Abstract
Damaging earthquakes result from the evolution of stress in the brittle upper-crust, but the understanding of the mechanics of faulting cannot be achieved by only studying the large ones, which are rare. Considering a fault as a complex system, microearthquakes allow to set a benchmark in the system evolution. Here, we investigate the possibility to detect when a fault system starts deviating from a predefined benchmark behavior by monitoring the temporal and spatial variability of different micro-and-small magnitude earthquakes properties. We follow the temporal evolution of the apparent stress and of the event-specific residuals of ground shaking. Temporal and spatial clustering properties of microearthquakes are monitored as well. We focus on a fault system located in Southern Italy, where the Mw 6.9 Irpinia earthquake occurred in 1980. Following the temporal evolution of earthquakes parameters and their time-space distribution, we can identify two long-lasting phases in the seismicity patterns that are likely related to high pressure fluids in the shallow crust, which were otherwise impossible to decipher. Monitoring temporal and spatial variability of micro-to-small earthquakes source parameters at near fault observatories can have high potential as tool for providing us with new understanding of how the machine generating large earthquakes works.
Highlights
Damaging earthquakes result from the evolution of stress in the brittle upper-crust, but the understanding of the mechanics of faulting cannot be achieved by only studying the large ones, which are rare
Near Fault Observatories (NFOs) based on dense networks of multi-parametric sensors installed close to faults that continuously record high quality data related to the common underlying earth instability processes over a broad time interval; NFOs integrate cross-disciplinary information and are deemed to be promising means for monitoring the spatial and temporal evolution of faults mechanical properties, and possibly to unveil the earthquakes preparatory phase, faulting mechanisms, and the role of high pressure fluids in the crustal rupture processes[1,2,3]
We analyze the temporal evolution of micro-to-small magnitude earthquakes at INFO, in southern Italy, in terms of apparent stress[15], between-event residuals[16] for the peak ground velocity (PGV) and applying a cluster analysis[17,18]
Summary
Damaging earthquakes result from the evolution of stress in the brittle upper-crust, but the understanding of the mechanics of faulting cannot be achieved by only studying the large ones, which are rare. Monitoring temporal and spatial variability of micro-to-small earthquakes source parameters at near fault observatories can have high potential as tool for providing us with new understanding of how the machine generating large earthquakes works. We consider one of the highest seismic risk areas in Europe, the Southern Apennines in Italy, a complex fault structure area with extensional kinematics characterized by a geodetic velocity of about 2 mm/ year This faults system generated several disastrous earthquakes in the last centuries, including the moment magnitude Mw 6.9, 1980 Irpinia earthquake[4,5], which caused almost 3,000 fatalities. We analyze the temporal evolution of micro-to-small magnitude earthquakes at INFO, in southern Italy, in terms of apparent stress (τa)[15], between-event residuals (δBe)[16] for the peak ground velocity (PGV) and applying a cluster analysis[17,18]. Along with τa, we monitor the temporal variability of δBe
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
