On July 22, 2013, an earthquake （Ms 6.6） occurred in Minxian, Gansu Province of China, causing a large number of landslides. Based on high resolution remote sensing images before and after this event, we made the vi...On July 22, 2013, an earthquake （Ms 6.6） occurred in Minxian, Gansu Province of China, causing a large number of landslides. Based on high resolution remote sensing images before and after this event, we made the visual interpretation to these coseismic landslides, and prepared a detailed inventory. The inventory registers totally 6 478 landslides in the study area. Of them, 3 322 landslides are larger than 100 m2. Based on 5 m resolution DEM, these landslides were used to perform spatial analyses using landslide number density （LND） and landslide area percentage （LAP）. The results show that the highest LND and LAP values are in the elevation range of 2 300-2 500 m and steeper slopes. Slopes facing E, SE, S and SW directions, slopes with larger absolute curvature values, ridges, scopes of gravel beds of Late Pleistocene （Qp） and the VIII-degree seismic intensity are more prone to sliding with high LND and LAP values. The largest LND and LAP values are in the scopes of 0.08 and 0.24 g, respectively. According to landslide distribution, we infer that F2-2 branch of Lintan-Dangchang fault is the seismogenic fault. With the increasing distances to this branch fault and drainages, LND and LAP values tend to decrease.展开更多
Choice of appropriate mapping units is important in landslide susceptibility mapping(LSM).There are various possible units for this choice,while it remains unclear which one is better in performance.The purpose of thi...Choice of appropriate mapping units is important in landslide susceptibility mapping(LSM).There are various possible units for this choice,while it remains unclear which one is better in performance.The purpose of this study is to make a quantitative comparison of two commonly-used units:slope-unit(SU)and raster-unit(RU)based on the landslides triggered by the 2013 Minxian,Gansu,China Mw5.9 earthquake.Ten landslide influencing factors were considered in this analysis.For each type of mapping units,the 70%samples were randomly selected and trained 20 times on the LR model,yielding 20 susceptibility maps,and the remaining 30%samples were tested for the accuracy of the modeling outcome.Different metrics,including the mean probability,model uncertainty,and model prediction skills,were used to evaluate the quality of the susceptibility maps.The results show that the resultant probability maps using two mapping units can largely predict the distribution of actual landslides,on which the high susceptibility area corresponds to the landslide-prone area.The AUC(area under curve)values,ranging from 0.8 to 0.86,show that the prediction ability of two mapping units is roughly the same.While comparing with the RU,the use of SU can lower the model uncertainties caused by the variation of training sets.We converted the RU-based assessment results into SU-based scheme.The results show that two assessment results are well fitted with good linear relationship,which implies that it is feasible to convert the RU-based landslide susceptibility mapping into the SU-based scheme.This analysis indicates that compared with the RU,the SU cannot improve the performance and accuracy of seismic landslide susceptibility mapping.展开更多
In this paper,based on Gansu Digital Seismic Network data since 1990,we calculated b-value and ⊿ b-value of the neighborhood area before the 2013 Minxian-Zhangxian M_S6. 6,earthquake. The results show that the earthq...In this paper,based on Gansu Digital Seismic Network data since 1990,we calculated b-value and ⊿ b-value of the neighborhood area before the 2013 Minxian-Zhangxian M_S6. 6,earthquake. The results show that the earthquake occurred at the margin of the significantly lower b-value area in southeast of Gansu and before the earthquake the neighborhood area had an obviously abnormal ⊿ b-value. From the earthquake and the spatial distribution of low b-value, the region still has the possibility of generating dangerous strong earthquakes.展开更多
Based on the waveform data observed by the regional seismic network of Gansu Province,we calculated the apparent stress of 422 earthquakes with M_L≥ 2. 0 occurring in the surrounding area of the Minxian earthquake fr...Based on the waveform data observed by the regional seismic network of Gansu Province,we calculated the apparent stress of 422 earthquakes with M_L≥ 2. 0 occurring in the surrounding area of the Minxian earthquake from January 2010 to July 2014 and obtained the temporal and spatial variation of apparent stress before and after the Minxian earthquake. Results show that( 1) the high value of apparent stress of earthquakes with M_L≥4. 0 was concentrated in the epicenter area before the Minxian earthquake while that of earthquakes with M_L< 4. 0 was not;( 2) Apparent stress around the epicenter area showed an obvious increasing process before the Minxian earthquake and the increasing process has continued after the main shock,which means that this study area is still in the danger of strong earthquakes.展开更多
On July 22, 2013, the Minxian-Zhangxian Ms6. 6 earthquake occurred on the east segment of Lintan-Dangchang fault. The analysis of digital elevation and remote sensing imaging shows that the east segment of Lintan-Dang...On July 22, 2013, the Minxian-Zhangxian Ms6. 6 earthquake occurred on the east segment of Lintan-Dangchang fault. The analysis of digital elevation and remote sensing imaging shows that the east segment of Lintan-Dangchang fault is still active and the main thrust feature of the fault switches to left lateral slip. With the field research of intensity and damage, several abnormal areas of degree VIII spread in the isoseismal line of degree VII and some abnormal areas of degree VII spread in the isoseismal line of degree VI. These abnormal areas are distributed along the hanging wall of the fault in a width of 2km. The analysis based on the remote sensing and digital elevation model shows that the segment of the Lintan-Dangchang fault south of Minxian mainly slips in left literal. The fault movement made the soil soft in the fault zone. The earthquake motion propagated along the fault zone. Therefore the strong earthquake motion caused foundation failure in the soft soil along the fault zone and the abnormal intense areas of disaster formed.展开更多
基金supported by the National Natural Science Foundation of China (No.41472202)Key Laboratory for Geo-hazards in Loess area,MLR (No.KLGLAMLR2014003)
文摘On July 22, 2013, an earthquake （Ms 6.6） occurred in Minxian, Gansu Province of China, causing a large number of landslides. Based on high resolution remote sensing images before and after this event, we made the visual interpretation to these coseismic landslides, and prepared a detailed inventory. The inventory registers totally 6 478 landslides in the study area. Of them, 3 322 landslides are larger than 100 m2. Based on 5 m resolution DEM, these landslides were used to perform spatial analyses using landslide number density （LND） and landslide area percentage （LAP）. The results show that the highest LND and LAP values are in the elevation range of 2 300-2 500 m and steeper slopes. Slopes facing E, SE, S and SW directions, slopes with larger absolute curvature values, ridges, scopes of gravel beds of Late Pleistocene （Qp） and the VIII-degree seismic intensity are more prone to sliding with high LND and LAP values. The largest LND and LAP values are in the scopes of 0.08 and 0.24 g, respectively. According to landslide distribution, we infer that F2-2 branch of Lintan-Dangchang fault is the seismogenic fault. With the increasing distances to this branch fault and drainages, LND and LAP values tend to decrease.
