In this paper, based on a new Geographic Information System (GIS) grid-based three-dimensional (3D) deterministic model and taken the slope unit as the study object, the landslide hazard is mapped by the index of the ...In this paper, based on a new Geographic Information System (GIS) grid-based three-dimensional (3D) deterministic model and taken the slope unit as the study object, the landslide hazard is mapped by the index of the 3D safety factor. Compared with the one-dimensional (1D) model of infinite slope, which is now widely used for deterministic model based landslide hazard assessment in GIS, the GIS grid-based 3D model is more acceptable and is more adaptable for three-dimensional landslide. Assuming the initial slip as the lower part of an ellipsoid, the 3D critical slip surface in the 3D slope stability analysis is obtained by means of a minimization of the 3D safety factor using the Monte Carlo random simulation. Using a hydraulic model tool for the watershed analysis in GIS, an automatic process has been developed for identifying the slope unit from digital elevation model (DEM) data. Compared with the grid-based landslide hazard mapping method, the slope unit possesses clear topographical meaning, so its results are more credible. All the calculations are implemented by a computational program, 3DSlopeGIS, in which a GIS component is used for fulfilling the GIS spatial analysis function, and all the data for the 3D slope safety factor calculation are in the form of GIS data (the vector and the grid layers). Because of all these merits of the GIS-based 3D landslide hazard mapping method, the complex algorithms and iteration procedures of the 3D problem can also be perfectly implemented.展开更多
In October 1790, a destructive earthquake occurred near Oran city in the western part of Algeria （MSK, Medvdev-Sponheuer-Kamik macroseismic intensity： X）. It generated a tsunami that inundated the Spanish and North...In October 1790, a destructive earthquake occurred near Oran city in the western part of Algeria （MSK, Medvdev-Sponheuer-Kamik macroseismic intensity： X）. It generated a tsunami that inundated the Spanish and North Africa coasts. The regional tectonic includes NW-SE compressional stress in Algeria and NE-SW strike-slip structures in the Alboran basin. In this work, we identified tsunami sources for the Alboran from numerical modeling. The sea bottom displacement is calculated from the Okada equations. The tsunami＇s propagation is simulated with the SWAN code. The identified tsunami source for the 1790 event is a 7.5 magnitude earthquake at the entrance of the Oran harbor, with a pure reverse faulting, probably associated with the Murdjajo fold The tsunami wave height profile that is obtained for the city of Oran showed an initial withdrawal of the sea that was followed by tsunami waves reaching 2 meters in height. The results obtained in Spain agree with the observations reported in the literature. Finally, the simulations led to a better understanding of the interdisciplinary approach to be considered as for tsunami sources in the Alboran. Sedimentary mass-movements should be now included as an additional component in the tsunami hazard assessment for the West Mediterranean. The contribution of sedimentary disturbance due to the series of canyons offshore the western margin could induce water waves higher than 2 meters in Western Algeria.展开更多
基金Under the auspices of Research Institute of Software Engineering(RISE)of Japan(No.01-004).
文摘In this paper, based on a new Geographic Information System (GIS) grid-based three-dimensional (3D) deterministic model and taken the slope unit as the study object, the landslide hazard is mapped by the index of the 3D safety factor. Compared with the one-dimensional (1D) model of infinite slope, which is now widely used for deterministic model based landslide hazard assessment in GIS, the GIS grid-based 3D model is more acceptable and is more adaptable for three-dimensional landslide. Assuming the initial slip as the lower part of an ellipsoid, the 3D critical slip surface in the 3D slope stability analysis is obtained by means of a minimization of the 3D safety factor using the Monte Carlo random simulation. Using a hydraulic model tool for the watershed analysis in GIS, an automatic process has been developed for identifying the slope unit from digital elevation model (DEM) data. Compared with the grid-based landslide hazard mapping method, the slope unit possesses clear topographical meaning, so its results are more credible. All the calculations are implemented by a computational program, 3DSlopeGIS, in which a GIS component is used for fulfilling the GIS spatial analysis function, and all the data for the 3D slope safety factor calculation are in the form of GIS data (the vector and the grid layers). Because of all these merits of the GIS-based 3D landslide hazard mapping method, the complex algorithms and iteration procedures of the 3D problem can also be perfectly implemented.
文摘In October 1790, a destructive earthquake occurred near Oran city in the western part of Algeria （MSK, Medvdev-Sponheuer-Kamik macroseismic intensity： X）. It generated a tsunami that inundated the Spanish and North Africa coasts. The regional tectonic includes NW-SE compressional stress in Algeria and NE-SW strike-slip structures in the Alboran basin. In this work, we identified tsunami sources for the Alboran from numerical modeling. The sea bottom displacement is calculated from the Okada equations. The tsunami＇s propagation is simulated with the SWAN code. The identified tsunami source for the 1790 event is a 7.5 magnitude earthquake at the entrance of the Oran harbor, with a pure reverse faulting, probably associated with the Murdjajo fold The tsunami wave height profile that is obtained for the city of Oran showed an initial withdrawal of the sea that was followed by tsunami waves reaching 2 meters in height. The results obtained in Spain agree with the observations reported in the literature. Finally, the simulations led to a better understanding of the interdisciplinary approach to be considered as for tsunami sources in the Alboran. Sedimentary mass-movements should be now included as an additional component in the tsunami hazard assessment for the West Mediterranean. The contribution of sedimentary disturbance due to the series of canyons offshore the western margin could induce water waves higher than 2 meters in Western Algeria.
