**5. Conclusion**

308 Earthquake Research and Analysis – Statistical Studies, Observations and Planning

amount of data and resolution of images, the magnitude *n* is established. According to the given format, a model file of different resolutions is generated, and then when modeling real-time rending, a series of irregular grids is used to imitate the terrain. According to their distance from the point of view and complexity of the terrain, we choose the relevant resolution terrain model within sight of the study area that is the closest to the view point. The more complex the terrain is, the higher the terrain series are, the more triangle grids in the drawing area, the more sophisticated the display terrain, and the higher the resolution. Conversely, if the view point is farther away or the terrain is flat, the series of the topography of the area shows will be lower, the number of mesh triangles will be fewer, the terrain rougher, and the resolution lower. Thus, minimizing the number of triangles and reducing memory consumption can make the images and models have identical effects or

In this paper we take the improved adaptive quaternary tree to construct layers of details. The quaternary tree index and the grading mode of organization management for largescale three-dimensional scenes can provide the chance for real-time interactive roaming analysis. In order to ensure the smoothness of scene rendering, we adopt a pre-loaded cache before the scene into the visible range. Then based on real-time rendering of the scene's rectangular range and the quaternary tree index, we can access related scenes' serial numbers quickly, which can be pre-loaded into memory. The scheduling management strategy can improve the rendering efficiency significantly, achieve real time, interactive terrain rendering, and improve the efficiency of disaster evaluation and analysis in the 3D

Exposed areas along the river valley include a regional north-east-trending thrust fault. The area exhibits many faults and tectonites, which are weak and vulnerable and form the detachment surfaces. Due to the earthquake's physical destruction combined with heavy rain, a large number of landslides, mud-rock flows, and other geological disasters occurred. Our system provides a qualitative and quantitative analysis and monitoring of these secondary disasters. A 3D system for the analysis of secondary disasters has the following

1. The three-dimensional system can reproduce the true disaster scene, and secondary disasters can be observed directly, including landslides and debris flows and their

2. Using DEM data, the analysis of landslide height and volume can give quantitative

3. The visual angle can rotate in a 3D system; providing omnidirectional observation of the target, which has obvious advantages in making decisions about rescue routes and

One example is a statistical analysis of the secondary disaster in Chenjiaba. High-resolution aerial remote sensing images from May 28 were integrated into the system. The system gives information on landslides and mud-rock flows in the area from Beichuan County, Zhixin Village, to Pingwu County Yaogouli. The study identifies the Chenjiaba section landslide debris and other secondary geological disasters as the most serious. The system also marks the distribution of the disaster and builds disaster level categories. There is a total of 135 landslides, covering an area of 508 square kilometers, 38 dilapidations, covering 75.6 square kilometers, and 9 mud-rock flows covering an area of 23.9 square kilometers.

estimates of damage due to the scope and extent of landslides.

gaps in a given range, closest to the real terrain.

**4.2 Three-dimensional terrain modeling and visualization** 

causes, occurrence and trends (Figure 8a).

environment.

advantages:

strategies.

Remote sensing monitoring of the Wenchuan and Yushu earthquakes' secondary geological disaster shows that high-resolution optical remote sensing, which can extract the seismic secondary disaster remote sensing characteristics accurately and monitor and evaluate the information of spatial distribution, damage degree and so on of earthquake secondary geological disasters has some advantages, such as intuition, large information and quantification. SAR has the advantages of all-weather data acquisition. The Yushu earthquake multi-mode SAR remote sensing monitoring study has proven that multi-mode SAR is effect and has important potential in earthquake disaster analysis and evaluation. Three-dimensional computing technology for measuring secondary geological disasters is an important technology, which not only improves the calculation and simulation accuracy of secondary geological disasters, but also can promote collaboration on three-dimensional simulation technology and auxiliary mitigation and provide analysis platforms for interactive operation in secondary geological disasters.

In addition, quantitative and reliable evaluation of secondary earthquake disaster depends on high-resolution Earth observation technology. But at present the automatic disaster monitoring algorithms and software for high-resolution Earth observation images still cannot meet actual needs, and 3D interactive analysis platform technology is still not mature. Meanwhile, secondary geological disaster monitoring relies heavily on traditional man-machine interactive visual interpretation technology.

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