Browse
Submit Data
Databases
API
Help

Dataset Information

42 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Episodic tremor and slip silently invades strongly locked megathrust in the Nankai Trough.

ABSTRACT: Recent seismic and geodetic observations in subduction zones have revealed that slow earthquakes have preceded some large earthquakes. Characterization of slow earthquakes and their relation to large earthquakes provides important clues to constrain a wide spectrum of slip rates on tectonic faults. Here, we report new evidence of a slow slip transient at the downdip edge of the strongly locked seismogenic zone in the western Nankai Trough in southwest Japan. This slow slip transient was excited during an episodic tremor and slip at the downdip extension of the locked zone. Through this triggering, the frequent occurrence of the deep episodic tremor and slip invades the strongly locked megathrust zone and may intermittently increase the probability of large earthquakes in the Nankai Trough.

SUBMITTER: Kano M

PROVIDER: S-EPMC6592932 | biostudies-literature | 2019 Jun

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Episodic tremor and slip silently invades strongly locked megathrust in the Nankai Trough.

Kano Masayuki M Kato Aitaro A Obara Kazushige K

Scientific reports 20190625 1

Recent seismic and geodetic observations in subduction zones have revealed that slow earthquakes have preceded some large earthquakes. Characterization of slow earthquakes and their relation to large earthquakes provides important clues to constrain a wide spectrum of slip rates on tectonic faults. Here, we report new evidence of a slow slip transient at the downdip edge of the strongly locked seismogenic zone in the western Nankai Trough in southwest Japan. This slow slip transient was excited ...[more]

PMID: 31239525

Similar Datasets

Seismic evidence for megathrust fault-valve behavior during episodic tremor and slip.

Project description:Fault slip behavior during episodic tremor and slow slip (ETS) events, which occur at the deep extension of subduction zone megathrust faults, is believed to be related to cyclic fluid processes that necessitate fluctuations in pore-fluid pressures. In most subduction zones, a layer of anomalously low seismic wave velocities [low-velocity layer (LVL)] is observed in the vicinity of ETS and suggests high pore-fluid pressures that weaken the megathrust. Using repeated seismic scattering observations in the Cascadia subduction zone, we observe a change in the seismic velocity associated with the LVL after ETS events, which we interpret as a response to fluctuations in pore-fluid pressure. These results provide direct evidence of megathrust fault-valve processes during ETS.

| S-EPMC6976297 | biostudies-literature

Shallow slow slip events along the Nankai Trough detected by GNSS-A.

Project description:Various slow earthquakes (SEQs), including tremors, very low frequency events, and slow slip events (SSEs), occur along megathrust zones. In a shallow plate boundary region, although many SEQs have been observed along pan-Pacific subduction zones, SSEs with a duration on the order of a year or with a large slip have not yet been detected due to difficulty in offshore observation. We try to statistically detect transient seafloor crustal deformations from seafloor geodetic data obtained by the Global Navigation Satellite System-Acoustic (GNSS-A) combination technique, which enables monitoring the seafloor absolute position. Here, we report the first detection of signals probably caused by shallow large SSEs along the Nankai Trough and indicate the timings and approximate locations of probable SSEs. The results show the existence of large SSEs around the shallow side of strong coupling regions and indicate the spatiotemporal relationship with other SEQ activities expected in past studies.

| S-EPMC6962047 | biostudies-literature

Effects of episodic slow slip on seismicity and stress near a subduction-zone megathrust.

Project description:Slow slip phenomena deep in subduction zones reveal cyclic processes downdip of locked megathrusts. Here we analyze seismicity within a subducting oceanic slab, spanning ~50 major deep slow slip with tremor episodes over 17 years. Changes in rate, b-values, and stress orientations of in-slab seismicity are temporally associated with the episodes. Furthermore, although stress orientations in the slab below these slow slips may rotate slightly, in-slab orientations 20-50 km updip from there rotate farther, suggesting that previously-unrecognized transient slow slip occurs on the plate interface updip. We infer that fluid pressure propagates from slab to interface, promoting episodes of slow slip, which break mineral seals, allowing the pressure to propagate tens of km further updip along the interface where it promotes transient slow slips. The proposed methodology, based primarily on in-slab seismicity, may help monitor plate boundary conditions and slow slip phenomena, which can signal the beginning stages of megathrust earthquakes.

| S-EPMC8692312 | biostudies-literature

High probability of successive occurrence of Nankai megathrust earthquakes.

