TY - JOUR A1 - Sen, Ali Tolga A1 - Cesca, Simone A1 - Bischoff, Monika A1 - Meier, Thomas A1 - Dahm, Torsten T1 - Automated full moment tensor inversion of coal mining-induced seismicity JF - Geophysical journal international N2 - Seismicity induced by coal mining in the Ruhr region, Germany, has been monitored continuously over the last 25 yr. In 2006, a dense temporary network (HAMNET) was deployed to locally monitor seismicity induced by longwall mining close to the town of Hamm. Between 2006 July and 2007 July, more than 7000 events with magnitudes M-L from -1.7 to 2.0 were detected. The spatiotemporal distribution of seismicity shows high correlation with the mining activity. In order to monitor rupture processes, we set up an automated source inversion routine and successfully perform double couple and full moment tensor (MT) inversions for more than 1000 events with magnitudes above M-L -0.5. The source inversion is based on a full waveform approach, both in the frequency and in the time domain, providing information about the centroid location, focal mechanism, scalar moment and full MT. Inversion results indicate a strong dominance of normal faulting focal mechanisms, with a steeper plane and a subhorizontal one. Fault planes are oriented parallel to the mining stopes. We classify the focal mechanisms based on their orientation and observe different frequency-magnitude distributions for families of events with different focal mechanisms; the overall frequency-magnitude distribution is not fitting the Gutenberg-Richter relation. Full MTs indicate that non-negligible opening tensile components accompanied normal faulting source mechanisms. Finally, extended source models are investigated for largest events. Results suggest that the rupture processes mostly occurred along the subvertical planes. KW - Geomechanics KW - Fracture and flow KW - Earthquake source observations KW - Seismicity and tectonics Y1 - 2013 U6 - https://doi.org/10.1093/gji/ggt300 SN - 0956-540X SN - 1365-246X VL - 195 IS - 2 SP - 1267 EP - 1281 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Maghsoudi, Samira A1 - Cesca, Simone A1 - Hainzl, Sebastian A1 - Kaiser, Diethelm A1 - Becker, Dirk A1 - Dahm, Torsten T1 - Improving the estimation of detection probability and magnitude of completeness in strongly heterogeneous media, an application to acoustic emission (AE) JF - Geophysical journal international N2 - Reliable estimations of magnitude of completeness (M-c) are essential for a correct interpretation of seismic catalogues. The spatial distribution of M-c may be strongly variable and difficult to assess in mining environments, owing to the presence of galleries, cavities, fractured regions, porous media and different mineralogical bodies, as well as in consequence of inhomogeneous spatial distribution of the seismicity. We apply a 3-D modification of the probabilistic magnitude of completeness (PMC) method, which relies on the analysis of network detection capabilities. In our approach, the probability to detect an event depends on its magnitude, source receiver Euclidian distance and source receiver direction. The suggested method is proposed for study of the spatial distribution of the magnitude of completeness in a mining environment and here is applied to a 2-months acoustic emission (AE) data set recorded at the Morsleben salt mine, Germany. The dense seismic network and the large data set, which includes more than one million events, enable a detailed testing of the method. This method is proposed specifically for strongly heterogeneous media. Besides, it can also be used for specific network installations, with sensors with a sensitivity, dependent on the direction of the incoming wave (e.g. some piezoelectric sensors). In absence of strong heterogeneities, the standards PMC approach should be used. We show that the PMC estimations in mines strongly depend on the source receiver direction, and cannot be correctly accounted using a standard PMC approach. However, results can be improved, when adopting the proposed 3-D modification of the PMC method. Our analysis of one central horizontal and vertical section yields a magnitude of completeness of about M-c approximate to 1 (AE magnitude) at the centre of the network, which increases up to M-c approximate to 4 at further distances outside the network; the best detection performance is estimated for a NNE-SSE elongated region, which corresponds to the strike direction of the low-attenuating salt body. Our approach provides us with small-scale details about the capability of sensors to detect an earthquake, which can be linked to the presence of heterogeneities in specific directions. Reduced detection performance in presence of strong structural heterogeneities (cavities) is confirmed by synthetic waveform modelling in heterogeneous media. KW - Seismic attenuation KW - Statistical seismology Y1 - 2013 U6 - https://doi.org/10.1093/gji/ggt049 SN - 0956-540X VL - 193 IS - 3 SP - 1556 EP - 1569 