共查询到20条相似文献，搜索用时 31 毫秒
1.
2.
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
3.
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
4.
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
5.
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
6.
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
7.
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
8.
Great earthquakes often occur along or near active fault belts. Thus, monitoring and research on fault deformation are quite important. Methods such as short-leveling, short- baseline and integrated monitoring profile across fault belts have been used to monitor fault activities for many years. GNSS observations are mainly used to obtain the horizontal velocity field in large areas and to study the activities and deformation of major blocks. GNSS technology has been used to monitor and study the deformation of faults from a different aspects, In this paper, some applications and new explorations of GNSS are discussed. They are： （1） Research and monitoring of strike-slip activities of faults with GNSS. （2） Research and monitoring of vertical activities of faults with GNSS. （3） Investigating the laws of deformation of blocks on the sides of fault zone and setting up strain models to deduce the activities and deformation of faults with respective models and compare the deduced results with the actual measurements across fault. It is concluded that a larger discrepancy between the deduced and the observed deformation indicates a stronger interaction between the blocks, which can be important for predicting the location of a strong earthquake and assessing seismic hazard, as well as the seismicity trend. 相似文献
9.
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
10.
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
11.
There occurred several eruptions from Changbaishan Tianchi volcano in Holocene, and at least three of them were believed to be true according to the formal studies. The products of three eruptions were yellow comenditic pumice of - 5000a B.P. （Eruption Ⅰ ）, gray comenditic pumice and pyroclastic flow of - 1000a B.P. （ Eruption II, i.e. the millennium explosive eruption）, black trachy pumice and welded tuff of - 300a B.P. （ Eruption Ⅲ ） respectively. There were a large number of melt inclusions found in phenocrysts, which differ in size and color. The Leitz 1350 heating stage experiments for melt inclusions in host feldspars from three Holocene eruptions of Changbaishan Tianchi volcano imply that there were little differences between the homogenization temperatures of melt inclusions from Eruptions Ⅰ and Ⅲ, whereas it was rather complicated for Eruption H, i.e. there might be two kinds of melt with different homogenization temperature periods, which gave the evidence for the assumption that the explosive millennium eruption of Tianchi volcano was triggered by injection and mixing of two different magmas. The experimental results also indicate that （ 1 ） small melt inclusion is easy to be homogenized, while the large one, especially the one with lots of daughter crystals, is rather difficult to be homogenized; （2） homogenization temperature closely correlates with the size of melt inclusion within host crystal, with the temperature point switching from high heating rate to low heating rate, and correlates with whether it is the first time to obtain homogenization as well; and （3） a melt inclusion can get different homogenization temperatures when it is repeatedly heated. Even more, the next homogenization temperature is usually higher than the former one, which testifies the phenomenon that hydrogen migration occurs during repeated heating. 相似文献
12.
The change of the confined aquifer level reflects the pore pressure change, and the pore pressure change of the aquifer is closely related to the aquifer pressure. This paper uses the tidal response of the well water level data in the North China region to calculate the tidal factor of each well and extract the effective water trend information. Then, the volumetric strain of an existing confined aquifer well in the North China region is inverted, and the contour maps are plotted on a half-year scale from 2009 to 2012. Results show that it can reflect the state of stress and strain in deep crust to a certain extent in the North China region. 相似文献
13.
We present a parallel hybrid algorithm based on pseudospectral method （PSM） and finite difference method （FDM） for two-dimensional （2-D） global SH- wavefield simulation. The whole-Earth model is taken as a cross section of spherical Earth, and corresponding wave equations are defined in 2-D cylindrical coordinates. Spatial derivatives in the wave equations are approximated with efficient and high accuracy PSM in the lateral and high-order FDM in the radial direction on staggered grids. This algorithm allows us to divide the whole-Earth into sub-domains in radial direction and implement efficient parallel computing on PC cluster, while retains high accuracy and efficiency of PSM in lateral direction. A transformation of moment tensor between 3-D spherical Earth and our 2-D model was proposed to give corre- sponding moment tensor components used in 2-D modeling. Comparison of modeling results with those obtained by direct solution method shows very good accuracy of our algorithm. We also demonstrate its feasibility with a lateral heterogeneous whole-Earth model with localized velocity perturbation. 相似文献
14.
This paper calculates the static Coulomb stress changes generated by four earthquakes in the Yutian area during 2008 ~ 2014 separately, then discusses the triggering influence, their accumulated Coulomb stress changes and their influence on nearby faults. The results indicate that the Ms5. 5 earthquake in 2011 and the Ms7. 3 earthquake in 2014 are both in the regions where the Coulomb stress change is positive, the stress changes are 0. 004MPa and 0. 021MPa, respectively, meaning they are triggered by prior earthquakes. The Ms6. 2 earthquake in 2012 occurred in the place where Coulomb stress change was negative, so it is postponed by the prior earthquakes. The image of Coulomb stress changes of the Ms 7. 3 earthquake in 2014 is in accord with aftershocks （ML ≥ 3. 0 ） distribution, but some regions on the fault where the Coulomb stress change is positive have few aftershocks, and strong aftershocks may occur at these districts in future. In addition, this paper calculates the Coulomb stress change on nearby faults, and finds that the Coulomb stress changes of different elements in the GGC fault are very different, and must receive strong triggered-influence, though the result may be influenced by the input finite fault model, so there is still a large earthquake-risk. The GGN, PLC, PLW and LBW faults were also triggered by the four earthquakes occurring between 2008 ~ 2014. Their maximum Coulomb stress changes all exceed 0. 002MPa, so they also have a strong earthquake hazard. 相似文献
15.
