Changes in seismicity before and after the 2011 Tohoku earthquake around its southern limit revealed by dense ocean bottom seismic array data

Nakatani, Yoshihito; Mochizuki, Kimihiro; Shinohara, Masanao; Yamada, Tomoaki; Hino, Ryota; Ito, Yoshihiro; Murai, Yoshio; Sato, Toshinori

doi:10.1002/2015gl063140

Cited by 13 publications

(21 citation statements)

References 25 publications

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“…The transition from suppressed areas off Miyagi Prefecture to activated areas probably represents the extent of the coseismic slip. This has been discussed in previous studies using focal mechanisms [ Kato and Igarashi , ] (green line in Figure a) and seismicity from OBS observations [ Nakatani et al , ]. The narrow suppressed areas (blue) connect the large slip area off Miyagi Prefecture and the largest ( M 7.6) aftershock that occurred 29 min after the Tohoku‐oki earthquake [ Kubo et al , ] (black contour).…”

Section: Discussionmentioning

confidence: 57%

“…Journal of Geophysical Research: Solid Earth 10.1002/2015JB012584 mechanisms (green line in Figure 9a) and seismicity from OBS observations [Nakatani et al, 2015]. The narrow suppressed areas (blue) connect the large slip area off Miyagi Prefecture and the largest (M7.6) aftershock that occurred 29 min after the Tohoku-oki earthquake [Kubo et al, 2013] (black contour).…”

Section: Journal Of Geophysicalmentioning

confidence: 98%

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Spatial distribution of the faulting types of small earthquakes around the 2011 Tohoku‐oki earthquake: A comprehensive search using template events

2016

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We developed a new method to classify the faulting types of small earthquakes using interevent waveform similarity and applied it to earthquakes in the northeast Japan subduction zone. In the method, we used separate time windows for P and S waves and established a relationship between waveform similarity and differences in focal mechanisms from event pairs whose focal mechanisms we know. Then we applied the relationship to many pairs of such focal‐mechanism‐known events (5607 from the moment tensor catalogue and 3623 events from the interplate repeating earthquakes catalogue) and focal‐mechanism‐unknown events for the period from 1984 to 2013. As a result, 8984 earthquakes were newly classified into interplate (N = 5401), noninterplate thrust (N = 631), normal (N = 1070), and strike‐slip faulting earthquakes (N = 165). From the new data set, which doubles the number of mechanism types, we confirmed that there have been almost no interplate earthquakes in the area of large coseismic slip of the Tohoku‐oki earthquake since that event. We also saw that this trend continued until at least the end of 2013, suggesting a nearly complete stress release and slow interplate stress recovery. The abundant interplate aftershocks also indicate the precise spatial extent of postsesimic slip, which is usually difficult to obtain from land‐based geodetic data. The postseismic slip also suggests stress concentration at the asperities of the 1968 Tokachi‐oki (M7.9) and 1994 Sanriku‐oki (M7.6) earthquakes. The present‐day faulting types offshore Tohoku correlated well with the static‐stress change from the Tohoku‐oki earthquake, suggesting a stress state change during the earthquake cycle of megathrust earthquakes.

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Section: Discussionmentioning

confidence: 57%

Section: Journal Of Geophysicalmentioning

confidence: 98%

Spatial distribution of the faulting types of small earthquakes around the 2011 Tohoku‐oki earthquake: A comprehensive search using template events

2016

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“…A number of studies have suggested that subducting basement relief strongly affects megathrust stress state and slip behavior (Das & Watts, 2009; Lallemand et al, 2018; van Rijsingen et al, 2018; Wang & Bilek, 2011, 2014), the rupture dynamics of subduction earthquakes (Kodaira et al, 2000; Lay, 2015; Nakatani et al, 2015; Ye et al, 2016, 2018), and long‐term margin evolution and mass transport as governed by subduction erosion and accretion (Bassett & Watts, 2015; Kopp, 2013; von Huene et al, 2004; von Huene & Scholl, 1991). The overall conceptual picture is one of a structurally disrupted upper plate, a highly heterogeneous stress state, pervasive shearing and fracturing promoted by the irregular geometry, and spatially complex patterns of basal erosion and material underplating.…”

Section: Discussionmentioning

confidence: 99%

Coupled Evolution of Deformation, Pore Fluid Pressure, and Fluid Flow in Shallow Subduction Forearcs

