On September 5,2022,the Luding M6.8 earthquake occurred in the Moxi-Shimian segment of the Xianshuihe fault,coinciding with the historical ruptured zone of the 1786 Moxi earthquake.Its seis-mogenic environment provide...On September 5,2022,the Luding M6.8 earthquake occurred in the Moxi-Shimian segment of the Xianshuihe fault,coinciding with the historical ruptured zone of the 1786 Moxi earthquake.Its seis-mogenic environment provides a foundation for comprehending the mechanism of the earthquake and its future hazard.In the Moxi-Shimian segment,we establish a series of near-field Global Navigation Satellite Systems(GNsS)stations to enhance the spatial resolution of observational data for the inversion of the interseismic kinematic parameters.In this study,with an elastic screw dislocation model con-strained by GNsS observations,the slip rate of the Moxi-Shimian segment is estimated to be 10.9±1.0 mm/yr,while the locking depth is 15.7±6.2 km.Additionally,we utilize a block-dislocation model to invert the interseismic fault coupling along the Kangding-Moxi-Shimian segment.The result indicates a gradual deepening of the locking depth along the section from Kangding to Shimian.The coseismic rupture of the 2022 event occurred within the high coupling regions in the Kangding-Moxi-Shimian segment,which indicates that the rupture kinematics in this event might be controlled by the interseismic deformation.The seismic moment accumulated within the ruptured zone of the Luding earthquake since 1786 ranges in[1.42-3.40]×10^(19) N-m,which is significantly greater than the seismic moment released during the 2022 event.As a result,we infer that the Luding earthquake released only a portion of the accumulated energy within the original rupture zone since 1786,indicating that the 2022 event has not caused a complete rupture in the Moxi-Shimian segment.Consequently,there remains a substantial seismic hazard in this area.展开更多
The 1:200,000 middle-large scale Bouguer gravity anomaly data covering the southern segment of the Liaocheng-Lankao fault(SLLF)and its vicinity are analyzed with two methods.First,the Bouguer gravity anomaly data are ...The 1:200,000 middle-large scale Bouguer gravity anomaly data covering the southern segment of the Liaocheng-Lankao fault(SLLF)and its vicinity are analyzed with two methods.First,the Bouguer gravity anomaly data are decomposed by two-dimensional(2 D)wavelet to make the family of multi-scale modes correspond with density structure at different depths.Second,a two and half dimension(2.5 D)human-computer interaction inversion of the Bouguer gravity anomaly data are conducted with the constraints provided by two deep seismic sounding profiles(DSS1 and DSS2)crossing the study area to get the crustal density profiles.Based on the integrated study,we can draw the following conclusions:1)SLLF appears to be a deep fault with almost vertical dipping and rooted into the uppermost mantle;2)In the middle to upper crust SLLF shows an clear turning patterns and segmentation features;3)In the study area the epicentral distributions of the precisely re-located small earthquakes and the historical large earthquakes have a good correspondence with the turning patterns and segmentation features of SLLF;and 4)The results of the horizontal slices from 2 D wavelet decomposition show that there are significant differences in the density structure on the two sides of the fault.A well-defined concave structure with low density exists in the upper crust of the Dongming Depression on the west side of the fault,with the concave center being estimated at a depth of about 8 km.In contrast,the upper crust on the east side presents a relative thinner pattern in depth with a bit higher density.Meanwhile,the low-density structure in the middle crust underneath the fault is presumably caused by the uplift of the upper mantle materials and their intrusion along the deep rupture system.This paper clarified the inconsistency of fault system and epicenters of small earthquakes from upper to lower crust.The results indicated that the fault system plays an important governing role to the seismicity in this area.展开更多
On the basis of the recent geological surveys and the relevant studies of the Xianshuihe fault zone, this paper analyzes the seismogenic mechanism of some faults and characteristic morphology on the fault zone by the ...On the basis of the recent geological surveys and the relevant studies of the Xianshuihe fault zone, this paper analyzes the seismogenic mechanism of some faults and characteristic morphology on the fault zone by the boundary element method and discusses the fault segmentation and the related distribution of the earthquake ruptures. The main conclusions are: For the first order segmentation, the Xianshuihe fault zone can be divided into three major segments (the northwestern Luhuo-Qianning segment, the middle linking fracture region and the southeastern Kangding segment). Among them, the differences are not only in geometry and structure, but also in mechanical property and dynamics. Some of the characteristic morphologies on the Xianshuihe fault zone reflect the effects in cumulative deformation due to long-term fault movement, and reveal the fault segmentation in different orders. Such morphologies control, to some extent, the developments and the distributions of the earthquake ruptures on the fault zone.展开更多
