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The río Grío depression (Iberian Chain, NE Spain). Neotectonic graben vs. fluvial valley

Abstract:

This contributon presents a geomorphological map of the Río Grío depression, located in the central sector of the Iberian Chain, NE Spain. In previous geological maps this depression, ca. 30 km long, has been interpreted as an erosional fuvial valley. Geomorphological mapping reveals that it corresponds to a neotectonic graben filled by alluvial fan deposits and subsequently dissected by the axial Grío River and its tributaries. The length of the normal faults indicates that some of the mapped neotectonic structures have the potential to generate earthquakes with moment magnitudes as high as 6.8. This work illustrates that there is limited knowledge on the distribution of recent faults in some sectors of Spain, and that a higher input on the geomorphology and Quaternary geology in the geological maps would help to overcome this weakness.