Seismites from a well core of palustrine deposits as a tool for reconstructing the palaeoseismic history of a fault

Abstract

The Concud Fault is located at the junction between the Jiloca and Teruel grabens (central-eastern Iberian Chain, Spain). The Late Pleistocene activity of this fault has been well logged from structural and palaeoseismological trench studies, but only scattered data of the Late Pliocene seismic activity exist. The Late Pliocene–Early Pleistocene syn-tectonic infill consists of an endorheic continental succession in which a 75 m-long continuous well was drilled near the Concud Fault. Along the entire well core, several types of soft-sediment deformation structures with variable morphology, size and frequency have occurred including clastic dykes, load structures and slumps. The rigorous analysis of the deformation structures, their relationships with the involved sedimentary facies, and the discrimination of possible deformation mechanisms and trigger processes allow us to interpret part of them as seismically-induced structures. The recognition of 21 deformed beds (seismites) allow the Late Pliocene–Early Pleistocene seismic history of the Concud Fault to be reconstructed. Therefore, 21 seismic events (with M ≥ 5) and an apparent recurrence period of about 45 ka have been inferred.