Rock and fault rheology explain differences between on fault and distributed seismicity.
Nat Commun 2022;
13:5627. [PMID:
36163188 PMCID:
PMC9512795 DOI:
10.1038/s41467-022-33373-y]
[Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Accepted: 09/15/2022] [Indexed: 11/17/2022] Open
Abstract
Analysis of seismicity can illuminate active fault zone structures but also deformation within large volumes of the seismogenic zone. For the Mw 6.5 2016–2017 Central Italy seismic sequence, seismicity not only localizes along the major structures hosting the mainshocks (on-fault seismicity), but also occurs within volumes of Triassic Evaporites, TE, composed of alternated anhydrites and dolostones. These volumes of distributed microseismicity show a different frequency-magnitude distribution than on-fault seismicity. We interpret that, during the sequence, shear strain-rate increase, and fluid overpressure promoted widespread ductile deformation within TE that light-up with distributed microseismicity. This interpretation is supported by field and laboratory observations showing that TE background ductile deformation is complex and dominated by distributed failure and folding of the anhydrites associated with boudinage hydro-fracturing and faulting of dolostones. Our results indicate that ductile crustal deformation can cause distributed microseismicity, which obeys to different scaling laws than on-fault seismicity occurring on structures characterized by elasto-frictional stick-slip behaviour.
A new study sheds light on earthquake physics, showing that lithological and rheological heterogeneities in the rocks composing the seismogenic layer strongly influence seismicity distributions and earthquake scaling laws.
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