An earthquake with Ms5.8 occurred on 10 March 2011 in Yingjiang county, western Yunnan, China. This earthquake caused 25 deaths and over 250 injuries. In order to better understand the seismotectonics in the region, w...An earthquake with Ms5.8 occurred on 10 March 2011 in Yingjiang county, western Yunnan, China. This earthquake caused 25 deaths and over 250 injuries. In order to better understand the seismotectonics in the region, we collected the arrival time data from the Yunnan seismic observational bulletins during 1 January to 25 March 2011, and precisely hand-picked the arrival times from high-quality seismograms that were recorded by the temporary seismic stations deployed by our Institute of Crustal Dynamics, China Earthquake Administration. Using these arrival times, we relocated all the earthquakes including the Yingjiang mainshock and its aftershocks using the double-difference relocation algorithm. Our results show that the relocated earthquakes dominantly occurred along the ENE direction and formed an upside-down bow-shaped structure in depth. It is also observed that after the Yingjiang mainshock, some aftershocks extended toward the SSE over about 10 km. These results may indicate that the Yingjiang mainshock ruptured a conjugate fault system consisting of the ENE trending Da Yingjiang fault and a SSE trending blind fault. Such structural features could contribute to severely seismic hazards during the moderate-size Yingjiang earthquake.展开更多
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
An Ms 6.4 earthquake occurred in Yangbi,Yunnan,China on May 21,2021,which has obvious foreshock activity and abundant aftershocks.Based on the seismic observation data recorded by the Yunnan Seismic Network three days...An Ms 6.4 earthquake occurred in Yangbi,Yunnan,China on May 21,2021,which has obvious foreshock activity and abundant aftershocks.Based on the seismic observation data recorded by the Yunnan Seismic Network three days before and seven days after the mainshock,a doubledifference location method was used to relocate 2133 earthquakes of the Yangbi sequence.Aftershocks are mostly distributed to the southeast of the mainshock in a unilateral rupture pattern.This sequence exhibits a SE-trending linear alignment with a length of about 25 km,and most of the focal depth is above 12 km.Integrated with the seismic distribution and focal mechanism results,we infer that the strike of the seismogenic fault is about 140°,and dipping to the SW.The fault structure revealed by the seismic sequence is complex,with the NW segment exhibiting a steep dip and relatively simple structure of strike-slip rupture and the SE segment consisting of several branching ruptures.The Yangbi Earthquake is a typical foreshock-mainshock-aftershock sequence,and the mainshock is likely triggered by the largest foreshock.This earthquake occurred in the boundary between high-and lowvelocity anomalous zone,where is susceptible to generate large earthquakes.展开更多
With the acceleration of the rise of central China and the western development drive, industrial relocation from China＇s eastern region to the central and western regions is in full swing. However, does the relocatio...With the acceleration of the rise of central China and the western development drive, industrial relocation from China＇s eastern region to the central and western regions is in full swing. However, does the relocation demonstrate industrial clustering effect？ Empirical studies based on twenty two-digit manufacturing industries in 27provinces from 2000 to 2009 demonstrate that industrial clustering effect appeared in central and western regions which had undertaken industrial relocation from eastern region; however, the studies do not show excessive administrative interference as evidenced by the significantly improved productivity of the relocated industries. Compared with non-labor- intensive manufacturing industries, labor-intensive manufacturing industries are easier to form cyclic accumulative effects. Studies also revealed that improvement in supporting infrastructure, industrial chain and higher labor quality in non-agriculture employment during urbanization are significant for central and western regions to undertake industrial relocation.展开更多
The double-difference earthquake relocation algorithm (DD algorithm) has been applied to the accurate relocation of 10057 earthquakes in the central-western China (21°-36°N, 98°-112E°) during the p...The double-difference earthquake relocation algorithm (DD algorithm) has been applied to the accurate relocation of 10057 earthquakes in the central-western China (21°-36°N, 98°-112E°) during the period of 1992-1999. In total, 79706 readings for P waves and 72169 readings for S waves were used in the relocation, and the source parameters of 6496 events were obtained. The relocation results revealed a more complete picture of the hypocentral distribution in the central-western China. In several seismic belts the relocated epicenters present a more defined lineation feature, reflecting the close correlation between the seismicity and the active tectonic structures. The relocated focal depths confirmed that most earthquakes (91 percent of the 6496 relocated events) in the central-western China were located at shallower depths not deeper than 20 km. The distribution of focal depths indicates that the seismogenic layer in the central-western China is located in the upper-mid crust with its thickness no deeper than 20 km.展开更多
