An example of a comparison between Thematic Mapper and radar images in the central Ebro basin

By analysing Landsat TM and ERS-1 SAR images, thousands of lineaments have been mapped within the Neogene materials of the central Ebro basin (north-east Spain). Comparison with data from previous field surveys proved that most of them are normal faults. The main trend represented in both systems is NW-SE. However in SAR other trends that correspond with smaller fractures appear to have certain significance. This fact can be a consequence of the physical characteristics of radar systems: when a surface has a consistent orientation and reflectivity it can be detected even if it is only a few centimetres high. Lineaments are also identified in zones where Quaternary deposits and farming activities prevent the recognition of fractures by conventional geological fieldwork. The study of TM and SAR images has improved geological knowledge of this area.