1 英语原文及翻译：EARTHQUAKE-INDUCED LANDSLIDE STABILITY ANALYSIS OF THE LAS COLINAS LANDSLIDE IN EL SALVADORH.Y. LUO, W. ZHOU, S.L. HUANG, G. CHENAbstract: The January 13, 2001 earthquake (M7.6) off the coast of El Salvador triggered widespread damaging landslides in many parts of the country. The Las Colinas landslide, located in Balsamo Ridge west of San Salvador, caused the greatest loss of life in a single location from the earthquake. The preearthquake and post-earthquake seismic stability analysis of the Las Colinas slope is studied using the limit equilibrium and finite element methods in this paper. The safety factor of the pre-earthquake slope was likely over 1.50 based on the low groundwater level, which was noted by local residents prior to the January 13 earthquake. The slope failed as the horizontal earthquake coefficient, kc, reached between 0.18g and 0.31g depending on the failure analysis methods (i.e. circle and trial surface methods) and the low soil strength assumed. The safety factor of the post-earthquake slope falls in a range from 1.851 at low water saturation to 1.337 when fully saturated. As compared with the pre-earthquake slope, the stability is about 8% higher for the post-earthquake slope.Keywords: Earthquake, landslide, seismic, stability, limit equilibrium, finite element.1、INTRODUCTION El Salvador locates on the Pacific coast of theisthmus and bordered by Guatemala to the west and Honduras to the north and the east. The country has experienced, on average, one destructive earthquake every decade during the last hundred years. The earthquake of January 13, 2001 that struck El Salvador was the first major seismicdisaster of the third millennium and the fifth destructive earthquake to affect this small Central America republic in 50 years (Bommer and Benito, 2002). The January 13 earthquake triggered the Las Colinas landslide off the steep northern flank of Balsamo Ridge. The landslide originated at an elevation of about 1,040m to 1,070m and traveled northward about 700m to 800m into the Las Colinas neighborhood of Santa Tecla, west of San Salvador. The vertical drop from the ridge to the neighborhood is about 160 m. The volume of the landslide material is estimated at about 250,000 m3 (Jibson and Crone, 2001).According to a prior investigation (Jibson and Crone, 2001), the landslide material exposed in the headwall scarp appeared somewhat moist but not saturated, but once this material mobilized it behaved as a semi-liquid mass with a soupy consistency; this allowed the mass to travel anunusually long distance from the base of the slope. The transformation of the landslide material from behaving as solid to fluid in the absence of large quantities of water (such as in a heavy storm) and the long runout distance indicate an abnormal material behavior that requires detailed investigation and analysis. Landslide hazards and stability study is carried out by several organizations in the earthquakerelated areas. The pre-earthquake and postearthquake seismic stability analysis and sensitivity analysis of the Las Colinas landslide are studied using both the limit equilibrium and the finite element methods in this paper. Safety analysis and suggestions are given in the following sections of the paper.2. GEOLOGY AND VOLCANIC SOIL The landslide scarp of the Las Colinas slope exposes the upper 25m - 30m of deposits involved in the landslide. The stratigraphy of these deposits is typical of the volcanic deposits for Balsamo Ridge and much of the surrounding Cordillera Balsamo. Based on the reconnaissance work by USGS, the locations of abundant earthquake induced landslides in the Cordillera Balsamo seem to be influenced by the presence of relatively thick deposits of TB (Tierra Blanca tephra), which erupted from a volcanic source near Lago de Ilopango about 10,000 years ago, and the overlying fresh and weathered tephra. Tierra Blanca is a dalacitic pumice ash composed of acidic and epiclastic deposits, which covers most of the upper part of San Salvador, and is poorly consolidated and originated from multiple volcanic eruptions that can reach up to 50 m thick. Study demonstrated that one of the most important factors in terms of seismic slope stability is the relatively weak cementation that is broken when the soil is subjected to even small strain (Bommeret al., 2001). It is most probably that the soils may experience a drastic reduction of shear strength during earthquake and hence as soon as the slope failure begins the material undergoes almost adebris flow.The strong ground shaking, along with the presence of thick, loose to poorly consolidated,young volcanic deposits, the steep topography on the northern flank of Balsamo Ridge, and possibly the presence of a relatively impermeable ancient soil at the top of the Balsamo Formation were contributing factors to the Las Colinas landslide. The cross-section of the Las Colinas slope is shown in Figure 1. Th