Potential of megathrust earthquakes along the southern Ryukyu Trench inferred from GNSS data

Kano, Masayuki; Ikeuchi, Aoi; Nishimura, Takuya; Miyazaki, Shuichi; Matsushima, Takeshi

doi:10.1186/s40623-021-01531-z

Cited by 3 publications

(3 citation statements)

References 46 publications

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“…However, based on available literature, large and great magnitude megathrust ruptures with recurrence intervals beyond that of the study time period are possible and remain a seismic and tsunami hazard, particularly in the Manila trench, which exhibits similarities to the far more presently active Sunda-Java trench in neighboring Indonesia (Figures 1,6,7,and 11; Table 4). The potential for a megathrust earthquake on the southern Ryukyu trench has been estimated by Kano et al (2021) from GNSS data. A slip deficit of about 30 mm/yr is estimated at depths of 20-25 km.…”

Section: Discussionmentioning

confidence: 99%

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Seismotectonics of the Philippine and Taiwan Subduction Systems and Implications for Seismic Hazards

Hutchings,

Mooney

2024

Geochem Geophys Geosyst

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The seismicity of the Philippines and Taiwan provides insight into the tectonics and seismic hazards of a region characterized by subduction and collision. We summarize the seismotectonics of the Philippines and Taiwan by documenting the distribution of hypocenters for earthquakes of magnitude M ≥ 4.6 and focal mechanisms for earthquakes of magnitude M ≥ 5.0 over ∼21 years. We quantify seismicity rates (earthquake frequency) and compare seismicity distributions with proposed tectonic and faulting models. 6,187 earthquakes of magnitude M ≥ 4.6 occurred between 1 January 2000 and 31 March 2021, 79% at depths <70 km and 70% having magnitudes M < 5.0. Approximately 88 earthquakes of magnitude M ≥ 5.0 occur per year, with 12 events of magnitude M ≥ 7.0 occurring since January 2000. Seismic activity decreases exponentially between 50 and 210 km depth at a rate ∼10% faster than the global average. Intermediate and deep earthquakes at depths >70 km trace the Wadati‐Benioff zones of subducting slabs, most of which are only seismically active to depths of ∼250 km. The distribution of earthquakes at depths >70 km is likely influenced by the subduction of young lithosphere, slab tearing, and phase boundary interactions between depths of 410 and 660 km. Shallow earthquakes at depths ≤70 km are generated by megathrust, crustal, and intraslab faulting. Crustal thrust and strike‐slip faulting are the most abundant and prevalent sources of damaging earthquakes. The Philippines and Taiwan are subject to high seismic risk, similar to nearby Indonesia.

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Section: Discussionmentioning

confidence: 99%

“…The potential for a megathrust earthquake on the southern Ryukyu trench has been estimated by Kano et al. (2021) from GNSS data. A slip deficit of about 30 mm/yr is estimated at depths of 20–25 km.…”

Section: Discussionmentioning

confidence: 99%

Seismotectonics of the Philippine and Taiwan Subduction Systems and Implications for Seismic Hazards

Hutchings,

Mooney

2024

Geochem Geophys Geosyst

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“…In conflict with the inference of a weakly Ando et al (2012) suggested the strong likelihood of a coupled portion in the Ryukyu subduction zone (by very low-frequency earthquake observations); Hsu et al (2012) considered that the plate interface could be fully locked in the southern Ryukyu subduction zone (using GPS data); Hsu et al (2013) proposed that a strong plate coupling condition due to the subducted Luzon-Okinawa fracture zone (LOFZ) could resist subduction; Tadokoro et al (2018) proposed a strongly coupled state in the central portion (seafloor crustal deformation measurement results). Kano et al (2021) proposed that Mw of 7.5 or larger earthquakes could occur in the southern Ryukyu Trench (from GNSS data analyzing). In brief, the strength of plate coupling and the potential for large earthquake occurrence in the Ryukyu subduction zone are still controversial.…”

Section: Introductionmentioning

confidence: 99%

Variations in the crustal structure and strength of plate coupling along the Ryukyu subduction zone

Doo,

Lo,

Huang

et al. 2023

Geosci. Lett.

