The central-southern part of the eastern border of the Sichuan-Yunnan rhombic block provides the research strategy of ‘trade space for time' with an interesting fault system, where the segments have similar focal...The central-southern part of the eastern border of the Sichuan-Yunnan rhombic block provides the research strategy of ‘trade space for time' with an interesting fault system, where the segments have similar focal mechanisms and cover almost continuous spectra of elapse rates. We experiment to study the seismological characteristics of different segments with different elapse rates. We employed the de-clustered earthquake catalog for the calculation of b values for each segment. The analysis revealed that different segments have similar b values,which implies that, although different segments have different periods of earthquake recurrence, the 'natural time' for the whole fault system elapses with a homogeneous pace. We extended the earthquake potential score(EPS)for nowcasting earthquakes to a quasi-EPS(q EPS). It is found that q EPS increases with the increase of elapse rates,albeit for those fault segments whose elapse rates have exceeded 1, q EPS may better reflect the seismic hazard.展开更多
Harvard Centroid Moment Tensor （CMT） solutions for earthquakes from 1977 to 2004 showed that the stress fields are obviously different in northwestern Sichuan sub-block （NWSSB）, western parts of Central Yunnan sub...Harvard Centroid Moment Tensor （CMT） solutions for earthquakes from 1977 to 2004 showed that the stress fields are obviously different in northwestern Sichuan sub-block （NWSSB）, western parts of Central Yunnan sub-block （CYSB） and eastern part of CYSB. The characteristics of the mean stress fields in these three regions are obtained by fitting to CMT solutions. The stress state in NWSSB is characterized by its sub-horizontal tensile principal axis of stress （T axis） in roughly N-S direction and west dipping compressive principal axis of stress （P axis）; the one in western part of CYSB is characterized by its ENE dipping T axis and sub-horizontal medium principal axis of stress （B axis） in roughly N-S direction; the one in eastern part of CYSB is characterized by its sub-horizontal P axis in roughly NNW-SSE direction and sub-horizontal T axis in roughly WSW-ENE direction. Finite element method simulation clearly shows that the Indian Plate imposes great extrusion on Sichuan-Yunnan rhombic block （SYRB） near Assam massif. The value of the simulated compressive principal stress decreases with the distance from Assam massif. The simulated directions of the T axes in SYRB form annular distribution encir cling Assam. For a homogeneous elastic medium with free boundary conditions on the top and bottom surfaces as well as the displacement boundary conditions derived from the GPS observations on the lateral boundaries, the computation results are consistent with the Harvard CMT solutions in NWSSB and western part of CYSB, while inconsistent with the Harvard CMT solutions in eastern part of CYSB. The inconsistency in eastern part of CYSB can be reduced when it includes inhomogeneous elastic media. The stress states in NWSSB and western part of CYSB revealed by the Harvard CMT solutions are not local, which are mainly controlled by the boundary force on the whole region. On the other hand, the stress state in eastern part of CYSB given by the Harvard CMT solutions is local, which may be affected by local topography, material inhomogeneity, and the drag force underneath.展开更多
Based on data from an across-fault survey along the Sichuan-Yunnan rhombic block boundaries, the recent deformation characteristics on each fault have been analyzed. It was found that the rate of crustal deformation i...Based on data from an across-fault survey along the Sichuan-Yunnan rhombic block boundaries, the recent deformation characteristics on each fault have been analyzed. It was found that the rate of crustal deformation is slowing down along the northern segment and increasing along the southern segment. Each fault has different features of deformation. The horizontal deformation is mainly characterized by left-lateral strike-slip. The rate of vertical deformation is less than that of the horizontal deformation. The faults have the feature of upper wall uplifting alternated with descending. The anomaly changes of crustal deformation at some sites are closely related to the seismicities near the sites.展开更多
