资源环境科技发展态势分析平台

Focal mechanisms of selected earthquakes, recorded in the Mount Pollino region (southern Italy) from 2010 through 2014, are used to infer the pore fluid pressure at hypocentre depths. The 3-D excess pore pressure field provides evidence that the sequence occurs in a fluid-filled volume with values reaching 35 MPa. The mechanisms underlying this swarm-like sequence and the triggering of earthquakes are investigated computing the cumulative static Coulomb stress change at hypocenter depths and analyzing the pore-pressure diffusion mechanism. The results indicate that static Coulomb stress change was lower than 0.01 MPa, which is the value generally assumed as threshold for the triggering, and seismicity distribution was actually driven by pore-pressure diffusion with relatively low diffusivity value. This latter mechanism could also explain the delayed triggering of the two larger events M_L 4.3 and M_L 5.0, respectively occurred about 150 days apart.