共查询到20条相似文献，搜索用时 78 毫秒
1.
Liu Jing Guan Peng Shen Xuhui Xu Yueren Shen Junfeng Jing Feng Hong Shunying 《中国地震研究》2010,24(4):467-477
As the most import fault of the Late Pleistocene in the Lhasa area,the Nalinlaka fault is a left-lateral thrust fault,striking NWW,dipping SSW with a high dip angle,and extending over 33km.According to studies on the latest strata on the Nalinlaka fault zone,this fault zone has been obviously active since the Late Pleistocene and the movement left behind some geomorphologic phenomena on the earth's surface,especially at the sites of the gully west of Cijiaolin and around Xiecun village.For example,some rivers,ridges and terraces are displaced,forming beheaded gullies and fault escarps.The horizontal displacements since the Late Pleistocene at the above two places are 54m ～ 87m,20m ～ 67m,respectively.Based on studies on the 4 trenches along the fault using the progressive constraining method,we conclude that there might have been 5 paleoearthquake events along the Nalinlaka fault since 70ka B.P.,the ages of each paleoearthquake are 68.53,54.40, 41.23,21.96,9.86ka B.P.,and the average recurrence interval is 14.67ka.Because of the limits of trenches and earthquake events exposed by each trench,no single trench completely revealed all 5 events.There may therefore be some errors in determining the upper and lower limits of some events in this article. 相似文献
2.
It is indicated by historical records and the exploratory trench on the Weihe fault that the Yaodian-Zhangjiawan segment of the Weihe fault zone has experienced a historical earthquake and 3 paleoearthquake events in the past 9110a. The historical earthquake, namely, event Ⅳ, occurred between 1487 and 1568 AD. The date of paleoseismic event Ⅰ is （9110 ＋ 90） a, and the ages of events Ⅱ and Ⅲ are unknown. The coseismic vertical displacement of events Ⅰ, Ⅱ and Ⅲ is 0.5m, 0.5m and 0.2m, respectively. The exploratory trench also indicates that the Yaodian-Zhangjiawan segment of the Weihe fault was active in the Holocene. 相似文献
3.
The Yuguang basin is a half-graben basin in the basin-range tectonic zone in northwest Beijing, located at the northern end of the Shanxi graben system, and the Yuguang basin southern marginal fault (YBSMF) controls the formation of this basin. A linear fault escarpment has formed in the proluvial fan on the piedmont fault zone of the Tangshankou segment of YBSMF. A trench across this escarpment reveals three paleo-earthquake events on two active faults. One fault ruptured at about 9ka for the first time, and then faulted again at about 7.3ka, causing the formation and synchronous activity of another fault. Finally, they faulted for the third time, but we cannot determine the faulting time due to the lack of relevant surface deposition. The accumulative vertical displacement of these three events is about 8.1m. We estimate that the average recurrence period of the piedmont fault is about 1.7ka, and the average slip rate of the piedmont fault is about 1.6mm/a. We also estimate the reference magnitude of each event according to the empirical formula. 相似文献
4.
Geomorphic study on Wjiahe segment of Serteng piedmont fault,Inner Mongolia is made.Throuth analysis of the available data in combination with the results of predecessors‘studies it can be obtained that average vertical displacement rate is 0.48-0.75mm/a along the Wujiahe segment since the late Pleistocene(14.450-22.340ka BP)and 0.56-0.88mm/s since the early-middle Holocene(5.570-8.830ka BP).Analyzing paleoseismic phenomena revealed in the excavated 5trenches in combination with the results of predecessors‘studies of paleoearthquakes on the fault,we determine five paleoseismic events on the Wujiahe segment of Serteng piedmont fault since 27.0ka BP and the recurrence interval to be about 4.300-4.400ka,A cluster of paleoearthquakes occurred probably during 8.000-9.000ka BP and two paleoeismic events in 10.000-20.000ka BP may be missed.A comparison between height of fault scarps and sum of displacement caused by paleoseismic events revealed in trenches,and recurrence interval of paleoseismic events obtained from average displacement rate along the fault and the disloca-tion by one event suggest that three paleoseismic events are absent in Alagaitu trench.Two paleoseismic events may be absent on the whole active fault segment. 相似文献
5.
