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Coseismic Coulomb stress changes induced by a 2020-2021 M_(W)>7.0 Alaska earthquake sequence in and around the Shumagin gap and its influence on the Alaska-Aleutian subduction interface
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作者 Lei Yang Jianjun Wang Caijun Xu 《Geodesy and Geodynamics》 EI CSCD 2024年第1期1-12,共12页
Three M_(W)>7.0 earthquakes in 2020-2021 occurred in the Shumagin seismic gap and its adjacent area of the Alaska-Aleutian subduction zone,including the Mw7.8 Simeonof thrust earthquake on July 22,2020,the M_(W)7.6... Three M_(W)>7.0 earthquakes in 2020-2021 occurred in the Shumagin seismic gap and its adjacent area of the Alaska-Aleutian subduction zone,including the Mw7.8 Simeonof thrust earthquake on July 22,2020,the M_(W)7.6 Sand Point strike-slip earthquake on October 19,2020,and the M_(W)8.2 Chignik thrust earthquake on July 29,2021.The spatial and temporal proximity of these three earthquakes prompts us to probe stress-triggering effects among them.Here we examine the coseismic Coulomb stress change imparted by the three earthquakes and their influence on the subduction interface.Our results show that:(1)The Simeonof earthquake has strong loading effects on the subsequent Sand Point and Chignik earthquakes,with the Coulomb stress changes of 3.95 bars and 2.89 bars,respectively.The Coulomb stress change caused by the Sand Point earthquake at the hypocenter of the Chignik earthquake is merely around 0.01 bars,suggesting the negligible triggering effect on the latter earthquake;(2)The triggering effects of the Simeonof,Sand Point,and Chignik earthquakes on aftershocks within three months are not well pronounced because of the triggering rates of 38%,14%,and 43%respectively.Other factors may have played an important role in promoting the occurrence of these aftershocks,such as the roughness of the subduction interface,the complicated velocity structure of the lithosphere,and the heterogeneous prestress therein;(3)The three earthquakes caused remarkable coseismic Coulomb stress changes at the subduction interface nearby these mainshocks,with an average Coulomb stress change of 3.2 bars in the shallow region directly inwards the trench. 展开更多
关键词 The 2020-2021 Alaska earthquake sequencE Coseismic Coulomb stress change mainshock-aftershock triggering The Alaska-Aleutian subduction interface The Shumagin gap
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Relationship between the earthquake sequences of Tangshan and Xingtai and the three dimensional velocity structure──Discussion on predicting strong earthquakes of swarm-type 被引量:5
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作者 梅世蓉 薛艳 尹京苑 《Acta Seismologica Sinica(English Edition)》 CSCD 1999年第2期175-182,共8页
In this paper, based on the results of tomographic image of Tangshan and Xingtai areas, the relations between thecharacteristics of the two strong earthquake sequences and their three-dimensional velocity structures a... In this paper, based on the results of tomographic image of Tangshan and Xingtai areas, the relations between thecharacteristics of the two strong earthquake sequences and their three-dimensional velocity structures are studied.The research results indicate that:① Mosaic distribution of low-velocity bodies and high-velocity bodies, especially the existence of high-velocity bodies with large size in crust are the common basis of development of thetwo earthquake sequences. ② Scale, depth, and heterogeneity of high-velocity and low-velocity bodies are theimportant factors to effect the characteristic of earthquake sequences. ③ The depth of the high-velocity body inTangshan area is less than that in Xingtai area, which is the principal reason why the dominant focal depth and thebiggest focal depth of Tangshan earthquake sequence are less than Xingtai's. ④ The depth of the high-velocitybodies in Ninghe area is more than that in Tangshan-Luanxian area, which lead to the biggest magnitude and epicentral intensity are lower. These results could be helpful for predicting the main shock of strong swarm-typeearthquakes and later strong aftershocks. 展开更多
关键词 strong earthquake sequence low-velocity anomalous body strong swarm-type earthquake dominant focal depth the biggest focal depth of aftershocks
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The Characteristic Analysis and Seismic Triggering Study of the M6.2 and M6.1 Dayao Earthquake Sequences in 2003 被引量:3
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作者 Hua Wei Liu Jie +1 位作者 Zheng Sihua Chen Zhangli 《Earthquake Research in China》 2006年第4期371-384,共14页
