Earthquake and Tsunami Scenarios as Basic Information to Prepare Next Nankai Megathrust Earthquakes

2017 ◽  
Vol 12 (4) ◽  
pp. 775-781 ◽  
Author(s):  
Takane Hori ◽  
Keyword(s):  
Basic Information ◽  
Earthquake Occurrence ◽  
Megathrust Earthquake ◽  
Megathrust Earthquakes ◽  
Tonankai Earthquake ◽  
Tsunami Scenarios ◽  
Nankai Earthquake

This paper describes earthquake and tsunami scenarios as basic information for preparing for the next Nankai megathrust earthquakes. Models to clarify the size of the Nankai megathrust earthquake and changes in occurrence intervals, simulations using such models, and simulations of crustal deformations and tsunamis based on the simulations were employed. This paper re-examines past earthquakes and tsunamis, the possibility of slightly larger earthquakes and tsunamis, their sizes, the necessity of countermeasures against subsidence caused by earthquakes in the Inland Sea, the possibility of the Nankai earthquake occurrence before the Tokai (Tonankai) earthquake, and the possibility of the triggering of the Nankai earthquake by the Hyuga-nada earthquake.

Toward Advanced Earthquake Cycle Simulation

2009 ◽  
Vol 4 (2) ◽  
pp. 99-105
Author(s):  
Kazuro Hirahara ◽  
Keyword(s):  
Earthquake Cycle ◽  
Activity Data ◽  
Megathrust Earthquake ◽  
Friction Laws ◽  
Megathrust Earthquakes ◽  
Cycle Simulation ◽  
Simulation Based ◽  
Rate And State Friction ◽  
Earthquake Cycle Simulation ◽  
Earthquake Cycles

Recent earthquake cycle simulation based on laboratory derived rate and state friction laws with super-parallel computers have successfully reproduced historical earthquake cycles. Earthquake cycle simulation is thus a powerful tool for providing information on the occurrence of the next Nankai megathrust earthquake, if simulation is combined with data assimilation for historical data and recently ongoing crustal activity data observed by networks extending from the land to the ocean floor. Present earthquake cycle simulation assumes simplifications in calculation, however, that differ from actual complex situations. Executing simulation relaxing these simplifications requires huge computational demands, and is difficult with present supercomputers. Looking toward advanced simulation of Nankai megathrust earthquake cycles with next-generation petaflop supercomputers, we present 1) an evaluation of effects of the actual medium in earthquake cycle simulation, 2) improved deformation data with GPS and InSAR and of inversion for estimating frictional parameters, and 3) the estimation of the occurrence of large inland earthquakes in southwest Japan and of Nankai megathrust earthquakes.

scholarly journals Structural Research on the Nankai Trough Using Reflections and Refractions

2009 ◽  
Vol 4 (2) ◽  
pp. 67-71 ◽  
Author(s):  
Yoshiyuki Kaneda ◽  
◽  
Shuichi Kodaira
Keyword(s):  
Large Scale ◽  
Nankai Trough ◽  
Disaster Mitigation ◽  
Seismic Survey ◽  
Seismogenic Zone ◽  
Significant Information ◽  
Megathrust Earthquake ◽  
Megathrust Earthquakes ◽  
Recurrence System ◽  
Splay Faults

To understand the megathrusut earthquake recurrence system around the Nankai trough southwestern Japan, the structural researches by seismic survey and observations will provide the significant information of megathrust earthquakes seimogenic zone. As previous structural researches, the subducting seamount in the Nankai earthquake seismogenic zone off Shikoku Island, the ridge subducting system in the Tokai earthquake seismogenic zone, splay faults in the Tonankai earthquake seismogenic zone and irregular structure in the boundary between the Tonankai and Nankai seismogenic zone off Kii peninsula.These structures and models are very important, significant and basical information to understand the recurrence system of megathrust earthquakes and rupture propagations.In this project, we will carry out seismic survey and tomography with dense arrays around the Nankai trough extending to off Hyuga sesimogenic zone. By 2004 Sumatra megathrust earthquake, we recognized such the large scale seismic linkage as 1960 Chile megathrust earthquake.Therefore, we will image large detailed large scale structures to understand structural components around the Nankai trough with off Hyuga area. Finally, we will construct the advanced structure model and develop the crustal medium model in close cooperation with other structural researches in this project. Based on these models, simulation and disaster mitigation researches will progress conspicuously.