Based on the seismic station data sets from Sichuan and Yunnan provinces,we employed a multi-step seismic location method( Hypo2000 + Velest + HypoDD) to precisely locate the 7,787 earthquakes that occurred during 201...Based on the seismic station data sets from Sichuan and Yunnan provinces,we employed a multi-step seismic location method( Hypo2000 + Velest + HypoDD) to precisely locate the 7,787 earthquakes that occurred during 2010-2015 along the eastern boundaries of the Sichuan-Yunnan rhombic block,namely from southern Dawu to the Qiaojia segment.The final results show that location precision is greatly advanced and epicenter distribution exhibits good consistency with the linear distribution of the seismic faults. Earthquake distribution is quite intensive at the intersection region in the southern segment of the Xianshuihe fault,the Anninghe fault zone,the Xiaojinhe fault zone and the Daliangshan fault zone to the east. The depth profile of seismicity shows a clear stepwise activity along the active seismic fault zones. The profile crossing the faults of the Xianshuihe,Anninghe,and Daliangshan presents a complex interaction among faults near the multiple faults intersection region,Shimian,where the earthquakes are obviously divided into two groups in depth. Earthquakes are very rare at the depth of 15km-20 km,which is consistent with the region of the plastic rheology between 14km-19 km calculated by Zhu Ailan et al.,( 2005).展开更多
Based on the existing materials of fault segmentation,characteristic earthquakes,and their empirical relationships,we calculated the parameters of the fault segments,such as length,width,magnitudes of characteristic e...Based on the existing materials of fault segmentation,characteristic earthquakes,and their empirical relationships,we calculated the parameters of the fault segments,such as length,width,magnitudes of characteristic earthquakes,etc.Constrained by GPS velocity field,the slip rates of these fault segments in depth were inversed using the 3-D half-space elastic dislocation model.As not all of the recurrence periods and co-seismic displacements of characteristic earthquakes are known,we selected the fault segments with these two parameters known and calculated the accumulation rate of average co-seismic displacement,which shows the faults' slip rate in seismogenic layer.Then,the slip rate in depth was compared with that in seismogenic layer,the relationship between them was obtained,and this relationship was used to get the recurrence periods and co-seismic displacements of all fault segments.After the studies above,we calculated the co-seismic deformation field of all the earthquakes larger than M s 6.8 from AD 1700 one by one and inversed the potential displacement in the co-seismic deformation field.Then,we divided the potential displacement by the slip rate from GPS inversion to get the influences of these fault segments,added the influences into the elapsed time of the characteristic earthquakes,and obtained the earthquake hazard degree of all the segments we studied in the form of the ratio of elapsed time to recurrence period;so,we name the ratio as the Impending Earthquake Risk (IER).Historical earthquake cases show that the fault segment is in safety when the IER is less than 1 but in danger after the IER becomes larger than 1.In 2009,the IER is larger than 1 on the following segments,1.35 on the Tagong segment of Xianshuihe fault,1 on the Menggu-Dongchuan segment,1.04 on the Dongchuan-Xundian segment,and 1.09 on the Yiliang-Chengjiang segment of Xiaojiang fault.展开更多
The Sichuan-Yunnan Block(SYB)is located at the SE margin of the Qinghai-Tibetan Plateau(TP).Under the influence of the southeastward movement of material originated from the TP,intense crustal deformation,frequent sei...The Sichuan-Yunnan Block(SYB)is located at the SE margin of the Qinghai-Tibetan Plateau(TP).Under the influence of the southeastward movement of material originated from the TP,intense crustal deformation,frequent seismic activity,and complex geological structures are observed in the SYB.The Lijiang-Xiaojinhe fault(LXF)goes through the central part of the SYB,dividing it into two blocks from north to south,and forming an intersecting fault system with the surrounding faults.This paper firstly