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Statistical properties of reported earthquake precursors show apparent focal mechanism dependence. Intensity of anomaly is
described by the ‘anomaly ratio’ as defined by the number of stations/items reporting anomalies before the target earthquake
over the number of stations/items in operation around the target earthquake. Variation of the ‘anomaly ratio’ with the magnitude
of the target earthquake was studied for dip-slip earthquakes all over China, strike-slip earthquakes in eastern China, and
strike-slip earthquakes in western China, respectively. It is observed that for strike-slip earthquakes, the ‘anomaly ratio’
increases linearly with the magnitude of the target earthquake, while earthquakes in eastern China and western China have
different slopes. For dip-slip earthquakes, however, the ‘anomaly ratio’ has no statistically significant change with the
magnitude of the target earthquake. Limited data imply that the ‘anomaly ratio’ seems proportional to the apparent stress
of the target earthquake. The result might be heuristic for the analysis of candidate earthquake precursors.
Foundation item: National Natural Science Foundation of China (40274013) and MOST Project (2001BA601B02).
Contribution No.04FE1020, Institute of Geophysics, China Earthquake Administration. 相似文献
3.
The 0S2~0S54 spheroidal modes of Earth’s free oscillations, triggered by the great Sumatra-Andaman earthquake of 26 December 2004 are retrieved from VHZ data recorded by seven upgraded stations of China Digital Seismograph Network (CDSN). We compare these spheroidal modes with theoretical free oscillation spectra calculated from the Preliminary Reference Earth Model (PREM) and find a coincidence between their periods. Spectral splitting phenomenon is observed obviously in 0S2, 0S3, 0S4, 2S1 and 1S2 free oscillation modes. What is most noticeable is that the oscillation mode 2S1 is reported for the second time (the first time by Rosat et al) without any data stacking. We simulated the split singlet of 0S2 mode on seven CDSN stations based on general focal mechanism and seismic moment of the earthquake. The result shows that seismic moment of the earthquake can reach 1023 N.m. We also find that the recording of Earth’s free oscillations carries abundant information of source mechanism and earthquake location, which is applicable to the detailed study of source rupture parameters. 相似文献
4.
The empirical Green’s function deconvolution technique is applied to the November 6, 1998,M
s=7.6, Yunnan, China earthquake to study the rupture process of this event. An aftershock ofM
s=6.3 is taken as the empirical Green’s function. Recordings of these two events at six stations of China Digital Seismographic
Network (CDSN) are employed. Deconvolution results show that this event is a relatively simple event. Directivity analysis
indicates that the rupture was initiated at hypocenter and propagated bilaterally and early symmetrically towards the northwest
and southeast directions with a total length of 70 km and a time duration of 19 s. The rupture velocity is estimated to be
about 2.0 km/s.
Contribution No. 98A01004, Institute of Geophysics, State Seismological Bureau, China.
This study is supported by the Chinese Joint Seismological Science Foundation(95-07-411). 相似文献
5.
Cities’ ability reducing earthquake disasters is a complex system involving numerous factors, moreover the research on evaluating
cities’ ability reducing earthquake disasters relates to multi-subject, such as earthquake science, social science, economical
science and so on. In this paper, firstly, the conception of cities’ ability reducing earthquake disasters is presented, and
the ability could be evaluated with three basic elements — the possible seismic casualty and economic loss during the future
earthquakes that are likely to occur in the city and its surroundings and time required for recovery after earthquake; based
upon these three basic elements, a framework, which consists of six main components, for evaluating city’s ability reducing
earthquake disasters is proposed; then the statistical relations between the index system and the ratio of seismic casualty,
the ratio of economic loss and recovery time are gained utilizing the cities’ prediction results of earthquake disasters which
were made during the ninth five-year plan; at last, the method defining the comprehensive index of cities’ ability reducing
earthquake disasters is presented. Thus the relatively comprehensive theory frame is set up. The frame can evaluate cities’
ability reducing earthquake disasters absolutely and quantitatively and consequently instruct the decision-making on reducing
cities’ earthquake disasters loss.
Foundation item: State Important Research Project of China (95130603). 相似文献
6.
