Project 567 - Earthquake Archaelogy - Archaeoseismology along the Alpine-Himalayan Seismic Zone
How can planners and politicians prepare for earthquakes? Damaging earthquakes on fault lines typically recur at intervals of centuries to millennia but the seismographs that register them have only been around for about hundred years. To reduce the hazard from earthquakes we need a longer record of them than can be provided from such instruments. On the assumption that future earthquakes will be like those of the geologically recent past, we need to look back in order to forecast forward. Archaeological evidence is especially valuable for determining earthquake activity over millennial time spans, especially where integrated with historical documents and geological evidence. Archaeology can be used in three ways to help confront the seismic-hazard threat.
- First, where archaeological relics are displaced they can be used to find earthquake faults, show in which direction they slipped during the earthquake and from these cultural ‘piercing points’ establish comparative fault slip-rates.
- Second, archaeological information can date episodes of faulting and shaking, with some cultural artifacts (e.g. epigraphic or numismatic (coins) data, pottery typology) yielding age estimates more precisely than high-resolution geological stratigraphies.
- Third, we can search for ancient signs of seismic damage. The obvious difficulty with the last approach is that it is hard to distinguish between damage caused by an earthquake and that caused by another destructive event, such as war or the natural failure of foundations.
Typologies of earthquake-characteristic damage have been proposed – most based on inferences drawn from seismic damage to modern constructions but some derived from engineering analysis of ancient structures – but rarely have they been subjected to a critical and systematic analysis. Consequently ‘archaeoseismic indicators’ are accepted by some earthquake scientists and rejected by others. An important element of this project will be to go from the shaking table to the archaeological remains in developing a broadly accepted methodological framework to what reliably constitutes seismic damage. The key element of this project is our contention that archaeological evidence has the potential to make a valuable contribution to long-term seismic-hazard assessment in earthquake-prone regions where there is a long and lasting cultural heritage. We have identified the Alpine-Himalayan region as the ideal laboratory, because the archaeoseismological studies that have already taken root in the Eastern Mediterranean can be extended to neighboring regions, most importantly south along North African shores, north into the Caucasus Mountains, and east into western Asia. As well as trying to establish a common methodological framework that is crucial for archaeoseismology to develop into a recognized and legitimate field of earthquake science, case studies from these regions will address specific questions relating to the locations, timing and size of past destructive earthquakes and so will aim to contribute specific information for seismic hazard analysis.
But there is a wider remit for our activities, because our research clearly has important humanitarian and economic implications. As illustrated by the 2003 collapse of the World Heritage site in the Bam (Iran) earthquake, cultural heritage sites themselves are threatened by seismic destruction. Clearly, there is a growing need to understand how ancient structures and monuments respond to faulting and ground shaking. On an even broader scale, our work will contribute to our understanding of ancient history, elucidating why some cities were abandoned or why former societies suffered decline, and confronting the enduring attraction of fault lines in luring peoples, ancient and modern, to settle along persistent danger zones. In other words, this project will contribute to our own cultural heritage.