introduces the morphology and the nature of the LXF,the distribution of the regional surface displacements and the focal mechanisms,and then analyzes the medium deformation and the effects of faults.Moreover,according to the regional tectonics and geophysical patterns,the paper discusses the characteristics of the north-south blocks of the SYB and the abrupt change of deep structure along the LXF zone.Since seismic anisotropy is an essential property for detecting crustal stress,deep structures and dynamical mechanisms,this paper is dedicated to the advances in seismic anisotropy at different depths and different scales in the study area.There are noteworthy differences in the anisotropic features between the north part and the south part of the SYB,possibly associated with a clear boundary adjacent to the LXF.Such phenomenon suggests some close correlation between anisotropic zoning boundary and the LXF,although this boundary is not consistent with the LXF in strike.The results from the deformation of the crust and the upper mantle elucidate the distribution patterns of the crust-mantle coupling in the north part and the crustmantle decoupling in the south part,even though this conclusion needs to be further verified by more studies.Presently,the scientific understanding of the deep tectonics and the media deformation around the“generalized”LXF i.e.the LXF with the Jinpingshan fault on its eastern side,is still insufficient,and related equivocal topics deserve more in-depth studies.展开更多
In the paper, the distribution characteristics of strong earthquakes in Sichuan-Yunnan area and their geological tectonic background, especially the relation to Sichuan-Yunnan and Sichuan-Qinghai crustal blocks have b...In the paper, the distribution characteristics of strong earthquakes in Sichuan-Yunnan area and their geological tectonic background, especially the relation to Sichuan-Yunnan and Sichuan-Qinghai crustal blocks have been studied. The main results are: a) Strong earthquakes in Sichuan-Yunnan area distribute mainly in Sichuan-Yunnan and Sichuan-Qinghai crustal blocks; b) Most of strong earthquakes of the two blocks distribute mainly along their boundary faults; c) A few strong earthquakes are not obviously related to active faults. It shows that the relation between strong earthquakes and geological tectonics can be very complex; d) There is a certain correlativity for seismic activities among boundary faults of the two blocks, but they have different features; e) There are some anomalous changes of velocity structures in the deep crust of boundary faults of the two blocks. Many boundary faults, especially Longmenshan fault, cut obviously the Moho discontinuity. The Xianshuihe fault, a typical strike-slip fault, has no obvious indication of cutting the Moho discontinuity, but has distinct low-velocity zone in different depths.展开更多
Based on P- and S-wave amplitudes and some clear initial P-wave motion data, we calculated focal mechanism solutions of 928 M≥2.5 earthquakes （1994-2005） in four sub-blocks of Sichuan and Yunnan Provinces, namely S...Based on P- and S-wave amplitudes and some clear initial P-wave motion data, we calculated focal mechanism solutions of 928 M≥2.5 earthquakes （1994-2005） in four sub-blocks of Sichuan and Yunnan Provinces, namely Sichuan-Qinghai, Yajiang, Central Sichuan and Central Yunnan blocks. Combining these calculation results with those of the focal mechanism solutions of moderately strong earthquakes, we analyzed the stress field characteristics and dislocation types of seismogenic faults that are distributed in the four sub-blocks. The orientation of principal compressive stress for each block is： EW in Sichuan-Qinghai, ESE or SE in Yajiang, Central Sichuan and Central Yunnan blocks. Based on a great deal of focal mechanism data, we designed a program and calculated the directions of the principal stress tensors, σ1, σ2 and σ3, for the four blocks. Meanwhile, we estimated the difference （also referred to as consistency parameter θ^- ） between the force axis direction of focal mechanism solution and the direction of the mean stress tensor of each block. Then we further analyzed the variation of θ^- versus time and the dislocation types of seismogenic faults. Through determination of focal mechanism solutions for each block, we present information on the variation in θ^- value and dislocation types of seismogenic faults.展开更多
