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1.
On July 20, 1995, an earthquake of M
L=4.1 occurred in Huailai basin, northwest of Beijing, with epicenter coordinates 40.326°N, 115.448°E and focal depth 5.5 km.
Following the main shock, seismicity sharply increased in the basin. This earthquake sequence was recorded by Sino-European
Cooperative Huailai Digital Seismograph Network (HDSN) and the hypocentres were precisely located. About 2 hours after the
occurrence of the main shock, a smaller event of M
L=2.0 took place at 40.323°N, 115.447°E with a focal depth of 5.0 km, which is very close to the main shock. Using the M
L=2.0 earthquake as an empirical Green’s function, a regularization method was applied to retrieve the far-field source-time
function (STF) of the main shock. Considering the records of HDSN are the type of velocity, to depress high frequency noise,
we removed instrument response from the records of the two events, then integrated them to get displacement seismogram before
applying the regularization method. From the 5 field stations, P phases in vertical direction which mostly are about 0.5 s
in length were used. The STFs obtained from each seismic phases are in good agreement, showing that the M
L=4.1 earthquake consisted of two events. STFs from each station demonstrate an obvious “seismic Doppler effect”. Assuming
the nodal plane striking 37° and dipping 40°, determined by using P wave first motion data and aftershock distribution, is
the fault plane, through a trial and error method, the following results were drawn: Both of the events lasted about 0.1 s,
the rupture length of the first one is 0.5 km, longer than the second one which is 0.3 km, and the rupture velocity of the
first event is 5.0 km/s, larger than that of the second one which is about 3.0 km/s; the second event took place 0.06 s later
than the first one; on the fault plane, the first event ruptured in the direction γ=140° measured clockwise from the strike
of the fault, while the second event ruptured at γ=80°, the initial point of the second one locates at γ=−100° and 0.52 km
from the beginning point of the first one. Using far-field ground displacement spectrum measurement method, the following
source parameters about the M
L=4.1 earthquake were also reached: the scalar earthquake moment is 3.3×1013 N·m, stress drop 4.6 MPa, rupture radius 0.16 km.
Contribution No. 99FE2022, Institute of Geophysics, China Seismological Bureau.
This study is supported by the Chinese Joint Seismological Science Foundation (95-07-411). 相似文献
2.
Based on digital teleseismic P-wave seismograms recorded by 28 long-period seismograph stations of the global seismic network,
source process of the November 14, 2001 western Kunlun Mountain M
S=8.1 (M
W=7.8) earthquake is estimated by a new inversion method. The result shows that the earthquake is a very complex rupture event.
The source rupture initiated at the hypocenter (35.95°N, 90.54°E, focal depth 10 km, by USGS NEIC), and propagated to the
west at first. Then, in several minutes to a hundred minutes and over a large spatial range, several rupture growth points
emerged in succession at the eastern end and in the central part of the finite fault. And then the source rupture propagated
from these rupture growth points successively and, finally, stopped in the area within 50 km to the east of the centroid position
(35.80°N, 92.91°E, focal depth 15 km, by Harvard CMT). The entire rupture lasted for 142 s, and the source process could be
roughly separated into three stages: The first stage started at the 0 s and ended at the 52 s, lasting for 52 s and releasing
approximately 24.4% of the total moment; The second stage started at the 55 s and ended at the 113 s, lasting for 58 s and
releasing approximately 56.5% of the total moment; The third stage started at the 122 s and ended at the 142 s, lasting for
20 s and releasing approximately 19.1% of the total moment. The length of the ruptured fault plane is about 490 km. The maximum
width of the ruptured fault plane is about 45 km. The rupture mainly occurred within 30 km in depth under the surface of the
Earth. The average static slip in the underground rocky crust is about 1.2 m with the maximum static slip 3.6 m. The average
static stress drop is about 5 MPa with the maximum static stress drop 18 MPa. The maximum static slip and the maximum stress
drop occurred in an area within 50 km to the east of the centroid position.
Foundation item: Joint Seismological Science Foundation of China (103066) and Foundation of the Seismic Pattern and Digital Seismic Data
Application Research Office of Institute of Earthquake Science of the China Earthquake Administration. 相似文献
3.
