Archaeoseismology and Palaeoseismology in the Alpine ... - Tierra

1 st INQUA‐IGCP‐567 International Workshop on Earthquake Archaeology and Palaeoseismology)
AN APPLICATION OF 3D LASER SCANNING IN ARCHAEOLOGY AND
ARCHAEOSEISMOLOGY: THE MEDIEVAL CESSPIT IN THE ARCHAEOLOGICAL
ZONE COLOGNE, GERMANY
S. Schreiber (1), K.G. Hinzen (1) and C. Fleischer (3)
(1) Earthquake Geology Group, Cologne University, Vinzenz‐Pallotti‐Str. 26, 51429 Bergisch Gladbach. GERMANY.
stephan.schreiber@uni‐koeln.de
Abstract: In 2007 the construction of a large museum area within remains of the Roman and medieval Cologne (Germany) started in the
historic city center. A medieval cesspit discovered during the excavations exhibits large deformations and heavy damages. The static
conditions of the cesspit demanded restoration work during the excavation. A 3D laser scanner was used to create a virtual model of the
unrestored structure. The damages were precisely mapped and a quantitative database for further investigation of the damages was
established. The collected data enhance the preservation efforts and present the cultural heritage in an unaltered in situ condition. In addition
to providing documentation of the restoration, the data are critical for investigating a possible seismogenic origin for the observed damages.
Key words: Archaeoseismology, 3D Laser Scanning, Cologne, Cultural Heritage
INTRODUCTION
The construction of the Archaeological Zone Cologne
(AZC) in the historic city center of Cologne, Germany
began in 2007 and entails excavation of large areas of the
Roman and medieval Cologne (Fig.1). Several buildings in
the AZC exhibit structural damage. 2003 Hinzen & Schütte
proposed a possible seismogenic cause for damages
observed in those sections that had been excavated in the
1950s and 1970s. The Deutsche Forschungsgemeinschaft
(DFG) funded a project to further test this hypothesis.
Part of the project is a detailed mapping of the excavated
buildings in the AZC using a phase based 3D laser scanner.
The resulting database of the structural damages will be a
cornerstone for finite or discrete element models of
selected building elements. The mapping focuses on the
Roman excavactions; however, during the excavation a
medieval cesspit was discovered in front of the historic
city hall of Cologne. After the excavation of the first few
meters of the cesspit, the static situation required
restoration of the walls before the excavation could
continue. This experience convinced the archaeologists
that the cesspit would have to be modified in its entirety
to be successfully excavated. Therefore, the only record
of the original cesspit was a virtual model provided by the
3D laser scan. We began mapping the cesspit before the
first reconstructions and continued successively for each
new section (0.5‐1.0m) excavated.
LOCATION
The investigated area is located in the old city center of
Cologne, Germany (Fig. 1A). Cologne is located in the
eastern part of the Lower Rhine Embayment (LRE) a
young sedimentary basin with ongoing seismic activity.
The LRE belongs to the most active seismic region north
of the Alps. The instrumental and historical records for
the region document more than 20 damaging
earthquakes in the last 300 years.
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Additional surface rupturing events are confirmed by
paleoseismological investigations in the area (e.g.
Camelbeeck & Meghraoui, 1998). Hinzen and Reamer
(2007) estimate a maximum magnitude of 7.0 for the
area.
Fig.1: Location of the investigation area in Germany (A) and in
the city of Cologne (B). C shows a map of the AZC: 1: Praetorium,
2: Octogon, 3: Eastern atrium of the synagogue with Roman well,
4: Roman sewer, 5: Roman city wall, 6: Porta Martis, 7: Jewish
Mikveh, 8: Synagogue with medieval cesspit, 9: Basement of
tower of the medieval city hall. (Fig. 1A: Google Earth, 2008; Fig.
1C: AZC, 2008)