Analysis of deformation data measured across the faults, regional vertical deformation data and GPS measurements in the Sichuan-Yunnan region made since the 1980s permitted us to conclude that the crustal deformation ...Analysis of deformation data measured across the faults, regional vertical deformation data and GPS measurements in the Sichuan-Yunnan region made since the 1980s permitted us to conclude that the crustal deformation in the region during this period of time was relatively weak and caused the occurrence of earthquakes (M S≥6.0), which were not distributed along the major boundary active faults in the region after the 1981 Dawu M S 6.9 earthquake and that the seismic activity is characterized by quasi-clockwise migration. Thus, it follows that earthquake prediction research should be focused on the central part of the Sichuan-Yunnan region in the coming years. Finally, a concept of temporal division of the region into active blocks is suggested and the preliminary result of the division is given in the paper.展开更多
In this paper, a new idea that combines Quasi-Accurate Detection of gross errors (QUAD) with discontinuous deformation positive analysis, is brought forward to divide the regional active blocks. The method can improve...In this paper, a new idea that combines Quasi-Accurate Detection of gross errors (QUAD) with discontinuous deformation positive analysis, is brought forward to divide the regional active blocks. The method can improve the demarcation of active blocks for areas lacking with observation data and offer a new train of through for the complete study of the regional deformation of active blocks. In addition, using the Sichuan-Yunnan area as example, the practice process of the method is introduced briefly.展开更多
Based on the earthquake activity characteristics of the diamond block in the Sichuan- Yunnan region and by using the method of the meso-scope damage dynamics and damage evolution, we studied the damage evolution proce...Based on the earthquake activity characteristics of the diamond block in the Sichuan- Yunnan region and by using the method of the meso-scope damage dynamics and damage evolution, we studied the damage evolution process for moderately strong earthquakes along two seismic belts. The original combination patterns of all the units which illuminate the changes from stable state to destroyed state are given. All these patterns can direct the earthquake prediction practice in this region.展开更多
利用CAP（Cut and paste）方法获取了川滇块体及周边区域2007年8月至2013年4月75次3.5级以上中等地震的震源机制解,结合哈佛大学历史地震震源机制解,分析了震源机制解和震源深度的空间分布特征,并探讨了其构造动力学背景.结果表明：1）...利用CAP（Cut and paste）方法获取了川滇块体及周边区域2007年8月至2013年4月75次3.5级以上中等地震的震源机制解,结合哈佛大学历史地震震源机制解,分析了震源机制解和震源深度的空间分布特征,并探讨了其构造动力学背景.结果表明：1）川滇块体各不同断裂带、块体内部各次级块体之间、块体内外表现出不同的震源机制解空间分布特征,揭示出位于青藏高原东南缘的川滇块体及周边地区应力场的非均匀性;2）研究区各主要断裂带所反映的与构造背景作用一致的震源机制分布特征表明,川滇块体及周边近期断层破裂方式主要受到各个断裂带的构造活动以及次级块体之间相互作用的控制;3）丽江-小金河断裂带上特殊的震源机制特征和发震应力轴的分布特征,进一步证实了丽江-小金河断裂带对高原逃逸物质的抵挡和屏蔽的作用;4）震源深度分布特征表明,川滇块体及周边地震震源深度主要分布于15km的上地壳,优势分布在5～ 15km的范围,揭示出研究区的地壳脆性孕震层位于5～ 15km的上地壳.展开更多
基金supported by the National Natural Science Foundation of China (NSFC, grant number U2039207)。
文摘The central-southern part of the eastern border of the Sichuan-Yunnan rhombic block provides the research strategy of ‘trade space for time' with an interesting fault system, where the segments have similar focal mechanisms and cover almost continuous spectra of elapse rates. We experiment to study the seismological characteristics of different segments with different elapse rates. We employed the de-clustered earthquake catalog for the calculation of b values for each segment. The analysis revealed that different segments have similar b values,which implies that, although different segments have different periods of earthquake recurrence, the 'natural time' for the whole fault system elapses with a homogeneous pace. We extended the earthquake potential score(EPS)for nowcasting earthquakes to a quasi-EPS(q EPS). It is found that q EPS increases with the increase of elapse rates,albeit for those fault segments whose elapse rates have exceeded 1, q EPS may better reflect the seismic hazard.
基金Foundation item: State Key Basic research and Development Project from Ministry of Science and Technology of China (2004cb418406)National Natural Science Foundation of China (40521002).
