Drainage of a deep magma reservoir near Mayotte inferred from seismicity and deformation

Cesca, Simone; Letort, Jean; Razafindrakoto, Hoby N. T.; Heimann, Sebastian; Rivalta, Eleonora; Isken, Marius; Nikkhoo, Mehdi; Passarelli, Luigi; Petersen, Gesa; Cotton, Fabrice; Dahm, Torsten

doi:10.1038/s41561-019-0505-5

Cited by 136 publications

(216 citation statements)

References 71 publications

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“…This observation suggests that the long duration very low frequency signal is linked to a source process rather than to a propagation effect. November 11 th , 2018 signal could be related to an oscillating source, in agreement with the model of resonance of a deep magma reservoir proposed by Cesca et al (2020) Long period seismicity is considered to be related to magmatic and hydrothermal processes in a volcanic context. Their signal can be linked to oscillations within an excited fluid-filled oscillator (e.g., Chouet, 2003).…”

Section: Very Low Frequency Monochromatic Seismic Eventssupporting

confidence: 84%

“…May 14 th , 2019 occurred within cluster 3, at 34 km depth, its reverse focal mechanism is incoherent with regional trans-tensional stress regime and cannot be explained by dike intrusion. As suggested by Cesca et al (2020) who reported more events of this type located in our Cluster 3, such thrust mechanisms should be linked to local processes, probably of magmatic origin.…”

Section: The 2018-2019 Seismic Sequencesupporting

confidence: 63%

“…6), which is beyond the error bars and confirms the hypothesis of upward migration. Depth migration is also confirmed by Cesca et al (2020) from moment tensor inversions and analysis of teleseismic depth phases. We distinguished two phases in this first cluster: cluster 1a from May 10 th to the beginning of June 2018, and cluster 1b covering early June to beginning of July 2018, that started at the beginning of the seismically very intense first week of June.…”

Section: The 2018-2019 Seismic Sequencementioning

confidence: 64%

“…However, they presented much larger period of oscillations (~16 s) and long lasting signals. Systematic detection and analysis of such events are reported by Satriano et al (2019), Poli et al (2019) or Cesca et al (2020) who reported more than 400 of such VLP events and located them in the vicinity of the cluster 3. The largest one, on November 11 th , 2018, well recorded worldwide, awoke the interest of the seismological community and the media (e.g.…”

Section: Very Low Frequency Monochromatic Seismic Eventsmentioning

confidence: 89%

“…There were also frequent episodic monochromatic Very Long Period (VLP) earthquakes (Feuillet et al, in rev. ;Satriano et al, 2019;Poli et al, 2019;Cesca et al, 2020) typical of active magmatic or hydrothermal processes as described in other cases (e.g., Chouet, 2003;McNutt, 2005;Shapiro et al, 2017).…”

Section: Introductionmentioning

confidence: 97%

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The 2018-2019 seismo-volcanic crisis east of Mayotte, Comoros islands: seismicity and ground deformation markers of an exceptional submarine eruption

Lemoine¹,

Briole²,

Bertil³

et al. 2019

Preprint

142

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On May 10th, 2018, an unprecedented long and intense seismic crisis started offshore, east of Mayotte, the easternmost of the Comoros volcanic islands. The population felt hundreds of events. Over the course of one year, 32 earthquakes with magnitude greater than 5 occurred, including the largest event ever recorded in the Comoros (Mw = 5.9 on May 15th, 2018). Earthquakes are clustered in space and time. Unusual intense long lasting monochromatic very long period events were also registered. From early July 2018, Global Navigation Satellite System stations and Interferometric Synthetic Aperture Radar registered a large drift, testimony of a large offshore deflation. We describe the onset and the evolution of a large magmatic event thanks to the analysis of the seismicity from the initiation of the crisis through its first year, compared to the ground deformation observation (GNSS and InSAR) and modelling. We discriminate and characterise the initial fracturing phase, the phase of magma intrusion and dike propagation from depth to the sub-surface, and the eruptive phase that starts on July 3rd, 2018, around fifty days after the first seismic events. The eruption is not terminated two years after its initiation, with the persistence of an unusual seismicity, whose pattern has been similar since summer 2018, including episodic very low frequency events presenting a harmonic oscillation with a period of ~16 s. From July 2018, the whole Mayotte Island drifted eastward and downward at a slightly increasing rate until reaching a peak in late 2018. At the apex, the mean deformation rate was 224 mm yr-1 eastward and 186 mm yr-1 downward. During 2019, the deformation smoothly decreased and in January 2020, it was less than 20% of its peak value. A deflation model of a magma reservoir buried in a homogenous half space fits well the data. The modelled reservoir is located 45 ± 5 km east of Mayotte, at a depth of 28 ± 3 km and the inferred magma extraction at the apex was ~94 m3 s-1. The introduction of a small secondary source located beneath Mayotte Island at the same depth as the main one improves the fit by 20%. While the rate of the main source drops by a factor of 5 during 2019, the rate of the secondary source remains stable. This might be a clue of the occurrence of relaxation at depth that may continue for some time after the end of the eruption. According to our model, the total volume extracted from the deep reservoir was ~2.65 km3 in January 2020. This is the largest offshore volcanic event ever quantitatively documented. This seismo-volcanic crisis is consistent with the trans-tensional regime along Comoros archipelago.

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