On the basis of the reality of recent tectonic movement and discarding such a viewpoint that the isostatic adjust-ment only results from excessive or insufficient compensation,we have discussed the tectonic stress causing ine-auality and regarded the isostatic anomaly as a load on the earth‘s interior,thus the earth‘s inner stress can be cal-culated.The research results show that in the East China Sea and its eastern marginal seas the change of the verti-cal stress derived from the isostatic gravity anomaly is more marked than that of the horizontal stress.Along the Ryukyu trench there is an enhancement of vertical stress by 5MPa,which evidently reflects the effect of plate subduction.On contrary,along the island are to the northwest of the trench the vertical stress weakens by about5MPa.The horizontal stresses in eastern and western parts are obviously different,the east westward stress on the oceanic crust σx is negative(while the pressure is positive)but on the continental crust in positive.These facts indicate the effect of compression between plates. 相似文献
7.
ZHANG Heng＇s Seismometer and Longxi earthquake in AD 134 总被引：1，自引：0，他引：1
8.
Introduction According to the Rapid Earthquake Information Release of CNDSN (Department of Earth- quake Monitoring and Prediction, China Earthquake Administration, 2002), an earthquake with surface wave magnitude MS=8.1 shook west of Kunlun Mountain Pass (KMP) at the juncture of Xinjiang, Qinghai and Xizang on November 14, 2001. This is the largest and the only MS>8.0 earthquake in Chinese mainland over 50 years since the August 15, 1950 MS=8.6 (MW=8.6) Chayuearthquake in Tibeta… 相似文献
9.
中国数字地震台网 (CDSN)地震事件数据库系统是一个数据服务软件系统。它以国际著名的 ORACLE数据库为开发环境 ,以 CDSN数字地震事件数据为基础 ,借鉴 IRIS等国际地震学机构优秀的数据服务方式 ,利用 rdseed、 SAC等地震学领域流行的数字软件 ,为网上用户共享 CDSN数字地震数据提供了一个全新的服务窗口。本文对该数据服务软件系统及分布数据库系统作相关的介绍。 相似文献
10.
Earthquake engineering in China 总被引：2，自引：0，他引：2
胡聿贤 《地震工程与工程振动(英文版)》2002,1(1):1-9
The development of earthquake engineering in China is described into three stages. The initial stage in 1950’s – 1960’s was
marked with the initiation of this branch of science from its creation in the first national 12-year plan of science and technology
by specifying earthquake engineering as a branch item and IEM was one participant. The first earthquake zonation map and the
first seismic design code were soon completed and used in engineering design. Site effect on structural design and site selection
were seriously studied. The second stage marked with the occurrence of quite a few strong earthquakes in China, from which
many lessons were learned and corresponding considerations were specified in our design codes and followed in construction
practice. The third stage is a stage of disaster management, which is marked by a series of government documentations, leading
by a national law of the People’s Republic of China on the protecting against and mitigating earthquake disasters adopted
at the meeting of the Standing Committee of the National People’s Congress of the People’s Republic of China in 1997, and
then followed by some provincial and municipal laws to force the actions outlined in the national law. It may be expected
that our society will be much more safer to resist the attack of future strong earthquakes with less losses. Lastly, possible
future developments are also discussed. 相似文献
11.
马钦忠 《地震学报(英文版)》2008,21(6):618-628
On July 4,2006,a MS5.1 earthquake occurred in Wen’an county of Hebei Province of which the epicenter is near the Beijing city.The six geoelectric field monitoring stations have been in operation for several years around the Beijing area to examine the relationship between electric field changes and earthquake.This paper firstly explains the principle of the eliminating noise method by using multi-dipole observation system of the geoelectric field.Then the data observed at the stations are studied and a lot of abnormal signals preceding the Wen’an earthquake are selected,of which five abnormal signals of the geoelectric field are finally recognized as the precursory signals.The result shows that 1 there probably exists the precursory signals of the geoelectric field preceding the Wen’an earthquake;2 there are sensitive sites in the spatial distribution of the abnormal variation of the geoelectric field before the quack;3 the anomalous signals do not appear synchronously,and their durations are not same at dif-ferent stations;4 the amplitudes of the abnormal signals recorded at Baodi station are small,but large at Changli station,while the latter is farther from the epicentral area than the former. 相似文献
12.
The spatial damage distribution of August 16, 2003, Inner Mongolia, China, M
S=5.9 earthquake is summarized through field investigation. The moment tensor solution and focal mechanism are inverted using
the digital long-period waveform records of China Digital Seismograph Network (CDSN). The relation between the spatial damage
distribution and focal mechanism is analyzed according to the focal mechanism, the aftershock distribution and the spatial
damage distribution. The possible relation between the characteristics of ground motion and the tectonic background of the
source region is discussed in terms of the global ground motion records, historical earthquake documents and the damage distribution.