文摘Harvard Centroid Moment Tensor （CMT） solutions for earthquakes from 1977 to 2004 showed that the stress fields are obviously different in northwestern Sichuan sub-block （NWSSB）, western parts of Central Yunnan sub-block （CYSB） and eastern part of CYSB. The characteristics of the mean stress fields in these three regions are obtained by fitting to CMT solutions. The stress state in NWSSB is characterized by its sub-horizontal tensile principal axis of stress （T axis） in roughly N-S direction and west dipping compressive principal axis of stress （P axis）; the one in western part of CYSB is characterized by its ENE dipping T axis and sub-horizontal medium principal axis of stress （B axis） in roughly N-S direction; the one in eastern part of CYSB is characterized by its sub-horizontal P axis in roughly NNW-SSE direction and sub-horizontal T axis in roughly WSW-ENE direction. Finite element method simulation clearly shows that the Indian Plate imposes great extrusion on Sichuan-Yunnan rhombic block （SYRB） near Assam massif. The value of the simulated compressive principal stress decreases with the distance from Assam massif. The simulated directions of the T axes in SYRB form annular distribution encir cling Assam. For a homogeneous elastic medium with free boundary conditions on the top and bottom surfaces as well as the displacement boundary conditions derived from the GPS observations on the lateral boundaries, the computation results are consistent with the Harvard CMT solutions in NWSSB and western part of CYSB, while inconsistent with the Harvard CMT solutions in eastern part of CYSB. The inconsistency in eastern part of CYSB can be reduced when it includes inhomogeneous elastic media. The stress states in NWSSB and western part of CYSB revealed by the Harvard CMT solutions are not local, which are mainly controlled by the boundary force on the whole region. On the other hand, the stress state in eastern part of CYSB given by the Harvard CMT solutions is local, which may be affected by local topography, material inhomogeneity, and the drag force underneath.
文摘Based on data from an across-fault survey along the Sichuan-Yunnan rhombic block boundaries, the recent deformation characteristics on each fault have been analyzed. It was found that the rate of crustal deformation is slowing down along the northern segment and increasing along the southern segment. Each fault has different features of deformation. The horizontal deformation is mainly characterized by left-lateral strike-slip. The rate of vertical deformation is less than that of the horizontal deformation. The faults have the feature of upper wall uplifting alternated with descending. The anomaly changes of crustal deformation at some sites are closely related to the seismicities near the sites.
基金funded by Study on the Optimal Time Window of Single Azimuth Angle,the Three-in-one Project of Earthquake Monitoring,Prediction and Scientific Research of China Earthquake Administration(CEA-JC/3JH-162305)the Special Training Project for Youth Talents for Seismic Network,China Earthquake Administration(20150422)
文摘Based on the seismic station data sets from Sichuan and Yunnan provinces,we employed a multi-step seismic location method( Hypo2000 + Velest + HypoDD) to precisely locate the 7,787 earthquakes that occurred during 2010-2015 along the eastern boundaries of the Sichuan-Yunnan rhombic block,namely from southern Dawu to the Qiaojia segment.The final results show that location precision is greatly advanced and epicenter distribution exhibits good consistency with the linear distribution of the seismic faults. Earthquake distribution is quite intensive at the intersection region in the southern segment of the Xianshuihe fault,the Anninghe fault zone,the Xiaojinhe fault zone and the Daliangshan fault zone to the east. The depth profile of seismicity shows a clear stepwise activity along the active seismic fault zones. The profile crossing the faults of the Xianshuihe,Anninghe,and Daliangshan presents a complex interaction among faults near the multiple faults intersection region,Shimian,where the earthquakes are obviously divided into two groups in depth. Earthquakes are very rare at the depth of 15km-20 km,which is consistent with the region of the plastic rheology between 14km-19 km calculated by Zhu Ailan et al.,( 2005).
