| This research is based on field surveys,historical literature review,satellite remote sensing image interpretation and other methods and is based on the theory of landscape pattern,nearest neighbor index and nuclear density.In terms of quantity,scale,distribution density,morphological characteristics,topography and other aspects,the evolution characteristics of Ludian rural settlement distribution from 1642 to 1980 and 1998 to 2018 are analyzed.The research results show that:(1)From 1642 to 1980,the number and scale of rural settlements in Ludian increased gradually and the spatial distribution agglomeration gradually weakened.The high value of agglomeration density increased from 0.89/km2 in 1642 to 1.65/km2 in 1980.The number of gathering centers increased and the scope expanded,distributed along the west of Ludian County,and formed a "one-primary and two-minor" spatial clustering state.(2)From 1998 to 2018,the evolution of rural settlement space in Ludian experienced three major stages: "rapid development,earthquake damage,and post-earthquake reconstruction".The number of rural settlement patches after the August 03 Ludian earthquake in 2014 increased by 1.7 times before the earthquake.However,the degree of fragmentation is increased,the spatial distribution is reduced in compactness,the spatial distribution range is expanded and an aggregation core is formed at the epicenter.From 2015 to 2018,the evolution of settlement space was affected by post-earthquake reconstruction,and its average area became larger.Compared with before the earthquake,it showed an orderly and regular expansion.In the southeast of Ludian,a large-scale aggregation core of 10.33/km2 is formed.(3)The quantity distribution of rural settlements increases first and then decreases as the elevation increases,and is concentrated in the elevation range of 1800 m ~ 2400 m.The number distribution of rural settlements has a negative correlation with slope elements,and is concentrated in areas with slopes less than 10 °.The impact of different slopes on the distribution of rural settlements is relatively balanced.On the other hand,based on the Spatial Analyst function of ArcGIS software,the relationship between the evolution of rural settlement space and the geological structure and earthquake is discussed.The correlation mechanism between the spatial evolution of rural settlements in Ludian and the factors of earthquake disasters and secondary geological disasters is studied.The research results show that:(1)The degree of fragmentation of rural settlements is negatively correlated with the intensity distribution of the "8 · 03" earthquake in Ludian.In areas with greater seismic intensity,the higher the degree of rural settlement fragmentation,the smaller the average patch area.(2)The degree of fragmentation of rural settlements increases as the distance from the fault structure decreases and the distribution density of geological hazard hidden points increases.After the earthquake,the rural settlements moved away from the fault structure and in areas with low distribution density of secondary geological disasters.(3)Compare the center of gravity of rural settlements from 1642 to the end of 1980 using the "center of gravity model" to compare the 1909 Ludianyuan earthquake and the 1917 Daguan Jili earthquake.The results show that the coordinates of the center of gravity of the rural settlement point after the earthquake appear to move away from the earthquake occurrence point. |
