The deadly Wenchuan Earthquake hit Wengchuan

a small city southwest of Sichuan Province

China

with a magnitude of 8.0

at 14∶28 local time of May 12.It shook more than half of China and brought devastation to more than fifty counties.The earthquake has not only caused numerous personnel casualties and destroyed kinds of facility directly

but also induced a lot of mountain hazards

and superimposed the hazards more severely.The extraction of earthquake-induced moutain hazards using remote sensing images has important significance for earthquake relief

assessment of bearing capacity of disaster area and reconstruction work after earthquake.The extraction of disaster area is realized by a method combination of information enhancement

information fusion and visual interpretation.According to the active characteristic and material combination of debris flows and landslides

we compare and analyze the spectral feature difference of different images and take ETM+ image as main data source.Debris flows and landslides have two distinct properties of higher water content and lower vegetation cover.The reflective features on remote sensing images are soil moisture and vegetation coverage

which can be reflected by wetness index and green index.After the extraction of wetness index and green index

tasseled cap transformation

image difference reinforcement

density slide and mask technology are used to build the quick extraction model for debris flows and landslides.The model is used to extract mountain hazards induced by Wenchuan earthquake.The distribution rule and feature of geo-hazard and genesis are analyzed by spatial overlay.Mountain hazards induced by the earthquake distribute mainly along Longmenshan Mountain earthquake zones and rivers on both hillsides.They have the following characteristics: 1.The types of mountain hazards are diverse

including collapses

landslides

rockfalls

imprisoned lakes

debris flows and so on.2.The relation is closed between the strong level of the action and the intensity of the earthquake.The mountain hazards are mainly present in the earthquake intensity area from 8 degree to 11 degree.With the intensity reduced

the gross area of geo-hazard decreased.3.The mountain hazards mainly occurred in areas 1000m to 2500m altitude.4.The gradient of the slop of generating geo-hazard mainly varied in the range from 20 to 50 degree.5.In quantity by collapseds

landslides

rockfalls primarily during aftershock and landslides

debris flows primarily during anaphase.6.Pair of ecological environment destruction is enormous.