Objective The 2014 Ludian Mw6.1 earthquake in Yunnan occurred in a mountainous area with complex tectonics and topography, which caused serious damage as well as co-seismic landslides of an unusual large scale. Becau...Objective The 2014 Ludian Mw6.1 earthquake in Yunnan occurred in a mountainous area with complex tectonics and topography, which caused serious damage as well as co-seismic landslides of an unusual large scale. Because the suspected seismogenic faults on the surface, distribution of aftershocks and focal mechanism solutions are not consistent, it remains difficult to determine what is the real causal fault or seismogenic structure for this event. Actually, it may imply the complicity of the seismic source at depth. In addition, the distribution of the co- seismic landslides also exhibits some diffusion that is different from general eases, likely associated with the seismic focus structure.展开更多
Using mobile gravity data from the central area of Sichuan and Yunnan Provinces, the relationship between gravity variation and earthquakes was studied based on the Ludian Ms6.5 earthquake that occurred on August 3rd,...Using mobile gravity data from the central area of Sichuan and Yunnan Provinces, the relationship between gravity variation and earthquakes was studied based on the Ludian Ms6.5 earthquake that occurred on August 3rd, 2014, and the Kangding Ms6.3 earthquake that occurred on November 22 nd, 2014; the mechanism of gravity variation was also explored. The results are as follows：（1） Prior to both earthquakes, gravity variation exhibited similar characteristics as those observed before both the Tangshan and Wenchuan earthquakes, in which typical precursor anomalies were positive gravity variation near the epicenter and the occurrence of a high-gravity-gradient zone across the epicenter prior to the earthquake.（2） A relatively accurate prediction of the occurrence locations of the two earthquakes was made by the Gravity Network Center of China（GNCC） based on these precursor anomalies. In the gravity study report on the 2014 earthquake trends submitted at the end of 2013, the Daofu-Shimian section at the junction of the Xianshuihe and Longmenshan fault zones was noted as an earthquake-risk region with a predicted magnitude of 6.5, which covered the epicenter of the Kangding Ms6.3 earthquake. In another report on earthquake trends in southwestern China submitted in mid-2014, the Lianfeng, Zhaotong fault zone was also classified as an earthquake-risk region with a magnitude of 6.0, and the central area of this region basically overlapped with the epicenter of the Ludian Ms6.5 earthquake.（3） The gravity variation characteristics are reasonably consistent with crustal movements, and deep material migration is likely the primary cause of gravity variation.展开更多
The cycle process of the tidal force niche for the Ludian M_S6.5 earthquake occurring in Ludian County, Yunnan Province, China on August 3, 2014 was calculated. The earthquake occurred near the middle point phase. It ...The cycle process of the tidal force niche for the Ludian M_S6.5 earthquake occurring in Ludian County, Yunnan Province, China on August 3, 2014 was calculated. The earthquake occurred near the middle point phase. It indicates that the type of seismogenic fault that the tide force acted on belongs to the thrust fault. According to the tidal niche cycle,the abnormal OLR( Outgoing Long-wave Radiation) change was analyzed based on NOAA satellite data around the whole land area of China before and after the earthquake.The result shows that the OLR changed evidently with tide force change. Temporally,the change went through the evolution process of initial OLR rise → strengthening → abnormal peaking → attenuation → returning to normal; and spatially,the abnormal area wound its way along the Zhaotong-Ludian fault and went through a scattered → conversion →scattered process. This process is similar to the change process of rock breaking under stress loading. The results indicate that the tidal force of a celestial body could trigger an earthquake when the tectonic stress reaches its critical breaking point and the OLR anomaly is proportional to the seismic tectonic stress change. It is of great use to combine OLR and tidal force in earthquake precursory observation.展开更多
A seismic array of twenty four seismometers(Qiaojia array) operated by the Institute of Geophysics,China Earthquake Administration was situated along the Zemuhe fault and the north end of Xiaojiang fault,which is a pa...A seismic array of twenty four seismometers(Qiaojia array) operated by the Institute of Geophysics,China Earthquake Administration was situated along the Zemuhe fault and the north end of Xiaojiang fault,which is a part of the east boundary of the Chuan-Dian( Sichuan-Yunnan) rhombus crustal mass. The Qiaojia array started operation at the end of February,2012. Since then the April 20,2013 Lushan MS7. 0 earthquake and the August 3,2014 Ludian MS6. 5 earthquake have occurred in the vicinity of the Qiaojia array. The earthquake catalogue recorded by the Qiaojia array since March,2012 is used in this study. The temporal variation of the earthquake count before the Lushan event and the Ludian event is analyzed. The results are as follows:(1) A very clear gradually increasing variation of the count of M ≥ 2. 0 earthquakes within the region,where all earthquakes recorded by the Qiaojia array coverage can be found before the Lushan event and the Ludian event,and the increasing range and duration of the count before the Ludian event are both larger than those before the Lushan event.