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1.
The Xianshuihe Fault, the boundary of Bayan Har active tectonic block and Sichuan-Yunnan active tectonic block, is one of the most active fault zones in the world. In the past nearly 300 years, 9 historical earthquakes of magnitude ≥ 7 have been recorded. Since 2008, several catastrophic earthquakes, such as Wenchuan MS8 earthquake, Yushu MS7.1 earthquake and Lushan MS7 earthquake, have occurred on the other Bayan Har block boundary fault zones. However, only the Kangding MS6.3 earthquake in 2014 was documented on the Xianshuihe Fault. Thus, the study of surface deformation and rupture behavior of large earthquakes in the late Quaternary on the Xianshuihe Fault is of fundamental importance for understanding the future seismic risk of this fault, and even the entire western Sichuan region. On the basis of the former work, combined with our detailed geomorphic and geological survey, we excavated a combined trench on the Qianning segment of Xianshuihe fault zone which has a long elapse time. Charcoal and woods in the trench are abundant. 30 samples were dated to constrain the ages of the paleoseismic events. Five events were identified in the past 9  000 years, whose ages are:8070-6395 BC, 5445-5125 BC, 4355-4180 BC, 625-1240 AD and the Qianning earthquake in 1893. The large earthquake recurrence behavior on this segment does not follow the characteristic earthquake recurrence model. The recurrence interval is 1000~2000 years in early period and in turn there is a quiet period of about 5 000 years after 4355-4180 BC event. Then it enters the active period again. Two earthquakes with surface rupture occurred in the past 1000 years and the latest two earthquakes may have lower magnitude. The left-lateral coseismic displacement of the 1893 Qianning earthquake is about 2.9m.  相似文献   

2.
Most earthquakes result from fault activity under heterogeneous loading and complex physical properties, also affected by fault structure and interaction between faults. Such a complicated mechanism makes often failures of the "seismic gap" theory in the effort of medium-and long-term earthquake prediction. This study attempts to address this issue using the finite element method(FEM).The friction behavior of faults can be used to simulate the non-uniformity of rupture processes of the seismogenic structure. So we use the FEM containing non-linear friction to simulate fault ruptures in the Daliangshan sub-block and adjacent areas, and compare the results with time-space evolution of historical MS ≥ 7 earthquakes since 1840 in this region. In the simulation, the sequence of large-batch fault contact nodes change from "stick state" to "slip state" in short time, which mimics the sudden fault slip and the occurrence of major earthquakes. The results show that the fault breaking lengths from simulation are largely consistent with the magnitudes of historical earthquakes in the study area, such as the 1850 Puge-Xichang MS7.5, and 1887 Shiping MS7.0 earthquakes. The simulation also shows the development of seismic gaps and "gap breaks" by major earthquakes on the Xianshuihe fault, such as 1955 Kangding MS7.5 earthquake. Especially, the results illustrated the very long time of the seismogenic process of the 2008 Wenchuan MS8.0 earthquake, and the corresponding sudden big rupture along the Longmenshan Fault, which is very similar to the observed surface rupture and very long incubation time and sudden co-seismic process. Then, this simulation is further applied to long-term earthquake prediction for the study area by calculation on a much longer time. The simulation results suggest that the Xiaojiang fault and the Zemuhe fault have relatively higher seismic risk, while moderate-sized earthquakes might occur on the Daliangshan fault and the Aninghe fault, and major earthquakes might rupture the northern segment of the Xianshuihe fault in a much longer time.  相似文献   

