Surface faulting earthquakes are known to cluster in time from historical and palaeoseismic studies, but the mechanism(s) responsible for clustering, such as fault interaction, strain-storage, and evolving dynamic topography, are poorly quantified, and hence not well understood. We present a quantified replication of observed earthquake clustering in central Italy. Six active normal faults are studied using 36Cl cosmogenic dating, revealing out-of-phase periods of high or low surface slip-rate on neighboring structures that we interpret as earthquake clusters and anticlusters. Our calculations link stress transfer caused by slip averaged over clusters and anti-clusters on coupled fault/shearzone structures to viscous flow laws. We show that (1) differential stress fluctuates during fault/shear-zone interactions, and (2) these fluctuations are of sufficientmagnitude to produce changes in strain-rate on viscous shear zones that explain slip-rate changes on their overlying brittle faults. These results suggest that fault/shear-zone interactions are a plausible explanation for clustering, opening the path towards process-led seismic hazard assessments.

Surface faulting earthquake clustering controlled by fault and shear-zone interactions

Alessandro M. Michetti
Investigation
;
2022

Abstract

Surface faulting earthquakes are known to cluster in time from historical and palaeoseismic studies, but the mechanism(s) responsible for clustering, such as fault interaction, strain-storage, and evolving dynamic topography, are poorly quantified, and hence not well understood. We present a quantified replication of observed earthquake clustering in central Italy. Six active normal faults are studied using 36Cl cosmogenic dating, revealing out-of-phase periods of high or low surface slip-rate on neighboring structures that we interpret as earthquake clusters and anticlusters. Our calculations link stress transfer caused by slip averaged over clusters and anti-clusters on coupled fault/shearzone structures to viscous flow laws. We show that (1) differential stress fluctuates during fault/shear-zone interactions, and (2) these fluctuations are of sufficientmagnitude to produce changes in strain-rate on viscous shear zones that explain slip-rate changes on their overlying brittle faults. These results suggest that fault/shear-zone interactions are a plausible explanation for clustering, opening the path towards process-led seismic hazard assessments.
https://www.nature.com/articles/s41467-022-34821-5#citeas
Earthquake surface faulting; Fault slip-rate; Normal fault; Central Apennines; Seismic hazard; Paleoseismology
Mildon, Zoë K.; Roberts, Gerald P.; Faure Walker, Joanna P.; Beck, Joakim; Papanikolaou, Ioannis; Michetti, Alessandro M.; Toda, Shinji; Iezzi, Francesco; Campbell, Lucy; Mccaffrey, Kenneth J. W.; Shanks, Richard; Sgambato, Claudia; Robertson, Jennifer; Meschis, Marco; Vittori, Eutizio
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11383/2142891
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