The high-resolution hypocenter locations of the mainshocks on July 21 (M6.2) and October 16, 2003 (M6.1) and their aftershock sequences are determined in Dayao, Yunnan by using a double-difference earthquake locat... The high-resolution hypocenter locations of the mainshocks on July 21 (M6.2) and October 16, 2003 (M6.1) and their aftershock sequences are determined in Dayao, Yunnan by using a double-difference earthquake location algorithm. The results show that the epicenters of the two mainshocks are very close to each other and the distribution of the aftershock sequence appears to be very linear. The distribution of the earthquake sequence is very consistent with the focal mechanism, and both mainshocks are of nearly vertical right-lateral fault. Unlike most other double earthquakes in the Yunmm area, the aftershock distribution of the M6.2 and M6.1 Dayao earthquakes does not appear to be a conjugated distribution but to be in a line, and there are some stacks in the two earthquake sequences. It can be inferred that they are all controlled by the same fault. The distribution of aftershocks is asymmetrical with respect to the mainshock location and appears to be unilateral. The aftershocks of the M6.2 mainshock centralize in the northwest of M6.2 earthquake and the aftershocks of the M6.1 earthquake are in the southeast of the mainshock, moreover, the M6.1 earthquake appears to be another rupture on the southeastern extensiou of the same fault as the M6.2 earthquake. The results of Coulomb failure static stress changes △σf show that the earthquake on July 21 (M6.2) apparently triggered the earthquake on October 16 (M6.1), the two mainshocks have stress triggering to their off-fault aftershocks to different extents, and the M6.5 earthquake that occurred in Yao'an in 2000 also triggered the occurrence of the two Dayao earthquakes. 展开更多
关键词 Double-difference earthquake location Master event location Seismic triggering Dayao earthquake sequences
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Comparison and analysis of the stress field in the source region of Tangshan and Lancang earthquake sequences
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作者 刁桂苓 于利民 李钦祖 《Acta Seismologica Sinica(English Edition)》 CSCD 1995年第3期379-386,共8页
The state of the stress fields in the source region is analysed systematically, on the basis of the focal mechanismsof 167 events with Ms≥4. 0 of Tangshan sequence and 163 moderate-small events of Lancang sequence re... The state of the stress fields in the source region is analysed systematically, on the basis of the focal mechanismsof 167 events with Ms≥4. 0 of Tangshan sequence and 163 moderate-small events of Lancang sequence respectively. The result indicates that the directions of the stress field in the source region are generally stable and thevariation is not obvious after the occurrence of strong shock. The dominant orientations of focal mechanisms ofthe aftershocks are consistent with that of the mainshock, there is still a small difference between some mechanisms of aftershocks and the mechanism of mainshock, and the difference decreases as time goes on. The numbers of solutions with dominant direction of Tangshan and Lancang sequences are similar to each other, it indicates that the controls of the strong earthquake sequences from the tectonic stress field are similar to each othertoo. Through the hierarchical clustering analysis of focal mechanism,it is found that the number of clusters ofTangshan sequence is larger than that of Lancang sequence,and their orientations are relatively disordered. Itmay be the cause that the tectonics in the Tangshan region are more complicated than those in the Lancang region. 展开更多
关键词 focal mechanism stress field Tangshan earthquake sequence Lancang earthquake sequence
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Characteristics of earthquake sequences in the Kuril Islands
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作者 刁桂苓 李钦祖 +2 位作者 陈敬伟 于利民 孙佩卿 《Acta Seismologica Sinica(English Edition)》 EI CSCD 1999年第3期292-297,共6页
A total of 6 earthquake sequences that occurred in the Kuril Islands region in 1964-1976 has been collected and their characteristics have been analyzed. When these sequences are judged from the spatial relation betw... A total of 6 earthquake sequences that occurred in the Kuril Islands region in 1964-1976 has been collected and their characteristics have been analyzed. When these sequences are judged from the spatial relation between their source distribution and the subduction zone, all of them belong to plate boundary earthquake sequences. The parameters of 5 ones among these sequences, which are located just in the subduction zone, are in fair agreement. For these 5 sequences, the major axis of epicenter distribution area is longer; the ratio of major axis to minor axis is high; the focal depths have a greater range; the directions of dip are consistent with the direction of subduction; the dip angles are of moderate value. It is estimated that the only exception is related to the low accuracy of data in the early stage. 展开更多