3.
2014年11月22日16时55分在四川省甘孜藏族自治州康定县发生的6.3级地震,结束了鲜水河断裂带近30多年以来没有较大地震发生的历史,其潜在的地震危险性再次引起国内外地学工作者的关注.为了研究鲜水河断裂带南东段深部孕震环境和探求康定MS6.3地震的成因,本文先利用四川区域数字地震台网和康定地区及周边所布设的流动地震台阵在2009年1月1日至2014年12月5日期间所记录到7397次区域地震事件的99287条P波到时资料,反演得到了鲜水河断裂带南东段上地壳范围内不同深度的三维P波速度结构特征;再对康定震区及周边的重力、航磁数据进行视密度、视磁化强度反演,得到了壳内不同深度密度的横向变化信息和视磁化强度的分布特征;在此基础上综合研究鲜水河断裂带南东段的深部孕震环境.研究结果表明,雅江—九龙一带的低速区与泸定—宝兴高速区的速度结构特征表明了鲜水河断裂带南东段两侧壳内物质存在显著的横向介质差异,康定MS6.3地震发生在该高低速异常区的分界线上;结合康定MS6.3地震的1028个余震序列的精确定位结果可以看出,重新定位后的余震沿着鲜水河断裂带南东段呈条带状分布,且震源深度优势分布层位深度为8~15km,该余震序列的空间分布特征与鲜水河断裂南东段的深部介质条件密切相关.鲜水河断裂带南东段特有的视密度和视磁化强度异常分布特征反映了康定地区东西两侧块体的基底性质存在明显差异,康定—石棉及其以东地区所表现出的磁异常高和重力高的位场特征,反映该区域由强磁性、高密度物质组成,而康定MS6.3地震就发生在康定—石棉重力梯度变化带上、雅安—泸定磁性穹窿区的西边界线上.随着川青块体向南东方向滑移,受到四川盆地西缘边界刚性基底对川青块体的强烈阻挡,加剧了康定—石棉及其以东地区基底岩层的褶皱变形并产生了强烈的应力积累,所积累的应力突然释放导致了康定MS6.3地震的发生,这正是此次鲜水河断裂带南东段康定地区强震孕育和发生的深部构造环境和介质特征.根据本文对鲜水河断裂带南东段深部孕震环境的综合研究成果可知,石棉段处于重磁异常梯级带上且其北东侧表现出的高密度、强磁性和高波速等物性特征有利于区域应力的相对集中,因此,鲜水河断裂带南东段石棉地区的地震活动趋势和地震危险性背景值得进一步关注和研究.  相似文献   

4.
The Hutubi MS6.2 earthquake of December 8, 2016 is a pure thrust event in the northern Tianshan thrust fold belt. The earthquake occurred between the Qigu Fault and the Junggar southern margin fault, which are both thrust faults. Based on mobile gravity measurements from 2013 to 2018 in the northern Tianshan, the gravity net adjustment was accomplished using Urumqi absolute gravity observation point as the datum, and the absolute gravity value of surface observation points were obtained. In order to eliminate the seasonal effect on gravity variation, the paper uses the observation data in May per annual as studying objects and obtains the temporal-spatial dynamic evolution images of gravity field differences in the northern Tianshan at different time scales as well as the time series of gravity variation of some points in the adjacent area of the epicenter. The characteristics of regional gravity variation before and after the Hutubi MS6.2 earthquake on December 8, 2016 and their relations are analyzed systematically. The results show that: 1)The gravity variations in the study area are dramatic in generally, and the contours of gravity variation are consistent with the main faults basically. There was a four-quadrant distribution near the epicenter before the earthquake, and the Hutubi MS6.2 earthquake occurred near the center of the four-quadrant distribution and at the turn of the gravity variation contour. The three years' cumulative gravity variation before the earthquake and the gravity variation after the earthquake are inversed, and the variation amplitudes are equivalent, suggesting that the MS6.2 earthquake has released the stress and the energy accumulated before the earthquake. 2)This paper focuses on the analysis of gravity variation at the observation points on both sides of the Junggar southern margin fault near the epicenter. Regional gravity variation and gravity time series show that gravity variations at the same side of the Junggar southern margin fault are basically consistent, however, gravity variations at the different sides of the Junggar southern margin fault are different from each other obviously, indicating the difference of material migration laws in different structural regions. In addition, the strain energy accumulated in the epicenter is basically released after the earthquake, and the area nearby the epicenter tends to be stable. 3)The Hutubi MS6.2 earthquake occurred near the center of the four-quadrant and at the turn of the high-gradient zone of gravity variation, reflecting the location of strong earthquake is related to the distribution of four-quadrant of regional gravity variation, the high-gradient zone of regional gravity variation and its turn. It has a unique advantage in determining the location of strong earthquake using gravity variation results. The regional spatial-temporal gravity variation before the earthquake is manifested as a systematic evolution process of “steady state→regional gravity anomaly→four-quadrant distribution→earthquake occurring in the reverse process”. Studying the temporal-spatial evolution characteristics of gravity field before and after Hutubi MS6.2 earthquake has important practical significance for understanding the occurrence law of large earthquakes and capturing the precursory information of earthquakes.  相似文献   