scholarly journals Self-similar stochastic slip distributions on a non-planar fault for tsunami scenarios for megathrust earthquakes

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Masaru Nakano ◽  
Shane Murphy ◽  
Ryoichiro Agata ◽  
Yasuhiko Igarashi ◽  
Masato Okada ◽  
...  
Keyword(s):  
Megathrust Earthquakes ◽  
Planar Fault ◽  
Self Similar ◽  
Tsunami Scenarios

scholarly journals Toward an Integrative Geological and Geophysical View of Cascadia Subduction Zone Earthquakes

2021 ◽  
Vol 49 (1) ◽  
Author(s):  
Maureen A.L. Walton ◽  
Lydia M. Staisch ◽  
Tina Dura ◽  
Jessie K. Pearl ◽  
Brian Sherrod ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Pacific Northwest ◽  
Current Knowledge ◽  
Cascadia Subduction Zone ◽  
Annual Review ◽  
Publication Date ◽  
Data Sets ◽  
Megathrust Earthquake ◽  
Megathrust Earthquakes ◽  
National Boundaries

The Cascadia subduction zone (CSZ) is an exceptional geologic environment for recording evidence of land-level changes, tsunamis, and ground motion that reveals at least 19 great megathrust earthquakes over the past 10 kyr. Such earthquakes are among the most impactful natural hazards on Earth, transcend national boundaries, and can have global impact. Reducing the societal impacts of future events in the US Pacific Northwest and coastal British Columbia, Canada, requires improved scientific understanding of megathrust earthquake rupture, recurrence, and corresponding hazards. Despite substantial knowledge gained from decades of research, large uncertainties remain about the characteristics and frequencies of past CSZ earthquakes. In this review, we summarize geological, geophysical, and instrumental evidence relevant to understanding megathrust earthquakes along the CSZ and associated uncertainties. We discuss how the evidence constrains various models of great megathrust earthquake recurrence in Cascadia and identify potential paths forward for the earthquake science community. ▪ Despite outstanding geologic records of past megathrust events, large uncertainty of the magnitude and frequency of CSZ earthquakes remains. ▪ This review outlines current knowledge and promising future directions to address outstanding questions on CSZ rupture characteristics and recurrence. ▪ Integration of diverse data sets with attention to the geologic processes that create different records has potential to lead to major progress. Expected final online publication date for the Annual Review of Earth and Planetary Sciences, Volume 49 is May 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Spatial changes in inclusion band spacing as an indicator of temporal changes in slow earthquake recurrence intervals

2021 ◽  
Author(s):  
Naoki Nishiyama ◽  
Kohtaro Ujiie ◽  
Masayuki Kano
Keyword(s):  
Fluid Pressure ◽  
Cycle Duration ◽  
Pressure Reduction ◽  
Earthquake Recurrence ◽  
Megathrust Earthquake ◽  
Megathrust Earthquakes ◽  
Slow Earthquake ◽  
Slow Earthquakes ◽  
Recurrence Intervals ◽  
Band Spacing

<p>Repeated slow earthquakes downdip of the seismogenic zones may trigger megathrust earthquakes by transferring stress to the seismogenic zones. Geodetic observations have suggested that the recurrence intervals of slow earthquakes decrease toward a next megathrust earthquake. However, the temporal variation in recurrence intervals of slow earthquakes during megathrust earthquake cycles remains poorly understood due to the limited duration of geodetic and seismological monitoring of slow earthquakes. The quartz-filled, crack-seal shear veins in the subduction mélange deformed near the downdip limit of seismogenic zone in warm-slab environments record the cyclic changes in the inclusion band spacing in the range of 5–65 μm. The two-phase primary fluid inclusions in quartz between inclusion bands show various vapor/liquid ratios regardless of inclusion band spacing, suggesting a common occurrence of fast quartz sealing due to a rapid decrease in quartz solubility associated with a large fluid pressure reduction. A kinetic model of quartz precipitation, considering a large fluid pressure change and inclusion band spacings, indicates that the sealing time during a single crack-seal event cyclically decreased and increased in the range of 0.2–2.7 years, with minimum one cycle duration estimated to be 31–93 years. The ranges of sealing time and one cycle duration may be comparable to the recurrence intervals of slow earthquakes and megathrust earthquakes, respectively. We suggest that the spatial change in the inclusion band spacing is a potential geological indicator of the temporal changes in slow earthquake recurrence intervals, particularly when large fluid pressure reduction occurred by brittle fracturing.</p>

scholarly journals Slipstream: an early Holocene slump and turbidite record from the frontal ridge of the Cascadia accretionary wedge off western Canada and paleoseismic implications