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The Ryukyu trench-arc-back arc system is part of the subduction margins of the Philippine Sea plate. Previous studies have indicated that several geophysical and geological characteristics reveal significant variations (including convergent rate, topography, subducting slab angle etc.) along this subduction system. In addition, the strength of plate coupling and the potential of large earthquake occurrence in the Ryukyu subduction zone have been major subjects of debate for decades. To gain new insights into the spatial variations in the crustal structure and strength of plate coupling along the Ryukyu subduction zone, in the present study, based on three P-wave seismic velocity profiles, we construct density models for 2-D gravity modeling. Then, we estimate the mantle lithosphere buoyancy (Hm) using these three density models to determine the strength of plate coupling between the subducting Philippine Sea plate and the overriding Eurasian plate, which could provide information for evaluating large earthquakes potential. 2-D gravity modeling results reveal that oceanic plateaus and/or submarine ridges with obviously less dense and thick oceanic crust are subducting in the northern and central parts of the Ryukyu Trench, which could increase the slab buoyancy in these regions. The Hm results indicate that the strength of plate coupling is almost weak in the north and is relatively strong in the central Ryukyu subduction zone.

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New source model for the 1771 Meiwa tsunami along the southern Ryukyu Trench inferred from high-resolution tsunami calculation

Nakata,

Goto,

Yanagisawa

2024

Prog Earth Planet Sci

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The 1771 Meiwa tsunami which struck the southern Ryukyu Islands (Sakishima Islands) had greater than 22 m run-up height, leaving about 12,000 casualties in its wake. At many places, the tsunami inundation or lack of inundation is well recorded in historical documents. Several tsunami source models have been proposed for this event using historical records as constraints of tsunami calculations. Nevertheless, the source model remains under discussion. This study re-evaluated the tsunami wave source model of the 1771 Meiwa tsunami using high-resolution (10 m mesh) bathymetric and topographical data for tsunami calculation, the latest historical record dataset, and seismological knowledge. Results demonstrated that a tsunami earthquake along the southern Ryukyu Trench was the likely cause of the 1771 event. However, it is noteworthy that assumption of a large slip with 30 m is necessary for a shallow and narrow region (fault depth = 5 km, fault width = 30 km, Mw = 8.49) of the plate boundary in the Ryukyu Trench, which is far larger than previously thought. This requirement of very large initial water level change at the source might involve not only the fault rupture along the plate boundary but also deformation by splay faults, inelastic deformation of unconsolidated sediments near the trench axis, and/or giant submarine landslides. Results also show that the effects of fault parameters on the run-up were quite different depending on the offshore coral reef width. This phenomenon strongly constrained the fault width to 30 km. Our tsunami ray tracing analysis further revealed the effects of bathymetry on tsunami propagation. It is noteworthy that meter-long huge tsunami boulders tend to be distributed along the specific coasts at which the tsunami was concentrated by bathymetric effects. This finding suggests that past tsunamis, including the 1771 event, might have affected the specific coral reefs on Sakishima Islands repeatedly, which is crucially important for understanding the heterogeneous distribution of tsunami boulders. This feature might also be useful to elucidate the effects of large tsunamis on the corals and reefs because a direct comparison of coral reefs that are damaged and not damaged by tsunami waves is testable in narrow areas in the case of the Sakishima Islands.

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Potential of megathrust earthquakes along the southern Ryukyu Trench inferred from GNSS data

Cited by 3 publications

References 46 publications

Seismotectonics of the Philippine and Taiwan Subduction Systems and Implications for Seismic Hazards

Seismotectonics of the Philippine and Taiwan Subduction Systems and Implications for Seismic Hazards

Variations in the crustal structure and strength of plate coupling along the Ryukyu subduction zone

New source model for the 1771 Meiwa tsunami along the southern Ryukyu Trench inferred from high-resolution tsunami calculation

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