5.
以2014年四川康定MS6.3和MS5.8地震为研究对象,计算了2次主震在近场和周围断层造成的库仑破裂应力变化,研究主震与余震的触发关系,以及2次主震对周围断层施加的应力负荷作用。结果表明:2次主震的共同作用控制了后续地震活动的演化趋势,其中康定MS6.3地震产生的库仑破裂应力变化对后续余震事件的触发占主导作用。鲜水河断裂带南段和安宁河断裂带受到了一定的应力加载作用,未来地震活动的趋势可能会加强。  相似文献   

6.
Complex geometrical structures on strike-slip faults would likely affect fault behavior such as strain accumulation and distribution, seismic rupture process, etc. The Xianshuihe Fault has been considered to be a Holocene active strike-slip fault with a high horizontal slip rate along the eastern margin of the Tibetan plateau. During the past 300 years, the Xianshuihe Fault produced 8 earthquakes with magnitude≥7 along the whole fault and showed strong activities of large earthquakes. Taking the Huiyuansi Basin as a structure boundary, the northwestern and southeastern segments of the Xianshuihe Fault show different characteristics. The northwestern segment, consisting of the Luhuo, Daofu and Qianning sections, shows a left-stepping en echelon pattern by simple fault strands. However, the southeastern segment(Huiyuansi-Kangding segment)has a complex structure and is divided into three sub-faults: the Yalahe, Selaha and Zheduotang Faults. To the south of Kangding County, the Moxi segment of the Xianshuihe Fault shows a simple structure. The previous studies suggest that the three sub-faults(the Yalahe, Selaha and Zheduotang Faults of the Huiyuansi-Kangding segment)unevenly distribute the strain of the northwestern segment of the Xianshuihe Fault. However, the disagreement of the new activity of the Yalahe Fault limits the understanding of the strain distribution model of the Huiyuansi-Kangding segment. Most scholars believed that the Yalahe Fault is a Holocene active fault. However, Zhang et al.(2017)used low-temperature thermochronology to study the cooling history of the Gongga rock mass, and suggested that the Yalahe Fault is now inactive and the latest activity of the Xianshuihe Fault has moved westward over the Selaha Fault. The Yalahe Fault is the only segment of the Xianshuihe Fault that lacks records of the strong historical earthquakes. Moreover, the Yalahe Fault is located in the alpine valley area, and the previous traffic conditions were very bad. Thus, the previous research on fault activity of the fault relied mainly on the interpretation of remote sensing, and the uncertainty was relatively large. Through remote sensing and field investigation, we found the geological and geomorphological evidence for Holocene activity of the Yalahe Fault. Moreover, we found a well-preserved seismic surface rupture zone with a length of about 10km near the Yariacuo and the co-seismic offsets of the earthquake are about 2.5~3.5m. In addition, we also advance the new active fault track of the Yalahe Fault to Yala Town near Kangding County. In Wangmu and Yala Town, we found the geological evidence for the latest fault activity that the Holocene alluvial fans were dislocated by the fault. These evidences suggest that the Yalahe Fault is a Holocene active fault, and has the seismogenic tectonic condition to produce a large earthquake, just like the Selaha and Zheduotang Faults. These also provide seismic geological evidence for the strain distribution model of the Kangding-Huiyuansi segment of the Xianshuihe Fault.  相似文献   

