January 07, 2002


Provided by: NASA Earth Observatory
Summary author: Jim Foster

The photo above shows a landslide, resulting from the Northridge earthquake, that severely damaged a house near Pacific Palisades, California. Landslides often occur in conjunction with natural hazards such as earthquakes, floods, or volcanic eruptions, but they can also be triggered by excessive precipitation or human activities, for example, deforestation or development. Anything that disturbs a natural slope's stability can result in land that flows, glides, slips or slides. On average, landslides in the United States cause $1 to $2 billion in property damage and more than 25 fatalities per year. Annual costs for the repair of slope failures that damage highways, railroads and pipelines exceed $100 million.

New methods are presently being explored to predict the occurrence of landslides. By combining two images from different satellite sensors, a third image containing geomorphic and topographic details, needed for making high-quality landslide maps, can be generated. The process, known as image fusion, combines, for instance, radar terrain data with visible and near-infrared Landsat land cover data. Techniques such as this, while still in its infancy, are very useful in characterizing landslides and can complement the air photo methods currently in use.

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