Coal Mining Induced Seismicity in the Ruhr Area, Germany

Bischoff, M., Cete, A., Fritschen, R. and Meier, T. (2010) Coal Mining Induced Seismicity in the Ruhr Area, Germany Pure and Applied Geophysics, 167 (1-2). pp. 63-75. DOI 10.1007/s00024-009-0001-8.

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Abstract

Over the last 25 years mining-induced seismicity in the Ruhr area has continuously been monitored by the Ruhr-University Bochum. About 1,000 seismic events with local magnitudes between 0.7 ≤ ML ≤ 3.3 are located every year. For example, 1,336 events were located in 2006. General characteristics of induced seismicity in the entire Ruhr area are spatial and temporal correlation with mining activity and a nearly constant energy release per unit time. This suggests that induced stresses are released rapidly by many small events. The magnitude–frequency distribution follows a Gutenberg–Richter relation which is a result from combining distributions of single longwalls that themselves show large variability. A high b-value of about 2 was found indicating a lack of large magnitude events. Local analyses of single longwalls indicate that various factors such as local geology and mine layout lead to significant differences in seismicity. Stress redistribution acts very locally since differences on a small scale of some hundreds of meters are observed. A regional relation between seismic moment M0 and local magnitude ML was derived. The magnitude–frequency distribution of a single longwall in Hamm was studied in detail and shows a maximum at ML = 1.4 corresponding to an estimated characteristic source area of about 2,200 m2. Sandstone layers in the hanging or foot wall of the active longwall might fail in these characteristic events. Source mechanisms can mostly be explained by shear failure of two different types above and below the longwall. Fault plane solutions of typical events are consistent with steeply dipping fracture planes parallel to the longwall face and nearly vertical dislocation in direction towards the goaf. We also derive an empirical relation for the decay of ground velocity with epicenter distance and compare maximum observed ground velocity to local magnitude. This is of considerable public interest because about 30 events larger than ML ≥ 1.2 are felt each month by people living in the mining regions. Our relations, for example, indicate that an event in Hamm with a peak ground velocity of 6 mm/s which corresponds to a local magnitude ML between 1.7 and 2.3 is likely to be felt within about 2.3 km radius from the event.

Document Type: Article
Keywords: Mining-induced seismicity, coal mining, magnitude–frequency distribution, b-value, energy release, ground velocity
Research affiliation: Kiel University
OceanRep > The Future Ocean - Cluster of Excellence
Refereed: Yes
DOI etc.: 10.1007/s00024-009-0001-8
ISSN: 0033-4553
Projects: Future Ocean
Date Deposited: 04 Oct 2017 16:02
Last Modified: 04 Oct 2017 16:02
URI: http://eprints.uni-kiel.de/id/eprint/39645

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