Late Quaternary surface deformation and rupture behavior of strong earthquake on the segment north of Mianning of the Anninghe fault 总被引：7，自引：0，他引：7
The Anninghe fault is an important active fault along the eastern boundary of Sichuan-Yunnan active tectonic block, and the study of its surface deformation and rupture behavior during strong earthquake in the late Quaternary is of fundamental importance for understanding the future seismic risk of the fault zone or even the entire western Sichuan region. Using the methods of detailed geomorphic and geological survey, digital image analysis, total station instrument survey, excavation of combined trench and dating, we analyze the geomorphologic sequences of the offset strata at several sites where the late Quaternary deformation remnants are fairly well preserved and obtain some new results as follows: Strong earthquake events with left-lateral displacements of about 3 m occurred at the two sites of Zimakua and Yejitong at 1634-1811, 1030-1050 and 280-550 a BP, respectively, and the recurrence interval is 520-660 a; The youngest event in the area of Dahaizi-Ganhaizi should be the earthquake of 1536, other events are at 1768-1826, 2755-4108 and 4108-6593 a BP, respectively, with a recurrence interval of 1300-1900 a. The strong earthquake activity shows a clustering character. The possibility of occurrence of a strong earthquake exists on the north segment of the Anninghe fault sometime in the future. 相似文献
6.
The Xiadian Fault is a very important concealed active fault in the Beijing Plain. It is the seismogenic fault of the Sanhe-Pinggu MS8.0 earthquake in 1679. The ancient earthquake sequence in the long historical period is of great significance to understand accurately the activity characteristics of the fault and effectively reduce the earthquake disaster risk in Beijing. We have re-interpreted the Dahuzhuang trench, and identified three layers of buried paleosol, six collapsed wedges and one sand liquefaction event. Further, through the comparison with the landmark strata and paleo-earthquake events revealed by other trenches on the fault, an ancient earthquake sequence with a long historical period of the Xiadian Fault was established:since the 31ka, the Xiadian Fault has 11 occurrences of earthquake events (including the 1679 earthquake), and the average recurrence interval is about 2.8ka. The paleo-seismic sequence also shows that there is an ancient earthquake cluster period from 25ka to 15ka, and there are 5 strong earthquakes in the cluster period. The average recurrence interval is about 2.0ka, which reflects the phase difference of the Xiadian Fault activity. 相似文献
7.
Zhang Shimin Wang Dandan Liu Xudong Ren Junjie Luo Minghui Zhang Guohong Zhao Guocun Wang Rui Zhang Yingli 《中国地震研究》2008,22(3):334-347
A test drilling exploration was implemented across the northern segment of the Nankou-Sunhe fault in the Beijing plain, and a combined borehole section was built by sequence stratigraphy, lithologic facies analysis, magnetic susceptibilityand absolute chronology to investigate the episodic activities of the fault since 60 ka BP. The results show that the active stages of the fault are 60 ka to 47 ka BP, 36 ka to 28 ka BP, and 16 ka BP to present. Other intervals are relatively stable. The average vertical slip rate is 0.35 mm/a from 60 ka to 37 ka BP, 0 mm/a from 37 ka to 3：2 ka BP,0.78 mm/a from 32 ka to 12 ka BP,and 0.35 mm/a since 12 ka BP. Compared with the conventional analyses on lithology and sedimentary facies, the sequence stratigraphy method has certain advantages in the studies of borehole strata comparison and episodic activity of buried faults. 相似文献
8.