2020

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Deformation and fluid flow in subduction zone forearcs are dynamically coupled, but our quantitative understanding of their coupling is incomplete. In this work, we investigate the hydrological and mechanical coupling in shallow forearcs, using a Lagrangian‐Eulerian finite element model that incorporates constitutive and transport properties of sediments and faults constrained by laboratory and field measurements. Wide‐ranging observations show that sediment thickness and composition, plate convergence rate, basement strength and roughness, and subducting slab dip angle vary between subduction zones. We therefore systematically study their effects on forearc stress and pore fluid pressure states, consolidation and dewatering patterns, and margin morphology. Our models, with the incorporation of a simple description of permeability enhancement along fault damage zones, yield a range of fault permeability (10−13–10−17 m2) consistent with previous estimates and describe the important role of upper plate splay faults in causing heterogeneous dewatering and consolidation patterns and in modulating effective normal stress on the plate interface. Spatial variations in tectonic loading and sediment consolidation can also be caused by subducting basement roughness such as a horst‐and‐graben structure. For typically observed relief and spacing, our models predict locally enhanced porosity reduction by up to 50% at the downdip edge of the horsts and anomalously high sediment porosity above the geometrical highs. At the margin scale, our results demonstrate that sediment permeability and thickness are dominant controls on fluid overpressure, sediment compaction, and megathrust strength. Rough and frictionally strong megathrusts produce similar effects in driving high wedge tapers.

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“…3). Nakatani et al 19 further discovered additional aftershock activity in area Z in Fig. 3 through ocean-bottom seismic array observation.…”

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confidence: 97%

Relationship of preseismic, coseismic, and postseismic fault ruptures of two large interplate aftershocks of the 2011 Tohoku earthquake with slow-earthquake activity

Kubo

Nishikawa

2020

Sci Rep

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to improve our understanding of the interactions between regular and slow earthquakes along the Japan trench, we investigated the spatial relationship of slow-earthquake activity with the preseismic, coseismic, and postseismic fault ruptures of interplate earthquakes off the Iwate and Ibaraki coasts, Japan, including two large interplate aftershocks of the 2011 Tohoku earthquake: the 2011 off Iwate earthquake (M JMA 7.4) and the 2011 off Ibaraki earthquake (M JMA 7.6). We found that the coseismic ruptures of these earthquakes did not overlap with the active areas of slow earthquakes, while their foreshocks and aftershocks occurred in slow-earthquake-prone areas. Moreover, the 2011 off Iwate earthquake and the previous M7-class events shared common fault rupture characteristics: coseismic rupture occurred in a common asperity area, and afterslip with many aftershocks was triggered in the active area of slow earthquakes. Off the Ibaraki coast, tremor activity on a subducting seamount located updip of the coseismic rupture of the 2011 off Ibaraki earthquake implies that the seamount acted as a soft barrier to the coseismic rupture of the 2011 off Ibaraki earthquake. This study demonstrates that large earthquakes off the Iwate and Ibaraki coasts feature similar rupture behaviors, spatially complementary distributions of coseismic ruptures with slow-earthquake activity and foreshock and aftershock activities within and around slow-earthquake-prone areas. This information is useful in considering future large earthquakes along the Japan Trench. Over the past few decades, a considerable number of studies have been carried out on "slow earthquakes", such as tectonic tremors, very-low-frequency earthquakes (VLFs), and slow slip events (SSEs) 1-5. These studies have shown that slow earthquakes frequently occur in regions neighboring megathrust seismogenic zone and sometimes trigger large interplate earthquakes. Therefore, the investigation of slow-earthquake activity can provide insight into the earthquake-rupture mechanism in subduction zones. To improve our understanding of the interactions between regular and slow earthquakes in subduction zones, it is important to investigate the relationship between the fault ruptures of large interplate earthquakes and the slow-earthquake activity. Nishikawa et al. 5 revealed the comprehensive spatial distribution of slow earthquakes along the Japan Trench and compared the resulting distribution with the coseismic rupture extents of the 2011 Tohoku earthquake and large interplate earthquakes that occurred before the 2011 Tohoku earthquake. The authors concluded that slow-earthquake activity spatially complements the coseismic ruptures of large interplate earthquakes and discussed the variation in fault slip behavior along the Japan Trench based on the regional characteristics of slow-earthquake activity. To expand our understanding of the variation in fault slip behavior along the Japan Trench, we probe the relationship between the preseismic, coseismic, and postseismic fault rupture...

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Changes in seismicity before and after the 2011 Tohoku earthquake around its southern limit revealed by dense ocean bottom seismic array data

Cited by 13 publications

References 25 publications

Spatial distribution of the faulting types of small earthquakes around the 2011 Tohoku‐oki earthquake: A comprehensive search using template events

Spatial distribution of the faulting types of small earthquakes around the 2011 Tohoku‐oki earthquake: A comprehensive search using template events

Coupled Evolution of Deformation, Pore Fluid Pressure, and Fluid Flow in Shallow Subduction Forearcs

Relationship of preseismic, coseismic, and postseismic fault ruptures of two large interplate aftershocks of the 2011 Tohoku earthquake with slow-earthquake activity

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