据中国地震台网测定,北京时间2015年4月15日15时39分,在内蒙古自治区阿拉善左旗（39.8°N,106.3°E）发生MS5.8地震,震源深度为10 km.地震发生后多家机构对其开展了研究,本文使用喜马拉雅Ⅱ期布设在南北地震带北段的台站观测数据,通过走时反演和波形拟合反演的迭代,获得了该地区地壳一维速度结构,接着利用直达P波观测与理论走时差对震中位置重定位,然后反演地震的最佳双力偶解以及震源深度,最终得到了区域速度结构、地震的三维坐标、发震时刻以及震源机制解.结果显示,此次地震发生于世界时2015年4月15日7时39分26.718s,震中（39.7663°N,106.4304°E）,震源矩心深度18 km,矩震级MW5.25,节面Ⅰ走向176°,倾角85°,滑动角-180°,节面Ⅱ走向86°,倾角90°,滑动角-5°.结合该区域断裂带构造运动分析,本文认为此次地震是左旋走滑破裂,略带正断分量,断层面是节面Ⅱ,走向为NEE（近E-W）向,发震构造为震中附近的E-W向隐伏断裂. 相似文献
4.
Seismic relocation,focal mechanism and crustal seismic anisotropy associated with the 2010 Yushu MS7.1 earthquake and its aftershocks 
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下载免费PDF全文 The 2010 Yushu MS7.1 earthquake occurred in Ganzi-Yushu fault, which is the south boundary of Bayan Har block. In this study, by using double difference algorithm, the locations of mainshock (33.13°N, 96.59°E, focal depth 10.22 km) and more than 600 aftershocks were obtained. The focal mechanisms of the mainshock and some aftershocks with MS>3.5 were estimated by jointly using broadband velocity waveforms from Global Seismic Network (GSN) and Qinghai Seismic Network as well. The focal mechanisms and relocation show that the strike of the fault plane is about 125° (WNW-ESE), and the mainshock is left-laterally strikeslip. The parameters of shear-wave splitting were obtained at seismic stations of YUS and L6304 by systematic analysis method of shear-wave splitting (SAM) method. Based on the parameters of shear-wave splitting and focal mechanism, the characteristics of stress field in seismic source zone were analyzed. The directions of polarization at stations YUS and L6304 are different. It is concluded that after the mainshock and the MS6.3 aftershock on April 14, the stress-field was changed. 相似文献
5.
2008年10月5日新疆乌恰Mw6.7级地震发生在南天山、帕米尔高原及塔里木盆地交汇地带,基于地震波反演的震源机制解确定的震源深度存在较大差异.本文利用日本ALOS卫星的PALSAR图像,获得了本次地震的同震形变场,基于卫星视线向（LOS）和方位向（Azimuth）的形变,采用均匀弹性半无限位错模型和有界最小二乘（BVLS）算法,以网格矩形位错元法对发震断层的几何产状、滑移及分布进行了估算,结果表明本次地震以逆断破裂为主,断层面上最大位错量接近3.4 m,形变中心位于73.8040°E,39.5335°N,深度约5 km,震级估算为Mw6.6;地震发生在走向46°,倾角48°的断层上,发震断层长30 km,宽14 km,闭锁深度9 km,符合该地区浅源地震多发的构造特点,发震断层为乌合沙鲁断裂带.InSAR反演的滑移形变主要集中于地下2~7 km,表明乌恰地震为浅源地震,可能与该断层附近历史地震未完全释放的残余应力积累有关.同时,InSAR反演的断层位错分布呈现双破裂特征,震级分别为Mw6.5和Mw6.1,可能与本次地震的主震和余震相对应,也可能是由主震激发而产生的两组破裂. 相似文献
6.
7.
本文利用福建省地震台网、广东省地震台网和台湾"中央"气象局17个台的宽频带记录,使用CAP方法反演了2018年11月26日台湾海峡M_S6.2地震震源机制解,得到节面1走向/倾角/滑动角为89°/82°/-173°,节面2走向/倾角/滑动角为358°/84°/-7°,最佳拟合深度14km,矩震级5.8.使用双差定位获取了94个M_L2.0以上地震的精定位结果,结果显示,主震位于北纬23.36°,东经118.62°,震源深度10.43km.根据小震分布和构造应力场反演得到余震断层面走向和倾角分别为88°和60°.研究认为,台湾海峡6.2级地震发震构造为近EW向的台湾浅滩断裂,受南海板块张裂拉伸发育而成,孕震过程中有东山隆起东缘断裂的参与,推测在菲律宾板块对欧亚板块NW-SE向挤压碰撞背景下,近EW向的台湾浅滩断裂与近NS向的东山隆起东缘断裂交接部位属于强度薄弱区,最终产生高倾角右旋走滑错动而引发地震,余震主要沿台湾浅滩断裂分布. 相似文献
8.