Li Zhimin Tian Qinjian Yao Shenghai Li Wenqiao Chen Youshun Zou Haining Gao Zhanwu 《中国地震研究》2008,22(3):348-355
The Datong fault belt is a NE trending fault in the northern Qinghai-Xizang （Tibet） Plateau and controls the boundary of the Xining Basin and Datong Basin. It consists of the Maziying- Miaogou （F1） fault and the Laoye Mountain-Nanmenxia fault （F2）. There is obvious displacement in vertical direction along the belt. The field investigation results show that this belt has long-term activity. There are several meters long crushed zones and veins along the fault side in the basement rock. On the fault section, the Cambria system thrusts over the red- brick-colored Quaternary Period gravel, and there is a fault gouge of several centimeters thick developed on the fault plane. The fault gouge date （ESR） on the fault plane is 610 ± 61ka. The covering deluvial loess is not dislocated, and the OSL result is 14.6 ± 1.5ka. So it can be concluded that the fault belt was active in the middle Pleistocene, but inactive in the late Pleistocene according to the age data and geomorphologic features. Interior formations of the Datong basin features fold with the major axis orienting northwest. According to the relation of fault and fold deformation, Datong fault is a trausversal tear, which is due to uneven compression of the folds in different parts and NNE trending regional compressive stress. It is common among the NE trending faults in the northeast of Qinghai-Xizang （Tibet） Plateau. These NE trending faults aren＇t large, and most are located in the active plate. They are all nearly vertical to the axis of the folds and compressive basins. 相似文献
9.
There are 18 gullies displaying sinistral contortions to different degrees along the western terminal segment about 10 km long of the active Daqingshan piedmont fault near the Donghe District, Baotou City. The contortion amount of gullies ranges from 20 m to 300 m. The contortion and length of the gullies are in direct proportion. The relation between piedmont terraces and gullies indicates that the gullies with upper reaches of about 1 ～ 5 km long and those smaller than one kilometer were formed at the end of Late Pleistocene and Holocene.Meanwhile, sandy gravel layer of alluvial-proluvial sediment on the upthrown wall is directly in contact with yellow clayey sand of the downthrown wall. During the Holocene, the sinistral strike-slip rate along the western terminal segment of the active Daqingshan piedmont fault reached 5 mm/a from age data of dislocated sediments. The evolutional mechanism of the active Daqingshan piedmont fault is also discussed in the paper. 相似文献
10.
Zheng Rongzhang 《中国地震研究》2004,18(4):385-395
The formation of strath and strath terrace is closely related to tectonic uplift in the drainage basin. Based on the investigation of straths at Yandantu and Changcaogou on the eastern segment of the northern margin fault of Altun, and in combination with the paleoclimatic data,the tectonic uplift since late Epipleistocene as revealed by stream terraces at the two places is discussed. At Yandantu, three levels of stream terraces( T1, T2 and T3 )have developed since 16ka BP, where T1, T3 and T2 are fill terraces and the buried major straths are exposed. The ages of three treads are dated to be about 16.1ka BP, 12 .Ska BP and 6.2ka BP, respectively. The three terraces reflect three tectonic uplift events, while the ages of the treads represent the occurrence time of these events. The stream is still beveling the bedrock and widening the channel at present, and the modern strath is being generated. The uplift rate is 4.8～4.5mm/a since 16.1 ka BP in this area. From 12.8ka B .P to 6.2ka BP, The uplift rate was 6.4mm/a.The uplift rate is 3. lmm/a since 6.2ka BP.At Changcaogou, four levels Of stream terraces(T1, T2, T3 and T1)have developed since 7ka BP. All of them are fill terraces. There are buried straths under the deposits. The buried major strath is exposed on T3 and T2 and the minor strath on T1‘and T1. The ages of treads of the three terraces (T3, T2 and T1’) are 7 ka BP, 3 ka BP and 2.5 ka BP, respectively. The four terraces reflect two uplift events induced by tectonic activities. One occurred in about 7 ka BP, and the other in 3ka BP. The uplift rate is 5.gmm/a since 7.0 ka BP at Changcaogou.From 7ka BP to 3ka BP, the uplift rate was 7.0mm/a, and since 3ka BP till now, the uplift rate is 4.7 mm/a. 相似文献
11.