Project description:Great earthquakes along the Nankai megathrust in south-western Japan feature in the top priority list of Japan's disaster management agenda. In May 2019, an alert system was incepted to issue public warnings when the probability of an earthquake occurrence along the Nankai megathrust became higher than usual. One of the cases that trigger the issuance of public warnings is when a great earthquake occurred and another one of the same scale is anticipated within a short period of time. Although such "twin ruptures" have occurred multiple times along the Nankai megathrust, the quantification of the probability of such twin ruptures has never been attempted. Based on global statistics and local earthquake occurrence history, we estimated the probability of a successive occurrence of two M8 or larger earthquakes within 3 years globally and along the Nankai megathrust to be 5.0-18% and 4.3-96%, respectively. The timing of the second earthquake followed the Omori-Utsu law in global statistics, which allowed the estimation of the probability for the successive occurrence of Nankai megathrust earthquakes in arbitrary time frames. The predicted probability for the one-week timeframe was 100-3600-fold higher than that of the norm, endorsing the necessity for the warning scheme.

| S-EPMC9832165 | biostudies-literature

Do slow slip events trigger large and great megathrust earthquakes?

Project description:Slow slip events have been suggested to trigger subduction earthquakes. However, examples to date have been poorly recorded, occurring offshore, where data are sparse. Better understanding of slow slip events and their influence on subsequent earthquakes is critical for hazard forecasts. We analyze a well-recorded event beginning 6 months before the 2012 M w (moment magnitude) 7.6 earthquake in Costa Rica. The event migrates to the eventual megathrust rupture. Peak slip rate reached a maximum of 5 mm/day, 43 days before the earthquake, remaining high until the earthquake. However, changes in Mohr-Coulomb failure stress at the hypocenter were small (0.1 bar). Our data contradict models of earthquake nucleation that involve power law acceleration of slip and foreshocks. Slow slip events may prove useful for short-term earthquake forecasts.

| S-EPMC6209384 | biostudies-literature

Distribution of dehalogenation activity in subseafloor sediments of the Nankai Trough subduction zone.

Project description:Halogenated organic matter buried in marine subsurface sediment may serve as a source of electron acceptors for anaerobic respiration of subseafloor microbes. Detection of a diverse array of reductive dehalogenase-homologous (rdhA) genes suggests that subseafloor organohalide-respiring microbial communities may play significant ecological roles in the biogeochemical carbon and halogen cycle in the subseafloor biosphere. We report here the spatial distribution of dehalogenation activity in the Nankai Trough plate-subduction zone of the northwest Pacific off the Kii Peninsula of Japan. Incubation experiments with slurries of sediment collected at various depths and locations showed that degradation of several organohalides tested only occurred in the shallow sedimentary basin, down to 4.7 metres below the seafloor, despite detection of rdhA in the deeper sediments. We studied the phylogenetic diversity of the metabolically active microbes in positive enrichment cultures by extracting RNA, and found that Desulfuromonadales bacteria predominate. In addition, for the isolation of genes involved in the dehalogenation reaction, we performed a substrate-induced gene expression screening on DNA extracted from the enrichment cultures. Diverse DNA fragments were obtained and some of them showed best BLAST hit to known organohalide respirers such as Dehalococcoides, whereas no functionally known dehalogenation-related genes such as rdhA were found, indicating the need to improve the molecular approach to assess functional genes for organohalide respiration.

| S-EPMC3638456 | biostudies-literature

A b map implying the first eastern rupture of the Nankai Trough earthquakes.

