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利用P波初动和直达P、S波最大速度振幅比联合求解小震震源机制的方法求出珊溪水库ML2.0以上地震的震源机制,得到了珊溪水库震源机制各参数时空特征如下:主压应力为SN向,主张应力为EW向,应力主要为水平应力,发震断层倾角较大且多为走滑断层。在个别4级左右地震前P轴方位都有偏离再恢复的现象。在北纬27.65°～27.69°间,P轴方位集中在0°±30°或者180°±30°,节面走向集中在45°±15°或者135°±15°。震源深度大于4km的地震倾角多集中在70°～90°度之间。 相似文献
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本文讨论了利用国际部署加速度仪台网(IDA)的超长周期瑞雷波记录,反演震源参数的有关理论和方法.对于震源深度大于30km的地震,地震矩张量的五个元素都可以测定;对于浅源(h≤30km)地震,其中两个元素变为无解.本文以1984年5月21日南黄海浅源地震为例,研究了在浅震难题的情况下,如何更多地提取震源信息的问题,测定了主震的断层机制为:走向北35°西,倾角52°,滑动方向54°,地震矩为1.2×10~(18)N·m,压应力主轴方向为北74.4°东,是一个走向北北西的左旋逆断层.本文还阐述了分布源模型问题。结果表明,采用分布源与采用点源模型对南黄海这种中强地震反演结果的影响不大.分析了震源有限性问题,提出了进行修正的一种明确表达式. 相似文献
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利用CAP方法反演了2010年6月5日阳曲MS4.6地震震源机制解,得到震级MW为4.5,节面I走向213°、倾角47°、滑动角-161°,节面II走向109°,倾角76°,滑动角-44°,属于倾滑型;精确定位显示震中处于石岭关隆起区,CAP反演和精定位结果推断本次地震的震源深度为17～20km。震源机制解节面参数与震中附近的山根底断裂和系舟山西麓断裂产状存在差异,这两条断裂不是阳曲地震的发震断裂,由于现场野外地质考察未发现地表断裂,不排除本次地震为隐伏断层活动的结果。 相似文献
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本文用多种数字地震学方法研究了2012年7月20日江苏高邮Ms4.9级地震的震源机制解和震源深度.首先用CAP方法反演了江苏高邮Ms4.9级地震的震源机制解和震源深度,最佳解节面Ⅰ走向角为109°,倾角85°,滑动角18°;节面Ⅱ走向角17°,倾角72°,滑动角175°;矩震级Mw为4.82;优势震源深度为10 km.为验证研究结果的可靠性,我们一方面用Snoke方法反演了高邮地震的震源机制解,反演结果与CAP方法反演的结果相差不大;另一方面,使用近震深度震相到时差的测量和对远震波形拟合的方法进一步研究震源深度,结果均表明江苏高邮Ms4.9级地震的震源深度在9～10 km左右,与CAP方法的结果一致.多种方法研究结果的一致性可以充分说明本文研究结果比较可靠.结合前人地质资料的研究成果和本文对高邮地震震源机制解的研究,我们认为滁河断裂很可能是江苏高邮Ms4.9级地震的发震构造. 相似文献
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利用湖北与重庆区域台网共9个台的宽频带数字地震记录,采用CAP法(Cut and Paste Method)反演了湖北巴东2013年12月16日MS5.1地震震源机制解,其最佳双力偶解为节面I：走向166°,倾角82°,滑动角41 °;节面Ⅱ：走向69°,倾角49°,滑动角169°;最佳震源深度主要集中分布在5.5 km附近。分析认为此次地震的发震断层为带有逆冲成分的走滑性质断层,主压应力P轴近EW向,主张应力轴近NS向。余震序列主要呈EW分布,少部分呈NS方向分布,较大余震的发震破裂滑动类型以正走滑型的居多,其次为逆倾滑型及逆走滑型。结合7次较大余震的机制解判断,近EW向节面为发震断层。 相似文献
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云南耿马7.2级地震破裂与震源应力场 总被引：2，自引：0，他引：2
1 98 8年 1 1月 6日在云南省澜沧县和耿马县境内先后发生了 7.6级和 7.2级强烈地震。其中 7.2级地震在震中区小黑江两岸灰岩裸露区出现了具有构造意义的地裂缝带。采用断层滑动矢量法反演出形成上述地裂缝带的应力张量为 :σ1走向 2 2 3°,倾角 2 8°;σ2 走向 42°,倾角6 2°;σ3 走向 1 3 3°,倾角 0°;应力比 R=0 .5 7,总体显示出走滑兼压性特征 ,基本代表了震源机制解所反映的震源应力场特征。断面滑动矢量解析可做为一种判定地裂缝是否是构造成因的方法 相似文献
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据中国地震台网测定 ,2 0 0 2年北京时间 3月 3 1日 1 4时 52分在我国台湾地区 ( 2 4.4°N,1 2 2 .1°E)发生 MS7.5地震。我们利用 CDSN的7个台站的数字波形资料初步反演了该地震的震源参数 ,结果如下 :最佳双力偶解节面 :走向 2 3 9°,倾角 49°,滑动角 91°;节面 :走向 58°,倾角 41°,滑动角 89°。应力轴T轴 :本征值 0 .92 ,方位 1 62°,仰角 86°;N轴 :本征值 -1 .1 1 ,方位 59°,仰角 1°;P轴 :本征值 -5.3 1 ,方位 3 2 9°,仰角 4°。标量地震矩 :M0 =2 .8× 1 0 2 0 N· m。矩震级 :MW=7.5图 1 震源机制的几何表示2002年3… 相似文献
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2008年5月12日四川汶川8.0级地震与部分余震的震源机制解 总被引：4，自引：0，他引：4