使用中国数字地震台网记录的区域宽频带波形,通过频率域和时间域多步反演,研究了2013年四川芦山“4·20”7.0级强烈地震的震源运动学特征.基于点源的震源机制解揭示：地震发震断层面参数分别为走向214°/倾角47°/滑动角96°,表现为一次高倾角的逆冲型事件.矩心在水平方向上位于震中（30.303°N/102.988°E）西南向约4.5 km,矩心深度约17 km.平均总标量地震矩M0为1.16×1019 N·m,矩震级Mw约6.6.进一步模拟高达0.5 Hz高频波形,获得了芦山地震破裂过程图像,结果显示：此地震为一次不对称双侧破裂事件.破裂半径约15 km,整个破裂面积为706.7 km2,平均滑动量约0.231 m.破裂在8 s内释放了大多数能量.震后0~3 s内,破裂以孕震点为中心向四周同时扩展,3 s后,破裂表现出明显的方向性,主要向北北东扩展,导致位于震中北东向多数台站视破裂持续时间总体偏小,最小值为4 s.破裂约8 s后基本停止. 相似文献
9.
A paleomagnetic study of about 95 samples from 16 sites sampled in the Early Cretaceous in Luanping basin in Hebei Province was reported. Stepwise thermal demagnetization was used to isolate magnetic components. Most samples have a characteristic direction with a high temperature component above 500°C. The tectonic-corrected data areD = 347.8°,I = 50.4°, α95 = 7.l°, and the corresponding pole position is at 76.1°N, 346.3°E,with dp =6.4°,dm = 3.8°, paleolatitude λ = 31.1°N. This result indicates a counterclockwise post-Cretaceous rotation of 30.7° ±9.8° with respect to the stable Ordos basin in the west of North China Block, and a non-significant northward motion. This rotation could be related to local fault action or structural detachment, or regional NNW-NWWward motion and collision of Kula-Pacific plate with eastern China since the Early Cretaceous.
相似文献10.
The Yecheng, Xinjiang, China, earthquake of February 14, 1980
—A destructive intermediate earthquake
—A destructive intermediate earthquake
In this study, we have checked the location and focal depth of the Yecheng earthquake (m
b
= 6.0, maximum intensity VII) of February 14, 1980. The result shows that this is an intermediate event with a focal depth
of 90 km. The microepicenter is located at 36. 4°N, 76, 9°E, while the macroepicenter is at 37.3°N, 76.9°E, 90 km to the north
of the microepicenter. This is the first destructive intermediate event in China which led to a damage as severe as of intensity
VII. The focal mechanism of the event is determined to be of thrust type. Combined with the analysis of seismological and
geological data in surrounding area, the possible relation between the event and plate movement has been discussed. The result
in this paper indicates that in some particular place, the destructive effect of intermediate event should be considered in
seismic hazard assessment.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, 137–143, 1992. 相似文献
11.
2021年5月21日晚21时48分,云南省大理州漾濞县(震中:25.67°N,99.87°E)发生M_S6.4地震,震源深度8 km。为快速获得此次地震同震形变场及断层几何参数,研究该次地震的发震构造等,文章基于震前、震后的sentinel-1A卫星升降轨SAR数据进行二轨法差分雷达干涉测量(DInSAR),并基于Okada弹性半空间位错模型反演断层几何参数。研究结果如下:(1)此次地震造成的同震形变场长约19 km,宽约20 km;(2)升轨雷达视线向最大形变约为8.2 cm,降轨雷达视线向最大形变约为8.7 cm;(3)地震断层走向为313.7°,倾角为87°,滑动角为175°,为右旋走滑型断层,最大滑动量为0.79 m,反演得出的地震矩为1.48×10~(18) N·m,矩震级为M_W6.1。在川滇块体向南挤出的构造背景下,块体西边界的维西—乔后断裂、红河断裂发生右旋走滑,本次地震便是维西—乔后断裂南段分支断裂右旋走滑活动的体现。 相似文献
12.
