directed slip vectors. An earthquake in northern Jamaica in 1957 shows pure strike-slip faulting, most likely along an east-west trending fault. Finally, an unusual sequence of events located in the Pedro Bank region ~70 km southwest of Jamaica has a mainshock with a reverse-oblique mechanism, suggesting continuity of the plate interface stress field well south of the northern Caribbean margin.     

汶川8.0级地震环境剪应力特征研究

基于甘肃强震固定台和流动观测记录的汶川8.0级地震主震及余震加速度资料,选用三分向记录均完整的87次地震(震级范围为3.0~8.0级),根据用位错理论二维断裂模式推导的震源峰值加速度与环境剪应力关系式计算汶川地震序列的环境剪应力值,探讨其环境剪应力场特征。结果表明,环境剪应力和矩震级有较好的相关性,3~5级地震对应的应力值多在3~6 MPa,5~6级多在6~9 MPa,6~7级多在9MPa以上,且环境剪应力对震源深度也有较强的依赖性。     

华北4次中、强地震前震源区及其附近应力场的变化

使用小震机制解资料 ,分析了 1975年海城 7 3级和 1976年唐山 7 8级强震及 1983年菏泽 5 9级和 1995年苍山 5 2级中强震前 ,震源区及其周围不同构造部位应力场的时、空变化 ,证实震前震源区附近应力场曾有某些异常改变 ,如唐山强震前震源区周围出现长达 4a多的小震机制解主应力轴一致性取向的现象 ,菏泽地震前小震机制解P轴“集中—转向” ,苍山地震前P轴偏转且一致性增强。同时还发现 ,唐山地震前应力场异常变化开始时间可能早于 1972年 ;震源区内的陡河台与源外区的昌黎台小震综合机制解反映出震前的受力差异 ;震源断层附近不同应力区内震源机制解和地震活动有时空动态差异。这些现象一定程度上提供了不同构造条件和应力背景下 ,中、强震前震源区不同构造部位力学状态的改变或地震孕育过程的信息 ,对研究不同地震的孕震过程及差异有一定意义。     

DETAILED TEMPORAL-SPATIAL DISTRIBUTION OF INDUCED EARTHQUAKES BY WATER INJECTION IN RONGCHANG,CHONGQING

Based on the seismic data collected from regional permanent stations and 6 temporal stations, we analyzed the seismic activity from October 2008 to July 2011 in Rongchang area. On the basis of HypoDD relocated results, we used Match&Locate method to detect and located the micro-earthquakes. We obtained the focal mechanism solutions of some earthquakes with M_L ≥ 3.5 by using CAP method. Then we analyzed the temporal-spatial distribution of earthquakes and discussed the characteristics of micro-seismicity before the M_L5.1 earthquake occurring on September 10, 2010. We totally detected 3 354 micro-earthquake events, which are nearly 5 times of the earthquakes in the seismic catalog issued by China Earthquake Networks Center. The magnitude of the detected events is mostly from M_L-1 to 1, and the focal depth is from 2 to 4km. The magnitude-frequency analysis shows that the catalog completeness is obviously improved after adding the detected earthquakes, with the lowest magnitude decreasing from M_L1.0 to 0.3. The earthquakes hypocenters are mainly clustered along faults or buried faults and in a dominant depth range consistent with the depth of injection wells, and also show a tendency of lateral extension from injection wells. The focal mechanism solutions of 9 earthquakes of M_L ≥ 3.5 presented reverse faulting, as the same as the preexisting faults, indicating that earthquakes were surely related to reactivation of the faults. The strike, dip and rate of the causative faults separated in wide ranges, which indicates not only obvious changes in structure and strike of preexisting faults but also the effect of increasing pore pressure on the local stress field. Before the M_L5.1 earthquake on September 10 of 2010, seismicity firstly showed clustering in time and covered the most part of the seismogenic fault in space. Then an obvious seismic quiescence occurred and lasted about 3 months. The phenomenon is consistent with the mechanism of creep sliding and resistance-uniformization along the fault zone, suggested on the basis of laboratory experiments, and it may be one of patterns of sub-instability along fault zone. However, such explanation needs to be further confirmed.     

Characteristics of the seismic source stress field in the joint region of Xianshuihe, Longmenshan and An(ninghe faults

IntroductionSichuan region is one of the extruded and connected parts between the Qinghai-Xizang (Tibet) Plateau and Yangtze block. And the joint region of Xianshuihe, Longmenshan and An(ninghe faults reflects the structure characteristics formed by the Qinghai-Xizang Plateau(s extruding to Yangtze block and the Sichuan basin evolutionary process as fore-land basin. The researches on seismic activity in Sichuan region were mainly around Xianshuihe, Longmenshan and An(ninghe faults separ…