Dynamics of the Seismicity in the Alto Tiberina Fault System revealed by
a High-Resolution Template Matching Catalog
Abstract
The Alto Tiberina Fault system located in the Northern Apennines (Italy)
consist of a low angle normal fault which radiates micro-seismicity on a
constant rate and is assumed to host continuous creep. In the hanging
wall, on top of the low angle normal fault, a network of syn- and
antithetic high angle faults frequently hosts swarm seismic sequences,
one of which has been associated to a transient aseismic deformation
signal. To study in detail the dynamics related to the seismic and its
relationships with aseismic deformation processes occurring in this
fault system, we apply template matching on seismic data recorded at an
array of borehole stations, to derive a high-resolution earthquake
catalog. We then quantify the time and space clustering of the
seismicity which reveals elevated clustering within the hanging wall
during an aseismic deformation period. This reflects the complex
evolution of aseismic slip together with the complexity of the shallow
fault system. On the other hand, we observe a bimodal seismicity along
the low angle normal fault, with continuous and diffuse seismicity, and
rapid bursts which could suggest rapid fluid releases. Along the low
angle normal fault, we additionally identify repeating earthquakes and
model them assuming a creep model. Our results open the possibility for
other models than the actual model of inter-seismic deformation to
explain the seismicity along the Alto Tiberina low angle normal fault.