基金supported by the National Basic Research Program of China (Grant No. 2008CB425704)the Open Foundation of State Key Laboratory of Earthquake Dynamics (Grant No. LED2009B02)
文摘Based on the existing materials of fault segmentation,characteristic earthquakes,and their empirical relationships,we calculated the parameters of the fault segments,such as length,width,magnitudes of characteristic earthquakes,etc.Constrained by GPS velocity field,the slip rates of these fault segments in depth were inversed using the 3-D half-space elastic dislocation model.As not all of the recurrence periods and co-seismic displacements of characteristic earthquakes are known,we selected the fault segments with these two parameters known and calculated the accumulation rate of average co-seismic displacement,which shows the faults' slip rate in seismogenic layer.Then,the slip rate in depth was compared with that in seismogenic layer,the relationship between them was obtained,and this relationship was used to get the recurrence periods and co-seismic displacements of all fault segments.After the studies above,we calculated the co-seismic deformation field of all the earthquakes larger than M s 6.8 from AD 1700 one by one and inversed the potential displacement in the co-seismic deformation field.Then,we divided the potential displacement by the slip rate from GPS inversion to get the influences of these fault segments,added the influences into the elapsed time of the characteristic earthquakes,and obtained the earthquake hazard degree of all the segments we studied in the form of the ratio of elapsed time to recurrence period;so,we name the ratio as the Impending Earthquake Risk (IER).Historical earthquake cases show that the fault segment is in safety when the IER is less than 1 but in danger after the IER becomes larger than 1.In 2009,the IER is larger than 1 on the following segments,1.35 on the Tagong segment of Xianshuihe fault,1 on the Menggu-Dongchuan segment,1.04 on the Dongchuan-Xundian segment,and 1.09 on the Yiliang-Chengjiang segment of Xiaojiang fault.
基金supported by National Natural Science Foundation of China Projects(42074065)Basic Research Operation Expenses of the Institute of Earthquake Prediction,China Earthquake Administration(2021IEF0103)。
文摘The Sichuan-Yunnan Block(SYB)is located at the SE margin of the Qinghai-Tibetan Plateau(TP).Under the influence of the southeastward movement of material originated from the TP,intense crustal deformation,frequent seismic activity,and complex geological structures are observed in the SYB.The Lijiang-Xiaojinhe fault(LXF)goes through the central part of the SYB,dividing it into two blocks from north to south,and forming an intersecting fault system with the surrounding faults.This paper firstly introduces the morphology and the nature of the LXF,the distribution of the regional surface displacements and the focal mechanisms,and then analyzes the medium deformation and the effects of faults.Moreover,according to the regional tectonics and geophysical patterns,the paper discusses the characteristics of the north-south blocks of the SYB and the abrupt change of deep structure along the LXF zone.Since seismic anisotropy is an essential property for detecting crustal stress,deep structures and dynamical mechanisms,this paper is dedicated to the advances in seismic anisotropy at different depths and different scales in the study area.There are noteworthy differences in the anisotropic features between the north part and the south part of the SYB,possibly associated with a clear boundary adjacent to the LXF.Such phenomenon suggests some close correlation between anisotropic zoning boundary and the LXF,although this boundary is not consistent with the LXF in strike.The results from the deformation of the crust and the upper mantle elucidate the distribution patterns of the crust-mantle coupling in the north part and the crustmantle decoupling in the south part,even though this conclusion needs to be further verified by more studies.Presently,the scientific understanding of the deep tectonics and the media deformation around the“generalized”LXF i.e.the LXF with the Jinpingshan fault on its eastern side,is still insufficient,and related equivocal topics deserve more in-depth studies.
文摘In the paper, the distribution characteristics of strong earthquakes in Sichuan-Yunnan area and their geological tectonic background, especially the relation to Sichuan-Yunnan and Sichuan-Qinghai crustal blocks have been studied. The main results are: a) Strong earthquakes in Sichuan-Yunnan area distribute mainly in Sichuan-Yunnan and Sichuan-Qinghai crustal blocks; b) Most of strong earthquakes of the two blocks distribute mainly along their boundary faults; c) A few strong earthquakes are not obviously related to active faults. It shows that the relation between strong earthquakes and geological tectonics can be very complex; d) There is a certain correlativity for seismic activities among boundary faults of the two blocks, but they have different features; e) There are some anomalous changes of velocity structures in the deep crust of boundary faults of the two blocks. Many boundary faults, especially Longmenshan fault, cut obviously the Moho discontinuity. The Xianshuihe fault, a typical strike-slip fault, has no obvious indication of cutting the Moho discontinuity, but has distinct low-velocity zone in different depths.
基金National Key Basic Research Development and Programming Project (2004CB418404) and Joint Seismological Science Foundation (105004).