利用四川省地震台网的震相数据和双差定位方法对芦山MS7.0级地震及其余震序列进行了精确定位,根据余震分布确定了发震断层的位置和断层面的几何特征,并对余震活动进行了分析.结果显示,芦山MS7.0级地震的震中位于30.28°N、102.99°E,震源深度为16.33 km.余震沿发震断层向主震两侧延伸,主要分布在长约32 km、宽约15~20 km、深度为5~24 km的范围内.地震破裂带朝西南方向扩展范围较大,东北方向略小,余震震级随时间迅速衰减.震源深度剖面清晰地显示出发震断层的逆冲破裂特征,推测发震断层为大川—双石断裂东侧约10 km的隐伏断层.该断层走向217°、倾向北西,倾角约45°,产状与大川—双石断裂相比略缓,它们同属龙门山前山断裂带的叠瓦状逆冲断层系.受发震断裂影响,部分余震沿大川—双石断裂分布,西北方向的余震延伸至宝兴杂岩体的东南缘,与汶川地震的破裂带之间存在50 km左右的地震空区,有可能成为未来发生强震的潜在危险区. 相似文献
13.
In this paper a heterogeneous fault model of the Tangshan earthquake is suggested, which consists of two southern sub-faults
striking N30°E and two northern sub-faults striking N50°E. Total length of the main shock fault is 114 km and seismic moment
is about 1.4 × 1020 N·m. The epicentre of the main shock is located at the southern part, near the intersection of the two bands. Accelerations
of two aftershocks (M
L 5.5, M
S 6.9) were used as empirical Green’s functions to synthesize the accelerations of the main shock in near and far field. A
method that small events and main shock are considered not satisfying the similarity relationship in the improved empirical
Green’s function is also applied in this paper. Peak values, duration and response spectra of synthesized accelerations in
far field are in agreement with the observed records. The synthesized results in near field are also in agreement with the
epicentral intensity distribution of the main shock. The results show that the peak acceleration of Tangshan earthquake in
epicentral region exceeds 1.1 g. It is consistent with the peak accelerations recorded in some large earthquakes occurred
in recent years.
The research is supported by the National Science Foundation of China. 相似文献
14.
Just after the occurrence of anM=5.2 earthquake in Shimian, Sichuan, two three-component seismometers were set up near the epicenter of the earthquake. Field
observations were made for the four-year period from 1989 to 1992. Analysis of the data recorded from either aftershocks following
theM=5.2 earthquake or from small earthquakes scattered in this region indicates the presence of shear wave splitting. And shear
wave splitting varies with time. The mean direction of polarization of the faster shear waves is N18°W during the period of
aftershock activity, which is consistent with the strike of the faulting plane of the mainshock; but has turned to N46°W from
1990 to 1992, which is consistent with the regional maximum compressive stress. The time delays between split shear waves
measured on records from 1990 to 1992 are about half of that in 1989. The results obtained from observations at two temporary
stations are similar. This indicates that the temporal changes may be related to the occurrence of theM=5.2 mainshock.
This study was supported by the Chinese Joint Seismological Science Foundation.
The English version is improved by Prof. Xin-Ling QIN, Institute of Geophysics, SSB, China. 相似文献
15.
16.
Ren Xi-xian 《地震学报(英文版)》2006,19(1):87-92
A new concept is suggested on tectonomagnetic research about the noise in simultaneous geomagnetic difference data caused
by the effect of S
q local-time variation, together with the method of theoretical calculation. The level of the noise and its contribution to
the total noises of the differences data are analyzed. The result indicates that the noise increases linearly with the increase
of the distance between the two stations in the range of 40° longitude-difference, and its increasing rate is about 0.4 nT/(°)
at latitude 40°N. The example calculated at a pair of sites with longitude-difference 0.357°, shows that the noise is about
one fifth of the total noises of the difference data on geomagnetic quiet-day.
Contribution No. 06FE3008, Institute of Geophysics, China Earthquake Administration. 相似文献
17.
