Real-Time Tsunami Inundation Forecast for a Recurrence of 17thCentury Great Hokkaido Earthquake in Japan

2014 ◽  
Vol 9 (3) ◽  
pp. 358-364 ◽  
Author(s):  
Yuichiro Tanioka ◽  
◽  
Aditya Riadi Gusman ◽  
Kei Ioki ◽  
Yugo Nakamura
Keyword(s):  
Real Time ◽  
Pacific Coast ◽  
Great Earthquake ◽  
Tsunami Deposit ◽  
Fault Models ◽  
Fine Grid ◽  
Tsunami Inundation ◽  
Inundation Area ◽  
The Pacific ◽  
Tsunami Waveforms

Paleotsunami studies have shown that several large tsunamis hit the Pacific coast. Many tsunami deposit data were available for the 17thcentury tsunami. The most recent tsunami deposit study in 2013 indicated that the large slip of about 25 m along the plate interface near the Kurile trench would be necessary and the seismic moment of this 17thcentury earthquake was 1.7 × 1022Nm. If a great earthquake like the 17thcentury earthquake occurs off the Pacific coast of Hokkaido, the devastating disaster along the coast is expected. To minimize the tsunami disaster, a development of the real-time forecast of a tsunami inundation area is necessary. Estimating a tsunami inundation area requires tsunami numerical simulation with a very fine grid system of less than 1 arcsecond. There is not enough time to compute the tsunami inundation area after a large earthquake occurs. In this study, we develop a real-time tsunami inundation forecast method using a database including many tsunami inundation areas previously computed using various fault models. After great earthquakes, tsunamis are computed using linear long-wave equations for fault models estimated in real time. Simulating such tsunamis takes only 1-3 minutes on a typical PC, so it is potentially useful for forecasting tsunamis. Tsunami inundation areas computed numerically using various fault models and tsunami waveforms at several locations near the inundation area are stored in a database. Those computed tsunami waveforms are used to choose the most appropriate tsunami inundation area by comparing them to the tsunami waveforms computed in real time. This method is tested at Kushiro, a city in Hokkaido. We found that the method worked well enough to forecast the Kushiro’s tsunami inundation area.

scholarly journals Subsidence by liquefaction-fluidization in man-made strata around Tokyo bay, Japan: from geological survey on damaged part at the 2011 off the Pacific Coast of Tohoku Earthquake

2015 ◽  
Vol 372 ◽  
pp. 221-226
Author(s):  
O. Kazaoka ◽  
S. Kameyama ◽  
K. Shigeno ◽  
Y. Suzuki ◽  
M. Morisaki ◽  
...  
Keyword(s):  
Pacific Coast ◽  
Tohoku Earthquake ◽  
Geological Survey ◽  
Japan Meteorological Agency ◽  
Tokyo Bay ◽  
Great Earthquake ◽  
Reclaimed Land ◽  
Chiba Prefecture ◽  
Detailed Classification ◽  
The Pacific

Abstract. Geological disaster by liquefaction-fluidization happened on southern part of the Quaternary Paleo-Kanto submarine basin at the 2011 Earthquake off the Pacific Coast of Tohoku. Liquefaction-fluidization phenomena occurred mainly in man-made strata over shaking 5+ intensity of Japan Meteorological Agency scale. Many subsided spots, 10–50 m width, 20–100 m length and less than 1 m depth, by liquefaction-fluidization distributed on reclaimed land around northern Tokyo bay. Large amount of sand and groundwater spouted out in the terrible subsided parts. But there are little subsidence and no jetted sand outside the terrible subsided part. Liquefaction-fluidization damaged part at the 1987 earthquake east off Chiba prefecture re-liquefied and fluidized in these parts at the 2011 great earthquake. The damaged area were more wide on the 2011 earthquake than the 1987 quake. Detailed classification maps of subsidence by liquefaction-fluidization on the 2011 grate earthquake were made by fieldwork in Chiba city around Tokyo bay. A mechanism of subsidence by liquefaction-fluidization in man-made strata was solved by geological survey with continuous large box cores on the ACE Liner and large relief peals of the cores at a typical subsided part.

Real-Time Tsunami Prediction System Using DONET

2017 ◽  
Vol 12 (4) ◽  
pp. 766-774 ◽  
Author(s):  
Narumi Takahashi ◽  
Kentaro Imai ◽  
Masanobu Ishibashi ◽  
Kentaro Sueki ◽  
Ryoko Obayashi ◽  
...  
Keyword(s):  
Real Time ◽  
Time Lag ◽  
Rupture Zone ◽  
Tsunami Source ◽  
Earthquake Rupture ◽  
Prediction System ◽  
Fault Models ◽  
Tsunami Height ◽  
Inundation Area ◽  
Selection Of