文摘Based on P- and S-wave amplitudes and some clear initial P-wave motion data, we calculated focal mechanism solutions of 928 M≥2.5 earthquakes （1994-2005） in four sub-blocks of Sichuan and Yunnan Provinces, namely Sichuan-Qinghai, Yajiang, Central Sichuan and Central Yunnan blocks. Combining these calculation results with those of the focal mechanism solutions of moderately strong earthquakes, we analyzed the stress field characteristics and dislocation types of seismogenic faults that are distributed in the four sub-blocks. The orientation of principal compressive stress for each block is： EW in Sichuan-Qinghai, ESE or SE in Yajiang, Central Sichuan and Central Yunnan blocks. Based on a great deal of focal mechanism data, we designed a program and calculated the directions of the principal stress tensors, σ1, σ2 and σ3, for the four blocks. Meanwhile, we estimated the difference （also referred to as consistency parameter θ^- ） between the force axis direction of focal mechanism solution and the direction of the mean stress tensor of each block. Then we further analyzed the variation of θ^- versus time and the dislocation types of seismogenic faults. Through determination of focal mechanism solutions for each block, we present information on the variation in θ^- value and dislocation types of seismogenic faults.
文摘Analysis of deformation data measured across the faults, regional vertical deformation data and GPS measurements in the Sichuan-Yunnan region made since the 1980s permitted us to conclude that the crustal deformation in the region during this period of time was relatively weak and caused the occurrence of earthquakes (M S≥6.0), which were not distributed along the major boundary active faults in the region after the 1981 Dawu M S 6.9 earthquake and that the seismic activity is characterized by quasi-clockwise migration. Thus, it follows that earthquake prediction research should be focused on the central part of the Sichuan-Yunnan region in the coming years. Finally, a concept of temporal division of the region into active blocks is suggested and the preliminary result of the division is given in the paper.
基金This research was sponsored by the Joint EarthquakeScience Foundation (603002) and 104011)the sub-project of the 10th"Five-Year"Key Research Program ofCEA,entitled"Variation patterns of tectonic deformation and strain accumulation state in the key areas on the Chinesecontinent".
文摘In this paper, a new idea that combines Quasi-Accurate Detection of gross errors (QUAD) with discontinuous deformation positive analysis, is brought forward to divide the regional active blocks. The method can improve the demarcation of active blocks for areas lacking with observation data and offer a new train of through for the complete study of the regional deformation of active blocks. In addition, using the Sichuan-Yunnan area as example, the practice process of the method is introduced briefly.
文摘Based on the earthquake activity characteristics of the diamond block in the Sichuan- Yunnan region and by using the method of the meso-scope damage dynamics and damage evolution, we studied the damage evolution process for moderately strong earthquakes along two seismic belts. The original combination patterns of all the units which illuminate the changes from stable state to destroyed state are given. All these patterns can direct the earthquake prediction practice in this region.
文摘利用CAP（Cut and paste）方法获取了川滇块体及周边区域2007年8月至2013年4月75次3.5级以上中等地震的震源机制解,结合哈佛大学历史地震震源机制解,分析了震源机制解和震源深度的空间分布特征,并探讨了其构造动力学背景.结果表明：1）川滇块体各不同断裂带、块体内部各次级块体之间、块体内外表现出不同的震源机制解空间分布特征,揭示出位于青藏高原东南缘的川滇块体及周边地区应力场的非均匀性;2）研究区各主要断裂带所反映的与构造背景作用一致的震源机制分布特征表明,川滇块体及周边近期断层破裂方式主要受到各个断裂带的构造活动以及次级块体之间相互作用的控制;3）丽江-小金河断裂带上特殊的震源机制特征和发震应力轴的分布特征,进一步证实了丽江-小金河断裂带对高原逃逸物质的抵挡和屏蔽的作用;4）震源深度分布特征表明,川滇块体及周边地震震源深度主要分布于15km的上地壳,优势分布在5～ 15km的范围,揭示出研究区的地壳脆性孕震层位于5～ 15km的上地壳.