According to the construction characteristic of RCC dam cast by layers, three-dimensional finite element relocating mesh method is developed to simulate construction process and compute temperature field. The computat...According to the construction characteristic of RCC dam cast by layers, three-dimensional finite element relocating mesh method is developed to simulate construction process and compute temperature field. The computation model of relocating mesh method is expatiated in detail; based on the thermodynamic properties of RCC materials, the feasibility and error of relocating mesh method are analyzed and demonstrated; The computation results in this article are verified by means of the temperature observation data of certain RCC gravity dam. The results show that the temperature field computed by three-dimensional finite element relocating mesh method can not only ensure the computation precision, but also improve the calculation efficiency greatly. This provides an effective method for simulating construction process and computing temperature field of RCC dam.展开更多
The three largest earthquakes in northern California since 1849 were preceded by increased decadal activity for moderate-size shocks along surrounding nearby faults. Increased seismicity, double-difference precise loc...The three largest earthquakes in northern California since 1849 were preceded by increased decadal activity for moderate-size shocks along surrounding nearby faults. Increased seismicity, double-difference precise locations of earthquakes since 1968, geodetic data and fault offsets for the 1906 great shock are used to re-examine the timing and locations of possible future large earthquakes. The physical mechanisms of regional faults like the Calaveras, Hayward and Sargent, which exhibit creep, differ from those of the northern San Andreas, which is currently locked and is not creeping. Much decadal forerunning activity occurred on creeping faults. Moderate-size earthquakes along those faults became more frequent as stresses in the region increased in the latter part of the cycle of stress restoration for major and great earthquakes along the San Andreas. They may be useful for decadal forecasts. Yearly to decadal forecasts, however, are based on only a few major to great events. Activity along closer faults like that in the two years prior to the 1989 Loma Prieta shock needs to be examined for possible yearly forerunning changes to large plate boundary earthquakes. Geodetic observations are needed to focus on identifying creeping faults close to the San Andreas. The distribution of moderate-size earthquakes increased significantly since 1990 along the Hayward fault but not adjacent to the San Andreas fault to the south of San Francisco compared to what took place in the decades prior to the three major historic earthquakes in the region. It is now clear from a re-examination of the 1989 mainshock that the increased level of moderate-size shocks in the one to two preceding decades occurred on nearby East Bay faults. Double-difference locations of small earthquakes provide structural information about faults in the region, especially their depths. The northern San Andreas fault is divided into several strongly coupled segments based on differences in seismicity.展开更多
基金supported by National Natural Science Foundation of China(Nos.40974201 and 40774044)to J.Lei
文摘An earthquake with Ms5.8 occurred on 10 March 2011 in Yingjiang county, western Yunnan, China. This earthquake caused 25 deaths and over 250 injuries. In order to better understand the seismotectonics in the region, we collected the arrival time data from the Yunnan seismic observational bulletins during 1 January to 25 March 2011, and precisely hand-picked the arrival times from high-quality seismograms that were recorded by the temporary seismic stations deployed by our Institute of Crustal Dynamics, China Earthquake Administration. Using these arrival times, we relocated all the earthquakes including the Yingjiang mainshock and its aftershocks using the double-difference relocation algorithm. Our results show that the relocated earthquakes dominantly occurred along the ENE direction and formed an upside-down bow-shaped structure in depth. It is also observed that after the Yingjiang mainshock, some aftershocks extended toward the SSE over about 10 km. These results may indicate that the Yingjiang mainshock ruptured a conjugate fault system consisting of the ENE trending Da Yingjiang fault and a SSE trending blind fault. Such structural features could contribute to severely seismic hazards during the moderate-size Yingjiang earthquake.
基金jointly funded by the National Key Research and Development Program of China (No. 2021YFC3000702)the Special Fund of the Institute of Geophysics, China Earthquake Administration (No. DQJB21Z05)the National Natural Science Foundation of China (No. 41804062)
文摘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.