We constructed a real-time tsunami prediction system using the Dense Oceanfloor Network System for Earthquakes and Tsunamis (DONET). This system predicts the arrival time of a tsunami, the maximum tsunami height, and the inundation area around coastal target points by extracting the proper fault models from 1,506 models based on the principle of tsunami amplification. Since DONET2, installed in the Nankai earthquake rupture zone, was constructed in 2016, it has been used in addition to DONET1 installed in the Tonankai earthquake rupture zone; we revised the system using both DONET1 and DONET2 to improve the accuracy of tsunami prediction. We introduced a few methods to improve the prediction accuracy. One is the selection of proper fault models from the entire set of models considering the estimated direction of the hypocenter using seismic and tsunami data. Another is the dynamic selection of the proper DONET observatories: only DONET observatories located between the prediction point and tsunami source are used for prediction. Last is preparation for the linked occurrence of double tsunamis with a time-lag. We describe the real-time tsunami prediction system using DONET and its implementation for the Shikoku area.

scholarly journals Rapid and Quantitative Uncertainty Estimation of Coseismic Slip Distribution for Large Interplate Earthquakes Using Real-time GNSS Data and Its Application to Tsunami Inundation Prediction

2021 ◽  
Author(s):  
Keitaro Ohno ◽  
Yusaku Ohta ◽  
Ryota Hino ◽  
Shunichi Koshimura ◽  
Akihiro Musa ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Markov Chain ◽  
Real Time ◽  
Uncertainty Estimation ◽  
Slip Distribution ◽  
Fault Models ◽  
Coseismic Slip ◽  
Plate Interface ◽  
Tsunami Inundation ◽  
Gnss Data

Abstract This study proposes a new method for the uncertainty estimation of coseismic slip distribution on the plate interface deduced from real-time global navigation satellite system (GNSS) data and explores its application for tsunami inundation prediction. Jointly developed by the Geospatial Information Authority of Japan and Tohoku University, REGARD (REal-time GEONET Analysis system for Rapid Deformation monitoring) estimates coseismic fault models (a single rectangular fault model and slip distribution model) in real time to support tsunami prediction. The estimated results are adopted as part of the Disaster Information System, which is used by the Cabinet Office of the Government of Japan to assess tsunami inundation and damage. However, the REGARD system currently struggles to estimate the quantitative uncertainty of the estimated result, although the obtained result should contain both observation and modeling errors caused by the model settings. Understanding such quantitative uncertainties based on the input data is essential for utilizing this resource for disaster response. We developed an algorithm that estimates the coseismic slip distribution and its uncertainties using Markov chain Monte Carlo methods. We focused on the Nankai Trough of southwest Japan, where megathrust earthquakes have repeatedly occurred, and used simulation data to assume a Hoei-type earthquake. We divided the 2951 rectangular subfaults on the plate interface and designed a multistage sampling flow with stepwise perturbation groups. As a result, we successfully estimated the slip distribution and its uncertainty at the 95% confidence interval of the posterior probability density function. Furthermore, we developed a new visualization procedure that shows the risk of tsunami inundation and the probability on a map. Under the algorithm, we regarded the Markov chain Monte Carlo samples as individual fault models and clustered them using the k-means approach to obtain different tsunami source scenarios. We then calculated the parallel tsunami inundations and integrated the results on the map. This map, which expresses the uncertainties of tsunami inundation caused by uncertainties in the coseismic fault estimation, offers quantitative and real time insights into possible worst-case scenarios.

Comprehensive Seismic Evaluation of HTTR Against the 2011 Off the Pacific Coast of Tohoku Earthquake

2018 ◽  
Vol 4 (2) ◽  
Author(s):  
Masato Ono ◽  
Kazuhiko Iigaki ◽  
Hiroaki Sawahata ◽  
Yosuke Shimazaki ◽  
Atsushi Shimizu ◽  
...  
Keyword(s):  
Seismic Response ◽  
Pacific Coast ◽  
Tohoku Earthquake ◽  
Reactor Power ◽  
Great Earthquake ◽  
Response Analysis ◽  
Seismic Response Analysis ◽  
Control Rod ◽  
The Pacific ◽  
Equipment And Instruments

On Mar. 11, 2011, the 2011 off the Pacific coast of Tohoku Earthquake of magnitude 9.0 occurred. When the great earthquake occurred, the high temperature engineering test reactor (HTTR) had been stopped under the periodic inspection and maintenance of equipment and instruments. A comprehensive integrity evaluation was carried out for the HTTR facility because the maximum seismic acceleration observed at the HTTR exceeded the maximum value of design basis earthquake. The concept of comprehensive integrity evaluation is divided into two parts. One is the “visual inspection of equipment and instruments.” The other is the “seismic response analysis” for the building structure, equipment and instruments using the observed earthquake. All equipment and instruments related to operation were inspected in the basic inspection. The integrity of the facilities was confirmed by comparing the inspection results or the numerical results with their evaluation criteria. As the results of inspection of equipment and instruments associated with the seismic response analysis, it was judged that there was no problem for operation of the reactor, because there was no damage and performance deterioration. The integrity of HTTR was also supported by the several operations without reactor power in cold conditions of HTTR in 2011, 2013, and 2015. Additionally, the integrity of control rod guide blocks was also confirmed visually when three control rod guide blocks and six replaceable reflector blocks were taken out from reactor core in order to change neutron startup sources in 2015.

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