Xie Xinsheng Zhao Jinquan Jiang Wali An Weiping Li Zihong Zhang Dawei Cheng Xinyuan Gao Shuyi Wang Chunhe Sun Changbin Yan Chengguo 《中国地震研究》2008,22(4):428-439
Xizhang trench is located 10 km northwest of Taiyuan city, Shanxi Province, in front of a NNW-trending scarp of 4.6m height on the northern segment of the Jiaocheng fault zone. The dimensions of the trench are 108m in length, 8m in width, and 10m in depth. There are 18 horizons revealed in the trench. The upper strata are sandy loam; the upper strata of the downthrown block of the fault are gravels, the lower ones are an interbed of brown loam and sandy loam. The strata on the upthrown block of the fault are sandy loam containing gravel. The trench shows 3 fault planes, and the upper offset point on the fault plane is 1.5m below the ground surface, the newest dislocated stratum is （3.74±0.06） ka BP. The trench reveals a lot of deformation traces, such as fault planes, dislocated strata, colluvial wedges and formation tilting. The relationship between strata and faults in the trench shows that 3 paleoearthquake events have occurred at the Jiaocheng fault zone since the Early Holocene, they are about （3.74±0.06）- （3.06±0.26）ka BP, （8.35±0.09）ka- （3.74±0.06）ka BP, and（ 10.66±0.85） - （8.35±0.09）ka BP. The average interval among the events is 2.6 - 3.6ka. The minimum coseismic vertical displacements of the 3 events are 3.0m, 2.5m and 3.2m, respectively. The significance of Xizhang trench is that the Jiaocheng fault used to be active thousands of years ago, though there is no M ≥ 7.0 earthquake recorded in historical documents. Evidence of new Jiaocheng fault zone activity during the Holocene is important for the earthquake safety assessment of Taiynan city in the future. 相似文献
16.
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
17.
An Ms7. 3 earthquake occurred on February 12, 2014 in Yutian County, Xinjiang Uygur Autonomous Region, which was followed by a series of aftershocks. This paper calculates the depth of the Ms7. 3 earthquake sequence by using the deterministic approach with the seismic phase data from the catalog database of the China Earthquake Networks Center, combined with original seismic wave records from the Digital Seismic Network Center of the Earthquake Administration of Xinjiang Uygur Autonomous Region. 相似文献
18.
In view of the correlation between tectonic activity and seismicity, the strong earthquake risk in the North-South Seismic Belt aroused wide concern after the 2014 Yutian Ms7. 3 earthquake. Using the seismic catalog of the China Earthquake Networks Center, the Benioff strain ratio in the North-South Seismic Belt is calculated in 30 days before and after the March 21, 2008 and February 12, 2014 Yutian Ms7. 3 earthquakes. Results show that in a year after the 2008 Yutian Ms7. 3 earthquake, M 〉 5. 0 earthquakes all occurred near the high strain ratio area or the junction between the low and high strain ratio areas, the activity of strong earthquakes obviously coincides with the high strain ratio area, which indicates that these areas have a higher stress level. The Yutian earthquakes promoted the release of small earthquakes in the high stress areas. This research is of certain indicating significance to the study of subsequent strong earthquakes of this region. 相似文献
19.
1,209 earthquakes occurred in Xianyou, Fujian from August 4, 2010 to October 4, 2013. The largest earthquake was ML5.0 on September 4, 2013. In order to study the Xianyou earthquake sequence and understand the causative structure and stress field of Xianyou, the focal mechanism solutions of six earthquakes （ ML 〉 3. 5 ） in the Xianyou earthquake sequence are calculated using the broadband digital data of the Fujian Seismic Network with the seismic moment tensor inverse method. The results show that the focal faults of the six earthquakes are similar, which are all strike-slip faults striking to the northwest with high dip angles. The direction of the principal compressive stress axes is near SN, which is different from the stress field of Fujian region. The Xianyou earthquake sequence may have been induced by the stress adjustment after the impoundment of Jinzhong reservoir. 相似文献
20.
In this paper, according to the Fujian Seismic Network earthquake catalog records, the Tnow method and the Four Stations Continuous Location method （hereinafter called FSCL） put forward by Jin Xing are inspected by using P-wave arrival information of the first four stations of each seismic event. Results show that for earthquakes within the network, both methods can obtain similar location results and location deviations are small for the majority of the events. For earthquakes outside the network, the location deviation may be amplified as the epicentral distance increases, owing to the seismic station distribution which spread toward the side of the epicenter and the small opening angle between seismic stations used for locating and epicenter. For the FSCL method, the impacts of the wave velocity on the location results may be significant for earthquakes outside the network. Thus, selecting a velocity model which is similar to the actual structure of the wave velocity will contribute to improving location results of earthquakes. The FSCL method can locate more seismic events than the Tnow method. It concludes that the Tnow method makes use of mistake information from some non-triggering stations in earthquake catalog, and some P-wave arrivals are not included in the earthquake catalog due to discontinuous records or unclear records of the seismic phase, which induces incorrect location. 相似文献