关键词 Kuril Islands earthquake sequence plate boundary earthquake
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Research on characteristics of magnitude structure of earthquake sequences
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作者 孙佩卿 李钦祖 +1 位作者 戴英华 赵军 《Acta Seismologica Sinica(English Edition)》 EI CSCD 1998年第1期41-46,共6页
Based on the research on 108 strictly selected earthquake sequences since 1965 in the Chinese mainland, why the magnitude structures of most of these sequences are not in accord with the G R relation has been analyze... Based on the research on 108 strictly selected earthquake sequences since 1965 in the Chinese mainland, why the magnitude structures of most of these sequences are not in accord with the G R relation has been analyzed and the fitting method with the division of the magnitude structure for the earthquake sequences has been suggested. The characteristic values of this method in the high magnitude interval have mainly been researched, and characteristic magnitude percent f and the slope ratio b 2 of the high magnitude interval, which are different for various sequence types are most obvious. The results show that the N M patterns of magnitude structures for 52.8% earthquake sequences are not in accord with the G R relation from the magnitude less than 80% of the maximum one and that for only 18.5% earthquake sequences show the decrease trend in the high magnitude interval. When b 2 <0 or 0 b 2 <3.0 and f is less, the strong aftershocks in the earthquake sequences are less; when b 2 3.0 for the sequence, several strong aftershocks often occurred; when 0b 2<3.0 and f is bigger, aftershocks with middle magnitude are more in these sequences. 展开更多
关键词 earthquake sequence MAGNITUDE magnitude characteristic
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A study on the focal parameters of Shidian M=5.9 earthquake sequences in 2001
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作者 秦嘉政 钱晓东 叶建庆 《Acta Seismologica Sinica(English Edition)》 CSCD 2005年第3期269-279,共11页
On the basis of about 300 earthquake wave forms observed in the Shidian MS=5.9 sequences on April 12, 2001 recorded in Kunming Digital Seismic Network, the spectra of shear wave have been used to estimate the focal pa... On the basis of about 300 earthquake wave forms observed in the Shidian MS=5.9 sequences on April 12, 2001 recorded in Kunming Digital Seismic Network, the spectra of shear wave have been used to estimate the focal parameters of these earthquake sequences. The results show that within the magnitude range of 1.5~5.3, the seis-mic moments are 1010~1016 N?m, the corner frequencies are 0.2~0.8 Hz, radii of the focal rupture are 200~2 500 m and the stress drops are 0.1×105~20×105Pa. Through the statistical analyses of variation of corner frequency fc and stress drop ?σ with time, it is discovered that the average corner frequency of the foreshock sequences is obviously lower than that of the aftershock sequences. Contrarily, the average stress drops ?σ of the foreshock sequences are clearly higher than that of the aftershocks. It is considered that these variation characteristics of av-erage corner frequency and stress drops before and after the main shock have index significance to the precursory information before a strong earthquake. The higher stress drops for the foreshock sequences show that the higher shear stresses have been stored in the area of main shock. After the main shock, most of the stresses have been released, so the aftershock sequences show a rupture process of lower stresses. 展开更多
关键词 digital seismic observation focal parameter earthquake sequence Yunnan region
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Researchonpredictionofthefolowingnotice┐ableshocksofearthquakesequences
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作者 刘蒲雄 陈修启 +1 位作者 吕晓健 韩丹 《Acta Seismologica Sinica(English Edition)》 CSCD 1996年第1期33-40,共8页
This paper shows the characteristics of noticeable shocks of 37 earthquake sequences with M ≥6 and the research on the tracing prediction method of them. The result shows that the variation of the strain release ... This paper shows the characteristics of noticeable shocks of 37 earthquake sequences with M ≥6 and the research on the tracing prediction method of them. The result shows that the variation of the strain release of the tracing earthquake sequence with time is an important means for predicting the following noticeable shocks. Predicting ultra late strong aftershocks needs to investigate the regional seismicities. 展开更多
关键词 earthquake sequence earthquake type aftershock prediction.
