| As a destructive geological event, geological disasters affect human life,property and living environment seriously, and restrict the sustainable development of human beings. In spite of our country in the field of geological disasters has achieved fruitful results during the past several decades,on the whole, In comparison to the international advanced level there are large gaps. Especially for certain characteristics of regional geological disaster, such as self-organized criticality, power-law dependence, laggregation,spatial-dependence of frequency and log-normal of parameters of scale, lack of qualitative or quantitative cognition. About the assessment of regional geological disasters, such as deep and systematic analysis of impact factor, comparison of results of susceptibility assessment,frequency on geological hazard and other related fields,there are exploration space. Ningqiang County is located in Qin-Ba mountains, there are many geological disasters.they has the extensive distribution in Shaanxi Province.but it is also a good experimental base for characteristic analysis and hazard assessment of geological disaster. Therefore, this paper takes Ningqiang county as an example, which in Hanzhong city of Shaanxi province, on the back of "13115" science and technology innovation engineering major technology special project (2008ZDKG-75) named"The evaluation research of secondary disasters based on3S technique in Ningqiang county of Shanxi Province", and then established the detailed catalogue of geological disasters and the database based on scrutinize in small scale geological disasters and the interpretation of remote sensing data such as SPOT5. On the bases of above, fist, analysis the characteristics of geological disaster systematically, then do some researches on susceptibility assessment and do some exploratory study on risk assessment of Ningqiang country, finally discusses the risk of geological disasters and risk management briefly. Made the following main conclusions:1. Some features of the regional geological disasters were explored and revealed quantitatively as below:①The main type of geo-hazard is landslide in Ningqiang county and the second is landfalls and debris flow. In the regional distribution, the types of geological hazards present1belt and3areas.In the scale, mainly with small, but the total area and the bulk volume of the landslide and collapse were controlled by large and giant landslide; In the distribution pattern, primarily with half-round and equal-length landslide; In the material composition, the main type of landslide is soil and debris landslide and collapse is rock collapse; In the space distribution, the types of geo-hazard have the characteristics of dispersion and clustering; the characteristic of clustering are showed in the scale, the threatened object, time and space. Especially in the clustering of space, this article further verified the characteristic of clustering by the nearest analysis and Ripley K function method.②Self-organized criticality of geological disasters was explored quantitatively by analysis the relationship between frequency and scale. And found "rollover effect" of frequent of landslides and collapse at home for the first time in double logarithmic coordinate when the scale of landslide is small.③Power law dependency of scale parameter of geological disasters was put forward, which was blank in the research at home and limited to power law dependency discussion on volume and area on abroad. This paper further put forward power law dependency between the parameters of area, length and width on the basis of revealing the power law dependency of volume and area, and put forward the formula.④The fractal and variable dimension fractal feature of geological disasters were analyzed quantitatively, calculate fractal dimension of monomer landslide and space distribution of geological disasters by using the box counting dimension method, and took the relationship of space distribution of landslide between elevations and slope for example, reveals its variable dimension fractal feature.⑤The frequency of space dependency and zoning of geo-hazard were discussed, putting forward the frequency of geo-hazard is the parameters of spatial distribution of geo-hazard. A reasonable target area should be chose when making evaluation zone of geo-hazard:regional geo-hazard zone, linear geo-hazard zone and the field zone.⑥The logarithm normal distribution characteristic of parameters of geo-hazard was pointed out, which was verified by box figure and QQ figure and fitted with normal, Weibull and Logistic distribution curves.2.The selection of mapping unit was discussed and the mapping unit comes down to5kinds:the grid unit, regional unit, uniform conditions unit, slope unit and terrain unit. According to the needs, the evaluation of the geological hazard in this paper chose slope unit and grid unit.3. An integrated index system of regional geo-hazard assessment has been established, the relationship between the geo-hazard and their evaluation factor has been analyzed and discussed systematically.By using information model, Logistic regression model, artificial neural network and support vector machine method to evaluate geo-hazard susceptibility,and using product method and synthesis method to evaluate landslide hazard. On this basis, divided landslide susceptibility of Ningqiang County into three zones:high susceptibility zones,middle susceptibility zones and low susceptibility zones. divided landslide hazard into three zones:high middle and low hazard zone.4. Provided the significance and method of comparison of assessment results of landslide susceptibility, pointed out that the classification relates to the cost. the costs are very different in different type of misclassification error. Accuracy statistics of model were divided into cutoff-dependent performance criteria and cutoff-independent performance criteria according to whether the statistics are constrained by the critical value.At last,by using the method of receiver operating characteristic, cohen's kappa and success-rate curves to make comparative analysis of susceptibility assessment.The results showed that:compared to other models and methods, the simulation results of artificial neural network model was more objective and reasonable.5.The geo-hazard in the probability of events and frequency distribution were explored, and the exceeding probability of landslide in different classes of area, volume on five years.10years and50years in Ningqiang county was calculated by using poisson distribution model. The frequency of the geological disasters is divided into:absolute frequency, relative frequency and indirect frequency, and the frequency of geo-hazard were reflected indirectly through geo-hazard in the past and future activity.6.The risk of geo-hazard, risk management and risk acceptable level were discussed, and the geological disaster risk management system and control system were established. In this article, the contradiction in geological disasters and the dynamic of risk were described. and pointed out that the essence of the disaster systems is "human-natural coupling system" in earth surface system.
|
PDF Full Text Request