Reicherter et al. 2008

Reicherter, K., Silva, P. G., Bardají, T., Lario, J., Grützner, C., Peltzer, M., Becker-Heidmann, P. (2008): Archeoseismic and paleoseismic records of Baelo Claudia (Gibraltar Arc area, southern Spain). – In: Ubertini, L., Manciola, P., Casadei, S., Grimaldi, S. (Hg.): Earth: Our changing planet, S. JSS006-1927. Umbria Scientific Meeting Association, Perugia, Italy

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Abstract:

The western Betic Cordilleras have experienced several moderate and partly strong earthquakes and earthquake-related hazards (landslides and tsunamis) during the last 2000 years. The ruins of the Roman village of Baelo Claudia (Tarifa) yield evidence for the first historic earthquake damage on the Iberian Peninsula. Roman settlement started in the II Cent. BC, last relicts are from the V-IV Cent. AD. We have found indications for two earthquakes, which destroyed Baelo. During the I. Cent. AD, probably an earthquake occurred, the village was restored and rebuilt (40-60 AD; Silva et al., 2005). Ground Penetrating Radar and geo-electrical studies were carried out in the ruins, across fault zones to map and mirror fossilized and active faults. Although kinematic indicators in the ruins of Baelo Claudia are often badly preserved, we encountered in several buildings typical evidence for coseismic deformation, i.e. high-energy events, e.g. shock-induced break-outs in the pavement, pull-ups, and joints in the flagstones of the Decumanus Maximus. Orientation of these indicators is systematic, pointing to a shock from the SW, and folding in NW-SE direction. The Isis temple area is partly excavated. Drums of fallen columns, wall and pillar collapses are directed in S to SW direction, and testify to coseismic building deformation. A crude stratigraphy based on Roman pottery allows us to date the collapse event in the IV. Century AD. The amphitheatre of the I. Cent. AD suffered not only earthquake and/or landsliding deformation, but also a lot of restoration. Open cracks in the walls and inclined walls are interpreted as generated by slow deformation. On the other hand, big fallen blocks of the tiers are attributed to coseismic damage. The eastern aqueduct outside the city walls crosses a little creek. The western part of the aqueduct collapsed downhill, and some of the arcs show rotational displacement around a horizontal axis, this might be interpreted as a slow deformational feature originating probably from small creek-parallel landslides. The city wall surrounds the village, and was built for representative and not defensive purposes. The walls are inclined up to 10 with varying directions. Keystones of arcs are subsided due to extension. The walls are partly displaced up to 17 cm, and/or rotated against each other. During the excavation older rests of a former city wall has been encountered, this wall is topped by a „demolition horizon“ with big blocks of wall boulders. This horizon may correspond to the 40-60 AD earthquake outlined by Silva et al. (2005). Silva, P.G. et al., 2005. Archaeoseismic Record at the ancient Roman city of Baelo Claudia (Cdiz, South Spain). Tectonophysics 408: 129-146. Acknowledgements This work has been supported by the Spanish-German Acciones Integradas Program HA2004-0098. The authors are grateful to the Director of the Archeological Site of Baelo Claudia, Angel Muoz Vicente for facilitating the work.

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