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Calculation of the h-value during Superposing of Strong Earthquake Sequences and Its Application in Earthquake Prediction
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作者 Yang Xin and Yu XingbaoSeismological Bureau of Xinjiang Uygur Autonomous Region, Urumqi 830011, China 《Earthquake Research in China》 1999年第3期38-48,共11页
For a strong earthquake swarm, the key to estimate the frequency attenuation coefficient h-value of ensuing strong earthquake sequence accurately lies in quantitative calculation and subtraction of the foreshock seque... For a strong earthquake swarm, the key to estimate the frequency attenuation coefficient h-value of ensuing strong earthquake sequence accurately lies in quantitative calculation and subtraction of the foreshock sequence effect.Taking the Jiashi strong earthquake swarm sequence as an example, we analyzed and compared the h-values when foreshock effect has been subtracted or not subtracted. The result shows that the boundary between the two great difference is the M56.6 earthquake on April 11,1997. The h-values with foreshock effect subtracted are all Iess than 1 before the moderately strong earthquakes, but after the earthquake, the h-values are all greater than 1. On the contrary, the h-values with foreshock effect do not show this kind of turning variation.Practical test results shows that quantitatively subtracting foreshock effect is beneficial to the judgement of the trend of the activity of the Jiashi strong earthquake swarm. This provides the basis for accurately grasping sequence development 展开更多
关键词 earthquake swarm sequence analysis earthquake FREQUENCY AFTERSHOCK FREQUENCY attenuation H-VALUE Jiashi.
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Some Tonal and Rhythmical Sequences in the Vocal Language of Dogs as Significant Earthquake Precursors
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作者 Giovanna de Liso 《Open Journal of Earthquake Research》 2018年第4期221-268,共48页
A monitoring of multiple physical parameters in a moderate seismic area in Western Piedmont (NW Italy) and the simultaneous observation of the behaviour of numerous species of domestic and wild animals gave in a perio... A monitoring of multiple physical parameters in a moderate seismic area in Western Piedmont (NW Italy) and the simultaneous observation of the behaviour of numerous species of domestic and wild animals gave in a period of over twenty years the possibility to distinguish the unusual animal behaviours due to local earthquake nucleation from other causes. In particular, the observation of the body and vocal language of dogs (Canis familiaris) in the same area has permitted not only to specify the different meanings of vocal language in connection to their body language, but also to classify the minimum elements into a vocal language that is linked together by tonal and rhythmical sequences of sounds that form a semantic lexicon. The usage of the same tonal and rhythmical vocal sequences in similar or identical situations, which are experienced by different groups of dogs, induces us to verify whether it could be possible to link particular vocal sequences to precise physical anomalies before earthquakes. The individuation of physical anomalies due to an earthquake nucleation or due to a hydro-geological destabilization, is possible thanks to a continuous long-term monitoring of some parameters. Moreover, the complexity of the vocal language of dogs increases if the dogs live in an area with a law population density. Then the correlation between some vocal sequences and some seismic precursors is better if dogs live free in yard or on farms, if they are in good health, and if they can establish a strong social relation of group. When dogs live closed in yards of houses that are far apart, they communicate with each other with an amazing vocal language, full of questions and answers, imitations of sequences, and information about situations that may be harmful to them. 展开更多
关键词 VOCAL Language DOGS RHYTHMICAL And Tonal sequences Syntax Formant VOCAL Tract Semantics Seismic Precursors earthquakes Magnetic DECLINATION Sudden COMMENCEMENT Infra-Sounds Brontides
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Analysis on Double-difference Earthquake Location and the Seismicity Pattern of the Yangjiang Earthquake Sequences
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作者 Kang Ying Yang Xuan Huang Wenhui Chen Xing Chen Guimei Lin Wei Wu Huadeng 《Earthquake Research in China》 2008年第1期73-81,共9页
The locations of about 400 earthquakes in Yangjiang, Guangdong Province are determined using the double, difference earthquake location algorithm (DDA). The seismicity pattern becomes concentrated from discrete grid... The locations of about 400 earthquakes in Yangjiang, Guangdong Province are determined using the double, difference earthquake location algorithm (DDA). The seismicity pattern becomes concentrated from discrete grids. The rupture characteristics of the Yangjiang earthquake sequence show a conjugated distribution in NW and NE directions. The major distribution trends NE and dips NE with an angle of 30^o and a length of 30km,and the minor distribution trends NW and dips SE with an angle of 30^o and a length of 20km. The focal depth is 5km - 15km. The distribution of the Enping earthquake sequence,which is not far from Yangjiang,is NW-trending. The relationship between hypocenter distribution and geological structure is discussed. 展开更多