On September 5,2022,a strong MS6.8 earthquake struck the Luding area in the Kangding-Moxi segment of the Xianshuihe fault zone,which is the northern boundary of the Sichuan-Yunnan rhombic block,causing considerable ca...On September 5,2022,a strong MS6.8 earthquake struck the Luding area in the Kangding-Moxi segment of the Xianshuihe fault zone,which is the northern boundary of the Sichuan-Yunnan rhombic block,causing considerable casualties.The Bamei-Kangding segment of the Xianshuihe fault zone,which is located only tens of kilometers away from the Luding earthquake,has hosted frequent moderate to strong earthquakes in history and is a dangerous earthquake-prone zone.Therefore,it is critical to investigate the regional seismogenic environment for strong earthquakes and to evaluate the impact of the Luding earthquake in this area.For this purpose,we deployed a dense seismic array comprising over 200 short-period nodes in this region from July to August,2022 and acquired seismic ambient noise for over 30 days.Using the collected data,we conducted surface wave tomography and obtained a high-resolution 3-D shear wave velocity model for the regional shallow crust down to 8 km in depth.The key findings include:(1)the Bamei-Kangding segment of the Xianshuihe fault zone exhibits widespread stripped lowvelocity anomalies,suggesting shear movements at a relatively high temperature of the Xianshuihe fault zone;the Zheduoshan granitic pluton situated between the Zheduotang and southern Selaha faults shows a distinct low-velocity anomaly,which may be attributed to the localized high-temperature anomaly resulted by a deep magmatic heat source and the recent rapid uplift of the Zheduoshan area;(2)a ten-kilometer-wide high velocity body found below 4 km in depth near the Zhonggu area in the Bamei segment coincides with the seismic gap of moderate to strong earthquakes in this region,suggesting that the high velocity body may act as a seismic barrier;(3)the heterogeneity of the velocity structure along the Bamei-Kangding segment of the Xianshuihe fault zone corresponds to the regional changes in temperature,which reveals the reason for the spatially varying seismogenic potential in this segment;especially,the Selaha and Zheduotang faults which are located along the boundaries between the high and low velocity anomalies may possess considerable seismogenic potential;(4)the Coulomb failure stress calculations indicate that the Luding earthquake has imposed nontrivial stress loading in the Bamei-Kangding segment,and may shorten the earthquake recurrence intervals of the southern Selaha fault,the Zheduotang fault,and the Xuemenkan segment of the Xianshuihe fault zone.Thus,the Luding earthquake may potentially pose threats to the Sichuan-Xizang railway passing through this region.展开更多
基金supported by Open Fund of Wuhan,Gravitation and Solid Earth Tides,National Observation and Research Station(WHYWZ202301)Scientific Research Fund from Institute of Seismology,CEA and National Institute of Natural Hazards,Ministry of Emergency Management of China grants IS202216316 and IS202226318+1 种基金State Key Laboratory of Geodesy and Earth's Dynamics,Innovation Academy for Precision Measurement Science and Technology,CAS SKLGED2023-2-5Science for Earthquake Resilience grant XH20038,and NSFC grant 42074015.
文摘On September 5,2022,the Luding M6.8 earthquake occurred in the Moxi-Shimian segment of the Xianshuihe fault,coinciding with the historical ruptured zone of the 1786 Moxi earthquake.Its seis-mogenic environment provides a foundation for comprehending the mechanism of the earthquake and its future hazard.In the Moxi-Shimian segment,we establish a series of near-field Global Navigation Satellite Systems(GNsS)stations to enhance the spatial resolution of observational data for the inversion of the interseismic kinematic parameters.In this study,with an elastic screw dislocation model con-strained by GNsS observations,the slip rate of the Moxi-Shimian segment is estimated to be 10.9±1.0 mm/yr,while the locking depth is 15.7±6.2 km.Additionally,we utilize a block-dislocation model to invert the interseismic fault coupling along the Kangding-Moxi-Shimian segment.The result indicates a gradual deepening of the locking depth along the section from Kangding to Shimian.The coseismic rupture of the 2022 event occurred within the high coupling regions in the Kangding-Moxi-Shimian segment,which indicates that the rupture kinematics in this event might be controlled by the interseismic deformation.The seismic moment accumulated within the ruptured zone of the Luding earthquake since 1786 ranges in[1.42-3.40]×10^(19) N-m,which is significantly greater than the seismic moment released during the 2022 event.As a result,we infer that the Luding earthquake released only a portion of the accumulated energy within the original rupture zone since 1786,indicating that the 2022 event has not caused a complete rupture in the Moxi-Shimian segment.Consequently,there remains a substantial seismic hazard in this area.