(2) In the region covered by the Qiaojia array,for earthquakes with depth h ≤10 km a rising process of the count was manifested before both events,along with a nearly same duration of about five and a half months,and for earthquakes with depths h > 10 km a rising-dropping process of the count was manifest before the Lushan event,before which the rising-dropping process appeared again. The variation of the count for earthquakes with depth h ≤ 10 km is the reverse of that for earthquakes with depth h > 10 km.(3) Within and near the region covered by the Qiaojia array,the variation of the count manifests a rising process for earthquakes with depth h ≤ 10 km or h > 10 km before the Lushan event and only for earthquakes with depth h ≤ 10 km before the Ludian event. The variation of the count manifests a weakening process for earthquakes with depth h > 10 km before the Lushan event. It is shown from the above results that the seismicity within and near the regioncovered by the Qiaojia array showed a steeply rising change before both the Lushan event and the Ludian event. This phenomenon could be revelatory to understanding the process of seismicity development.展开更多
1 Geography Location At 16：30 on August 3rd, 2014, Ludian County, Zhaotong City, Yunnan Province （27.1°N, 103.3°E） was hit by Ms 6.5 earthquake, with the maximum intensity is 9 and epicenter depth is aro...1 Geography Location At 16：30 on August 3rd, 2014, Ludian County, Zhaotong City, Yunnan Province （27.1°N, 103.3°E） was hit by Ms 6.5 earthquake, with the maximum intensity is 9 and epicenter depth is around 12 km （Figs. 1 and 2）.展开更多
Significant anomalies were observed at the geomagnetic stations in the southwest region of China before the Yingjiang M_S6. 1 earthquake and the Ludian M_S6. 5 earthquake in 2014.We processed the geomagnetic vertical ...Significant anomalies were observed at the geomagnetic stations in the southwest region of China before the Yingjiang M_S6. 1 earthquake and the Ludian M_S6. 5 earthquake in 2014.We processed the geomagnetic vertical component diurnal variation data by the spatial correlation method. The results show that during the period from April 1 to May 20,2014,there existed quasi-synchronous decrease changes in the coefficient curves between the five geomagnetic stations of Guiyang,Hechi,Nanshan,Muli,Yongning and Xinyi and Hongshan stations. Furthermore,there was a high gradient zone in the normalized correlation coefficient contour map with background values removed. The epicenters of the Yingjiang M_S6. 1 earthquake and the Ludian M_S6. 5 earthquake are located in the gradient zone or near the gradient zone.展开更多
The 3 August 2014 Ludian, Yunnan, China Mw 6.2(Ms 6.5) earthquake triggered a large number of coseismic landslides. Based on pre-and post-quake high-resolution optical satellite images, this study established a new, c...The 3 August 2014 Ludian, Yunnan, China Mw 6.2(Ms 6.5) earthquake triggered a large number of coseismic landslides. Based on pre-and post-quake high-resolution optical satellite images, this study established a new, complete and objective database of these landslides with field investigations. The updated inventory shows that this earthquake triggered at least 12 817 landslides with a total occupation area of 16.33 km2, covering a nearly circular area about 600 km2, which all exceed those in our previous work and other relevant studies. In addition, we used this database to examine the correlations of the landslides with topographic, geologic, and seismic factors. Results show that the landslides occurred mostly at places with slope gradients 10o–40o, showing an increase tendency with steeper slopes. Affected by the propagation direction of the earthquake rupture, the eastward-facing slopes are more prone to landsliding. The differences between the landslide susceptibility in different strata indicate that lithology is also an important controlling factor. The landslide density of the places with peak ground acceleration(PGA) greater than 0.16 g is obviously larger than those with PGA less than 0.16 g. Meanwhile, the greater the distance from the epicenter, the lower the susceptibility of landslides is. This study suggests that when using satellite images to create coseismic landslide inventories, it should meet certain conditions, including high resolution, whole coverage, and timely data collection. The correct criteria of coseismic landslide inventorying also should be followed. Such inventories can provide a reliable basis for hazard assessment of earthquake-triggered landslides and other quantitative studies.展开更多
基金supported by the National Natural Science Foundation of China(grant No.41572194)the Institute of Geology,China Earthquake Administration(grant No.IGCEA1604)the National Key Basic Research Program of China(grant No.2013CB733205)
文摘Objective The 2014 Ludian Mw6.1 earthquake in Yunnan occurred in a mountainous area with complex tectonics and topography, which caused serious damage as well as co-seismic landslides of an unusual large scale. Because the suspected seismogenic faults on the surface, distribution of aftershocks and focal mechanism solutions are not consistent, it remains difficult to determine what is the real causal fault or seismogenic structure for this event. Actually, it may imply the complicity of the seismic source at depth. In addition, the distribution of the co- seismic landslides also exhibits some diffusion that is different from general eases, likely associated with the seismic focus structure.