关键词 Double-difference earthquake location algorithm Location image Rupturecharacteristic Yangjiang earthquake sequences
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The Precursory Significance of Cumulative Slip of Repeating Earthquake Sequences Prior to Moderately Strong Earthquakes A Case Study of Four Remarkable Earthquake Sequences of Haicheng- Xiuyan
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作者 Li Yutong Zhang Bo +1 位作者 Wang Liang Li Tongxia 《Earthquake Research in China》 CSCD 2016年第1期22-32,共11页
The Haicheng-Xiuyan region is an earthquake-prone area in Liaoning Province where earthquake sequences frequently occur and is regarded as the regional seismic window. In this area we found many earthquake events with... The Haicheng-Xiuyan region is an earthquake-prone area in Liaoning Province where earthquake sequences frequently occur and is regarded as the regional seismic window. In this area we found many earthquake events with the highest waveform similarity in the records of the same station from some remarkable seismic sequences,namely repeating earthquake sequences. In principle,rupture areas of the repeating events overlap with each other and are most closely located. Therefore these events may reflect the seismic process near the earthquake fault. In this paper, we identified four remarkable earthquake sequences of Haicheng-Xiuyan by waveform cross-correlation. The result shows that the cumulative slip of repeating earthquakes is related to moderately strong earthquakes,among which the Xiuyan M_S5. 4 foreshock sequence has the strongest and most apparent pre-shock accelerating-like slip behavior. 展开更多
关键词 earthquake sequence Repeating earthquake Waveform correlationHaicheng-Xiuyan
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Comparative Study of Changes in Stress-drop of the Jinggu MS6.6 and Ludian MS6.5 Earthquake Sequences
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作者 Zhou Shaohui Jiang Haikun Qu Junhao 《Earthquake Research in China》 CSCD 2017年第2期151-168,共18页
The earthquake stress-drop values of two sequences were accurately calculated after taking away the effects due to regional earthquake anelastic attenuation and station site response,using waveform data and seismic ph... The earthquake stress-drop values of two sequences were accurately calculated after taking away the effects due to regional earthquake anelastic attenuation and station site response,using waveform data and seismic phase data of sequences of the Jinggu M_S6. 6,and Ludian M_S6. 5 earthquakes in Yunnan. These results show that the stress drop with magnitude increases within the scope of this study of magnitude. After eliminating the influence of the magnitude,the average value of stress-drop in the Jinggu sequence is higher than that of the Ludian sequence at the same magnitude range. This may be related to the stress state in different regions. In terms of the changes of time and space of stress-drop,before M_S5. 8 strong aftershock,the stress-drop is "slowing down-turning up-keeping a high value"after the mainshock,meanwhile,almost all of the abnormally high stress drop value is distributed around the M_S5. 8 strong aftershock, showing that the stress environment in the region was increasing after the mainshock. And after the M_S5. 9 strong aftershock,stress-drop rapidly declines to a relatively stable state,meanwhile,the high value of stress-drop is distributed around the strong aftershock,showing that the regional tectonic stress gets more fully release,its stress environment begins to rapidly decrease.For the Ludian sequence without a strong aftershock occurring,the average value of stress drop is lower than that of the Jinggu earthquake sequence at the same magnitude range,while at the same time,the stress-drop of the aftershock sequence almost hasn't changed much. In the time after the mainshock,combined with the release characteristics of the main energy,the stress in the region is excessively released,the subsequent stress in the region gradually returns to normal. This may be the reason why the activity of Ludianaftershocks significantly was weaker and subsequently there were no strong aftershocks occurred. 展开更多
关键词 Stress-drop Aftershock sequence Ludian earthquake Jinggu earthquake
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Prediction of the Earlier Strong Aftershocks in the Earthquake Sequences by the Pseudo-Periodicity Method
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作者 Wang Chunzhen, Huang Hanming, and Wang BiquanInstitute of Geophysics, CSB, Beijing 100081, China 《Earthquake Research in China》 1998年第3期69-75,共7页
We propose the pseudo-periodicity method and its quantitative prediction indexes for the occurrence time of earlier strong aftershock. We conducted tests of regressive prediction, and the R-value of the tests is 0.45,... We propose the pseudo-periodicity method and its quantitative prediction indexes for the occurrence time of earlier strong aftershock. We conducted tests of regressive prediction, and the R-value of the tests is 0.45, indicating that this method is effective for prediction. 展开更多
关键词 earthquake PREDICTION STRONG AFTERSHOCK earthquake sequence Pseudo-period.
