Landslide Recognition And Susceptibility Assessment After Earthquake Supported By InSAR

The rapid and accurate acquisition of the distribution characteristics for the earthquake-induced landslides,and the analysis the risk of future landslides in the disaster areas have important guiding significance for post-earthquake rescue,disaster area reconstruction and earthquake prevention.The paper takes the Jiuzhaigou earthquake as an example.Based on object-oriented image analysis method,the distribution characteristics of landslides after earthquakes was obtained.The surface coseismic deformation factor extracted by InSAR technology was introduced into the AHP-information quantity evaluation model which combines subjective and objective factors,and the landslide susceptibility evaluation in the study area was realized.The main work and conclusions of the thesis are as follows:(1)Extraction of surface deformation information in the earthquake zone based on D-InSAR technology.Due to the imaging geometry of satellite in different LOS directions and the movement characteristics of seismogenic faults,the method of integrating ascending and descending orbits SAR data to obtain post-earthquake surface deformation was adopted in this study.The main result obtained from the descending orbit data is uplift,and the maximum uplift and settlement are 15cm and 9 cm,respectively.However,the result obtained from ascending orbit data is mainly sedimentation,with a maximum settlement of 22 cm.Based on the deformation results from different lines of sight by InSAR,the distribution range of earthquake-induced landslides was determined.Also,the paper introduced the deformation information as an seismic disturbance intensity factor into the landslide susceptibility evaluation system.(2)Research on object-oriented landslide identification method based on NDVI difference change detection after the earthquake.The difference NDVI data was calculated by using two optical remote sensing images before and after the earthquake.The landslide body classification extraction rules were constructed with reference to the surface slope and the surface deformation information.The object-oriented method was used to accurately extract the landslide information.It is show that the earthquake triggered more than 800 landslides with a total area of 11.96 km~2 and an impact area of625 km~2.Through comparison and analysis with other research results,the accuracy and completeness of the landslide information extracted were verified.(3)Research on the sensitivity factor of earthquake landslide susceptibility.The paper not only selected the landslide susceptibility factors commonly used for slope,aspect,elevation,road,water system and fault,but also introduced InSAR surface deformation information as a sensitive factor into the landslide susceptibility evaluation model.Statistics show that the area of landslide body distributes in the surface slope greater than 40 degrees account for 86.78%of the study total landslide area.And the elevation of the landslide is mainly between 2900m and 3100m.The aspect is the least sensitive factor,but in comparison,the area of the landslide in the east and northeast is the largest.Also,the landslide is mainly distributed in the region where the deformation value is greater than 10cm.Overall,the distribution density of the landslide body increases gradually with the distance from the road,river and fracture.(4)Evaluation of landslide susceptibility based on GIS.According to the selected landslide susceptibility sensitive factor,the AHP-information model combined with qualitative and quantitative evaluation was constructed,and the whole research area was divided into five grades,including extremely high,high,medium,low,and extremely low vulnerable areas.The AUC values of the ROC curves for the model including and excluding the surface deformation factor are 0.918 and 0.817,respectively.Results show that the surface deformation factor improves the accuracy of the model.It is also indicating that the introduction of the InSAR surface deformation factor is effective.As a consequence,the extremely high and high grade areas are mainly distributed in the V-shaped canyon zone,which is also distributed along the several major roads and rivers.The area above the medium grade level accounts for 63.2%of the total area.The above-mentioned susceptibility evaluation results can provide technical support for the prevention and control of landslide disasters in the Jizhaigou earthquake-stricken area.