基金jointly supported by the Director Foundation of Institute of Seismology,China Earthquake Administration(IS201326121)the special earthquake research grant offered by the China Earthquake Administration(201208009,201308009)the National Natural Science Foundation of China(41304059)
文摘Using mobile gravity data from the central area of Sichuan and Yunnan Provinces, the relationship between gravity variation and earthquakes was studied based on the Ludian Ms6.5 earthquake that occurred on August 3rd, 2014, and the Kangding Ms6.3 earthquake that occurred on November 22 nd, 2014; the mechanism of gravity variation was also explored. The results are as follows：（1） Prior to both earthquakes, gravity variation exhibited similar characteristics as those observed before both the Tangshan and Wenchuan earthquakes, in which typical precursor anomalies were positive gravity variation near the epicenter and the occurrence of a high-gravity-gradient zone across the epicenter prior to the earthquake.（2） A relatively accurate prediction of the occurrence locations of the two earthquakes was made by the Gravity Network Center of China（GNCC） based on these precursor anomalies. In the gravity study report on the 2014 earthquake trends submitted at the end of 2013, the Daofu-Shimian section at the junction of the Xianshuihe and Longmenshan fault zones was noted as an earthquake-risk region with a predicted magnitude of 6.5, which covered the epicenter of the Kangding Ms6.3 earthquake. In another report on earthquake trends in southwestern China submitted in mid-2014, the Lianfeng, Zhaotong fault zone was also classified as an earthquake-risk region with a magnitude of 6.0, and the central area of this region basically overlapped with the epicenter of the Ludian Ms6.5 earthquake.（3） The gravity variation characteristics are reasonably consistent with crustal movements, and deep material migration is likely the primary cause of gravity variation.
基金Science for Earthquake Resilience-Based on the Application of Atmospheric Temperature Vertical Stratification 3D Remote Sensing Technology in Earthquake Prediction(Project number:XH15050)
文摘The cycle process of the tidal force niche for the Ludian M_S6.5 earthquake occurring in Ludian County, Yunnan Province, China on August 3, 2014 was calculated. The earthquake occurred near the middle point phase. It indicates that the type of seismogenic fault that the tide force acted on belongs to the thrust fault. According to the tidal niche cycle,the abnormal OLR( Outgoing Long-wave Radiation) change was analyzed based on NOAA satellite data around the whole land area of China before and after the earthquake.The result shows that the OLR changed evidently with tide force change. Temporally,the change went through the evolution process of initial OLR rise → strengthening → abnormal peaking → attenuation → returning to normal; and spatially,the abnormal area wound its way along the Zhaotong-Ludian fault and went through a scattered → conversion →scattered process. This process is similar to the change process of rock breaking under stress loading. The results indicate that the tidal force of a celestial body could trigger an earthquake when the tectonic stress reaches its critical breaking point and the OLR anomaly is proportional to the seismic tectonic stress change. It is of great use to combine OLR and tidal force in earthquake precursory observation.
