Three‐Dimensional Electrical Resistivity Distribution Beneath the Beppu–Shimabara Graben With a Focus on Aso Caldera, Southwest Japan Subduction Zone

Hata, Masayoshi; Uyeshima, Makoto; Tanaka, Yoshikazu; Hashimoto, Takeshi; Oshiman, Naoto; Yoshimura, Ryokei

doi:10.1029/2018jb015506

Cited by 14 publications

(10 citation statements)

References 31 publications

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“…This observation holds true across tectonic settings, and all differentiation trends. 56 , Vs 57 , and Magnetotellurics 58 . Stars for St Helens refer to pressure estimates from experimental petrology 59,50 .…”

Section: A Sweet Spot Around 2 Kbarmentioning

confidence: 99%

Optimal depth of subvolcanic magma chamber growth controlled by volatiles and crust rheology

et al. 2019

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Storage pressures of magma reservoirs influence the style, frequency and magnitude of volcanic eruptions. Neutral buoyancy or rheological transitions are commonly assumed to control where magmas accumulate and form such reservoirs. However, the density of volatile-rich silicic magmas is typically lower than the surrounding crust, and the rheology of the crust alone does not control the depth of the brittle-ductile transition around a magma reservoir. Yet, typical storage pressures inferred from geophysical inversions or petrological methods seem to cluster around 2  0.5 kbar in all tectonic settings and crustal compositions. Here, we use thermo-mechanical modeling to show that storage pressure is controlled by volatile exsolution and crustal rheology. At pressures ≲1.5 kbar, and for geologically realistic water contents, reservoir volumes, and recharge rates, the presence of an exsolved magmatic volatile phase hinders reservoir growth because eruptive volumes are typically larger than recharges feeding the system during periods of dormancy. At pressures ≳2.5 kbar, the viscosity of the crust in long-lived magmatic provinces is sufficiently low to inhibit most eruptions. Sustainable eruptible magma reservoirs are able to develop only within a relatively narrow range of pressures around 2  0.5 kbar, where the amount of exsolved volatiles fosters growth while the high viscosity of the crust promotes the necessary overpressurization for eruption. Over the last decades, a polybaric view of magmatic differentiation has emerged (see early ideas in 1,2), referred to as "crustal distillation columns" with multiple levels of storage and differentiation 3. However, the depth/pressure at which magmas stall and the processes that control those storage depths remain controversial 4. Magmas are typically thought to accumulate first at the crust-mantle boundary, forming deep crustal mush zones (MASH 5 or hot zones 6) and then again at shallow depths, potentially leading to two main storage levels 3 .

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Section: A Sweet Spot Around 2 Kbarmentioning

confidence: 99%

Optimal depth of subvolcanic magma chamber growth controlled by volatiles and crust rheology

et al. 2019

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“…The final 3‐D model can be assumed to be sensitive to the 18 parts of these conductive blocks because the RMS misfits of all test models increase the RMS misfit from the final model value. In addition, we examined the RMS variations of the sensitivity test models using an F test for the (67 × 16 × 12 − 1 =) 12,863 degrees of freedom of the data at the 95% confidence level (e.g., Hata et al, ; Hata et al, ; Tada et al, ; Yamaya et al, ). The upper cumulative distribution of the F test ( F = 1.0352) provides a F RMS misfit of 1.2856 based on the RMS misfit of 1.2636 of the final model:

F_{RMS} misfit = \sqrt{{1.2636}^{2} \times 1.0352}

.…”

Section: Resultsmentioning

confidence: 99%

Three‐Dimensional Electrical Resistivity Structure Beneath a Volcanically and Seismically Active Island, Kyushu, Southwest Japan Arc

et al. 2020

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To understand the subduction dynamics around Kyushu Island, Southwest Japan Arc, the distribution of fluids is imaged by resolving three‐dimensional (3‐D) electrical resistivity structure beneath a subregion the island, including volcanic and nonvolcanic areas. The nonvolcanic region in central Kyushu is situated between two regions with numerous Quaternary volcanic structures along a volcanic front aligned N30°E and related to subduction of the Philippine Sea Plate. Two source areas of slow slip events lie at depths of 20–40 km along the eastern coast of Kyushu, whereas earthquakes spread along the subducting Philippine Sea Plate plane over the eastern coast and toward the volcanic front at depths of 20 to >100 km. Our 3‐D resistivity model detects prominent conductors, indicating the presence of fluids, which might control volcanic and seismic activity. The most robust features of the model are three regions of high conductivity. A magma system and a fluid system are imaged as two vertical conductors extending from a depth of ~70 km, both related to slab‐derived fluid and located along the volcanic front, beneath the volcanic and nonvolcanic regions, respectively. The third conductor, which suggests the presence of slab‐derived fluid and hydrated sediments at the plate interface and the presence of serpentinite in the mantle wedge, appears in an area devoid of slow slip events at depths of <~30 km along the southeastern coast.

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“…1a) but at a shallower depth. It is also near the upper end of a high conductivity anomaly 41 . We suggest that the source of the inflation/deflation event corresponds to a shallow magma storage zone (SMSZ) beneath the Aso volcano, connecting the source of LPT in the shallow conduit from above and the magma chamber from below (Fig.…”

Section: The Nature Of Inflation/deflation Event In a Renewed Plumbing System Beneath Aso Volcanomentioning

confidence: 88%

Episodic transport of discrete magma batches beneath Aso volcano

Niu

Song

2021

Preprint

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Magma ascent, storage, and discharge in the trans-crustal magma plumbing system are key to long-term volcanic output and short-term eruption dynamics. Petrological analytics, geodetic deformations and mechanical modeling have shaped the current understanding of magma transport. However, due to the lack of observations, how a distinct magma batch transports from a crystal-rich mush region to a crystal-poor pool with eruptible magma remains enigmatic. Through stacking of tilt and seismic waveform data, we find that episodic long-period tremors (LPTs) located near sea level beneath the Aso volcano are accompanied by a synchronous deformation event, which initiates ~50 seconds before individual LPT event and concludes seconds after. The episodic deformation source corresponds to either an inflation or a deflation event located ~3 km below sea level, with a major volumetric component (50-440 cubic meters per event) and a minor high-angle normal-fault component. We suggest that these deformation events likely represent short-lived, episodic upward transport of discrete magma batches accompanied by high-angle shear failure near the roof of the inferred magma chamber at relatively high temperature, whereas their recurrences, potentially composition dependent, are regulated by the brittle-to-ductile transition rheology under low differential stress and high strain rate due to the surge of magma from below, regulating long-term volcanic output rate. The magma ascent velocity, decompression rates, and cumulative magma output deduced from the episodic deformation events before recent eruptions in Aso volcano are compatible with retrospective observations of the eruption style, tephra fallouts, and plume heights, promising real-time evaluation of upcoming eruptions.

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Three‐Dimensional Electrical Resistivity Distribution Beneath the Beppu–Shimabara Graben With a Focus on Aso Caldera, Southwest Japan Subduction Zone

Cited by 14 publications

References 31 publications

Optimal depth of subvolcanic magma chamber growth controlled by volatiles and crust rheology

Optimal depth of subvolcanic magma chamber growth controlled by volatiles and crust rheology

Three‐Dimensional Electrical Resistivity Structure Beneath a Volcanically and Seismically Active Island, Kyushu, Southwest Japan Arc

Episodic transport of discrete magma batches beneath Aso volcano

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