Constraints in identifying historical earthquakes using archaeological information
|Location||International Geological Congress,oslo 2008|
|Author||Pavlides, Spyros; Chatzipetros, Alexandros|
|Holding Date||04 October 2008|
Archaeological data and methods are increasingly used in earthquake geology, as tools for identifying the surface effects of historical earthquake and, possibly, deduce quantitative palaeoseismological information. This is particularly useful in earthquake-prone areas with long period of inhabitance. It is however clear that there are a lot of uncertainties when interpreting the data, especially when no surface fracturing is evident. Indirect effects on structures should be treated very carefully, as they can be the result of a great number of causes, taking also into account poor workmanship and local geotechnical conditions. This paper reviews the results of the research team on two case studies in Greece of both clear and unclear indications of earthquake occurrence; the Mikri Doxipara – Zoni site and the Aghios Konstantinos site. Chief site archaeologists were D. Triantafyllos and M. Papakonstantinou respectively.
Mikri Doxipara - Zoni is located at the low seismicity area of Evros and Ardas rivers (NE Greece), very close to the triple border junction of Bulgaria, Greece and Turkey. It is a burial tumulus of four local nobles during the early Roman period (2nd century AD). Retrieved artifacts include a couple of carriages with their accompanying horses, making this a unique site for Greece. On one of the brick altars that was revealed after archaeological excavations since 2002, shows clear evidence of surface faulting, as it appear to be displaced and distorted. As a matter of fact, the pits dug by archaeologists exhibit an outcrop of a wide normal fault zone, which has a total net slip of 90 cm. Surface ruptures of the Neogene basement, in which the tombs were constructed, are clear indications of a large earthquake that hit the area and caused surface faulting at exactly the site of the tumulus. This earthquake postdates the construction of the burial mount and is possibly associated with the strong 1752 Edirne event.
Aghios Konstantinos site is located at central Greece, and virtually on one of the western bounding faults of northern Euboic gulf. The researched site is a small settlement uphill the modern town, consisting mainly of houses and a small temple of classical to Hellenistic times. There are indications that it was also been hit by an earthquake, the most valid of which is a surface rupture that runs through some of the foundations and is parallel to the main fault zone. Certain other indications, such as rotated blocks and tilted foundations, support the earthquake destruction hypothesis. Furthermore, a fault zone has been detected by normal palaeoseismological techniques at a nearby pit. Despite the abundance of data, one should be skeptic on the interpretation, as the site is built on a very steep hillside, and the observed indications could also be explained as a result of creeping.