Earthquake Research: No Forecast, but Knowledge of Threat
The conviction of Italian seismologists in consequence of the L'Aquila earthquake once again highlighted the fact that earthquakes cannot be predicted. Yet why should this be so, what with plate tectonics providing such an excellent and well-established concept for explaining the processes on and within our planet?
Indeed, as a result of evaluating contemporary and historic earthquakes, the major earthquake zones are well-known today. On this basis, seismologists can estimate the degree of probability of earthquakes happening in a given location and their expected magnitude. Yet even such a vague estimation of potential threat poses a challenge, because some earthquake cycles can run as long as several hundred years.
Deterministic forecasting proves to be even more complex: In order to be of any use for short-term measures, the point in time would have to be known to the day, the location to an accuracy of 10 kilometres and the earthquake's intensity down to half a magnitude – a dream, which cannot be realised by today's state of knowledge. Occupying themselves in the field of earthquake research, the scientists at the Helmholtz Centre Potsdam – German Research Centre for Geosciences GFZ work on a broad range of topics: "Basic research, such as the seismic tomography of the Earth and geodynamic modelling, the global registration and evaluation of earthquakes, our tectonic plate boundary observatories, annual training courses on the seismology of and in endangered regions, the assessment of earthquake threats in many regions worldwide and the cooperation in the development of standards for earthquake-resistant building: all these are various facets of one and the same subject matter," explains Prof. Dr Michael Weber, Director of the GFZ department "Physics of the Earth". "The geosciences play a decisive role in assessing the risk of natural threats."
At the GFZ, earthquake risk research is conducted at various levels. A "Global Earthquake Threat Map" illustrates the main areas of risk in high resolution. Developed under the leadership of GFZ researcher Prof. Dr Gottfried Grünthal and translated into currently 30 languages, the European Macroseismic Scale is considered the bible of its field. Such research serves in the development of standards for earthquake-adequate building by providing engineers with information as regards threat and constantly alerts both the decision makers and the population of earthquake regions to be aware of the risk.
Precaution and early warning are decisive. Early warning, but no forecast. "The warning as regards severe ground motion, which is possible after the onset of an earthquake with warning lead times of some ten seconds, can help to automatically shut down industrial facilities and traffic infrastructure," says Prof. Dr Torsten Dahm, Head of the GFZ section "Earthquake Risk and Early Warning". The best known example for early warning is the GITEWS tsunami warning system for the Indian Ocean, which can quickly and accurately assess an earthquake within a few minutes and issue a tsunami warning.