Spatiotemporal Distribution of Shallow Tremors Along the Nankai Trough, Southwest Japan, as Determined From Waveform Amplitudes and Cross‐Correlations

Tamaribuchi, Koji; Ogiso, Masashi; Noda, Akemi

doi:10.1029/2022jb024403

Cited by 20 publications

(44 citation statements)

References 62 publications

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“…Annotation: KP=Kii Peninsula; CM = Cape Muroto; CA = Cape Ashizuri. (Baba & Cummins, 2005); and the down-dip extent of tremor epicenters (Araki et al, 2017;Tamaribuchi et al, 2022;Yamashita et al, 2015) and clusters of very-low frequency earthquakes (Nakano et al, 2018) Along-strike variations in the width of the outer-wedge are also apparent in our model from cross-sections (Figures 8 and 9) and in map view (Figure 11). To obtain regional 3D constraints on the geometry of the backstop, we calculate the thickness of crustal material (V P ≥ 5 km/s) overlying the megathrust (Figure 12a).…”

Section: Model Implications For Shallow Megathrust Slip Behavior At N...mentioning

confidence: 54%

“…Color and contours show the thickness of crustal rocks ( V P ≥ 5 km/s) overlying the megathrust and the up‐dip extent of the crustal backstop (orange dashed line). Colored squares show the backstop broadly coincides with the up‐dip extent of co‐seismic slip in great earthquakes in 1944 and 1946 (Baba & Cummins, 2005); and the down‐dip extent of tremor epicenters (Araki et al., 2017; Tamaribuchi et al., 2022; Yamashita et al., 2015) and clusters of very‐low frequency earthquakes (Nakano et al., 2018) linked to slow‐slip events beneath the outer‐forearc. (b) Residual bathymetry.…”

Section: Discussionmentioning

confidence: 99%

“…Large and Great earthquakes are focused beneath the backstop, and along‐strike variability in the up‐dip extent of co‐seismic slip broadly follows the backstop geometry (Nakanishi, Kodaira, et al., 2002). Slow earthquake phenomena accommodate strain beneath the outer‐forearc (Araki et al., 2017; Nakano et al., 2018; Tamaribuchi et al., 2022; Yamashita et al., 2015) and along‐strike variability in their down‐dip extent is similarly broadly correlated with the position of the backstop. These relationships support existing hypotheses linking the structure of the overthrusting plate with the up‐dip transition from seismic to aseismic slip (e.g., Byrne et al., 1988; Byrne et al., 1993), and suggest they may be applicable at Nankai Trough (Nakanishi, Kodaira, et al., 2002).…”

Section: Discussionmentioning

confidence: 99%

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Crustal Structure of the Nankai Subduction Zone Revealed by Two Decades of Onshore‐Offshore and Ocean‐Bottom Seismic Data: Implications for the Dimensions and Slip Behavior of the Seismogenic Zone

et al. 2022

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Two‐decades of onshore‐offshore, ocean‐bottom seismometer, and passive‐source data are integrated to obtain high‐resolution 3‐D constraints on the architecture of the Nankai subduction zone. Our model reveals large along‐strike variability in the width of the outer‐forearc, with the crustal backstop (VP ≥ 5 km/s) extending within 50 km of Nankai Trough offshore Tokai and Kii Peninsula, but is a factor of 2 further landward (90–115 km) offshore Cape Muroto and Kyushu. The crustal backstop broadly coincides with the down‐dip extent of shallow slow‐earthquakes and the up‐dip extent of co‐seismic slip and geodetic locking, suggesting a link with the shallow frictional transition. In the inner‐forearc, high seismic‐velocities (VP > 6.6 km/s) in Kii Peninsula reflect Miocene plutons, impacting the nucleation and segmentation of large megathrust earthquakes. The complex geometry of the subducting slab drives spatial variability in the location of the down‐dip frictional transition. Variability in the width of the outer‐forearc, the dip of the subducting slab, and the depth distribution of deep slow‐slip events combine to produce large changes in the width of the seismogenic zone. This is most pronounced across Bungo channel, where the seismogenic zone narrows from 90 to 120 km in Shikoku to <60 km offshore Kyushu. Pinching of the seismogenic zone may explain the smaller area, and thus magnitude, of earthquakes offshore Kyushu and the reduction in slip‐deficit rate. Our results suggest crustal‐scale architecture is a key driver of profound along‐strike transitions in the location of frictional transition zones, and the width and slip behavior of the intervening seismogenic zone at Nankai Trough.