采用区域和远台Pn或Pg初至波初动符号,利用下半球等面积投影,求解了2008年5月12日四川汶川8.0级地震和截止到2008年12月10日发生的部分4级以上余震的震源机制解。汶川8.0级地震的震源机制为:节面Ⅰ的走向为5°,倾角为48°,滑动角为39°;节面Ⅱ的走向为247°,倾角为62°,滑动角为131°。P轴方位角为309°,仰角为8°,T轴方位角为208°,仰角为54°,B轴方位角为44°,仰角为35°。结合地质构造和余震空间分布,可以确定节面Ⅱ为发震断层面。根据震源机制解,引发本次地震的断层活动主要表现为逆冲,主破裂面为S67°W与该地震所在断层的走向基本一致(断裂总体走向N45°E)[1];主压应力轴P轴为N51°W,主压应力轴P轴方位与该区域构造应力场方向基本一致。根据余震震源机制解结果,龙门山断裂带南段发生的余震与北段发生的余震的震源机制都具有优势分布,且两者差异明显。早期发生在南段的余震的破裂是以逆倾滑动为主,兼有走向滑动;而随着时间的推移,余震向北段迁移,在龙门山构造的北段地震震源的破裂方式以走向滑动为主,兼有一定的逆倾滑动;龙门构造带南段震源应力场受主震应力场的控制,而龙门构造带北段震源应力场不仅受区域应力场的影响,还受主震应力场的影响。 相似文献
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汶川8.0级地震序列的小震震源机制及应力场特征 总被引：4，自引：1，他引：3
利用区域地震台网的数字地震波记录资料,由垂直向记录P和S振幅比值,结合部分清晰的P波初动记录资料,反演得到了2008年5月12日至2009年4月12日汶川8.0级地震序列中829个ML≥3.5的小震震源机制解。采用统计和力轴张量计算方法,分析了震源机制解参数并求取了余震区平均应力场。结果表明:用余震区北段小震震源机制解求得的节面为直立或倾斜,走向为NNE-SSW向,主压应力P轴方位为SWW-NEE方向,计算得到的平均应力张量σ1方向为77.1°;用余震区南段小震震源机制解求得的节面倾角较陡,在50°～90°之间,走向相对较分散,平均应力张量σ1方向为92.4°,呈EW向。从余震区南、北段的平均应力场方位随时间演化过程可以看出,余震区在2008年8月、9月、12月和2009年1月处于应力场调整阶段。最后研究了余震区南、北段的震源机制一致性参数θ及逆冲型地震类型随时间的变化,得到了一些有意义的结果。 相似文献
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通过分析昭苏6．1级地震序列特征、震源与介质破裂特性、震源环境与历史地震活动类比及区域地震和前兆资料的异常变化等，对该震前的区域地震活动背景、震后的震情趋势等有了较为细致的了解和判定。主要结果有：①在2003年新疆境内中强地震成组活动的背景下，于现代地震活动很弱的昭苏盆地内发生了6．1级地震；②6．1级地震为主一余型地震序列，震后序列衰减正常；③主震震源机制解结果与现代区域构造应力场特征吻合，表明构造活动具有明显的继承性，并对地震活动有着控制作用；④震源区域构造应力释放充分，区域应力场处于相对稳定的调整状态。综合各类分析结果后认为，震区发生更大地震的可能性很小。 相似文献
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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 相似文献
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利用双差定位法对2021年5月22日玛多MS7.4地震序列中1 434个地震进行重新定位,使用TDMT矩张量反演方法求解玛多地震序列M≥4.5地震的震源机制解,综合分析得到如下结论:(1)玛多地震序列震中整体走向为NWW-SEE向,与昆仑山口—江错断裂展布方向相吻合,序列总长度170 km,呈NWW向和SEE向双侧破裂,主震西北侧存在NW向条带,可能是此次地震的分支断裂活动,在南东侧存在余震稀疏段以及横穿玛多—甘德断裂的余震分布带,推测可能是地下速度结构差异所致;(2)主震附近地震序列以左旋走滑型地震为主,优势走向为NWW向,倾向NE,倾角较高,与昆仑山口—江错断裂性质基本一致,结合余震定位结果推断昆仑山口—江错断裂为本次地震的发震断层;(3)主震附近地震序列P轴平均方位角为237°,P轴,T轴平均倾角分别为15°、16°,N轴平均倾角为65°,结合研究区构造特征推断,本次地震是由NEE-SWW向水平挤压应力推动NWW-SEE向断裂发生左旋走滑错动所致。 相似文献
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《中国地震研究》2016,(2)
Earthquakes of M_S5. 6 and M_S6.1 occurred in Yingjiang,Yunnan on May 24 and May 30,2014 respectively. In this paper,we use the waveform data recorded by mobile seismic stations( KAC) which were set up in the source area after the Yingjiang MS5. 6earthquake on May 24,2014 to study the shear-wave splitting characteristics of Yingjiang M_S6.1 earthquake sequence with the SAM method. The result shows that predominant polarization of fast shear-waves before the M_S6.1 earthquake is consistent with the direction of regional principal compressive stress,and predominant polarization of fast shear-waves before the M_S6.1 earthquake show better consistency and smaller dispersion compared to after the M_S6.1 earthquake,and there may be a deflection for the fast shearwaves predominant polarization between the M_S6.1 earthquake sequence and foreshock sequence. We found that the time-delays generally exhibited a lower level before the M_S6.1earthquake and a relatively higher value after the M_S6.1 earthquake. 相似文献
