Atlas of Switzerland

The Swiss Seismological Service (SED) at ETH Zurich produces a ShakeMap for every earthquake recording a magnitude of 2.5 or higher. These maps provide a quick estimate of the ground motion generated by the quake and the effects relating to this. ShakeMaps present significantly more information than conventional earthquake maps, which only show the epicentre and magnitude. In the event of an earthquake, this more detailed data can be used by both the people affected and rescue services as a source of information and a basis for action. ShakeMaps also offer an opportunity to illustrate earthquake scenarios in order to improve earthquake mitigation. ShakeMaps® were originally developed in by the US Geological Survey, which also provides the software required for them. The objectives of a ShakeMap: Powerful earthquakes can cause a great deal of human suffering and tremendous damage to buildings and infrastructure. In the immediate aftermath of a major quake, it is often difficult to gain a clear overview of the situation in order to take appropriate action. In such cases, ShakeMaps are a helpful crisis management tool. They show which areas have been particularly heavily affected and thus enable authorities and helpers to focus their efforts and resources where they are needed. The media and the general public can also draw on them as a useful source of information. In the case of relatively minor tremors, ShakeMaps depict where these have been felt and how strongly, and whether any damage can be expected. In terms of earthquake mitigation, ShakeMaps projecting potential scenarios can help illustrate what might happen if a quake were to hit a particular location. How a ShakeMap is produced: The SED’s ShakeMaps are generated in several stages: first of all, the epicentre and magnitude of the earthquake are input into the system. These factors are then combined with the maximum levels of shaking, which are either measured or modelled at the SED’s seismic stations, and supplemented with model-based assumed ground motions. In order to process the data using a 12-point macroseismic intensity scale (EMS-98 scale), local amplification effects also need to be taken into account. The SED calibrates the ShakeMap calculation specifically for Switzerland. Nevertheless, the intensity values shown on a ShakeMap are subject to considerable uncertainty, which is why the actual impact of an earthquake may vary from what is predicted. What is shown on a ShakeMap: The epicentre of the earthquake is indicated by a star symbol. The different colours show how strong the assumed ground motions would be at certain locations and what degree of damage can be expected. The colour scale adopted for the ShakeMaps is based on the European Macroseismic Scale (EMS-98), which is used as a standardised means of depicting the impact of earthquakes across Europe. Colours ranging from mauve to blue represent minor shaking, while green to yellow suggest clearly discernible tremors with potential to cause slight building damage, and orange to red tones indicate severe building damage. Intensities higher than level IX cannot be reliably modelled and are therefore not differentiated in the colour scale.