Very detailed seismic pattern and migration inferred from the April 2010 Pietralunga (northern Italian Apennines) micro-earthquake sequence

An analysis of waveform similarity was performed at a reference station by merging the capability of the cross-correlation technique and the bridging algorithm. The detected mutiplets allow us to emphasize the anisotropic spatial and temporal migrations of the seismicity that occurred along a 307° N strike direction with an averaged propagation velocity of ca. 0.4 km/day. We explain the highlighted anisotropic behavior of the migration with the hypothesized presence of overpressured fluids and with physical properties of Triassic evaporites. This suggests the importance of such very detailed relocation of weak and micro-seismicity for improvement of our knowledge of fault system geometry and its evolution.