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利用双差定位方法对2018年松原MS5.7地震序列中ML≥1.0地震重新定位，之后使用CAP方法求解松原MS5.7地震序列中强地震的震源机制解，再借助MSATSI软件包反演得到松原地区的区域应力场。综合分析以上研究结果得到如下结论:① 松原MS5.7地震序列发生在NW走向的第二松花江断裂与NE走向的扶余—肇东断裂交会处，将地震精定位结果沿两条断层走向作剖面分析，NW向剖面主轴长度约为5 km，震中分布均匀，NE向剖面主轴长度亦约为5 km，震中呈倾向NE的高倾角分布；② 该序列中的4次ML≥3.7地震的震源机制解具有良好的一致性:节面Ⅰ走向为NE向，节面Ⅱ走向为NW向，均为高倾角走滑断层。中强地震的震源机制节面解与第二松花江断裂性质基本一致，由此推断第二松花江断裂是本次松原地震的发震断层；③ 松原地区的主压应力方位角为N86°E，倾角为7°，主张应力方位角为N24°E，倾角为71°。松原地区的区域应力场既受到大尺度的板块构造运动的控制，又受到区域构造运动的影响。在太平洋板块对北东亚板块向西俯冲作用下，东北地区产生了近EW向的主压应力，受周边地质构造控制，松辽盆地内NE向断裂与NW向断裂交会处易发生走滑型地震，2018年松原MS5.7地震正是在这种构造作用控制下发生的中强地震。 相似文献
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FOCAL MECHANISM AND SEISMOGENIC STRUCTURE OF THE M5.0 YUEXI EARTHQUAKE ON 1 OCT. 2014, SOUTHWESTERN CHINA 
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下载免费PDF全文 The Oct.1,2014 M5.0 Yuexi earthquake occurred on the Daliang Shan fault zone where only several historical moderate earthquakes were recorded.Based on the waveform data from Sichuan regional seismic network,we calculated the focal mechanism solution and centroid depth of the M5.0 Yuexi earthquake by CAP (Cut and Paste) waveform inversion method,and preliminarily analyzed the seismogenic structure.We also calculated the apparent stress values of the M5.0 earthquake and other 14 ML≥4.0 events along the Shimian-Qiaojia fault segment of the eastern boundary of the Sichuan-Yunnan block.The result indicates that the parameters of the focal mechanism solution are with a strike of 256°,dip of 62°,and slip of 167° for the nodal plane Ⅰ,and strike of 352°,dip of 79°,and slip of 29° for the nodal plane Ⅱ.The azimuth of the P axis is 121° with dip angle of 11°,the azimuth of T axis is 217° with dip angle of 28°,and the centroid depth is about 11km,and moment magnitude is MW5.1.According to the focal mechanism solution and the fault geometry near the epicenter,we infer that the seismogenic fault is a branch fault,i.e.,the Puxiong Fault,along the central segment of the Daliang Shan fault zone.Thus,the nodal plane Ⅱ was interpreted as the coseismic rupture plane.The M5.0 Yuexi earthquake is a strike-slip faulting event with an oblique component.The above findings reveal the M5.0 Yuexi earthquake resulted from the left-lateral strike-slip faulting of the NNW Dalang Shan fault zone under the nearly horizontal principal compressive stress regime in an NWW-SEE direction.The apparent stress value of the Yuexi earthquake is 0.99MPa,higher than those of the ML ≥ 4.0 earthquakes along the eastern boundary of the Sichuan-Yunnan block since 2008 Wenchuan M8.0 earthquake,implying a relatively high stress level on the seismogenic area and greater potential for the moderate and strong earthquake occurrence.It may also reflect the current increasing stress level of the entire area along the eastern boundary,and therefore,posing the risk of strong earthquakes there. 相似文献