基金supported by the Basic Scientific and Research Fund from the National Institute of Natural Hazards,Ministry of Emergency Management of China(former Institute of Crustal Dynamics,China Earthquake Administration)(No.ZDJ2019-25)the National Natural Science Foundation of China(No.41661144037)。
文摘Choice of appropriate mapping units is important in landslide susceptibility mapping(LSM).There are various possible units for this choice,while it remains unclear which one is better in performance.The purpose of this study is to make a quantitative comparison of two commonly-used units:slope-unit(SU)and raster-unit(RU)based on the landslides triggered by the 2013 Minxian,Gansu,China Mw5.9 earthquake.Ten landslide influencing factors were considered in this analysis.For each type of mapping units,the 70%samples were randomly selected and trained 20 times on the LR model,yielding 20 susceptibility maps,and the remaining 30%samples were tested for the accuracy of the modeling outcome.Different metrics,including the mean probability,model uncertainty,and model prediction skills,were used to evaluate the quality of the susceptibility maps.The results show that the resultant probability maps using two mapping units can largely predict the distribution of actual landslides,on which the high susceptibility area corresponds to the landslide-prone area.The AUC(area under curve)values,ranging from 0.8 to 0.86,show that the prediction ability of two mapping units is roughly the same.While comparing with the RU,the use of SU can lower the model uncertainties caused by the variation of training sets.We converted the RU-based assessment results into SU-based scheme.The results show that two assessment results are well fitted with good linear relationship,which implies that it is feasible to convert the RU-based landslide susceptibility mapping into the SU-based scheme.This analysis indicates that compared with the RU,the SU cannot improve the performance and accuracy of seismic landslide susceptibility mapping.
基金jointly sponsored by the Technology Research and Development Program of Institute of Earthquake Science,CEA(XH14049,XH15042)the Science Research Fund Programs of Gansu Province(Grant No.145RJZA186)+1 种基金the National Natural Science Foundation(41304048)Special Fund for the Seismic Industry of China(20160107)
文摘In this paper,based on Gansu Digital Seismic Network data since 1990,we calculated b-value and ⊿ b-value of the neighborhood area before the 2013 Minxian-Zhangxian M_S6. 6,earthquake. The results show that the earthquake occurred at the margin of the significantly lower b-value area in southeast of Gansu and before the earthquake the neighborhood area had an obviously abnormal ⊿ b-value. From the earthquake and the spatial distribution of low b-value, the region still has the possibility of generating dangerous strong earthquakes.
基金sponsored by the regular project of earthquake monitoring and prediction in 2016(16C23ZX327)
文摘Based on the waveform data observed by the regional seismic network of Gansu Province,we calculated the apparent stress of 422 earthquakes with M_L≥ 2. 0 occurring in the surrounding area of the Minxian earthquake from January 2010 to July 2014 and obtained the temporal and spatial variation of apparent stress before and after the Minxian earthquake. Results show that( 1) the high value of apparent stress of earthquakes with M_L≥4. 0 was concentrated in the epicenter area before the Minxian earthquake while that of earthquakes with M_L< 4. 0 was not;( 2) Apparent stress around the epicenter area showed an obvious increasing process before the Minxian earthquake and the increasing process has continued after the main shock,which means that this study area is still in the danger of strong earthquakes.
基金supported by basic scientific research operating expenses of Institute of Earthquake Science,China Earthquake Administration(2012IES010202)
文摘On July 22, 2013, the Minxian-Zhangxian Ms6. 6 earthquake occurred on the east segment of Lintan-Dangchang fault. The analysis of digital elevation and remote sensing imaging shows that the east segment of Lintan-Dangchang fault is still active and the main thrust feature of the fault switches to left lateral slip. With the field research of intensity and damage, several abnormal areas of degree VIII spread in the isoseismal line of degree VII and some abnormal areas of degree VII spread in the isoseismal line of degree VI. These abnormal areas are distributed along the hanging wall of the fault in a width of 2km. The analysis based on the remote sensing and digital elevation model shows that the segment of the Lintan-Dangchang fault south of Minxian mainly slips in left literal. The fault movement made the soil soft in the fault zone. The earthquake motion propagated along the fault zone. Therefore the strong earthquake motion caused foundation failure in the soft soil along the fault zone and the abnormal intense areas of disaster formed.