基金financial support from China Scholarship Councilthe support from the Seismic Youth Founding of GEC (Grant No. YFGEC2016008)the National Natural Science Foundation of China(Grant No. 41474077)
文摘The 1:200,000 middle-large scale Bouguer gravity anomaly data covering the southern segment of the Liaocheng-Lankao fault(SLLF)and its vicinity are analyzed with two methods.First,the Bouguer gravity anomaly data are decomposed by two-dimensional(2 D)wavelet to make the family of multi-scale modes correspond with density structure at different depths.Second,a two and half dimension(2.5 D)human-computer interaction inversion of the Bouguer gravity anomaly data are conducted with the constraints provided by two deep seismic sounding profiles(DSS1 and DSS2)crossing the study area to get the crustal density profiles.Based on the integrated study,we can draw the following conclusions:1)SLLF appears to be a deep fault with almost vertical dipping and rooted into the uppermost mantle;2)In the middle to upper crust SLLF shows an clear turning patterns and segmentation features;3)In the study area the epicentral distributions of the precisely re-located small earthquakes and the historical large earthquakes have a good correspondence with the turning patterns and segmentation features of SLLF;and 4)The results of the horizontal slices from 2 D wavelet decomposition show that there are significant differences in the density structure on the two sides of the fault.A well-defined concave structure with low density exists in the upper crust of the Dongming Depression on the west side of the fault,with the concave center being estimated at a depth of about 8 km.In contrast,the upper crust on the east side presents a relative thinner pattern in depth with a bit higher density.Meanwhile,the low-density structure in the middle crust underneath the fault is presumably caused by the uplift of the upper mantle materials and their intrusion along the deep rupture system.This paper clarified the inconsistency of fault system and epicenters of small earthquakes from upper to lower crust.The results indicated that the fault system plays an important governing role to the seismicity in this area.
文摘On the basis of the recent geological surveys and the relevant studies of the Xianshuihe fault zone, this paper analyzes the seismogenic mechanism of some faults and characteristic morphology on the fault zone by the boundary element method and discusses the fault segmentation and the related distribution of the earthquake ruptures. The main conclusions are: For the first order segmentation, the Xianshuihe fault zone can be divided into three major segments (the northwestern Luhuo-Qianning segment, the middle linking fracture region and the southeastern Kangding segment). Among them, the differences are not only in geometry and structure, but also in mechanical property and dynamics. Some of the characteristic morphologies on the Xianshuihe fault zone reflect the effects in cumulative deformation due to long-term fault movement, and reveal the fault segmentation in different orders. Such morphologies control, to some extent, the developments and the distributions of the earthquake ruptures on the fault zone.
基金supported by the National Key Research and Development Project of China(Grant No.2021YFC3000602)the Special Fund of Key Laboratory of Earthquake Prediction,CEA(Grant No.2021IEF0103).
文摘On September 5,2022,a strong MS6.8 earthquake struck the Luding area in the Kangding-Moxi segment of the Xianshuihe fault zone,which is the northern boundary of the Sichuan-Yunnan rhombic block,causing considerable casualties.The Bamei-Kangding segment of the Xianshuihe fault zone,which is located only tens of kilometers away from the Luding earthquake,has hosted frequent moderate to strong earthquakes in history and is a dangerous earthquake-prone zone.Therefore,it is critical to investigate the regional seismogenic environment for strong earthquakes and to evaluate the impact of the Luding earthquake in this area.For this purpose,we deployed a dense seismic array comprising over 200 short-period nodes in this region from July to August,2022 and acquired seismic ambient noise for over 30 days.Using the collected data,we conducted surface wave tomography and obtained a high-resolution 3-D shear wave velocity model for the regional shallow crust down to 8 km in depth.The key findings include:(1)the Bamei-Kangding segment of the Xianshuihe fault zone exhibits widespread stripped lowvelocity anomalies,suggesting shear movements at a relatively high temperature of the Xianshuihe fault zone;the Zheduoshan granitic pluton situated between the Zheduotang and southern Selaha faults shows a distinct low-velocity anomaly,which may be attributed to the localized high-temperature anomaly resulted by a deep magmatic heat source and the recent rapid uplift of the Zheduoshan area;(2)a ten-kilometer-wide high velocity body found below 4 km in depth near the Zhonggu area in the Bamei segment coincides with the seismic gap of moderate to strong earthquakes in this region,suggesting that the high velocity body may act as a seismic barrier;(3)the heterogeneity of the velocity structure along the Bamei-Kangding segment of the Xianshuihe fault zone corresponds to the regional changes in temperature,which reveals the reason for the spatially varying seismogenic potential in this segment;especially,the Selaha and Zheduotang faults which are located along the boundaries between the high and low velocity anomalies may possess considerable seismogenic potential;(4)the Coulomb failure stress calculations indicate that the Luding earthquake has imposed nontrivial stress loading in the Bamei-Kangding segment,and may shorten the earthquake recurrence intervals of the southern Selaha fault,the Zheduotang fault,and the Xuemenkan segment of the Xianshuihe fault zone.Thus,the Luding earthquake may potentially pose threats to the Sichuan-Xizang railway passing through this region.