Project description:The Nankai Trough megathrust earthquakes inflicted catastrophic damage on Japanese society and more widely. Most research is aimed at identifying strongly coupled regions that are considered as a major source of future disastrous earthquakes. Here we present a b-value map for the entire Nankai Trough zone. The b value, which represents the rate of occurrence of small earthquakes relative to larger ones, is inversely dependent on differential stresses, and has been used to detect highly stressed areas on fault planes in various tectonic situations. A remarkable finding is that the b value is inversely correlated with the slip-deficit rate (SDR). Moreover, the b value for the areas of high SDR in the eastern part is lower than that in the western part, indicating that differential stress on asperities in the eastern part is higher than that in the western part. This may explain the history of the Nankai Trough earthquakes, in which the eastern part tends to rupture first.

| S-EPMC5856758 | biostudies-literature

Tremor activity inhibited by well-drained conditions above a megathrust.

Project description:Tremor occurs on megathrusts under conditions of near-lithostatic pore-fluid pressures and extremely weakened shear strengths. Although metamorphic reactions in the slab liberate large amounts of fluids, the mechanism for enhancing pore-fluid pressures along the megathrust to near-lithostatic values remains poorly understood. Here we show anti-correlation between low-frequency earthquake (LFE) activity and properties that are markers of the degree of metamorphism above the megathrust, whereby LFEs occur beneath the unmetamorphosed overlying plate but are rare or limited below portions that are metamorphosed. The extent of metamorphism in the overlying plate is likely controlled by along-strike contrasts in permeability. Undrained conditions are required for pore-fluid pressures to be enhanced to near-lithostatic values and for shear strength to reduce sufficiently for LFE generation, whereas well-drained conditions reduce pore-fluid pressures at the megathrust and LFEs no longer occur at the somewhat strengthened megathrust. Our observations suggest that undrained conditions are a key factor for the genesis of LFEs.

| S-EPMC5187422 | biostudies-literature

Strength of tremor patches along deep transition zone of a megathrust.

Project description:Deep low frequency tremors are indicators of slow slip transients in the brittle-ductile transition zone along subducting plates. Investigation of comprehensive tremor activities is therefore an important issue for understanding the seismic/aseismic characteristics in transition zones. Here, we focus on the radiated energy from tremors to reveal the along-strike heterogeneity in the strength of tremor patches. Based on a tremor catalog that more accurately evaluates radiated energy, we examine the spatio-temporal activity of tremors accompanied by slow slip events (SSEs) in western Shikoku, southwestern Japan. The new finding of this study is that the energy radiated from tremors is positively correlated with the speed of tremor migration front and the slip rate along the plate interface during a SSE. This can be qualitatively explained by a stress diffusion model, which consists of along-strike heterogeneities in the effective strength of tremor patches embedded in a ductile shear zone. This effective strength heterogeneity is supported by a lateral variation in the stress drop of a SSE; it is consistent with the fluid pressure distribution along the plate boundary fault and the tidal sensitivity of tremors. Accurate evaluation of tremor activities, especially the radiated energy, can be used to infer the spatial distribution of the strength of tremor patches in transition zones worldwide.

| S-EPMC5826920 | biostudies-literature

Shallow very-low-frequency earthquakes accompany slow slip events in the Nankai subduction zone.

Project description:Recent studies of slow earthquakes along plate boundaries have shown that tectonic tremor, low-frequency earthquakes, very-low-frequency events (VLFEs), and slow-slip events (SSEs) often accompany each other and appear to share common source faults. However, the source processes of slow events occurring in the shallow part of plate boundaries are not well known because seismic observations have been limited to land-based stations, which offer poor resolution beneath offshore plate boundaries. Here we use data obtained from seafloor observation networks in the Nankai trough, southwest of Japan, to investigate shallow VLFEs in detail. Coincident with the VLFE activity, signals indicative of shallow SSEs were detected by geodetic observations at seafloor borehole observatories in the same region. We find that the shallow VLFEs and SSEs share common source regions and almost identical time histories of moment release. We conclude that these slow events arise from the same fault slip and that VLFEs represent relatively high-frequency fluctuations of slip during SSEs.

| S-EPMC5852141 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data