7.
In this paper, according to the synthetic gravity anomaly of a horizontally infinite cylindrical geologic body, gravity gradient in horizontal direction was calculated by potential field discrete cosine transformation in frequency domain. In the calculation, the minimum curvature method was used to extend edge lines. We found that the gravity gradient field from the potential field transformation was dependable by comparison with synthetic gravity gradient, except the data in the edges. Then, the accumulative horizontal gravity gradients before Lushan MS7.0 earthquake were calculated for the accumulative gravity anomaly from September 2010 to October 2012. In the north-south direction, gravity gradient in Daofu-Kangding-Shimian and Markang-Lixian-Lushan exhibited a positive high value, and the strike of the high value zone was in line with the strike of Xianshuihe Faults and Markang Faults. In the east-west direction, high value zone was not as obvious as that in the north-south direction. Gravity gradients in the direction along and vertical to the strike of Longmenshan Faults were calculated by the definition of directional derivative. In the along-strike direction, high gravity gradient values appeared in Markang-Lixian areas along Markang Faults and Daofu-Kangding-Shimian areas along Xianshuihe Faults, and extremum appeared in Kangding-Shimian and the area nearby Lixian. In the direction vertical to the strike of Longmenshan fault zone, high gravity gradient values appeared in Lixian-Lushan-Kangding-Shimian areas, and the extremum appeared in the area nearby Kangding. The results indicate that gravity gradient in the direction along and vertical to the strike of faults can better show the relative gravity change on the two sides of faults. Lushan MS7.0 earthquake is located at the transition zone between the two high value zones of gravity gradient. The total horizontal gravity gradient shows that the location and strike of the high value zone are basically consistent with regional faults, and the extremums of total horizontal gravity gradient appeared nearby Lixian, Kangding and Shimian.  相似文献   

8.
Northwest Guangxi is located in the Youjiang fold belt and the Hunan-Guangxi fold belt of secondary structure unit of South China fold system. The South China fold was miogeosyncline in the early Paleozoic, the Caledonian fold returned and transformed into the standard platform, and the Indosinian movement ended the Marine sedimentary history, which laid the basic structural framework of this area. Since the neotectonic period, large areas have been uplifted intermittently in the region and Quaternary denudation and planation planes and some faulted basins have been developed. Affected by the strong uplift of Yunnan-Guizhou plateau, the topography of the region subsides from northwest to southeast, with strong terrain cutting and deep valley incision. Paleozoic carbonate rocks and Mesozoic clastic rocks are mainly exposed on the earth's surface, and its geomorphology is dominated by corrosion and erosion landforms. The dating results show that most of the structures in northwest Guangxi are middle Pleistocene active faults, and the movement mode is mainly stick-slip. According to the seismogeological research results of the eastern part of the Chinese mainland, the active faults of the middle Pleistocene have the structural conditions for generating earthquakes of about magnitude 6. In the northwest Guangxi, the crustal dynamic environment and geological structure are closely related to Sichuan and Yunnan regions. Under the situation that magnitude 6 earthquakes occurred successively in Sichuan and Yunnan region and magnitude 7 earthquakes are poised to happen, the risk of moderately strong earthquakes in the northwest Guangxi region cannot be ignored. Based on the analysis of deep structure and geophysical field characteristics, it is concluded that the Tian'e-Nandan-Huanjiang area in the northwestern Guangxi is not only the area with strong variation of the Moho surface isobath, but also the ML3.0 seismic gap since September 2015, and the abnormal low b value area along the main fault. Regions with these deep structural features often have the conditions for moderately strong earthquakes. The paper systematically analyzes the spatial and temporal distribution features and mechanism of regional gravitational field and horizontal crust movement and further studies and discusses the changes of regional gravitational field, crustal horizontal deformation and interaction between geologic structure and seismic activity based on 2014-2018 mobile gravity measurements and 2015-2017 GPS observation data in the northwestern Guangxi. The results show that:1)On July 15, 2017, a MS4.0 earthquake in Nandan happened near the center of four quadrants of changes of gravity difference, and the center of abnormal area is located at the intersection of the Mulun-Donglang-Luolou Fault, the Hechi-Nandan Fault and the Hechi-Yizhou Fault. The dynamic graph of differential scale gravitational field reflects the gravity changes at the epicenter before and after the Nandan earthquake, which is a process of system evolution of "local gravity anomaly to abnormal four-quadrant distribution features → to earthquake occurring at the turning point of gravity gradient zone and the zero line to backward recovery variation after earthquake". Meanwhile, according to the interpretation of focal mechanism of the Nandan earthquake, seismogram and analysis of seismic survey results, the paper thinks that the four-quadrant distribution of positive and negative gravity, which is consistent with the effect of strike-slip type seismogenic fault before Nandan earthquake, demonstrates the existence of dextral strike-slip faulting; 2)The pattern of spatial distribution of gravitational field change in northwestern Guangxi is closely related to active fault. The isoline of cumulative gravity generally distributes along Nandan-Hechi Fault and Hechi-Yizhou Fault. The gravity on both sides of the fault zone is different greatly, and gradient zone has influences on a broad area; the spatial distribution of deformation field is generally featured by horizontal nonuniformity. Tian'e-Nandan-Huanjiang area is located at the high gradient zone of gravity changes and the horizontal deformation surface compressional transition zone, as well as near the intersection of Hechi-Yizhou Fault, Hechi-Nandan Fault and Du'an-Mashan Fault; 3)The geometric shape of gravitational field in northwestern Guangxi corresponds to the spatial distribution of horizontal crustal movement, which proves the exchange and dynamic action of material and energy in the region that cause the change and structural deformation of fault materials and the corresponding gravity change on earth's surface. The recent analysis of abnormal crustal deformation in northwestern Guangxi shows that Tian'e-Nandan-Huanjiang is a gradient zone of abnormal gravity change and also a horizontal deformation surface compressional transition zone. It locates at the section of significant change of Moho isobaths, the seismicity gap formed by ML3.0 earthquakes and the abnormal low b-value zone. According to comprehensive analysis, the region has the risk of moderately strong earthquake.  相似文献   