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STUDY ON SOURCE PARAMETERS OF THE 8 AUGUST 2017 M7.0 JIUZHAIGOU EARTHQUAKE AND ITS AFTERSHOCKS,NORTHERN SICHUAN 下载免费PDF全文
下载免费PDF全文 WU Wei-wei WEI Ya-ling LONG Feng LIANG Ming-jian CHEN Xue-fen SUN Wei ZHAO Jing 《地震地质》1979,42(2):492-512
On August 8, 2017, a strong earthquake of M7.0 occurred in Jiuzhaigou County, Aba Prefecture, northern Sichuan. The earthquake occurred on a branch fault at the southern end of the eastern section of the East Kunlun fault zone. In the northwest of the aftershock area is the Maqu-Maqin seismic gap, which is in a locking state under high stress. Destructive earthquakes are frequent along the southeast direction of the aftershocks area. In Songpan-Pingwu area, only 50~80km away from the Jiuzhaigou earthquake, two M7.2 earthquakes and one M6.7 earthquake occurred from August 16 to 23, 1976. Therefore, the Jiuzhaigou earthquake was an earthquake that occurred at the transition part between the historical earthquake fracture gap and the neotectonic active area. Compared with other M7.0 earthquakes, there are few moderate-strong aftershocks following this Jiuzhaigou earthquake, and the maximum magnitude of aftershocks is much smaller than the main shock. There is no surface rupture zone discovered corresponding to the M7.0 earthquake. In order to understand the feature of source structure and the tectonic environment of the source region, we calculate the parameters of the initial earthquake catalogue by Loc3D based on the digital waveform data recorded by Sichuan seismic network and seismic phase data collected by the China Earthquake Networks Center. Smaller events in the sequence are relocated using double-difference algorithm; source mechanism solutions and centroid depths of 29 earthquakes with ML≥3.4 are obtained by CAP method. Moreover, the source spectrum of 186 earthquakes with 2.0≤ML≤5.5 is restored and the spatial distribution of source stress drop along faults is obtained. According to the relocations and focal mechanism results, the Jiuzhaigou M7.0 earthquake is a high-angle left-lateral strike-slip event. The earthquake sequence mainly extends along the NW-SE direction, with the dominant focal depth of 4~18km. There are few shallow earthquakes and few earthquakes with depth greater than 20km. The relocation results show that the distribution of aftershocks is