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  - 
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  -