9.
CHENG Jia  XU Xi-wei 《地震地质》2018,40(1):133-154
Since 1997, several major earthquakes occurred around the Bayan Har block in the Tibetan plateau, providing an opportunity to further understanding the mechanism of intraplate earthquakes. What is the effect of interactions among these events on the earthquake occurrence pattern is an issue to be addressed. In this article, we use the visco-elastic Coulomb stress changes model to calculate the stress interactions among the historical events close to or large than MS7.0 since 1893 in the Bayan Har block. We apply the relationships between the slip rate and stress accumulation rate to transform the Coulomb stress changes into the influenced time. Then we remove such influence time from the occurrence years, and analyze the effects of the earthquake interactions on the clustering patterns of the historical earthquakes in the Bayan Har block. The results show that the major earthquakes in the Bayan Har block are characterized by a quasi-period of about 16 years from 1893 to 1973 and a clustering occurrence time period from 1997 to present following a relatively long quiescence period. The Bayan Har block is still in the active period with high probabilities of major quakes. We calculate the conditional probabilities of the rupture segments that did not rupture since 1893 of the boundary faults of the Bayan Har block in the next 30 years. The following faults or fault sections seem to be of major risk:The Maqin segment and the Maqu fault of the East Kunlun fault zone, the Awanang fault, the Luocha segment of the Tazhong fault, the Moxi segment of the Xianshuihe fault, and the Dangjiang fault. Other Fault segments in the Bayan Har block without seismic events since 1893 probably also have hazard of MS7 earthquakes in the future.  相似文献   

10.
Before 2013 Lushan MS7.0 earthquake, the bedrock ground temperature in Kangding station, the cross-fault deformation and the borehole strain in Guza station all show that regional stress changes possibly occurred along the Xianshuihe Fault. In this paper, further analysis is made on the observation data of bedrock ground temperature in the three stations in the Xianshuihe fault zone, and the results are compared with borehole strain, seismometry and cross-fault deformation data. Stress temperature in the three stations dropped suddenly synchronously a few days before the Lushan earthquake, indicating the enhanced tension characteristics of the regional stress in the Qianning-Kangding zone. High-frequency components of bedrock temperature in the three stations also showed synchronous changes in the 80 days before the Lushan earthquake, with an estimated stress change range of 0.98~1.96MPa, an average of about 1.47MPa, which is close to the seismometry results. Besides, tensional mutation in borehole strain is consistent with the enhanced tensional characteristics of regional stress revealed by bedrock ground temperature. Comparison with cross-fault deformation shows that the stress change was different in different active segments of the Xianshuihe Fault in different time periods before the Lushan earthquake, but the regional stress change did appear along the Xianshuihe fault zone before the Lushan earthquake.  相似文献   