On the basis of elastic rebound theory, using the horizontal velocity field of the Chinese mainland calculated from GPS data during three observation periods from 1999 to 2007, the velocity components that are parallel and plumb to the fault zone are calculated respectively for different periods, and then relative ground movements of two sides of the fault zone are analyzed with power function fitting and graphics. The results show that the relative ground movement shows right-lateral shear deformation before the Wenchuan Ms8. 0 earthquake, and at the same time the movement was hindered by the Longmenshan fault zone. Thus, this result has positive significance for distinguishing the elastic strain energy accumulation and deformation anomaly in an earthquake preparation process, and for conducting further research on earthquake prediction. 相似文献
12.
13.
A trend increase in apparent resistivity has been observed in the N30°E monitoring direction at Garze Seismic Station since July 2011. This increase trend in geo-electric resistivity has been observed in the N60°W direction since 2012. During the period of the increase, the national highway No.317 was expanded in the monitoring area, so the potential electrodes in the N30°E direction had to be moved 10m towards the current electrodes. We interpreted the electric sounding data of Garz6 Seismic Station with a horizontally layered model. Analysis based on this model showed that the shift of potential electrodes can cause a 4 l-l.m rise to the measurements in the N30°E direction. Therefore, apparent resistivity of the two directions increased in the same time in 2012 after offsetting the effects from electrodes shift. Sensitivity coefficients of the two observation directions were also obtained using the model. Sensitivity coefficients of both directions were negative for the shallow layers, which can well explain the unexpected annual variations of Garze Seismic Station. In order to quantitatively analyze the effects from the expansion of the national highway on the observation, we constructed a finite element model based on the electrical structure. Analysis results also suggested that the expansion of the national highway could only cause a 0. 15 Ω·m decrease in the N60°W monitoring direction and 0. 1 Ω· m increase in the N30°E direction. Additionally, the valley values of annual variation of 2013 were distinctively higher than that of other years since 2008, meaning that there was an abnormal rise in apparent resistivity in the two observation directions at Garz~ Seismic Station before the Lushan earthquake. However, the rise was contrary to the decline variation before the Wenchuan earthquake. Therefore, it is still unsure whether or not the rise variation is related to the Lushan earthquake. 相似文献
14.
In 1997 - 2003, 27 earthquakes with M≥ 5.0 occurred in the Jiashi-Bachu area of Xinjiang. It was a rare strong earthquake swarm activity. The earthquake swarm has three time segments of activity with different magnitudes in the years 1997, 1998 and 2003. In different time segments, the seismic activity showed strengthenin-qguiet changes in various degrees before earthquakes with M ≥ 5.0. In order to delimitate effectively the precursory meaning of the clustering （strengthening） quiet change in sequence and to seek the time criterion for impending prediction, the nonlinear characteristics of seismic activity have been used to analyze the time structure characteristics of the earthquake swarm sequence, and further to forecast the development tendency of earthquake sequences in the future. Using the sequence catalogue recorded by the Kashi Station, and taking the earthquakes with Ms≥ 5.0 in the sequence as the starting point and the next earthquake with Ms = 5.0 as the end, statistical analysis has been performed on the time structure relations of the earthquake sequence in different stages. The main results are as follows： （1） Before the major earthquakes with M ≥ 5.0 in the swarm sequence, the time variation coefficient （δ-value） has abnormal demonstrations to different degrees. （2） Within 10 days after δ= 1, occurrence of earthquakes with M ≥ 5.0 in the swarm is very possible. （3） The time variation coefficient has three types of change. （4） The change process before earthquakes with M5.0 is similar to that before earthquakes with M6.0, with little difference in the threshold value. In the earthquake swarm sequence, it is difficult to delimitate accurately the attribute of the current sequences （foreshock or aftershock sequence） and to judge the magnitude of the follow-up earthquake by δ-value. We can only make the judgment that earthquakes with M5.0 are likely to occur in the sequence. （5） The critical clustering characteristics of the sequence are hierarchical. Onl 相似文献
15.
