Resúmenes de la 1ª Reunión Ibérica sobre Fallas Activas y Paleosismología, Sigüenza, España (2010) THE EL CAMP FAULT REVISITED: A 300 KA LONG PALEOSEISMIC HISTORY OF A LOW-SLIP NORMAL FAULT IN NORTHEASTERN IBERIA Reinterpretación de la falla del camp: registro paleosísmico de 300 ka en una falla normal de baja velocidad P. Santanach (1), E. Masana (1), and H. Perea (2) (1) Dpt. Geodinamica i Geofisica, Facultat de Geologia, Universitat de Barcelona. C/ Marti i Franques s/n. Barcelona 08028. Eulalia.masana@ub.edu (2) Instituto Dom Luiz, Faculdade de Ciências, Universidade de Lisboa. Edif. C6, Piso 2º, Campo Grande, 1746-016 Lisboa. Resumen: Se presentan nuevas evidencias de actividad paleosísmica de la falla de El Camp (nordeste de la Península Ibérica) que permiten extender el registro hasta 300 ka. El contexto indica una tasa de sedimentación baja y poco completa. A pesar de ello se prueba el acontecimiento de, al menos, cinco paleoterremotos. Se aporta evidencia también para otros acontecimientos de deformación. La velocidad de deformación de la falla, de 0.02 mm/a, sugerida aquí para los últimos 300 ka, es igual a la publicada para los últimos 125 ka. Palabras clave: Paleosismicidad, velocidad de deslizamiento baja, falla normal, Nordeste de Iberia. Abstract: New data extend the published 125 ka paleoseismic history of the El Camp fault (NE Iberian Peninsula) back to 300 ka. A setting with low sedimentation andslip rates makes it difficult to detect the whole seismic history. In spite of this, evidence for five paleoseismic events is described. Further deformation events, which are not related to clearly seismogenetic features, are also present. According to the total vertical displacement of the lower beds, a similar slip-rate to the published one for the last 125 ka. (ca 0.02 mm.yr -1 ) can be suggested for the last 300 ka. Key words: Paleoseismicity, low-slip normal fault, NE Iberia. INTRODUCTION The El Camp fault is a Neogene NE-SW trending normal fault belonging to the Neogene fault system of Eastern Iberia (Banda and Santanach, 1992). Currently it is a seismically silent fault but its paleoseismic activity in recent times has been proven. Although the seismic history for the last 125 ka of this fault has been published (Masana et al., 2001a and b), the data included in Santanach et al. (2001) and further fieldwork permitted us to extend this paleoseismic history back to 300 ka. The aim of this work is to present the new data and its paleoseismic interpretation. THE DATA Along the southern part of the El Camp fault (Fig.1), between Montroig del Camp and the sea shore, eight trenches located in six sites on alluvial fans were used for paleoseismic analysis (Masana et al. 2001; Perea et al., 2003). The oldest age yield by calcrete on top of G3 fans is 125 ka (TL and U/Th) and the oldest one obtained on calcrete on top of G2 fans is 300 ka. Between both units important erosion occurred with excavation of deep creeks. Paleomagnetic analysis revealed normal polarity for G3 units, whereas G2 fans yielded reverse polarity, except for few samples close to the top of the unit (Jaramillo chron?). TL ages obtained inside unit G3 are comprised between 300 and 125 ka. Sediments of unit G2 are attributed to the late Matuyama. The top of the unit may have an age comprised between 735 and 300 ka; unit G3, between 300 and 125 ka, and G4, younger than 125 ka (Santanach et al., 2001). Fig. 1. The southern El Camp fault cutting the apical part of the El Camp alluvial fan system. Four generations of fans have been distinguished: G1 to G4, from old to young. 23