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Abstract:
The analysis of satellite images showed that the strain energy accumulation deep in the Earth's crust that precedes a strong earthquake can be detected by applying a lineament extraction technique. A lineament is a straight or a somewhat curved feature in a satellite image, which is possible to detect by a special processing of images based on directional filtering and/or Hough transform. We analyzed tens of earthquakes that took place in the Pacific coast of South America with a Richter scale magnitude over 4.5, using ASTER/TERRA and LANDSAT satellite images. All events were located in regions with small seasonal variations and limited vegetation to facilitate the tracking of features associated with the seismic activity only. The images were taken during the time interval of one year before and after an earthquake. It was found that the number and orientation of lineaments changes significantly one month before an earthquake approximately, and a few months later the system returns to its initial state. This effect increases with the earthquake magnitude. The application of the same technique to volcanoes showed that the behavior of lineaments associated to their seismic activity is opposite to that obtained previously for earthquakes. This discrepancy can be explained assuming that the main reason of earthquakes is compression and accumulation of strain in the Earth's crust due to subduction of tectonic plates, whereas in the case of volcanoes we deal with the inflation of a volcano edifice due to elevation of pressure and magma intrusion.