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Heimann, Sebastian A1 - Gonzalez, Alvaro A1 - Wang, Rongjiang A1 - Cesca, Simone A1 - Dahm, Torsten T1 - Seismic characterization of the Chelyabinsk Meteor's terminal explosion JF - Seismological research letters Y1 - 2013 U6 - https://doi.org/10.1785/0220130042 SN - 0895-0695 VL - 84 IS - 6 SP - 1021 EP - 1025 PB - Seismological Society of America CY - Albany ER - TY - JOUR A1 - Grigoli, Francesco A1 - Cesca, Simone A1 - Vassallo, Maurizio A1 - Dahm, Torsten T1 - Automated seismic event location by travel-time stacking an application to mining induced seismicity JF - Seismological research letters Y1 - 2013 U6 - https://doi.org/10.1785/0220120191 SN - 0895-0695 VL - 84 IS - 4 SP - 666 EP - 677 PB - Seismological Society of America CY - Albany ER - TY - GEN A1 - Dahm, Torsten A1 - Becker, Dirk A1 - Bischoff, Monika A1 - Cesca, Simone A1 - Dost, B. A1 - Fritschen, R. A1 - Hainzl, Sebastian A1 - Klose, C. D. A1 - Kuhn, D. A1 - Lasocki, S. A1 - Meier, Thomas A1 - Ohrnberger, Matthias A1 - Rivalta, Eleonora A1 - Wegler, Ulrich A1 - Husen, Stephan T1 - Recommendation for the discrimination of human-related and natural seismicity T2 - Journal of seismology N2 - Various techniques are utilized by the seismological community, extractive industries, energy and geoengineering companies to identify earthquake nucleation processes in close proximity to engineering operation points. These operations may comprise fluid extraction or injections, artificial water reservoir impoundments, open pit and deep mining, deep geothermal power generations or carbon sequestration. In this letter to the editor, we outline several lines of investigation that we suggest to follow to address the discrimination problem between natural seismicity and seismic events induced or triggered by geoengineering activities. These suggestions have been developed by a group of experts during several meetings and workshops, and we feel that their publication as a summary report is helpful for the geoscientific community. Specific investigation procedures and discrimination approaches, on which our recommendations are based, are also published in this Special Issue (SI) of Journal of Seismology. KW - Triggered seismicity KW - Induced seismicity Y1 - 2013 U6 - https://doi.org/10.1007/s10950-012-9295-6 SN - 1383-4649 VL - 17 IS - 1 SP - 197 EP - 202 PB - Springer CY - Dordrecht ER - TY - INPR A1 - Cesca, Simone A1 - Dost, Bernard A1 - Oth, Adrien T1 - Preface to the special issue "Triggered and induced seismicity: probabilities and discrimination" T2 - Journal of seismology Y1 - 2013 U6 - https://doi.org/10.1007/s10950-012-9338-z SN - 1383-4649 VL - 17 IS - 1 SP - 1 EP - 4 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Cesca, Simone A1 - Braun, Thomas A1 - Maccaferri, Francesco A1 - Passarelli, Luigi A1 - Rivalta, Eleonora A1 - Dahm, Torsten T1 - Source modelling of the M5-6 Emilia-Romagna, Italy, earthquakes (2012 May 20-29) JF - Geophysical journal international N2 - On 2012 May 20 and 29, two damaging earthquakes with magnitudes M-w 6.1 and 5.9, respectively, struck the Emilia-Romagna region in the sedimentary Po Plain, Northern Italy, causing 26 fatalities, significant damage to historical buildings and substantial impact to the economy of the region. The earthquake sequence included four more aftershocks with M-w, >= 5.0, all at shallow depths (about 7-9 km), with similar WNW-ESE striking reverse mechanism. The timeline of the sequence suggests significant static stress interaction between the largest events. We perform here a detailed source inversion, first adopting a point source approximation and considering pure double couple and full moment tensor source models. We compare different extended source inversion approaches for the two largest events, and find that the rupture occurred in both cases along a subhorizontal plane, dipping towards SSW Directivity is well detected for the May 20 main shock, indicating that the rupture propagated unilaterally towards SE. Based on the focal mechanism solution, we further estimate the co-seismic static stress change induced by the May 20 event. By using the rate-and-state model and a Poissonian earthquake occurrence, we infer that the second largest event of May 29 was induced with a probability in the range 0.2-0.4. This suggests that the segment of fault was already prone to rupture. Finally, we estimate peak ground accelerations for the two main events as occurred separately or simultaneously. For the scenario involving hypothetical rupture areas of both main events, we estimate M-w = 6.3 and an increase of ground acceleration by 50 per cent. The approach we propose may help to quantify rapidly which regions are invested by a significant increase of the hazard, bearing the potential for large aftershocks or even a second main shock. KW - Earthquake dynamics KW - Earthquake source observations Y1 - 2013 U6 - https://doi.org/10.1093/gji/ggt069 SN - 0956-540X VL - 193 IS - 3 SP - 1658 EP - 1672 PB - Oxford Univ. Press CY - Oxford ER -