Zifang Meng Yunshan Deng Zhaohai Ding Yanpeng Zheng Yong&#;an Li Dongjiang Sun 《中国科学:地球科学(英文版)》1998,41(2):91-104
Paleomagnetic samples were collected from four localities located in the southern rim of the Tarim basin. The samples were taken from volcanic rocks erupted between Jurassic and Quaternary. Detailed analysis of all samples has been carried out with progressive thermal demagnetization. A characteristic remanence (ChRM) with higher unblocking temperature has been isolated from all samples. The pole position from the middle Jurassic is at 52.5°N, 187.9°E(dp = 3.7°,dm =6.5°); the directions of the ChRM of Cretaceous correspond to a paleopole at 69.7°N, 211.6°E (dp = 9.8°,dm = 15.9°); the Quaternary pole from the Pulu site is at 79. 9°N, 183.1°E(dp = 1.6°.dm =2.4°). On the basis of these new paleomagnetic data, tectonic evolution of Tarim block is presented.
相似文献18.
Ali K. Abdel-Fattah Saad M. Mogren Sattam Almadani 《Studia Geophysica et Geodaetica》2016,60(2):268-279
The relative movement between African, Arabian and Eurasian plates has significantly controlled the tectonic process of Sinai subplate region, although its kinematics and precise boundaries are still doubtful. The respective subplate bounded on both sides by the Aqaba-Dead Sea transform fault to the east and the Gulf of Suez, the only defined part, to the west. Seismicity parameters, moment magnitude relation and fault plane solutions were combined to determine the active tectonics along the aforementioned boundaries. Seven shallow seismogenic zones were defined by the heterogeneity in stress field orientations. Along the eastern boundary, the average fault plane solution obtained from the moment tensor summation (MTS) reveals a sinistral strike-slip faulting mechanism. The corresponding seismic strain rate tensor showed that the present tectonic stress producing earthquakes along the boundary is dominated by both NW-SE compression and NE-SW dilatation. Towards the north, the average focal mechanism showed a normal faulting mechanism of N185°E compression and an N94°E extension in the Carmel Fairi seismic zone. On the other hand, the active crustal deformation along the western boundary (Gulf of Suez region) showed a prevailing tensional stress regime of NE to ENE orientations; producing an average fault plane solution of normal faulting mechanism. The seismic strain rate tensor reveals a dominant stress regime of N58°E extension and N145°E compression in consistence with the general tectonic nature in northeastern Africa. Finally, the extensional to strike-slip stress regimes obtained in the present study emphasize that the deformation accommodated along the Sinai subplate boundaries are in consistence with the kinematics models along the plate boundaries representing the northern extremity part of the Red Sea region. 相似文献
19.
GUI-PING LIU 《地震学报(英文版)》1999,12(3):277-284
The time and spatial feature of the regional seismicity triggered by the Hyogo-Ken Nanbu, Japan, M=7.2 earthquake on January 17,1995, was studied. The concerned region is about several hundred kilometers in length and breadth surrounding the epicenter (33°～37°N, 133°～138°E). It is divided into 16 subregions. The seismicity of these subregions from January of 1976 to June of 1996 has been analyzed. It is showed that,① there were significant seismicity changes in 10 subregions triggered by the Hyogo-Ken Nanbu, Japan, M=7.2 earthquake on January 17, 1995. These changes passed a Z statistic test exceeding 0.95 confidence level and the greatest epicenter distance of these subregions was 280 km;②seismicity changes were triggered within 1～5 days in three subregions near the main shock while in other subregions the seismicity changes were triggered within several ten days after the main shock;③ the greatest triggered event is 5.4, which is about the same size as the greatest aftershock;④the regional stress change resulted from the main shock may be the triggered mechanism of the regional seismicity. 相似文献
20.
Tomography sounding data for the first half of November 2007 are presented. The sounding was conducted over three points located
at the same meridian—Yuzhno-Sakhalinsk (47° N, 143° E), Poronaisk (49° N, 143° E), and Nogliki (51° N, 143° E)—in order to
find the possible influence of a tropical cyclone on the upper ionosphere. A change in the foF2 parameter by on average no more than 10–20% is a possible response of the upper ionosphere localized over the tropical cyclone
(TC) zone (in the given case, 25°–30° northward and 5°–20° eastward) at a distance of approximately 3800–5500 km from it.
A decrease or, vice versa, an increase in foF2 is related to the delay of the measurement moment relative to the beginning of the TC action. The complexity of a morphological
analysis of the given event is that a tropical cyclone is a “wideband” (in the longitudinal and, to a lesser degree, in the
latitudinal directions) and lasting disturbance source. 相似文献