Link between the Nankai underthrust turbidites and shallow slow earthquakes

Park, Jin-Oh; Hondori, Ehsan Jamali

doi:10.1038/s41598-023-37474-6

Cited by 3 publications

(1 citation statement)

References 42 publications

(77 reference statements)

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“…Fujie et al [2020] thus suggest that disturbance and thermal metamorphism associated with this recent volcanic activity modify and shape the size and distribution of interplate earthquakes off NE Japan. In the Nankai subduction zone, Park and Jamali Hondori [2023] suggest that the underthrust turbidites cause low pore-fluid overpressure and high effective vertical stress across the decollement inhibiting the slow earthquakes occurrence. Similar heterogeneities were also found in the shallow part of the subduction interface along the Hikurangi margin [Gase et al, 2022].…”

Section: Nature Of the Incoming Sedimentmentioning

confidence: 99%

Accretion versus erosion and sediment transfer balance near the subduction interface

Lallemand,

Peyret,

Arcay

et al. 2024

Comptes Rendus. Géoscience

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The nature and amount of sediment transferred from one plate to the other near the subduction interface partly determines the tectonic and seismogenic regime of a margin. Examination of over 500 multichannel seismic lines has enabled us to build up a global database of subduction zone front characteristics at unprecedented spatial resolution. The total thickness of sediment in the trench below the deformation front, as well as that of the subduction channel at a distance from the trench, combined with other indices such as the tectonic regime of the forearc or the migration of the volcanic front, have enabled us to revisit the accretionary or erosional character of active margins. Preliminary conclusions, based on ∼3/4 of sufficiently documented subduction zones, show a predominance of the erosive character of subduction over the last million years. The flux of solid matter through the shallow part of the subduction channel is of the order of 1.5 km 3 /yr, and that of pore fluids 0.4 km 3 /yr. Some subduction zones, such as the Mediterranean, are characterized by exceptional solid flux in the channel, while fluid flux is comparatively moderate. This is due to the fact that channel sediments are compacted even before subduction. Overall, fluid flux in the channel is greater under erosive margins, due to the higher rate of subduction and often higher porosity. Maximum porosity in the channel is reached when there is neither accretion nor tectonic erosion.

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Section: Nature Of the Incoming Sedimentmentioning

confidence: 99%

Accretion versus erosion and sediment transfer balance near the subduction interface

Lallemand,

Peyret,

Arcay

et al. 2024

Comptes Rendus. Géoscience

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A review of shallow slow earthquakes along the Nankai Trough

Takemura,

Hamada,

Okuda

et al. 2023

Earth Planets Space

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Slow earthquakes occur at deep and shallow plate boundaries along the Nankai Trough. Deep slow earthquakes are continuously distributed along the 30–40 km depth contours of the upper surface of the subducted Philippine Sea Plate. In contrast, shallow slow earthquakes occur in limited regions: Hyuga-nada, off Cape Muroto, and southeast off the Kii Peninsula. This review provides an overview of the up-to-date seismological, geodetic, geological, and experimental results in the shallow Nankai area for a unified understanding of the spot-like occurrence of shallow slow earthquakes. Shallow slow earthquakes tend to be distributed in transitional regions between the frictionally locked and stably sliding zones on the plate boundary. Based on geological and experimental studies, the lithology of incoming sediments and their friction coefficients can be variable along the Nankai Trough. Laboratory friction experiments revealed that sediments under shallow plate boundary conditions often exhibit positive (a − b) values, while negative (a − b) is possible via several processes. Subducted seamounts create complex fracture networks and stress shadows in their surrounding areas; however, not all subducted seamounts are related to shallow slow earthquake activities. This incomplete correlation suggests that alternative factors are required to explain the spot-like distribution of shallow slow earthquakes in the Nankai subduction zone. High pore fluid pressure conditions around shallow slow earthquake zones were interpreted based on seismological structural studies. In addition, ambient noise monitoring revealed temporal changes in seismic velocity structures associated with shallow slow earthquake migrations. This result suggests a close link between pore fluid migration and shallow slow earthquake episodes. Because transient changes in pore fluid pressure can lead to various slip behaviors, the episodic migration of pore fluid around the plate boundary could promote shallow slow earthquake activity along the Nankai Trough. Graphical Abstract

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Thick slab crust with rough basement weakens interplate coupling in the western Nankai Trough

Arai,

Shiraishi,

Nakamura

et al. 2024

Earth Planets Space

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The westernmost Nankai Trough, southwest Japan, exhibits a rapid along-strike reduction in plate coupling in the proximity to the subducting Kyushu-Palau ridge. Yet how and to what extent the ridge subduction impacts physical properties at the megathrust have not been investigated. Here we present high-resolution seismic P-wave velocity models along the forearc wedge in the western Nankai Trough derived from full-waveform inversion analyses of seismic refraction data. The velocity models show that where the plate coupling is weak and the plate boundary presumably hosts slow earthquakes, the upper plate exhibits lower seismic velocities indicating higher degree of fracturing over a ~ 100 km length along trough. Intriguingly, the extent of the upper-plate low-velocity features is significantly larger than the surficial width of the Kyushu-Palau ridge, and this low-velocity zone is underthrust by the slab with increased crustal thickness by 2–4 km. Seismic reflection images consistently reveal that the thicker slab crust has appreciable basement roughness extending ~ 60 km from the eastern margin of the Kyushu-Palau ridge beneath the western Shikoku basin. We suggest that such a thicker and rugged slab crust, together with the main body of the Kyushu-Palau ridge, can cause significant fracture zones in the overriding plate, decrease the interplate coupling and produce preferable conditions for shallow slow earthquakes to occur when subducted. The results may also provide structural constraints on the western limit of future megathrust earthquakes in the Nankai Trough. Graphical Abstract

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Link between the Nankai underthrust turbidites and shallow slow earthquakes

Cited by 3 publications

References 42 publications

Accretion versus erosion and sediment transfer balance near the subduction interface

Accretion versus erosion and sediment transfer balance near the subduction interface

A review of shallow slow earthquakes along the Nankai Trough

Thick slab crust with rough basement weakens interplate coupling in the western Nankai Trough

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