The Statistical Analysis of Migration of Strong Earthquakes─Taking the North China Region as an Example

The migration of strong earthquakes is an important research topic because the migration phenomena reflect partly the seismic mechanism and involve the prediction of tendency of seismic activity. Research on migration of strong earthquakes has mostly focused on finding the phenomena. Some attempts on getting regularity were comparatively subjective. This paper suggests that there should be indices of migration in earthquake dataset and the indexes should have statistical meaning if there is regularity in the migration of strong earthquakes. In this study, three derivative attributes of migration, i.e., migration orientation, migration distance and migration time interval, were statistically analyzed. Results in the North China region show that the migration of strong earthquakes has statistical meaning. There is a dominant migration orientation (W by S to E by N), a dominant distance (≤100km and on the confines of 300～700km), and a dominant time interval (≤1a and on the confines of 3～4a). The results also show that the migration will differ slightly with different magnitude range or earthquake activity phase.

Spatial hazard analysis and prediction on rainfall-induced landslide using GIS

The application of landslide hazard model cou-pled with GIS provides an effective means to spatial hazard [(analysis and predic)(tion on)] rainfall-induced landslides. A modified SINMAP model is established based upon the sys-tematic investigation on previous GIS-based landslide analy-sis models. By integration the landslide deterministic model with the hydrological distribution model based on DEM, this model deeply studied the effect of underground water dis-tribution due to rainfall on the slope stability and landslide occurrence, including the effect of dynamic water pressure resulting from the down slope seepage process as well as that of static water pressure. Its applicability has been testified on the Xiaojiang watershed, the rainfall-induced landslides widespread area in Southeast China. Detailed discussion was carried out on the spatial distribution characteristics of landslide hazard and its extending trend, as well as the quantitative relationship between landslide hazard with pre-cipitation, slope angle and specific catchment area in the Xiaojiang watershed. And the precipitation threshold for landslide occurrence was estimated. These analytical results are proved useful for geohazard control and engineering decision-making in the Xiaojiang watershed.