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

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/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.

SUBMITTER: Mildon ZK

PROVIDER: S-EPMC9681762 | biostudies-literature | 2022 Nov

REPOSITORIES: biostudies-literature

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

Mildon Zoë K ZK Roberts Gerald P GP Faure Walker Joanna P JP Beck Joakim J Papanikolaou Ioannis I Michetti Alessandro M AM Toda Shinji S Iezzi Francesco F Campbell Lucy L McCaffrey Kenneth J W KJW Shanks Richard R Sgambato Claudia C Robertson Jennifer J Meschis Marco M Vittori Eutizio E

Nature communications 20221121 1

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 <sup>36</sup>Cl cosmogenic dating, revealing out-of-phase periods of high or low surface ...[more]

PMID: 36414645

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Project description:Volcanic islands are often subject to flank instability, resulting from a combination of magmatic intrusions along rift zones and gravitational spreading causing extensional faulting at the surface. Here, we study the Koa'e fault system (KFS), located south of the summit caldera of Kīlauea volcano in Hawai'i, one of the most active volcanoes on Earth, prone to active faulting, episodic dike intrusions, and flank instability. Two rift zones and the KFS are major structures controlling volcanic flank instability and magma propagation. Although several magmatic intrusions occurred over the KFS, the link between these faults, two nearby rift zones and the flank instability, is still poorly studied. To better characterize the KFS and its structural linkage with the surrounding fault and rift zones, we performed a detailed structural analysis of the extensional fault system, coupled with a helicopter photogrammetric survey, covering part of the south flank of Kīlauea. We generated a high-resolution DEM (~ 8 cm) and orthomosaic (~ 4 cm) to map the fracture field in detail. We also collected ~ 1000 ground structural measurements of extensional fractures during our three field missions (2019, 2022, and 2023). We observed many small, interconnected grabens, monoclines, rollover structures, and en-echelon fractures that were in part previously undocumented. We estimate the cumulative displacement rate across the KFS during the last 600 ~ 700 years and found a decrease toward the west of the horizontal component from 2 to 6 cm per year, consistent with GNSS data. Integrating morphology observations, fault mapping, and kinematic measurements, we propose a new kinematic model of the upper part of the Kīlauea's south flank, suggesting a clockwise rotation and a translation of a triangular wedge. This wedge is bordered by the extensional structures (ERZ, SWRZ, and the KFS), largely influenced by gravitational spreading. These findings illustrate a structural linkage between the two rift zones and the KFS, the latter being episodically affected by dike intrusions.Supplementary informationThe online version contains supplementary material available at 10.1007/s00445-024-01735-7.

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

Publications

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

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