基金financially supported by National Science Foundation of China(No.41774067)the National Key R&D Program of China(No.2018YFC1503400)+1 种基金the Special Fund of the Institute of GeophysicsChina Earthquake Administration(No.DQJB20X07)。
文摘An Ms 6.4 earthquake occurred in Yangbi,Yunnan,China on May 21,2021,which has obvious foreshock activity and abundant aftershocks.Based on the seismic observation data recorded by the Yunnan Seismic Network three days before and seven days after the mainshock,a doubledifference location method was used to relocate 2133 earthquakes of the Yangbi sequence.Aftershocks are mostly distributed to the southeast of the mainshock in a unilateral rupture pattern.This sequence exhibits a SE-trending linear alignment with a length of about 25 km,and most of the focal depth is above 12 km.Integrated with the seismic distribution and focal mechanism results,we infer that the strike of the seismogenic fault is about 140°,and dipping to the SW.The fault structure revealed by the seismic sequence is complex,with the NW segment exhibiting a steep dip and relatively simple structure of strike-slip rupture and the SE segment consisting of several branching ruptures.The Yangbi Earthquake is a typical foreshock-mainshock-aftershock sequence,and the mainshock is likely triggered by the largest foreshock.This earthquake occurred in the boundary between high-and lowvelocity anomalous zone,where is susceptible to generate large earthquakes.
文摘With the acceleration of the rise of central China and the western development drive, industrial relocation from China＇s eastern region to the central and western regions is in full swing. However, does the relocation demonstrate industrial clustering effect？ Empirical studies based on twenty two-digit manufacturing industries in 27provinces from 2000 to 2009 demonstrate that industrial clustering effect appeared in central and western regions which had undertaken industrial relocation from eastern region; however, the studies do not show excessive administrative interference as evidenced by the significantly improved productivity of the relocated industries. Compared with non-labor- intensive manufacturing industries, labor-intensive manufacturing industries are easier to form cyclic accumulative effects. Studies also revealed that improvement in supporting infrastructure, industrial chain and higher labor quality in non-agriculture employment during urbanization are significant for central and western regions to undertake industrial relocation.
文摘The double-difference earthquake relocation algorithm (DD algorithm) has been applied to the accurate relocation of 10057 earthquakes in the central-western China (21°-36°N, 98°-112E°) during the period of 1992-1999. In total, 79706 readings for P waves and 72169 readings for S waves were used in the relocation, and the source parameters of 6496 events were obtained. The relocation results revealed a more complete picture of the hypocentral distribution in the central-western China. In several seismic belts the relocated epicenters present a more defined lineation feature, reflecting the close correlation between the seismicity and the active tectonic structures. The relocated focal depths confirmed that most earthquakes (91 percent of the 6496 relocated events) in the central-western China were located at shallower depths not deeper than 20 km. The distribution of focal depths indicates that the seismogenic layer in the central-western China is located in the upper-mid crust with its thickness no deeper than 20 km.
文摘According to the construction characteristic of RCC dam cast by layers, three-dimensional finite element relocating mesh method is developed to simulate construction process and compute temperature field. The computation model of relocating mesh method is expatiated in detail; based on the thermodynamic properties of RCC materials, the feasibility and error of relocating mesh method are analyzed and demonstrated; The computation results in this article are verified by means of the temperature observation data of certain RCC gravity dam. The results show that the temperature field computed by three-dimensional finite element relocating mesh method can not only ensure the computation precision, but also improve the calculation efficiency greatly. This provides an effective method for simulating construction process and computing temperature field of RCC dam.
文摘The three largest earthquakes in northern California since 1849 were preceded by increased decadal activity for moderate-size shocks along surrounding nearby faults. Increased seismicity, double-difference precise locations of earthquakes since 1968, geodetic data and fault offsets for the 1906 great shock are used to re-examine the timing and locations of possible future large earthquakes. The physical mechanisms of regional faults like the Calaveras, Hayward and Sargent, which exhibit creep, differ from those of the northern San Andreas, which is currently locked and is not creeping. Much decadal forerunning activity occurred on creeping faults. Moderate-size earthquakes along those faults became more frequent as stresses in the region increased in the latter part of the cycle of stress restoration for major and great earthquakes along the San Andreas. They may be useful for decadal forecasts. Yearly to decadal forecasts, however, are based on only a few major to great events. Activity along closer faults like that in the two years prior to the 1989 Loma Prieta shock needs to be examined for possible yearly forerunning changes to large plate boundary earthquakes. Geodetic observations are needed to focus on identifying creeping faults close to the San Andreas. The distribution of moderate-size earthquakes increased significantly since 1990 along the Hayward fault but not adjacent to the San Andreas fault to the south of San Francisco compared to what took place in the decades prior to the three major historic earthquakes in the region. It is now clear from a re-examination of the 1989 mainshock that the increased level of moderate-size shocks in the one to two preceding decades occurred on nearby East Bay faults. Double-difference locations of small earthquakes provide structural information about faults in the region, especially their depths. The northern San Andreas fault is divided into several strongly coupled segments based on differences in seismicity.