Investigation reveals that the meizoseismal region is in east-west direction, which is consistent with the nodal plane of
focal mechanism inversion. The meizoseismal area is relatively large and the damage of single-story adobe houses or masonry
houses is more severe. This may have relations with local seismotectonic environment.
Foundation item: The Special Funds for Major State Basic Research Project (2002CB412706).
Contribution No. 05FE3009, Institute of Geophysics, China Earthquake Administration. 相似文献
13.
YU Jinhai & ZHANG Chuanding . Institute of Geodesy Geophysics of Chinese Academy of Sciences Wuhan China . Zhengzhou Information Engineering University Zhengzhou China 《中国科学D辑(英文版)》2005,48(3):398-405
Boundary value problem (BVP) plays a funda-mental role in physical geodesy that aims at determin-ing the earth’s shape and its external gravity field. TheMolodensky BVP and the Stokes BVP are typical inphysical geodesy, and the gravity anomaly is a kind ofbasic data. With the wide use of GPS, measurementaccuracy of the earth’s surface can reach one centime-ter, while that of the gravity measurement can reachμgals. Hence, it is necessary to establish a new kind ofBVP which can satisfy… 相似文献
14.
The relation between the gravity variation features and Ms=8.1 earthquake in Qinghai-Xizang monitoring area is analyzed preliminarily,by using spatial dynamic variation results of regional gravity field from absolute gravity and relative gravity observation in 1998 and 2000.The results show that:1)Ms\8.1 earthquake in Kulun mountain pass westem occurred in the gravity variation high gradient near gravity‘s high negative variation;2)The Main tectonic deformation and emnergy accumulation before MS=8.1 earthquake are distributed at south side of the epicenter;3)The range of gravity‘s high negative variation at east of the MS=8.1 earthquake epicenter relatively coincides with that rupture region according to field geology investigation;4)Gravity variation distribution in high negative value region is just consistent with the second shear strain‘s high value region of strain field obtained from GPS observation. 相似文献
15.
A large earthquake (M
W=7.6) occurred in Jiji (Chi-Chi), Taiwan, China on September 20, 1999, and was followed by many moderate-size shocks in the
following days. Two of the largest aftershocks with the magnitudes of M
W=6.1 and M
W=6.2, respectively, were used as empirical Green’s functions (EGFs) to obtain the source time functions (STFs) of the main
shock from long-period waveform data of the Global Digital Seismograph Network (GDSN) including IRIS, GEOSCOPE and CDSN. For
the M
W=6.1 aftershock of September 22, there were 97 pairs of phases clear enough from 78 recordings of 26 stations; for the M
W=6.2 aftershock of September 25, there were 81 pairs of phases clear enough from 72 recordings of 24 stations. For each station,
2 types of STFs were retrieved, which are called P-STF and S-STF due to being from P and S phases, respectively. Totally,
178 STF individuals were obtained for source-process analysis of the main shock. It was noticed that, in general, STFs from
most of the stations had similarities except that those in special azimuths looked different or odd due to the mechanism difference
between the main shock and the aftershocks; and in detail, the shapes of the STFs varied with azimuth. Both of them reflected
the stability and reliability of the retrieved STFs. The comprehensive analysis of those STFs suggested that this event consisted
of two sub-events, the total duration time was about 26 s, and on the average, the second event was about 7 s later than the
first one, and the moment-rate amplitude of the first event was about 15% larger than that of the second one.
Foundation item: State Natural Science Foundation of China (49904004) and IPGP of France.
Contribution No. 02FE2007, Institute of Geophysics, China Seismological Bureau. 相似文献
16.
2-D crustal Poisson’s ratio from seismic travel time inversion in Changbaishan Tianchi volcanic region 总被引：1，自引：0，他引：1
Based on the inversion method of 2D velocity structure and interface, the crustal velocity structures of P-wave and S-wave
along the profile L
1 are determined simultaneously with deep seismic sounding data in Changbaishan Tianchi volcanic region, and then its Poisson’s
ratio is obtained. Calculated results show that this technique overcomes some defects of traditional forward calculation method,
and it is also very effective to determine Poisson’s ratio distribution of deep seismic sounding profile, especially useful
for study on volcanic magma and crustal fault zone. Study result indicates that there is an abnormally high Poisson’s ratio
body that is about 30 km wide and 12 km high in the low velocity region under Tianchi crater. Its value of Poisson’s ratio
is 8% higher than that of surrounding medium and it should be the magma chamber formed from melted rock with high temperature.
