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
On May 18, 2020, an M_(w)5.1 earthquake occurred in Qiaojia County, Yunnan Province, China. This moderate-sized event triggered massive coseismic landslides, resulting in some damage. In this work, through visual inte...On May 18, 2020, an M_(w)5.1 earthquake occurred in Qiaojia County, Yunnan Province, China. This moderate-sized event triggered massive coseismic landslides, resulting in some damage. In this work, through visual interpretation of high-resolution(0.8–2 m) Gaofen satellite images before and after the earthquake, 167 landslides were delineated, 18 of which were inspected in the field. Using the landslide number density(LND) and landslide area percentage(LAP), we characterized the spatial distribution of these landslides, and analyzed their possible influence factors and tectonic significance. The results show that these landslides are distributed mostly in the NW-SE direction, roughly parallel to the long axis of seismic intensity zones and the strike of the Xiaohe-Baogunao fault(XBF). The LND and LAP decrease with increasing distances to the fault and from the epicenter to fault ends of the XBF. These permit to suggest that the seismogenic fault of the Qiaojia earthquake is likely a hidden branch of the XBF. All of the landslides induced by this event occurred in the region with the seismic intensity of six degrees or greater of the 2014 M_(w)6.2 Ludian earthquake. Therefore, it was inferred that the 2020 Qiaojia earthquake was probably the subsequent release of accumulated elastic strain after the 2014 Ludian earthquake in a same tectonic stress regime.展开更多
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.
基金This work was supported by the National Natural Science Foundation of China(No.42077259)the National Institute of Natural Hazards,Ministry of Emergency Management of China(No.ZDJ2019-31).
文摘On May 18, 2020, an M_(w)5.1 earthquake occurred in Qiaojia County, Yunnan Province, China. This moderate-sized event triggered massive coseismic landslides, resulting in some damage. In this work, through visual interpretation of high-resolution(0.8–2 m) Gaofen satellite images before and after the earthquake, 167 landslides were delineated, 18 of which were inspected in the field. Using the landslide number density(LND) and landslide area percentage(LAP), we characterized the spatial distribution of these landslides, and analyzed their possible influence factors and tectonic significance. The results show that these landslides are distributed mostly in the NW-SE direction, roughly parallel to the long axis of seismic intensity zones and the strike of the Xiaohe-Baogunao fault(XBF). The LND and LAP decrease with increasing distances to the fault and from the epicenter to fault ends of the XBF. These permit to suggest that the seismogenic fault of the Qiaojia earthquake is likely a hidden branch of the XBF. All of the landslides induced by this event occurred in the region with the seismic intensity of six degrees or greater of the 2014 M_(w)6.2 Ludian earthquake. Therefore, it was inferred that the 2020 Qiaojia earthquake was probably the subsequent release of accumulated elastic strain after the 2014 Ludian earthquake in a same tectonic stress regime.
