Synthetic seismograms for assessing areas of potential damage after induced events for legal regulations in Germany

Induced and triggered seismicity in Germany is related to various mining operations such as hydrocarbon extraction, geothermal exploitation and classical mining techniques, i.e. coal and potash mining.

After some larger events small damages to buildings were observed that might have been caused by the ground shakings. This led to public discussions on compensation and to political discussions on improving legal regulations. The possibility of damages caused by mining induced seismic events and difficulties in financial compensation reduced the acceptance of mining projects in the past, e.g. geothermal projects are inhibited.

In case of verified damage due to an induced event, the causative mining company has to pay compensations. In 2016 new legal regulations entered into force. The Federal Mining Act was revised with an improved legal situation for the population by expanding the prima facie evidence on mining activities using boreholes. The new legal regulations define, that damages at buildings are assumed to be caused by the seismic event in the responsibility of the operator of the mining activities, if they occur within a certain area defined by the mining authority (impact area, German: “Einwirkungsbereich”).

From the seismological perspective, local measurements of PGV are often rare. Thus, it is difficult to assess the damage potential of the seismic events in detail, especially if intensities are around V (EMS-98). In many cases, a relation between individual damages at buildings and the seismic event is only hardly verifiable. Actually, detailed survey reports could neither prove nor disprove the relation between damages and seismic events in some cases. In conclusion, some of the widely discussed events might have led to small damages.

A brief introduction about the existing legal regulations will be presented. We used synthetic seismogram to model the wave propagation and amplitude effects for induced seismic events in the magnitude range between ML 2.9 and 3.6, for which it was necessary to define the impact area for legal regulations. Results from amplitude measurements at existing seismic stations were taken to calibrate the absolute amplitudes of the modeling. The synthetic seismograms could help to quantify the effects from the radiation pattern of the source and the impact of sediment coverage between source and receivers. They could improve the definition of the area of impact.