Millennial Record of Earthquakes in the Carpathian-Pannonian Region: Historical and Archaeoseismology
Miklós Kázmér and Erzsébet Győri
Eötvös Loránd University, MTA–ELTE Geological, Geophysical and Space Science Research Group; Kövesligethy Radó Seismological Observatory
This is a short essay on earthquakes in the Carpathian-Pannonian region and its surroundings. Earthquakes have been recorded using seismographs since 1902 in Hungary. The relatively small number of seismic events and the long return period of major earthquakes make it necessary to use historical data in order to assess seismic hazard. Historical earthquake catalogues aim for exhaustiveness both in time and space, but they are limited by the lack of documentary data. A simple arithmetical assessment is provided to estimate our lack of knowledge of past seismic events. All destructive earthquakes of the twentieth century (above magnitude 5) are included in the catalogue (100%). Of the seismic events which took place in the seventeenth, eighteenth, and nineteenth centuries, only 23% are on record, while this figure drops to 4.6 percent for the eleventh–sixteenth centuries and 0.2 percent for the first millennium AD. On average, we have no information about 90% of the destructive earthquakes which occurred in the Carpathian-Pannonian region over the course of the past two millennia.
According to both instrumental measurements and historical sources, there were relatively few earthquakes in the central era of the period of time in question. This era coincides roughly with the two centuries of Ottoman rule (the sixteenth and seventeenth centuries). Were there really few earthquakes over the course of these two centuries, or we do not have the relevant records? We contend that warfare resulted in the destruction of settlements and the annihilation of documents.
Fragile historical documents can be supplemented by the study of robust edifices, an approach to the study of the past which is known as archaeoseismology. Evidence of damage and destruction can be identified, and earthquake parameters can be assessed. One can find evidence corroborating other sources indicating an earthquake (e.g. Savaria), and one can also identify traces of previously unknown seismic events (Visegrád). One can also assign intensity values to the existing historical records. Damage observed to a Roman road in Savaria, to the medieval donjon of Nagyvázsony offers support for our fundamental contention. In order to understand the seismic hazard that was faced in the Carpathian-Pannonian region, renewed study of historical sources and new archaeoseismological investigations are needed.
Keywords: earthquakes, archaeoseismology, historical sources, Carpathian-Pannonian region