There is a high Poisson’s ratio zone ranging from magma chamber to the top of crust, which may be the uprise passage of hot
substance. The lower part with high Poisson’s ratio, which stretches downward to Moho, is possibly the extrusion way of hot
substance from the uppermost mantle. The conclusions above are consistent with the study results of both tomographic determination
of 3D crustal structure and magnetotelluric survey in this region.
Foundation item: Key Project from China Earthquake Administration and the Project (95-11-02-01) from Ministry of Science and Technology (2001DIA10003).
Contribution No. RCEG200401, Geophysical Exploration Center, China Earthquake Administration. 相似文献
17.
中国数字地震台网记录的昆仑山口西地震的球型自由振荡 总被引：14，自引：0，他引：14
利用中国数字地震台网 (CDSN)改造后的7个台站的VHZ波形资料, 采用功率谱密度估计方法, 利用中国数字地震台网地震仪对低频信号压制的特点, 在没有对资料去除固体潮影响的情况下, 提取了2001年11月14日昆仑山口西地震激发的0S4~0S76地球球型自由振荡, 并与地球初步参考模型(PREM)的理论自由振荡周期进行对比, 结果表明与PREM预测的球型自由振荡周期符合得很好。 该地震的地球自由振荡信息, 可用于地震震源机制研究和地球内部结构研究。 相似文献
18.
On July 4, 2006, an earthquake of MS5.1 took place in Wen’an, Hebei Province, just at the south center of China’s Capital Circle area digital seismograph network. It is the strongest event recorded ever since the network went into operation in 2002. We processed the vast amounts of phase data yielded by the 107 digital seismic stations between 2002~2007 using Wadati method. In order to improve the precision and stability of shear and compressional wave velocities (vP/vS) calculation, we impose a number of restrictions on the computation environment and condition, e.g., the earthquakes are densely concentrated, selected stations are limited in range, the number of stations in- volved in the computation is larger than 5 and linear fitting features high precision and small error. Under these restrictions, the study shows that vP/vS in and around Wen’an and Tangshan underwent a normal-low-normal proc- ess one year before Wen’an earthquake, vP/vS became obviously low and the low ratio lasted for about one year, meanwhile, little variation of vP/vS was seen in Xingtai, northwest of Beijing, southwest of Beijing, Beijing-Tianjin and Beijing; after the quake, the vP/vS returned normal in Wen’an and Tangshan. Error and stability analysis of the calculated result for vP/vS shows it is convincible that anomaly appeared in and around Wen’an and Tangshan be- fore Wen’an earthquake. 相似文献
19.
Coseismic stress-triggering is becoming a new hot spot of research. Coseismic strain steps recorded by borehole strainmeters are particularly valuable in studying coseismic stress-triggered fault slips. Based on the theory of dis location, one can invert the triggered fault slips with such data if he/she has a well understanding about the local faults. Genetic algorithm can be applied to significantly raise the efficiency of searching a best solution among all possibilities in this kind of inversion. A testifying check of the program and analyses of each parameter＇s influence may further enhance the reliability of inversion results. Taking complexity of geological structure into account, the inversion results should be regarded as the predominant property or a comprehensive effect of triggered local faults＇ activities. As an attempt, we inverted the assumingly active faults＇ slips triggered by the Ms=8.1 Kunlun Mountain earthquake over Beijing area. 相似文献
20.
Based on the latest displacement of Huoshan piedmont fault, Mianshan west-side fault and Taigu fault obtained from the beginning of 1990‘s up to the present, the characteristics of distribution and displacement of surface rupture zone of the 1303 Hongtong M = 8 earthquake, Shanxi Province are synthesized and discussed in the paper. If Taigu fault, Mianshan west-side fault and Huoshan piedmont fault were contemporarily active during the 1303 Hongtong M = 8 earthquake, the surface rupture zone would be 160 km long and could be divided into 3 segments, that is, the 50-km-long Huoshan piedmont fault segment, 35-km-long Mianshan west-side fault segment and 70-km-long Taigu fault segment, respectively. Among them, there exist 4 km and 8 km step regions. The surface rupture zone exhibits right-lateral features. The displacements of northern and central segments are respectively 6～7 m and the southern segment has the maximum displacement of 10 m. The single basin-boundary fault of Shanxi fault-depression system usually corresponds to M ≈ 7 earthquake, while this great earthquake (M = 8) broke through the obstacle between two basins. It shows that the surface rupture scale of great earthquake is changeable. 相似文献