2015 ◽  
Vol 52 (6) ◽  
pp. 405-430 ◽  
Author(s):  
T.S. Hamilton ◽  
Randolph J. Enkin ◽  
Michael Riedel ◽  
Garry C. Rogers ◽  
John W. Pohlman ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Tectonic Setting ◽  
Physical Property ◽  
Early Holocene ◽  
Accretionary Wedge ◽  
Megathrust Earthquake ◽  
Megathrust Earthquakes ◽  
Age Model ◽  
Reservoir Age ◽  
Channel Systems

Slipstream Slump, a well-preserved 3 km wide sedimentary failure from the frontal ridge of the Cascadia accretionary wedge 85 km off Vancouver Island, Canada, was sampled during Canadian Coast Guard Ship (CCGS) John P. Tully cruise 2008007PGC along a transect of five piston cores. Shipboard sediment analysis and physical property logging revealed 12 turbidites interbedded with thick hemipelagic sediments overlying the slumped glacial diamict. Despite the different sedimentary setting, atop the abyssal plain fan, this record is similar in number and age to the sequence of turbidites sampled farther to the south from channel systems along the Cascadia Subduction Zone, with no extra turbidites present in this local record. Given the regional physiographic and tectonic setting, megathrust earthquake shaking is the most likely trigger for both the initial slumping and subsequent turbidity currents, with sediments sourced exclusively from the exposed slump face of the frontal ridge. Planktonic foraminifera picked from the resedimented diamict of the underlying main slump have a disordered cluster of 14C ages between 12.8 and 14.5 ka BP. For the post-slump stratigraphy, an event-free depth scale is defined by removing the turbidite sediment intervals and using the hemipelagic sediments. Nine 14C dates from the most foraminifera-rich intervals define a nearly constant hemipelagic sedimentation rate of 0.021 cm/year. The combined age model is defined using only planktonic foraminiferal dates and Bayesian analysis with a Poisson-process sedimentation model. The age model of ongoing hemipelagic sedimentation is strengthened by physical property correlations from Slipstream events to the turbidites for the Barkley Canyon site 40 km south. Additional modelling addressed the possibilities of seabed erosion or loss and basal erosion beneath turbidites. Neither of these approaches achieves a modern seabed age when applying the commonly used regional marine 14C reservoir age of 800 years (marine reservoir correction ΔR = 400 years). Rather, the top of the core appears to be 400 years in the future. A younger marine reservoir age of 400 years (ΔR = 0 years) brings the top to the present and produces better correlations with the nearby Effingham Inlet paleo-earthquake chronology based only on terrestrial carbon requiring no reservoir correction. The high-resolution dating and facies analysis of Slipstream Slump in this isolated slope basin setting demonstrates that this is also a useful type of sedimentary target for sampling the paleoseismic record in addition to the more studied turbidites from submarine canyon and channel systems. The first 10 turbidites at Slipstream Slump were deposited between 10.8 and 6.6 ka BP, after which the system became sediment starved and only two more turbidites were deposited. The recurrence interval for the inferred frequent early Holocene megathrust earthquakes is 460 ± 140 years, compatible with other estimates of paleoseismic megathrust earthquake occurrence rates along the subduction zone.

scholarly journals Uncertainty quantification of tsunami inundation in Kuroshio, Kochi Prefecture, Japan, using the Nankai–Tonankai megathrust rupture scenarios

2020 ◽  
Vol 20 (11) ◽  
pp. 3039-3056
Author(s):  
Katsuichiro Goda ◽  
Tomohiro Yasuda ◽  
Nobuhito Mori ◽  
Ario Muhammad ◽  
Raffaele De Risi ◽  
...  
Keyword(s):  
Tsunami Hazard ◽  
Grid Data ◽  
Seismic Region ◽  
Tsunami Inundation ◽  
Megathrust Earthquakes ◽  
Tsunami Risk ◽  
Hazard Assessments ◽  
Tsunami Scenarios ◽  
Management Council ◽  
Kochi Prefecture

