Construction of the DONET real-time seafloor observatory for earthquakes and tsunami monitoring

Kawaguchi, Katsuyoshi; Kaneko, Sho; Nishida, T.; Komine, T

doi:10.1007/978-3-642-11374-1_10

Cited by 136 publications

(67 citation statements)

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“…Recent advances in ocean bottom and borehole instruments, especially permanent ocean bottom network DONET (Dense Oceanfloor Network System for Earthquakes and Tsunamis; gray diamonds in Figure 1; Kaneda et al, 2015;Kawaguchi et al, 2015), have precisely constrained not only SVLFEs (e.g., Nakano et al, 2018;Sugioka et al, 2012;Toh et al, 2018) but also shallow LFTs (Annoura et al, 2017;Yabe et al, 2019) and SSEs (purple dashed line in Figure 1; Araki et al, 2017). Epicenters of SVLFEs using DONET (Nakano et al, 2018) are concentrated beneath the accretionary prism toe (blue filled circles in Figure 1).…”

Section: Research Lettermentioning

confidence: 99%

Structural Characteristics of the Nankai Trough Shallow Plate Boundary Inferred From Shallow Very Low Frequency Earthquakes

Takemura

Matsuzawa

Noda

et al. 2019

Geophysical Research Letters

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The spatial distributions of shallow slow earthquakes are related to stress accumulation and structural characteristics of the shallow plate boundary, which are important for understanding megathrust earthquakes. To investigate spatiotemporal variation of shallow very low frequency earthquake (SVLFE) activity along the Nankai Trough, we conducted centroid moment tensor inversion method incorporating effects of offshore heterogeneous structures. By applying centroid moment tensor method into long‐term onshore seismograms, we obtained spatiotemporal variation of SVLFE activity occurred from June 2003 to May 2018. We find that SVLFE activities are related to the spatial variations of the slip‐deficit rate and pore fluid around the Philippine Sea plate boundary. SVLFEs are effectively activated by mechanical weakening due to rich pore fluid in areas surrounding strongly locked zones. Our results imply that spatial variations of long‐term SVLFE activity provide information on tectonic environments, which could constrain the rupture behavior of shallow plate boundaries during future megathrust earthquakes.

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Section: Research Lettermentioning

confidence: 99%

Structural Characteristics of the Nankai Trough Shallow Plate Boundary Inferred From Shallow Very Low Frequency Earthquakes

Takemura

Matsuzawa

Noda

et al. 2019

Geophysical Research Letters

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“…We used ocean‐floor observation data from off the Kii Peninsula obtained by temporarily deployed broadband ocean‐bottom seismometers (BBOBSs; Sugioka et al, ) and by the permanent Dense Oceanfloor Network System for Earthquakes and Tsunamis (DONET1; Kaneda et al, ; Kawaguchi et al, ; Figure ). VLFE activity was observed in this region in 2009, 2015, and 2016 (Nakano et al, , ; Sugioka et al, ), and tremor activity was detected in 2018.…”

Section: Datamentioning

confidence: 99%

Event Size Distribution of Shallow Tectonic Tremor in the Nankai Trough

Yabe

Sugioka

Shinohara

et al. 2019

Geophysical Research Letters

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Slow earthquake size distributions have been found to follow either a power law or an exponential law, depending on the data set. We investigated the size distribution of shallow tectonic tremor events along the Nankai trough, southwestern Japan, observed in 2009, 2015, 2016, and 2018 and estimated the seismic energy radiated during the events as a measure of event size. The obtained size distributions mostly followed a power law with a b value of about 1, but an exponential law also fits well the data of the largest events; this result indicates that the size distribution follows the Gutenberg‐Richter law with an exponential taper. If only the largest events were observed, an exponential size distribution would be obtained. This exponential taper could be attributed to a source fault limitation. Because the maximum event size differed among activity periods, the source fault size varied among them, although the source areas largely overlap.

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“…The recent development of a permanent seafloor observation network called the Dense Oceanfloor Network System for Earthquakes and Tsunamis (DONET) ( Fig. 1 and Additional file 1: Figure S1) has facilitated continuous monitoring of offshore seismic activities Kawaguchi et al 2015). These observations revealed that, in recent years, earthquake activities along the Nankai Trough have mostly occurred in the oceanic crust or upper mantle of the subducting PSP (Obana et al 2004Obana and Kodaira 2009;Mochizuki et al 2010;Akuhara et al 2013;Nakano et al 2013Nakano et al , 2014Nakano et al , 2015Akuhara and Mochizuki 2014).…”

Section: Introductionmentioning

confidence: 99%

The 2016 Mw 5.9 earthquake off the southeastern coast of Mie Prefecture as an indicator of preparatory processes of the next Nankai Trough megathrust earthquake

Hyodo

Nakanishi

Yamashita

et al. 2018

Prog Earth Planet Sci

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Megathrust earthquakes have occurred repeatedly at intervals of 100 to 150 years along the Nankai Trough, situated in the southwest of Japan. Given that it has been 70 years since the last event, the occurrence of the next devastating earthquake is anticipated in the near future. On April 1, 2016, a moderate earthquake (M w 5.9, M JMA 6.5) occurred off the southeastern coast of Mie Prefecture in the source region of the 1944 Tonankai earthquake (M w 8.2). In this study, we investigated the influence of the 2016 earthquake on future megathrust earthquakes. We first determined the hypocenter distributions using a precise velocity structure obtained from seismic surveys in the source region. Using data obtained from the DONET ocean-bottom observation network, we found that this earthquake occurred along the plate boundary fault, which is also believed to have slipped during past megathrust earthquakes. We then performed a preliminary numerical simulation to reproduce the occurrence of a moderate earthquake in the middle of a megathrust earthquake cycle. We used a hierarchical asperity model, in which smaller asperities causing moderate earthquakes are embedded in a hyper-asperity that serves as the source region of megathrust earthquakes. The simulation shows that moderate earthquakes, caused by ruptures of a smaller asperity, occur as a result of shrinkage of strongly coupled areas in the hyper-asperity. This result is consistent with the observation that the hypocenter of the 2016 earthquake was located at the edge of a strongly coupled region along the plate boundary. The simulation also reproduced postseismic slip (afterslip/slow slip) along the plate boundary updip of the hyper-asperity, which is consistent with the observations of slow slip events and very-low-frequency earthquakes after the 2016 earthquake. Thus, the occurrence of the moderate earthquake offshore southeastern Mie Prefecture in the middle of the megathrust earthquake cycle implies that the shrinkage of the strongly coupled area along the plate boundary is occurring as a preparatory process for the next megathrust earthquake in the region.

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Construction of the DONET real-time seafloor observatory for earthquakes and tsunami monitoring

Cited by 136 publications

References 0 publications

Structural Characteristics of the Nankai Trough Shallow Plate Boundary Inferred From Shallow Very Low Frequency Earthquakes

Structural Characteristics of the Nankai Trough Shallow Plate Boundary Inferred From Shallow Very Low Frequency Earthquakes

Event Size Distribution of Shallow Tectonic Tremor in the Nankai Trough

The 2016 Mw 5.9 earthquake off the southeastern coast of Mie Prefecture as an indicator of preparatory processes of the next Nankai Trough megathrust earthquake

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