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Deformation-controlled long-period seismicity in low-cohesion volcanic sediments


Volcano seismicity is an important tool in monitoring and forecasting activity at volcanoes globally. Volcanic earthquakes show diverse spectral characteristics, of which shallow long-period (low-frequency) seismicity and long-duration tremor are generally interpreted as indicators of fluid migration, and as potential eruption precursors. Here we show that a common low-cohesion volcanic sediment from the Campi Flegrei caldera (Italy) produces low-frequency and long-duration seismicity as it undergoes deformation in dry conditions. We employed acoustic-emission rock-deformation experiments at a range of strain rates to produce events that, when normalized for scale, were spectrally indistinguishable from the long-period and tremor seismicity observed in natural volcanic settings. The generation of these signals was enhanced at lower laboratory strain rates. Correlated X-ray tomography of the samples before and after deformation constrained the source as distributed damage.

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Fig. 1: Example XCT virtual slices of a sample before and after a low-strain-rate deformation experiment.
Fig. 2: Event representations of typical natural volcanic events (left column) and typical experimental (right column) events recorded in this work.
Fig. 3: Comparison of peak seismic frequencies in slow and fast deformation experiments.
Fig. 4: Varied duration and seismic character of LP-type events.

Data availability

The data used in this work are held at the National Geoscience Data Centre, as item number 163527. These include the 1 Hz deformation logs, 10 MHz 12-channel AE event recordings, raw XCT slices from before and after deformation, and the processing code used to generate the statistical analyses and sonograms54.


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We are grateful to E. Butcher for the sample preparation work, E. Pegge for collating the event classifications and F. Cappuccio for measuring the postdeformation porosity values. We acknowledge support from the Zeiss Global Centre at the University of Portsmouth for providing the X-ray microscopy facilities used in this study, and the assistance of the National Geoscience Data Centre in accommodating our dataset.

Author information




P.R. drafted the paper. P.R. and P.B. carried out the laboratory experiments. P.R., P.B. and C.B. discussed results, carried out the analysis and edited the draft paper.

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Correspondence to Pete Rowley.

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The authors declare no competing interests.

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Peer review information Nature Geoscience thanks Christopher Kilburn, Ben Kennedy and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Primary Handling Editor(s): Stefan Lachowycz.

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Supplementary information

Supplementary Data 1

Dimensional data and calculations to generate the volumetric strain value for the slow deformation experiment.

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Rowley, P., Benson, P.M. & Bean, C.J. Deformation-controlled long-period seismicity in low-cohesion volcanic sediments. Nat. Geosci. 14, 942–948 (2021).

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