| Wenchuan Ms8.0earthquake induced a large number of geohazards and potentialproblems in the Longmen Mountain and its surrounding areas. Based on the spacestatistical method, differentiation characteristics of the seismic geohazards spatialdistribution and corresponding relation between lithology and the possibility ofdisaster to happen were found. They show that the surface response to the earthquakewill be nonlinear if the geohazards are made to be the parameter. Although there aresome rules to earthquake-induced geohazards, there are still lack of valid quantitativeindicators and a unified theoretical tool to interpret the macroscopic statistical laws,and the exploration of geohazards mechanism is limited to micro stage. The way tocarry out point by point will inevitably lead to the non-rigorous results. Furthermore,the surface and near surface material composition, structure and weathering are verycomplex, then the surface-critical physical parameters is unable to obtain continuously.As a result, even if we stimulate the seismic waves and restore the vibration of thetarget area when the earthquake happens, we still can not determine which landformsparts or which lithology block will show high geological disaster-prone properties.This causes a bottleneck both in technology and theory. It is not enough to call thecoupling relationship between secondary geohazards and the landscape the"geomorphic unit abnormal response‖. So this paper made earthquake-inducedgeohazards as response instruction and fractal dimension as quantitative media todiscuss that the coupling relationship between secondary geohazards and landscape isan important part of the mountain surface stability evaluation as well as a prospectivestudy both to measure the quality of the geological environment and to support riskmanagement.This paper made5.12quake-hit Beichuan as the study area to collect necessaryinformation and data then to do some sub-segment segmentation, and to make somesub-dimension algorithm design and program development. What’s more, after thematrix of fractal dimension calculated under the sliding window, the paper discussedthe coupling characteristics of the relationships among those components such aselevation, slope, lithology and geomorphology fractal dimension model (FDM), aswell as geohazards. Finally it managed to establish the FDM model of earthquake response.The main research achievements obtained by the paper as follows:(1)Geomorphology fractal dimension algorithm design and programimplementationThe fractal dimension of the triangulation algorithm is a kind ofsurface morphology valuation process based on the Triangulation network area ofalgorithm. Its calculation results are the fractal dimension of digital matrix, and theycan be directly quantified the terrain complexity. Its essence is a digital elevationmodel (DEM) potential information mining. Geomorphology fractal dimension modelis not only the quantitative indicators of surface seismic response characteristics, butalso one of an integral data part of the seismic response model for computing. Thepaper achieved the DEM visualization of fractal dimension computing according tothe algorithm above and NET platform programming, combined with the secondarydevelopment of GIS.(2) Coupling relationship between the fractal dimension matrix and geohazard.Including:①establishment of the slope-FDM quantitative relationship in varioussub-study areas, and discussion of the distribution characteristics of geohazards indifferent slopes range as well as extracted high-response gradient range using thefractal dimension values range;②establishment of elevation-FDM couplingrelationship in various sub-study areas to explore the characteristics of the distributionof geohazards in different elevations, and to segment elevation segment using fractaldimension values range;③explored the relationship of the study area of thecatchment basin-FDM "and analyzed a watershed sensitivity;④explored therelationship characteristics of―strata lithology-FDM‖in the study area, and madelithology response sort accordingly;⑤Analyzed the relationship between "specialgeomorphological site (microrelief)–FDM and made seismic sensitivity analysis.(3) Fractal dimension seismic response model of the geomorphic unit. It analyzedthe seismic response mechanism and its main controlling factors according togeomorphological relationship between fractal dimension and geohazards in thespatial distribution. It also created a fractal dimension of the response model and keyparameters to do the preliminary calculation According to the surface dynamicresponse law obtained by the dimensional eigenvalue analysis of the distribution areaof the study area in the strong earthquake.Considering geomorphic sub-dimensional model as a quantitative bridge, thepaper explored the coupling relationship between FDM and geohazards in the bigearthquake background then built a landform seismic response model of fractaldimension unit, and provided a quantitative reference and the scientific basis forpotential adverse geological environment recognition of the mountain from a newangle. |