bounded by the M7.0 main shock, which shows obvious segmental characteristics in space, and the aftershock area is divided into NW segment and SE segment. The NW segment is about 16km long and 12km wide, with scattered and less earthquakes, the dominant focal depth is 4~12km, the source stress drop is large, and the type of focal mechanism is complicated. The SE segment is about 20km long and 8km wide, with concentrated earthquakes, the dominant depth is 4~12km, most moderate-strong earthquakes occurred in the depth between 11~14km. Aftershock activity extends eastward from the start point of the M7.0 main earthquake. The middle-late-stage aftershocks are released intensively on this segment, most of them are strike-slip earthquakes. The stress drop of the aftershock sequence gradually decreases with time. Principal stress axis distribution also shows segmentation characteristics. On the NW segment, the dominant azimuth of P axis is about 91.39°, the average elevation angle is about 20.80°, the dominant azimuth of T axis is NE-SW, and the average elevation angle is about 58.44°. On the SE segment, the dominant azimuth of P axis is about 103.66°, the average elevation angle is about 19.03°, the dominant azimuth of T axis is NNE-SSW, and the average elevation angle is about 15.44°. According to the fault profile inferred from the focal mechanism solution, the main controlling structure in the source area is in NW-SE direction, which may be a concealed fault or the north extension of Huya Fault. The northwest end of the fault is limited to the horsetail structure at the east end of the East Kunlun Fault, and the SE extension requires clear seismic geological evidence. The dip angle of the NW segment of the seismogenic fault is about 65°, which may be a reverse fault striking NNW and dipping NE. According to the basic characteristics of inverse fault ruptures, the rupture often extends short along the strike, the rupture length is often disproportionate to the magnitude of the earthquake, and it is not easy to form a rupture zone on the surface. The dip angle of the SE segment of the seismogenic fault is about 82°, which may be a strike-slip fault that strikes NW and dips SW. The fault plane solution shows significant change on the north and south sides of the main earthquake, and turns gradually from compressional thrust to strike-slip movement, with a certain degree of rotation. 相似文献
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通过地震分布及地震机制解所反映的日本海-鄂霍次克海俯冲带的形态及应力状态,研究了俯冲带深部形变及650km间断面的穿透问题.日本海Benioff带较直,连续性较好;鄂霍次克海Benioff带弯度稍大,220-320km深度之间地震很少.两俯冲带在浅部及深部地震密集,100-200km深度之间有双地震层.应力状态随深度变化,200km深度以下P,T轴方向相对集中,P轴接近俯冲方向,在约100-200km深度附近,P,T轴均接近俯冲方向.观测和理论地震图拟合分析表明,地震断层面走向接近俯冲带走向,断裂的结果使俯冲带在深部倾角变小. 相似文献