11.
Yingjiang area is located in the China-Burma border,the Sudian-Xima arc tectonic belt,which lies in the collision zone between the Indian and Eurasian plates.The Yingjiang earthquake occurring on May 30th,2014 is the only event above MS6.0 in this region since seismicity can be recorded.In this study,we relocated the Yingjiang MS5.6 and MS6.1 earthquake sequences by using the double-difference method.The results show that two main shocks are located in the east of the Kachang-Dazhuzhai Fault,the northern segment of the Sudian-Xima Fault.Compared with the Yingjiang MS5.6 earthquake,the Yingjiang MS6.1 earthquake is nearer to the Kachang-Dazhuzhai Fault.The aftershocks of the two earthquakes are distributed along the strike direction of the Kachang-Dazhuzhai Fault (NNE).The rupture zone of the main shock of Yingjiang MS6.1 earthquake extends northward approximately 5km.The aftershocks of two earthquakes are mainly located in the eastern side of the Kachang-Dazhuzhai Fault with a significant asymmetry along the fault,which differ from the characteristics of the aftershock distribution of the strike-slip earthquake.It may indicate that the Yingjiang earthquakes are conjugate rupture earthquakes.The non-double-couple components are relatively high in the moment tensor.We speculate that the Yingjiang earthquakes are related to the fractured zone caused by the long-term seismic activity and heat effect in the deep between Kachang-Dazhuzhai Fault and its neighboring secondary faults.Aftershock distribution of the Yingjiang MS6.1 earthquake on the southern area crosses a secondary fault on the right of the Kachang-Dazhuzhai Fault,suggesting that the coseismic rupture of the secondary fault may be triggered by the dynamic stress of the main shock.  相似文献   

12.
Based on the mobile gravity observation data in 2014-2016 in Guangxi and its adjacent areas, this paper systematically analyzed the changes of regional gravity field and its relation to the MS5.4 Cangwu, Guangxi earthquake on July 31, 2016, and combined with GPS observation data and seismic geological survey results, discussed the temporal and spatial distribution characteristics of the changes of regional gravity field and its mechanism. The results show that:(1) Before and after the MS5.4 Cangwu earthquake, the gravity anomaly changes near the earthquake area were closely related to the major faults in space, which reflects the crustal deformation and tectonic activities that caused the surface gravity change along the seismogenic fault in the period of 2014-2016; (2) The gravity changes near the epicenter before and after the MS5.4 Cangwu earthquake showed an evolution process in which the positive gravity anomaly zone changed to the negative gravity anomaly zone, a gravity gradient belt appeared along NNE direction and the earthquake occurred in its reverse change process; (3) The epicenter of the MS5.4 Cangwu earthquake located both near the gravity gradient belt and in the zero transition zone of the surface strain gradient and the edge of the high maximum shear strain rate area, the observational fact further proved that the dynamic image of gravitational field and deformation field have important instruction significance to the location prediction of strong earthquakes; (4) in recent years, the gravity dynamic change in northwestern Guangxi presented a four-quadrant distribution pattern, and there is the risk of generating earthquake of magnitude about 5 in the center of the quadrants.  相似文献   

13.
In this paper we present results of spectral structure of crustal velocity inhomogeneity beneath the southeastern margin of Tibetan plateau and its adjacent region based on the S wave envelope broadening algorithm. The spectral structure of 8~16Hz band is selected to analyze the special character of crustal inhomogeneity and discuss the correlation between strong earthquakes and inhomogeneities. The result shows that strong and complex inhomogeneities of crustal medium are found in the southeastern margin of Tibetan plateau and its adjacent region. In the upper part of upper crust, the strong and small scale inhomogeneities are imaged in the Longmengshan fault zone and the north of the Anninghe fault zone, the weak and large scale inhomogeneites are imaged in the section from Huolu to Daofu of Xianshuihe fault zone and the south of the Anninghe fault zone. In the lower part of upper crust, strong inhomogeneites are found in the Longmengshan fault zone, Lianfeng fault zone, the north of the Anninghe fault zone and the sections from Huolu to Daofu of the Xianshuihe fault zone, weak inhomogeneites are found in the section from Daofu to Kangding of Xianshuihe fault zone. In the middle crust, strong inhomogeneities are observed in the section of the Baoxing to Dujiangyan, the Baoxing to Kangding, and Kangding to Shimian, and weak inhomogeneities are observed in the northwestern section from Huolu to Kangding, and the Lianfeng fault zone. Comparing the medium inhomogeneities with the location of the strong earthquakes, our results suggest existence of high correlation between them. Strong earthquakes are often located in the transitionary zone between the strong and the weak inhomogeneities. The spatial distribution of the strong and the weak medium inhomogeneities may be related to the broken medium from the strong movement of geological tectonic and the heat flow upwelling along active faults induced by frequent tectonic and volcanic activity.  相似文献   

