We analyse variations in Brune stress drop (Delta sigma), apparent stress (tau(a)) and Savage-Wood radiation efficiency (eta(sw) = tau(a)/Delta sigma) during the 2010-2014 Pollino seismic swarm (Southern Apennines, Italy). This prolonged sequence included multiple swarms, with a M-w 5.2 event in October 2012, preceded by a M-w 4.3 event in May 2012, followed by aseismic slip. Seismicity clusters into two groups: one near the M-w 5.2 event and another around the M-w 4.3 event, raising questions about fault geometry and dip. Spectral analysis of 106 earthquakes (M-L > 2.2) shows Delta sigma and tau(a) scale with magnitude, while eta(sw) does not. The Savage-Wood radiation efficiency ranges from 0.08 to 0.50, averaging 0.23, aligning with the pure omega-square model. Previous studies suggest fluids influence swarm nucleation. By integrating our results with geophysical data, we propose that high eta(sw) events originate in zones of elevated pore pressure, helping constrain the fault plane of the east.
Influence of Fluids and Geological Setting on Source Parameters of the 2010–2014 Pollino (Italy) Seismic Swarm
Ponte M.;La Rocca M.;
2025-01-01
Abstract
We analyse variations in Brune stress drop (Delta sigma), apparent stress (tau(a)) and Savage-Wood radiation efficiency (eta(sw) = tau(a)/Delta sigma) during the 2010-2014 Pollino seismic swarm (Southern Apennines, Italy). This prolonged sequence included multiple swarms, with a M-w 5.2 event in October 2012, preceded by a M-w 4.3 event in May 2012, followed by aseismic slip. Seismicity clusters into two groups: one near the M-w 5.2 event and another around the M-w 4.3 event, raising questions about fault geometry and dip. Spectral analysis of 106 earthquakes (M-L > 2.2) shows Delta sigma and tau(a) scale with magnitude, while eta(sw) does not. The Savage-Wood radiation efficiency ranges from 0.08 to 0.50, averaging 0.23, aligning with the pure omega-square model. Previous studies suggest fluids influence swarm nucleation. By integrating our results with geophysical data, we propose that high eta(sw) events originate in zones of elevated pore pressure, helping constrain the fault plane of the east.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