Abstract. Nankai–Tonankai megathrust earthquakes and tsunamis pose significant risks to coastal communities in western and central Japan. Historically, this seismic region hosted many major earthquakes, and the current national tsunami hazard assessments in Japan consider megathrust events as those having moment magnitudes between 9.0 and 9.1. In responding to the lack of rigorous uncertainty analysis, this study presents an extensive tsunami hazard assessment for the Nankai–Tonankai Trough events, focusing on the southwestern Pacific region of Japan. A set of 1000 kinematic earthquake rupture models is generated via stochastic source modelling approaches, and Monte Carlo tsunami simulations are carried out by considering high-resolution grid data of 10 m and coastal defence structures. Significant advantages of the stochastic tsunami simulation methods include the enhanced capabilities to quantify the uncertainty associated with tsunami hazard assessments and to effectively visualize the results in an integrated manner. The results from the stochastic tsunami simulations can inform regional and local tsunami risk reduction actions in light of inevitable uncertainty associated with such tsunami hazard assessments and complement conventional deterministic tsunami scenarios and their hazard predictions, such as those developed by the Central Disaster Management Council of the Japanese Cabinet Office.

scholarly journals Spatial changes in inclusion band spacing as an indicator of temporal changes in slow slip and tremor recurrence intervals

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Naoki Nishiyama ◽  
Kohtaro Ujiie ◽  
Masayuki Kano
Keyword(s):  
Fluid Pressure ◽  
Temporal Changes ◽  
Pressure Reduction ◽  
Slow Slip ◽  
Megathrust Earthquake ◽  
Megathrust Earthquakes ◽  
Slow Earthquakes ◽  
Recurrence Intervals ◽  
Band Spacing ◽  
Cyclic Changes

AbstractSlow slip and tremor (SST) downdip of the seismogenic zones may trigger megathrust earthquakes by frequently transferring stress to seismogenic zones. Geodetic observations have suggested that the recurrence intervals of slow slip decrease toward the next megathrust earthquake. However, temporal variations in the recurrence intervals of SST during megathrust earthquake cycles remain poorly understood because of the limited duration of geodetic and seismological monitoring of slow earthquakes. The quartz-filled, crack-seal shear veins in the subduction mélange deformed near the downdip limit of the seismogenic zone in warm-slab environments record cyclic changes in the inclusion band spacing in the range from 4 ± 1 to 65 ± 18 μm. The two-phase primary fluid inclusions in quartz between inclusion bands exhibit varying vapor/liquid ratios regardless of inclusion band spacing, suggesting a common occurrence of fast quartz sealing due to a rapid decrease in quartz solubility associated with a large fluid pressure reduction. A kinetic model of quartz precipitation, considering a large fluid pressure change and inclusion band spacing, indicates that the sealing time during a single crack-seal event cyclically decreased and increased in the range from 0.16 ± 0.04 to 2.7 ± 0.8 years, with one cycle lasting at least 27 ± 2 to 93 ± 5 years. The ranges of sealing time and duration of a cycle may be comparable to the recurrence intervals of SST and megathrust earthquakes, respectively. We suggest that the spatial change in inclusion band spacing is a potential geological indicator of temporal changes in SST recurrence intervals, particularly when large fluid pressure reduction occurs by brittle fracturing.

Introduction

1978 ◽  
Vol 36 (3) ◽  
pp. 543-544
Author(s):  
W. Bernard
Keyword(s):  
Molecular Weight ◽  
Electron Microscope ◽  
Nucleic Acid ◽  
Gene Mapping ◽  
Molecular Genetics ◽  
Cell Biology ◽  
Gene Activity ◽  
Close Connection ◽  
Basic Information ◽  
Simple Systems

In comparison to many other fields of ultrastructural research in Cell Biology, the successful exploration of genes and gene activity with the electron microscope in higher organisms is a late conquest. Nucleic acid molecules of Prokaryotes could be successfully visualized already since the early sixties, thanks to the Kleinschmidt spreading technique - and much basic information was obtained concerning the shape, length, molecular weight of viral, mitochondrial and chloroplast nucleic acid. Later, additonal methods revealed denaturation profiles, distinction between single and double strandedness and the use of heteroduplexes-led to gene mapping of relatively simple systems carried out in close connection with other methods of molecular genetics.

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