A statistical analysis on earthquake activity in the Kashi-Wuqia intersection area triggered by earth tide is done by Schuster＇s test and the Permutation test on daily and monthly scales. The north-south, east-west component of the tidal force and tidal body stress are chosen as the tidal curve in the daily scale. The results show that most of the earthquakes occurred near the maximum 0° of the three kinds of tidal curves, the predominant tidal phases of the earthquake are - 5. 86°, 6. 60° and - 15. 52°, and the frequency of the earthquakes increases with the increase of the tide; with three kinds of tidal curves （the north-south, east-west component of the tidal force and tidal body stress ）, the Ps of Schuster＇s test for all the earthquakes is 10. 52 %, 2. 40 % and 2. 06 %, and the pp of the Permutation test is 10. 90%, 2. 40% and 2. 06%, and the results ofps andpp based on the east-west component of the tidal force and tidal body stress are below the threshold of 0. 05 that tidal triggering of earthquakes. In the monthly scale, both the Ps and pp are very low （ close to 0 ）, far below the threshold of 0. 05 of tidal triggering of earthquakes, and the predominant tidal phase for earthquake triggering is - 18. 95°, close to the maximum 0° （ new moon and full moon） of the earth tide in monthly scale. Regarding the statistical test result of tidal triggering of earthquakes, a preliminary explanation is given as to why the trigger effect in the east-west direction is greater than that in north-south direction. 相似文献
16.
A rotary-shear low to high-velocity friction apparatus in Beijing to study rock friction at plate to seismic slip rates 总被引：2，自引：0，他引：2
Shengli Ma ;Toshihiko Shimamoto ;Lu Yao ;Tetsuhiro Togo ;Hiroko Kitajima 《地震学报(英文版)》2014,(5):469-497
This paper reviews 19 apparatuses having highvelocity capabilities,describes a rotary-shear low to highvelocity friction apparatus installed at Institute of Geology,China Earthquake Administration,and reports results from velocity-jump tests on Pingxi fault gouge to illustrate technical problems in conducting velocity-stepping tests at high velocities.The apparatus is capable of producing plate to seismic velocities（44 mm/a to 2.1 m/s for specimens of 40 mm in diameter）,using a 22 kW servomotor with a gear/belt system having three velocity ranges.A speed range can be changed by 103 or 106by using five electromagnetic clutches without stopping the motor.Two cam clutches allow fivefold velocity steps,and the motor speed can be increased from zero to 1,500 rpm in 0.1-0.2 s by changing the controlling voltage.A unique feature of the apparatus is a large specimen chamber where different specimen assemblies can be installed easily.In addition to a standard specimen assembly for friction experiments,two pressure vessels were made for pore pressures to 70 MPa;one at room temperature and the other at temperatures to 500 °C.Velocity step tests are needed to see if the framework of rate-and-state friction is applicable or not at high velocities.We report results from velocity jump tests from 1.4 mm/s to 1.4 m/s on yellowish gouge from a Pingxi fault zone,located at the northeastern part of the Longmenshan fault system that caused the 2008 Wenchuan earthquake.An instantaneous increase in friction followed by dramatic slip weakening was observed for the yellowish gouge with smooth sliding surfaces of host rock,but no instantaneous response was recognized for the same gouge with roughened sliding surfaces.Instantaneous and transient frictional properties upon velocity steps cannot be separated easily at high velocities,and technical improvements for velocity step tests are suggested. 相似文献
17.