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Characteristics of Seismic Sequences and Early Tendency Judgment for Yutian M_S7.3 Earthquake in 2014
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作者 Song Chunyan Zhang Linlin +2 位作者 Nie Xiaohong Xia Aiguo Wei Yunyun 《Earthquake Research in China》 CSCD 2015年第3期352-362,共11页
The basic parameters,seismogenic structure and seismic sequences characteristics of the Yutian MS7. 3 earthquake on February 12,2014 are introduced and compared to the Yutian MS7. 3 earthquake in 2008. The results sho... The basic parameters,seismogenic structure and seismic sequences characteristics of the Yutian MS7. 3 earthquake on February 12,2014 are introduced and compared to the Yutian MS7. 3 earthquake in 2008. The results show that the MS5. 4 earthquake is regarded as an immediate foreshock of the Yutian MS7. 3 main shock. The frequency of strong aftershock sequences was low and their number declined quickly,and the maximum aftershock was a MS5. 7 earthquake. According to analysis of the historical earthquake sequence type,and parameter of h-value,b-value and energy release ratio between main shock and sequence etc.,we found the preliminary conclusion that the Yutian MS7. 3 earthquake sequence in 2014 was a foreshock-main shock-aftershock type. 展开更多
关键词 Yutian Ms7. 3 earthquake Seismic sequence Strong aftershock
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Research on Stress Drops and the Focal Mechanisms of the Xinyuan- Hejing ML6.8 Earthquake Sequences
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作者 Liu Jianming Wang Qiong +4 位作者 Liu Jie Deng Fei Xiang Yuan Yang Wen Li Jin 《Earthquake Research in China》 CSCD 2017年第1期25-38,共14页
Based on the digital waveform data recorded by Xinjiang Digital Seismic Network for the Xinyuan-Hejing M_L6.8 earthquake sequences of June 30,2012,this paper analyzes the stress drops of earthquake sequences and the c... Based on the digital waveform data recorded by Xinjiang Digital Seismic Network for the Xinyuan-Hejing M_L6.8 earthquake sequences of June 30,2012,this paper analyzes the stress drops of earthquake sequences and the correlation coefficients of focal mechanisms significant for strong aftershocks.Firstly,the source parameters of the Xinyuan-Hejing M_L6.8 earthquake sequences are obtained by applying the spectrum analysis and the Brunes source model.Then,the correlation coefficients of spectral amplitudes are calculated using the low-frequency spectral amplitude recorded by the same station for the different events.Finally,based on the results of the correlation coefficients of spectral amplitudes,the events with similar focal mechanisms are grouped using the clustering method.The results show that:(1)The stress drop values show a steady trend in the aftershock sequence calm period and the stress drop values show a rise-fall in strong aftershocks.(2)The moving average correlation coefficient of amplitude spectrum begins to spread after the main shock.It shows that the correlation decreases between the main shock and the aftershocks in mechanisms.(3)The results of focal mechanism groups show that the earthquake sequences are mainly strike slips.The stress distribution of the main pressure axis is nearly NS,which is the same as the structural stress field.(4)The magnitude and mechanism show that there is an agreement before the strong aftershock,which shows that the regional stress field is enhanced. 展开更多
关键词 Xinyuan-Hejing ML6. 8 earthquake sequences Stress drop The correlationof the focal mechanism Body-wave spectral amplitude Clustering group
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Geometry and tectonic deformation of the seismogenic structure for the 8 August 2017 M_S 7.0 Jiuzhaigou earthquake sequence,northern Sichuan, China 被引量:22
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作者 Feng Long GuiXi Yi +2 位作者 SiWei Wang YuPing Qi Min Zhao 《Earth and Planetary Physics》 CSCD 2019年第3期253-267,共15页
To reveal the geometry of the seismogenic structure of the Aug. 8, 2017 M_S 7.0 Jiuzhaigou earthquake in northern Sichuan,data from the regional seismic network from the time of the main event to Oct. 31, 2017 were us... To reveal the geometry of the seismogenic structure of the Aug. 8, 2017 M_S 7.0 Jiuzhaigou earthquake in northern Sichuan,data from the regional seismic network from the time of the main event to Oct. 31, 2017 were used to relocate the earthquake sequence by the tomoDD program, and the focal mechanism solutions and centroid depths of the M_L ≥ 3.5 events in the sequence were determined using the CAP waveform inversion method. Further, the segmental tectonic deformation characteristics of the seismogenic faults were analyzed preliminarily by using strain rosettes and areal strains(As). The results indicate:(1) The relocated M_S 7.0 Jiuzhaigou earthquake sequence displays a narrow ~ 38 km long NNW-SSE-trending zone between the NW-striking Tazang Fault and the nearly NSstriking Minjiang Fault, two branches of the East Kunlun Fault Zone. The spatial distribution of the sequence is narrow and deep for the southern segment, and relatively wide and shallow for the northern segment. The initial rupture depth of the mainshock is 12.5 km, the dominant depth range of the aftershock sequence is between 0 and 10 km with an average depth of 6.7 km. The mainshock epicenter is located in the middle of the aftershock region, showing a bilateral rupture behavior. The centroid depths of 32 M_L ≥ 3.5 events range from 3 to 12 km with a mean of about 7.3 km, consistent with the predominant focal depth of the whole sequence.