Study On The Early Remot Sensing Identification And Evolution Characteristics Of Typical Geological Disaster In High Intensity Earthquake Zone

The geological conditions of high intensity earthquake zone are complex,and the new tectonic movement is active,which is the high incidence and prone area of geological disasters.In recent years,a number of clusters catastrophic landslides and debris flow disasters got relevant government administrative department and a large number of technical personnel's attention and thinking.The focus of the work in investigation and research of geological disasters was gradually turned from the post-disaster survey disaster and known hazards investigation into pre-disaster survey and early recognition of unknown disaster,becoming a hotspot in research of geological disasters.However,due to the factors restricting geological disasters is too many and the geological conditions are complex,the work still faces many difficulties and challenges.Especially in the high-risk and high-altitude areas,relying on manpower survey will make the efficiency be low and the cycle be longer.In contrast,remote sensing technology has great advantages in the early identification of geological disasters and the research on the characteristics of post-earthquake evolution.In this paper,combining remote sensing geology and disaster science,from the perspective of remote sensing technology in combination with disaster conditions,corresponding early identification methods and remote sensing identification marks are established respectively for landslides and debris flow disasters.At the same time,a remote sensing analysis method for the dynamic evolution of debris flows in the strong earthquake zone is proposed,and the following aspects are obtained:(1)Remote sensing technology has the characteristics of macroscopic,objective,intuitive and periodical,which can heip the information be extracted and recorded before and after the landslide and capture the sliding deformation characteristics before the landslide;the recognition effect is significant.Statistical analysis and remote sensing comparative interpretation of randomly selected samples show that the effective recognition rate is about 50%.(2)According to the reflection and recognition degree of slope deformation characteristics from different remote sensing data sources,the remote sensing model of early recognition of landslide is roughly divided into three categories:(1)The slope unit with obvious deformation characteristics.The direct interpretation sign of it's early identification is"slope deformation fracture"and the indirect interpretation signs are"circle chair shape,tongue shape,dustpan shape,semicircle and other morphological characteristics".(2)The old landslide and ancient landslide having the condition of revival.The direct interpretation sign of its early identification is the feature of landslide elements and the indirect interpretation signs are"landform or double groove homologous micro geomorphology,the abnormal concave or concave cavity of the slope"etc.(3)The rock slope unit with effective joint development.The direct interpretation sign of it's early identification is"the slope unit development has obvious parallel linear combination image features,and a group of direction is aligned with the slope towards the same or small angle intersect"and the indirect interpretation signs are"characteristics of early landslide accumulation body in slope"or"abnormal cavity of slope surface".(3)Based on statistical analysis method,established the formulas for calculating volume of remote sensing for landslide and collapse,and its validity is analyzed,the results show that remote sensing to estimate the volume and the actual volume is generally consistent.(4)Put forward the two indicators of the conceptual model and calculation formula,"distribution of debris flow provenance distance index(L_x)"and"debris flow provenance distribution difference index(H_x)",and introduced into the early identification index of debris flow in strong earthquake zone.(5)Based on the samples of landslide remote sensing interpretation and analysis,determined 5 landslide remote sensing early factor:"the source volume density","the basin area","the main ditch slope","the distribution of the source distance index"and"the source distribution difference index",consider a watershed with“provenance volume density?<5×10~4 m~3/km~2”as a non-debris flow gully;consider a watershed with provenance volume density“5×10~4m~3/km~2??<10×10~4m~3/km~2,and L_x>0.6,H_x>0.5”or a watershed with”10×10~4m~3/km~2???20×10~4m~3/km~2,and L_x>0.5,H_x>0.5”,or a watershed with”?>20×10~4m~3/km~2,and main ditch slope I>200”as a non-debris flow gully.(6)Remote sensing analysis method for dynamic evolution of debris flow in strong earthquake zone including quick accessing of remote sensing data,surveying and mapping of the large scale topographic map,the interpretation and comparative analysis of multistage remote sensing image,etc;Data source multistage acquisition,uav aerial photography and large scale topographic map production are the basis and premise of this work.(7)Comparison and analysis of dynamic remote sensing of debris flow in strong earthquake area mainly includes three aspects,the dynamic change in provenance accumulation zone of debris flow,the evolution of debris flow accumulation zone and development trend of debris flow analysis;The application of typical debris flow shows that the advantage of comparative multi-stage remote sensing technology can be used for qualitative and quantitative determination of the development trend of debris flow.