14.
鲜水河断裂带地震活动特征及强震发生随时间增长概率   总被引：3，自引：0，他引：3  
王贵宣  郑大林 《地震研究》1995,18(3):221-226
作者等仔细分析了鲜水河断裂带从１７２５年到现在的地震资料，并利用乌莫洛夫Ｔ─Ｓ、Ｍ为参数的作图法及强震发生随时间增长概率，绘制了地震活动图件及地震发生概率曲线以及Ｍ─Ｔ图和鲜水河断裂应变释放曲线。根据这些资料可以清楚地看出鲜水河断裂带自１７２５年到现在可分为两个大的活动周期，其中６．０级以上地震有由康定依次向甘孜迁移的特点。在每一个大的地震活动周期中，地震基本上两次重复由康定向甘孜迁移的过程，而且较强地震多发生在第二次迁移过程中，１９８２年甘孜地震标志着断裂带在第二幕地震活动高潮中，中强震已经完成了最后一次由断裂带东南端向西北端迁移的过程。同时考虑到断裂带应变释放曲线的特征，估计鲜水河断裂带目前已进入新的平静阶段。前两个大的活动周期之间，平静了近一个世纪。按历史上地震定向迁移规律，估计在新的活动期地震仍将从康定方向开始，逐步向甘孜发展。  相似文献   

15.
There was an earthquake swarm of two major events of MS6.3 and MS5.8 on the Xianshuihe fault in November, 2014. The two major earthquakes are both strike-slip events with aftershock zone along NW direction.We have analyzed the characteristics of this earthquake sequence. The b value and the h value show the significant variations in different periods before and after the MS5.8earthquake. Based on the data of historical earthquakes, we also illustrated the moderate-strong seismic activity on the Xianshuihe fault. The Kangding earthquake swarm manifests the seismic activity on Xianshuihe fault may be in the late seismic active period. The occurrence of the Kangding earthquake may be an adjustment of the strong earthquakes on the Xianshuihe fault. The Coulomb failure stress changes caused by the historical earthquakes were also given in this article. The results indicate that the earthquake swarm was encouraged by the historical earthquakes since1893, especially by the MS7.5 Kangding earthquake in1955. The Coulomb failure stress changes also shows the subsequent MS5.8 earthquake was triggered by the MS6.3earthquake.  相似文献   

16.
大凉山断裂带是大型走滑断裂鲜水河-小江断裂系的重要组成部分,其活动性是认识和探讨青藏高原东南缘现今地震活动和构造变形机制的重要基础资料.相较于中段和南段,关于大凉山断裂带北段活动性的相关研究成果,尤其是古地震资料非常缺乏.文中基于野外地质地貌调查,在石棉断裂联合村处开挖了一组(2个)探槽,揭露出断裂全新世活动的直接证据...  相似文献   

17.
鲜水河断裂带的应力积累与释放   总被引：1，自引：1，他引：1       下载免费PDF全文
黄福明  杨智娴 《地震学报》1987,9(2):128-142
本文根据历史地震(Ms6.0)的资料,研究了鲜水河断裂带的地震活动性,并利用断层的位错模式进一步研究该断裂带的应力积累和释放过程.结果表明,该断裂带的强震活动大致以道孚为界,形成北西和南东两个活动地段,呈现南北交替活动的特征.地震能量的这种交替释放似具有准周期性质,Ms7.0级地震的平均复发周期为27.6年.给出该断裂带在三个不同时间段(1700-1811,1816-1967,1816-1982)强震断层作用引起的应力释放图象,讨论了前两个时间段地震应力场对其后发生的第一个大地震的重要影响.计算了1893年以来在断裂带南东段(相对闭锁段)的应力积累,示出相应的最大剪应力和流体静应力等值线图.最后,根据应力积累、附加应力变化、地震活动规律和应变释放曲线特征,估计了鲜水河断裂带的地震趋势.认为在本世纪末,在断裂带南东段的(1)康定-磨西段或(2)道孚-乾宁段或(3)乾宁-康定段将可能发生 Ms=7.40.3地震.   相似文献   