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Section: Model Implications For Shallow Megathrust Slip Behavior At N...mentioning

confidence: 54%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Crustal Structure of the Nankai Subduction Zone Revealed by Two Decades of Onshore‐Offshore and Ocean‐Bottom Seismic Data: Implications for the Dimensions and Slip Behavior of the Seismogenic Zone

et al. 2022

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“…The DONET data and F-net waveforms used in this work are available via the website of the National Research Institute for Earth Science and Disaster Resilience, Japan (at the following URL: http://www.hinet.bosai.go.jp/). The LFEs catalogue are attributed to Tamaribuchi, et al 33 . The VLFs catalogue are attributed to Takemura, et al 34 .…”

Section: Data Availabilitymentioning

confidence: 99%

A comprehensive dynamic source model of shallow very low-frequency earthquakes

Wei

Liu

et al. 2023

Preprint

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Very low-frequency earthquakes, which exhibit longer source durations and smaller stress drops than regular earthquakes of similar magnitude, possess abundant low-frequency energy but are depleted in high-frequency energy. The source processes that govern the occurrence of very low-frequency earthquakes remain unclear. Here, we implement a unified dynamic source model to illustrate the source characteristics of very low-frequency earthquakes. By comparing the source parameters of observed shallow very low-frequency earthquakes with those of numerically simulated ruptures, we conclude that very low-frequency earthquakes are slow self-arresting earthquakes that self-terminate within the nucleation patch. In addition, a composite slow self-arresting model is adopted to reproduce the source processes of VLF and LFE in Nankai area. Comparison of synthetic seismograms obtained from the composite model with the Nankai VLFs shows that slow self-arresting ruptures have the potential to explain different types of slow earthquakes. Our results indicate that very low-frequency earthquakes, low-frequency earthquakes and regular earthquakes can be explained uniformly in the same dynamic rupture phase diagram.

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“…DONET also allowed us to investigate the activity of shallow tremors in the high-frequency (2-8 Hz) band (e.g., Annoura ), we roughly estimated the moment rates from the energy rates of the shallow tremors (Tamaribuchi et al 2022). The scaled energy is the ratio of the tremor energy and the synchronized VLFE seismic moment.…”

Section: The Catalogs Of Shallowmentioning

confidence: 99%

Detectability analysis of very low frequency earthquakes: Methods and application in Nankai using F-net and DONET broadband seismometers

Takemura

Baba

Yabe

et al. 2022

Preprint

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For a more quantitative discussion of slow earthquake activity, we evaluated the detectable limits of very low frequency earthquakes (VLFEs), which are seismic slow earthquakes observed in very low frequency (< 0.05 Hz) bands, in the Nankai subduction zone. We performed numerical simulations using a local three-dimensional model and used the observed noise level of permanent broadband seismometers. First, we investigated the effects of the source-time functions on the maximum amplitudes of the VLFE signals at a certain station. The maximum amplitudes of the VLFE signals were controlled by the VLFE moment rate. The detectable limit of VLFEs at each source location can be defined as the lowest moment rate of detectable VLFEs, which radiate signals larger than the noise levels of any component at ≥ 3 stations. For inland seismometers only, the detectable limits of VLFEs at deep (30–40 km) and shallow (≤ 10 km) depths were 1012.5–1012.8 and 1013.2 Nm/s, respectively. Due to the geometrical spreading of VLFE signals and large noise levels in horizontal components, offshore seismometers improved the detectability of shallow VLFEs in regions where seismometers were densely deployed. Based on our detectability and published catalogs, shallow slow earthquakes are less active south-southwest off the Kii Peninsula, where geodetic studies expect mechanical coupling.

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Spatiotemporal Distribution of Shallow Tremors Along the Nankai Trough, Southwest Japan, as Determined From Waveform Amplitudes and Cross‐Correlations

Cited by 20 publications

References 62 publications

Crustal Structure of the Nankai Subduction Zone Revealed by Two Decades of Onshore‐Offshore and Ocean‐Bottom Seismic Data: Implications for the Dimensions and Slip Behavior of the Seismogenic Zone

Crustal Structure of the Nankai Subduction Zone Revealed by Two Decades of Onshore‐Offshore and Ocean‐Bottom Seismic Data: Implications for the Dimensions and Slip Behavior of the Seismogenic Zone

A comprehensive dynamic source model of shallow very low-frequency earthquakes

Detectability analysis of very low frequency earthquakes: Methods and application in Nankai using F-net and DONET broadband seismometers

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