IASPEI - Picture Gallery

IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy
(S) - IASPEI - International Association of Seismology and Physics of the Earth's
Interior
JSS006 Oral Presentation 1927
Archeoseismic and paleoseismic records of Baelo Claudia (Gibraltar Arc
area, southern Spain)
Prof. Klaus Reicherter
Neotectonics and Natural Hazards RWTH Aachen University
Pablo G. Silva, Teresa Bardaj, Javiten Lario, Christoph Grtzner, Marcel Peltzer,
Peter Becker-Heidmann
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.
Keywords: archeoseismology, paleoseismology, roman remains