18.
徐晶  邵志刚  刘静  季灵运 《地球物理学报》2019,62(11):4189-4213
本研究基于分层黏弹介质模型,考虑强震或大地震同震位错、震后黏滞松弛及主断层段震间构造应力加载三方面效应,给出1480年以来,川滇菱形块体东边界鲜水河断裂带、安宁河断裂带、则木河断裂带和小江断裂带共20个断层段由三方面效应引起的累积库仑应力变化随时间的演化,分析强震间相互作用和强震发生的应力累积背景,定性分析各断层段的地震危险性.同时,分别采用现今台网地震目录和川滇菱形块体东边界各断层段强震复发间隔两种资料,定量计算2030年各断层段的强震发生概率;并基于摩擦本构理论,将周边强震引起的库仑应力变化量作为应力扰动,修正强震发生概率的计算结果.各断层段累积库仑应力演化的结果表明,鲜水河断裂带中部八美段、色拉哈段及南部磨西段、安宁河断裂带冕宁-西昌段、小江断裂带北部巧家-东川段和南部建水段的累积库仑应力显著增加.修正的强震发生概率计算结果显示,鲜水河断裂带中部八美-色拉哈-康定一带、安宁河断裂带冕宁-西昌段、小江断裂带南部华宁-建水一带强震发生概率较高,地震危险性值得关注.本研究基于库仑应力演化计算定性分析强震危险性的同时,基于摩擦本构律理论,结合地震引起的应力扰动和强震发生背景,定量计算修正的强震发生概率,为川滇菱形块体东边界强震危险地点及中长期发震紧迫程度判定提供方法和依据.  相似文献   

19.
汶川地震对芦山地震及周边 断层发震概率的影响   总被引：6，自引：0，他引：6  
大震后区域静态库仑应力变化常常被用于解释区域地震活动性速率的变化、 主震断层外余震的发生以及即将失稳断层的地震发生概率的变化. 2013年4月20日芦山MS7.0地震的发生重新引起了对2008年5月12日汶川MS8.0大地震的热议. 利用含(滑移)速率和状态的摩擦定律, 结合汶川大地震前后的地震活动性水平, 定量化计算了汶川地震后雅安地区发震概率的变化, 并着重解释了芦山地震发震的可能根源. 此外, 还对库仑应力明显增加的鲜水河断层和熊坡断层进行了发震概率的定量化计算, 计算结果与中国地震台网中心的地震目录基本符合. 鲜水河断层从汶川地震后至今近5年来未发生M>6.0地震, 而M>6.0的发震概率已约为60%; 熊坡断层自汶川地震以来尚未发生M>4.0地震, 芦山地震后M>4.0的发震概率已接近90%. 所以, 我们认为鲜水河断层附近将成为M>6.0地震的重点防范地区, 熊坡地区将来仍旧存在发生中强地震的危险性.   相似文献   

20.
中国大陆西部重力场变化与强震危险性关系   总被引：7，自引：2，他引：5       下载免费PDF全文
陈石  徐伟民  蒋长胜 《地震学报》2015,37(4):575-587
本文基于中国大陆西部流动重力测量获得的区域重力场变化数据, 尝试对其进行多种位场变换, 在一定空间尺度约束下定义了6种区域重力场变化指标量. 在此基础上, 以中国大陆2002年、 2005年和2008年等3期数据为研究对象, 计算并统计了中国大陆西部MS≥6.0地震震中位置处震前重力场变化及各种导出参数值, 尝试初步构建以地震预报为目的的地震重力学科指标体系参数. 研究结果表明, 震前区域重力场变化与地震发生位置没有显著的统计关系, 但是重力场变化的垂直梯度和解析信号模量具有一定的地震预报意义, 适合作为地震前兆异常使用.   相似文献   

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