(2) The geometric structure of the seismogenic fault on the southern section of the aftershock area(south of the mainshock) is relatively simple, with overall strike of ~150° and dip angle ~75°, but the dip angle and dip-orientation exhibit some variation along the segment. The seismogenic structure on the northern segment is more complicated; several faults, including the Minjiang Fault, may be responsible for the aftershock activities. The overall strike of this section is ~159° and dip angle is ~59°, illustrating a certain clockwise rotation and a smaller dip angle than the southern segment. The differences between the two segments demonstrate variation of the geometric structure along the seismogenic faults.(3) The focal mechanism solutions of 32 M_L ≥ 3.5 events in the earthquake sequence have obvious segmental characteristics. Strike-slip earthquakes are dominant on the southern segment, while 50% of events on the northern segment are thrusting and oblique thrusting earthquakes, revealing significant differences in the kinematic features of the seismogenic faults between the two segments.(4) The strain rosettes for the mainshock and the entire sequence of 31 M_L ≥ 3.5 aftershocks correspond to strike-slip type with NWW-SEE compressional white lobes and NNE-SSW extensional black lobes of nearly similar size. The strain rosette and As value of the entire sequence of 22 M_L ≥ 3.5 events on the southern segment are the same as those of the M_S 7.0 mainshock,indicating that the tectonic deformation here is strike-slip. However, the strain rosette of the entire sequence of 10 M_L ≥ 3.5 events on the northern segment show prominent white compressional lobes and small black extensional lobes, and the related As value is up to 0.52,indicating that the tectonic deformation of this segment is oblique thrusting with a certain strike-slip component. Differences between the two segments all reveal distinctly obvious segmental characteristics of the tectonic deformation of the seismogenic faults for the Jiuzhaigou earthquake sequence. 展开更多
关键词 MS 7.0 Jiuzhaigou earthquake sequence RELOCATION focal mechanism SEISMOGENIC structure GEOMETRY tectonic deformation
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Spatial distribution features of sequence types of moderate and strong earthquake in Chinese mainland 被引量:5
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作者 蒋海昆 李永莉 +4 位作者 曲延军 华爱军 郑建常 代磊 侯海峰 《Acta Seismologica Sinica(English Edition)》 EI CSCD 2006年第4期417-427,共11页
Based on 294 earthquake sequences with magnitude greater than or equal to 5.0 occurred in Chinese mainland since 1970, the spatial distribution features of sequence types have been studied. In southwestern China, it t... Based on 294 earthquake sequences with magnitude greater than or equal to 5.0 occurred in Chinese mainland since 1970, the spatial distribution features of sequence types have been studied. In southwestern China, it takes mainshock-aftershock sequence type (MAT) as the major in Chuan-Dian rhombic block and concerned Xianshuihe-Anninghe-Xiaojiang seismic belt, as well as in Jinshajiang-Honghe seismic belt. Multiple mainshock type (MMT) mainly distributes in western Yunnan, and Longlin and Lancang areas in Tengchong-Baoshan block in west of Nujiang-Lancangjiang fault zone. A few isolated earthquake type (IET) mainly occurred in northwestern Sichuan and there is no IET occurred in Yunnan region. In northwestern China, it takes mainshock-aftershock sequence type (MAT) as the major in west segment of South Tianshan in Xinjiang region. Some MMT also occurred in this area in the intersection of Kalpin block and the Puchang fault zone. It takes IET as the major in middle Tianshan in Xinjiang. Along the Qilianshan seismic belt, most of sequences are MAT. In Qinghai region, it takes MAT as the major, but the regional feature of the spatial distribution of sequence types is not very clear. In North China, it takes MAT as the major in Yinshan-Yanshan-Bohai seismic belt, north edge of North China, and in Hebei plain seismic belt, as well as in sub-plate of lower river area of Yangtze River. In intersection of north segment of Shanxi seismic belt and the NW-trending Yinshan-Yanshan-Bohai seismic belt, there are several