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/shear-zone structures to viscous flow laws. We show that (1) differential stress fluctuates during fault/shear-zone interactions, and (2) these fluctuations are of sufficient magnitude 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.
|Original language||English (US)|
|State||Published - Nov 21 2022|
Bibliographical noteKAUST Repository Item: Exported on 2022-11-28
Acknowledgements: This work was funded by NERC Standard Grant NE/I024127/1 (G.P.R.), NERC Large Grant NE/J016497/1 (G.P.R.), NERC Standard Grant NE/E01545X/1 (G.P.R. and K.J.W.M. as co-I’s), NERC Studentship NE/L501700/1 (Z.K.M.), NERC Urgency Grant NE/P01660X/1 (J.P.F.W. and Z.K.M., EEFIT Reconnaissance Mission to the Amatrice, Italy, 24/09/2016 Earthquake), Japan Society for the Promotion of Science (JSPS) Short Term Fellowship PE15776 (Z.K.M.), the Jeremy Willson Charitable Trust (Z.K.M.), Geological Society Mike Coward fieldwork fund (Z.K.M.), and GBSF (Great Britain Saskawa Foundation) grant 4602 (J.P.F.W.). We thank Laura Gregory for discussions, participation in fieldwork, chemical analyses and preparation of the 36Cl samples. We thank Patience Cowie for many discussions and ideas that helped to lead us to this study. We thank Andrew Watson and Luke Wedmore for their assistance in the field during sampling. We thank Richard Phillips for setting up the cosmogenic lab at the University of Leeds where the sample preparation took place. Finally we thank the reviewers for their constructive feedback which helped to improve this paper.
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)
- Physics and Astronomy(all)