基金funded by the operational object of China Earthquake Science Experiment
文摘A seismic array of twenty four seismometers(Qiaojia array) operated by the Institute of Geophysics,China Earthquake Administration was situated along the Zemuhe fault and the north end of Xiaojiang fault,which is a part of the east boundary of the Chuan-Dian( Sichuan-Yunnan) rhombus crustal mass. The Qiaojia array started operation at the end of February,2012. Since then the April 20,2013 Lushan MS7. 0 earthquake and the August 3,2014 Ludian MS6. 5 earthquake have occurred in the vicinity of the Qiaojia array. The earthquake catalogue recorded by the Qiaojia array since March,2012 is used in this study. The temporal variation of the earthquake count before the Lushan event and the Ludian event is analyzed. The results are as follows:(1) A very clear gradually increasing variation of the count of M ≥ 2. 0 earthquakes within the region,where all earthquakes recorded by the Qiaojia array coverage can be found before the Lushan event and the Ludian event,and the increasing range and duration of the count before the Ludian event are both larger than those before the Lushan event.(2) In the region covered by the Qiaojia array,for earthquakes with depth h ≤10 km a rising process of the count was manifested before both events,along with a nearly same duration of about five and a half months,and for earthquakes with depths h > 10 km a rising-dropping process of the count was manifest before the Lushan event,before which the rising-dropping process appeared again. The variation of the count for earthquakes with depth h ≤ 10 km is the reverse of that for earthquakes with depth h > 10 km.(3) Within and near the region covered by the Qiaojia array,the variation of the count manifests a rising process for earthquakes with depth h ≤ 10 km or h > 10 km before the Lushan event and only for earthquakes with depth h ≤ 10 km before the Ludian event. The variation of the count manifests a weakening process for earthquakes with depth h > 10 km before the Lushan event. It is shown from the above results that the seismicity within and near the regioncovered by the Qiaojia array showed a steeply rising change before both the Lushan event and the Ludian event. This phenomenon could be revelatory to understanding the process of seismicity development.
文摘1 Geography Location At 16：30 on August 3rd, 2014, Ludian County, Zhaotong City, Yunnan Province （27.1°N, 103.3°E） was hit by Ms 6.5 earthquake, with the maximum intensity is 9 and epicenter depth is around 12 km （Figs. 1 and 2）.
基金sponsored by the Spark Program for Earthquake Science and Technology,China Earthquake Administration(Serial No.XH17010Y)the Seismic Tracking and Orientation Task,China Earthquake Administration(Serial No.2018010401)Major Scientific and Technical Project of Science and Technology Department of Inner Mongolia in 2016(Strong Earthquake Track in the Short Stage and Integration Innovation of Stereoscopic Observation Technology in Space and Ground)
文摘Significant anomalies were observed at the geomagnetic stations in the southwest region of China before the Yingjiang M_S6. 1 earthquake and the Ludian M_S6. 5 earthquake in 2014.We processed the geomagnetic vertical component diurnal variation data by the spatial correlation method. The results show that during the period from April 1 to May 20,2014,there existed quasi-synchronous decrease changes in the coefficient curves between the five geomagnetic stations of Guiyang,Hechi,Nanshan,Muli,Yongning and Xinyi and Hongshan stations. Furthermore,there was a high gradient zone in the normalized correlation coefficient contour map with background values removed. The epicenters of the Yingjiang M_S6. 1 earthquake and the Ludian M_S6. 5 earthquake are located in the gradient zone or near the gradient zone.
基金supported by the National Key Research and Development Program of China (No. 2017YFB0504104)the National Natural Science Foundation of China (No. 41661144037)。
文摘The 3 August 2014 Ludian, Yunnan, China Mw 6.2(Ms 6.5) earthquake triggered a large number of coseismic landslides. Based on pre-and post-quake high-resolution optical satellite images, this study established a new, complete and objective database of these landslides with field investigations. The updated inventory shows that this earthquake triggered at least 12 817 landslides with a total occupation area of 16.33 km2, covering a nearly circular area about 600 km2, which all exceed those in our previous work and other relevant studies. In addition, we used this database to examine the correlations of the landslides with topographic, geologic, and seismic factors. Results show that the landslides occurred mostly at places with slope gradients 10o–40o, showing an increase tendency with steeper slopes. Affected by the propagation direction of the earthquake rupture, the eastward-facing slopes are more prone to landsliding. The differences between the landslide susceptibility in different strata indicate that lithology is also an important controlling factor. The landslide density of the places with peak ground acceleration(PGA) greater than 0.16 g is obviously larger than those with PGA less than 0.16 g. Meanwhile, the greater the distance from the epicenter, the lower the susceptibility of landslides is. This study suggests that when using satellite images to create coseismic landslide inventories, it should meet certain conditions, including high resolution, whole coverage, and timely data collection. The correct criteria of coseismic landslide inventorying also should be followed. Such inventories can provide a reliable basis for hazard assessment of earthquake-triggered landslides and other quantitative studies.