moderate or strong MMT with magnitude from 5.0 to 6.0 occurred. In south of North China around the latitude line of 35°N, it takes IET as the major. The spatial distribution of sequence types is relevant to the patterns of tectonic movements. MAT is mostly produced by the ruptures of locked units or asperities or the neonatal separating segments inside the fault zones. MMT is generally relevant to the conjugate structures or intersection of many tectonic settings. Further extension of simple fault often produces IET. Spatial distribution of sequence types is also correlative to the regional and deep environment of crustal medium to some extent. MAT mainly distributes in high velocity area in upper crust or in the transition zone between high velocity area and low velocity area, MMT mostly occurred in the low velocity area in upper crust. 展开更多
关键词 spatial distribution of sequence types isolated earthquake malnshock-aftershock sequence multi-ple malnshock type patterns of tectonic movement medium environment in depth of the earth
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High-precision relocation of the aftershock sequence of the January 8,2022,M_(S)6.9 Menyuan earthquake 被引量:21
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作者 Liping Fan Boren Li +2 位作者 Shirong Liao Ce Jiang Lihua Fang 《Earthquake Science》 2022年第2期138-145,共8页
The 2022 Menyuan M_(S)6.9 earthquake,which occurred on January 8,is the most destructive earthquake to occur near the Lenglongling(LLL)fault since the 2016 Menyuan M_(S)6.4 earthquake.We relocated the mainshock and af... The 2022 Menyuan M_(S)6.9 earthquake,which occurred on January 8,is the most destructive earthquake to occur near the Lenglongling(LLL)fault since the 2016 Menyuan M_(S)6.4 earthquake.We relocated the mainshock and aftershocks with phase arrival time observations for three days after the mainshock from the Qinghai Seismic Network using the double-difference method.The total length and width of the aftershock sequence are approximately 32 km and 5 km,respectively,and the aftershocks are mainly concentrated at a depth of 7-12 km.The relocated sequence can be divided into 18 km west and 13 km east segments with a boundary approximately 5 km east of the mainshock,where aftershocks are sparse.The east and west fault structures revealed by aftershock locations differ significantly.The west fault strikes EW and inclines to the south at a 71°-90°angle,whereas the east fault strikes 133°and has a smaller dip angle.Elastic strain accumulates at conjunctions of faults with different slip rates where it is prone to large earthquakes.Based on surface traces of faults,the distribution of relocated earthquake sequence and surface ruptures,the mainshock was determined to have occurred at the conjunction of the Tuolaishan(TLS)fault and LLL fault,and the west and east segments of the aftershock sequence were on the TLS fault and LLL fault,respectively.Aftershocks migrate in the early and late stages of the earthquake sequence.In the first 1.5 h after the mainshock,aftershocks expand westward from the mainshock.In the late stage,seismicity on the northeast side of the east fault is higher than that in other regions.The migration rate of the west segment of the aftershock sequence is approximately 4.5 km/decade and the afterslip may exist in the source region. 展开更多
关键词 Menyuan earthquake aftershock sequence double-difference relocation Lenglongling fault Tuolaishan fault
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A priliminary study on the sequence characteristics and focal mechanism solution of the Jiashi strong earthquake swarm 被引量:2
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作者 XIN YANG GUO YING GAO Seismological Bureau of Xinjiang Uygur Autonomous Region, rümqi 830011, China 《Acta Seismologica Sinica(English Edition)》 CSCD 1998年第6期16-23,共8页
The sequence characteristics and focal mechanism solution of the Jiashi, Xinjiang strong earthquake swarm are analyzed and studied in this paper. The result shows that before the M S=6.6 earthquake, value h o... The sequence characteristics and focal mechanism solution of the Jiashi, Xinjiang strong earthquake swarm are analyzed and studied in this paper. The result shows that before the M S=6.6 earthquake, value h of sequence frequency attenuation coefficient was less than 1, then value h was more than 1. Before occurrence of M S6.0 earthquakes the energy is released either in a continuously strengthened way or a sharply strengthened way, and before M S5.0 earthquakes the sequence frequency shows calm. The study on the focal mechanism solution of the strong earthquake swarm shows that the source faults are mainly in a right lateral, strike slip way and the faults have characteristics of tensor shear. 展开更多
关键词 earthquake swarm sequence characteristics focal mechanism SOLUTION focal displacement feature JIASHI
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