It is well known that quantitative estimation of slip distributions on fault plane is one of the most important issues for earthquake source inversion related to the fault rupture process. The characteristics of slip distribution on the main fault play a fundamental role to control strong ground motion pattern. A large amount of works have also suggested that variable slip models inverted from longer period ground motion recordings are relevant for the prediction of higher frequency ground motions. Zhang et al. （Chin J Geophys 56：1412-1417, 2013） and Wang et al. （Chin J Geophys 56：1408-1411,2013） published their source inversions for the fault rupturing process soon after the April 20, 2013 Lushan earthquake in Sichuan, China. In this study, first, we synthesize two forward source slip models： the value of maximum slip, fault dimension, size, and dimension of major asperities, and comer wave number obtained from Wang＇s model is adopted to constrain the gen- eration of k-2 model and crack model. Next, both inverted and synthetic slip models are employed to simulate the ground motions for the Lushan earthquake based on the stochastic finite-fault method. In addition, for a comparison purpose, a stochastic slip model and another k-2 model （k 2 model II） with 2 times value of comer wave number of the original k-2 model （k 2 model I） are also employed for simulation for Lushan event. The simulated results characterized by Modified Mer- calli Intensity （MMI） show that the source slip models based on the inverted and synthetic slip distributions could capture many basic features associated with the ground motion patterns. Moreover, the simulated MMI distributions reflect the rupture directivity effect and the influence of the shallow velocity structure well. On the other hand, the simulated MMI bystochastic slip model and k 2 model II is apparently higher than observed intensity. By contrast, our simulation results show that the higher frequency ground motion is sensitive to the degree of sli 相似文献
18.
The focal mechanism parameters of small earthquakes are determined by the maximum velocity and displacement amplitude ratio of the direct ^-P- and ^-S-waves recorded by digital stations. The displacement is obtained from the velocity by emulation, and the two results are compared and analyzed. Results of theoretical analysis and practical measurement indicate that the two results of velocity and displacement are consistent, and it is feasible that the maximum displacement amplitude ratio be replaced by the maximum velocity amplitude ratio of the direct ^-P-and ^-S- waves recorded by regional seismic networks when determining focal mechanism solutions of small earthquakes. 相似文献
19.
The paper begins with a brief review of the research history of earthquake size measurement. On this basis, the author pointed out the following points： ① In recent decades, ML, mb （mH ）, Ms magnitude scales are widely used as measures of earthquake size. However, these magnitude scales have a deficiency of ＂overgeneralization＂ and ＂magnitude saturation＂. Moreover, since they do not fully take into account the regional difference of seismic attenuation, especially the difference of site effects on the amplification of ground motion, these magnitude scales are but inaccurate measures of earthquake size. ② Seismic moment M0 not only has clear physical meaning, but also overcomes the deficiencies existing in ML, mb （mB ） and Ms magnitude scales, so it is the most suitable physical quantity for measuring earthquake size scientifically. In order to continue to use the term ＂magnitude＂, Kanamori defined the moment magnitude scale Act. Although its prerequisite assumptions remain to be studied, it is still a reasonable scale used as a measure of the relative size of an earthquake. ③ For measuring the earthquake size more scientifically, we must make full use of a large amount of waveform data from modern regional digital seismograph networks, strengthen the research on seismic wave attenuation characteristics, site effect, calculation of source parameters and the related scaling relations. In improving the measurement methods for ML, mb （mB ） and Ms magnitude, we should focus on the improvement of Mw scale and carry forward the work as gradually taking Mw magnitude scale as the uniform physical quantity to measure the relative size of earthquakes, so as to lay a more solid foundation for research in earthquake science and earthquake prediction. 相似文献
20.
5·12汶川特大地震造成人民生命财产重大损失。四川省防震减灾科普示范学校由于平时注重在学生中进行防震减灾知识教育和避震应急演练,在此次地震中均能做到临危不乱,快速撤到安全地带,将灾害损失降到了最低。鲜活的事例说明,有无防震减灾知识和自救互救技能,地震后的效果大不一样。 相似文献