Tohoku Area Research Articles

Rupture behaviors of the 2011 Tohoku earthquake and its strongest foreshock through an empirical Green’s function deconvolution analysis

An empirical Green’s function (EGF) deconvolution analysis was applied to study the source characteristics of the 2011 Mw9.0 Tohoku and 2011 Mw7.4 Sanriku-Oki earthquakes. For the 2011 Tohoku earthquake, we demonstrate that nucleation released weak but high-frequency energy and that the rupture propagated downward and sped toward the deep region after the up-dip slip extended to the trench. Moreover, the 2011 Sanriku-Oki earthquake results and a previous study on the 1994 Sanriku-Oki earthquake suggest that large earthquakes in the subduction zone around the Tohoku area prefer to rapidly rupture toward the deeper (down-dip) region.

Rapidmap – rapid mapping and information dissemination for disasters using remote sensing and geoinformation

Abstract. FP7 INCO project frame for enhancing research cooperation between European countries and Japan on two topics, one of which is Resilience Against Disasters. The project started in June 2013 and has a duration of 2 years. In the paper, we will outline the aims of the project, methodologies and techniques to be developed and some test data. Remote Sensing (RS) and Geographic Information System (GIS) are powerful technologies for collecting useful information on the damages of disasters in short time. However, since many different types of RS data are available (satellite, aerial, UAV, terrestrial), data co-registration, information integration and feature extraction need reliable and advanced methodologies. In the RAPIDMAP project, we will develop practical ways to integrate RS data processing tools in near-real-time and allow users to use this data soon after the disasters by means of WebGIS tools. This will help not only decision makers but also end-users in the disaster area. The key components of this project are: (1) Near-real-time monitoring: the procedure of near-real-time monitoring with satellites as well as Unmanned Airborne Vehicles (UAV) will be set up and demonstrated. (2) Data co-registration: in disasters, various images as well as maps come from different sources. The co-registration of multiple images is a key technology for information integration. In this project, a system to co-register multiple images in near-real-time will be developed. (3) Data fusion and change detection: one of the advantages of RS is to collect information with multiple sensors. Various methods for fusing optical with active microwave (SAR) sensor data for information extraction and change detection will be developed. (4) Decision Support System (DSS) based on WebGIS technologies: the collected and integrated information has to be easily accessible and visible by decision makers and end-users in near-real-time and worldwide. By using WebGIS technologies, wireless networks and portable terminals, a DSS will allow easy access, retrieval and visualization of all information (fused data, images, maps, etc.) in very short time after data collection and processing. The project will be practically tested and demonstrated at the Tohoku area in Japan and another test site, which were recently affected by large disasters.

Interviewing insights regarding the fatalities inflicted by the 2011 Great East Japan Earthquake

Abstract. One hundred fifty survivors of the 11 March 2011 Great East Japan Earthquake (Tohoku-oki earthquake) (Mw = 9.0) were interviewed to study the causes of deaths from the associated tsunami in coastal areas of Tohoku. The first official tsunami warning underestimated the height of the tsunami and 40% of the interviewees did not obtain this warning due to immediate blackouts and a lack of communication after the earthquake. Many chose to remain in dangerous locations based on the underestimated warning and their experiences with previous smaller tsunamis and/or due to misunderstanding the mitigating effects of nearby breakwaters in blocking incoming tsunamis. Some delayed their evacuation to perform family safety checks, and in many situations, the people affected misunderstood the risks involved in tsunamis. In this area, three large tsunamis have struck in the 115 yr preceding the 2011 tsunami. These tsunamis remained in the collective memory of communities, and numerous measures against future tsunami damage, such as breakwaters and tsunami evacuation drills, had been implemented. Despite these preparedness efforts, approximately 18 500 deaths and cases of missing persons occurred. The death rate with the age of 65 and above was particularly high, four times higher than that with other age groups. These interviews indicate that deaths resulted from a variety of reasons, but if residents had taken immediate action after the major ground motion stopped, most residents might have been saved. Education about the science behind earthquakes and tsunamis could help save more lives in the future.

Foreigners’ Evacuation Behavior in the Great East Japan Earthquake: A Case of Iwaki City in Fukushima Prefecture

A primary challenge for foreigners living in the disaster stricken Tohoku area in Japan was information that made many suffer from the dilemma of to either evacuate or stay. The purpose of this study is to investigate foreigners’ information gathering behavior and its impact on their evacuation decisions. This study applied a questionnaire survey and interview methods and collected 124 samples from foreigners in Iwaki. Results show that (i) nuclear radiation was the main reason for their evacuation decision; (ii) they had to collect information from national broadcasters as there was no local information dissemination; and (iii) average Japanese language ability did not impose a barrier to their lives, but a better command might have prevented them from evacuation. They had the desire to stay and offer volunteer services for the victims. A more coordinated action from local public organizations is recommended including networking with foreigners. This paper checks the possibility and finds the scope.

Disaster preparedness: Looking through the lens of hospitals in Japan

Critical facilities, such as hospitals, play a crucial role in the socioeconomic and psychological recovery of the population after a disaster. Hospitals are considered important due to their roles in saving lives in the affected population and must be able to withstand hazards and remain functioning during and after a disaster. This article assesses earthquake preparedness of hospitals in eight Japanese cities using a questionnaire survey. The questionnaire consists of six parameters and 21 indicators from the “four pillars of hospital preparedness” including structural, nonstructural, functional, and human resources. The results show that the majority of the respondent hospitals fulfill the functional preparedness, which is useful during the emergency period of a disaster, while the other three pillars-structural, nonstructural, and human resources-need to be strengthened. This study helps to assess the status of disaster preparedness as well as the gaps for these hospitals in the Tohoku and Nankai Trough regions, drawing lessons from the Great East Japan Earthquake and Tsunami of the Tohoku area. This status and the gaps are used as a departure point to indicate how to enhance preparedness and resilience to future disaster risks.

The Chronic Difficulties in Isolating Chronically Infected Parvovirus B19 Patients

to April 1 of the following three years were studied retrospectively: after the earthquake (2011); 2one year before the earthquake (2010); 3one year after the earthquake (2012). Saka General Hospital is located in Sendai-city along the Pacific coastline in the Tohoku area, and its laboratory facility was not damaged by the earthquake and tsunami. Data including the number of hospitalized patients, age, sex, laboratory data, kinds of antibacterial drug and consumption, duration of hospitalization, severity of pneumonia , and mortality rate were collected. RESULTS: Patients diagnosed as pneumonia after the earthquake in 2011 had a 2-4 times increase compared to those of 2010 and 2012. As already reported (Takahashi et al., 2011), after the earthquake Moraxella catarrhalis was isolated from 31.3% of cases with pneumonia. The predominant pathogenic bacteria in 2010 and 2012 were Haemophilus influenza and Streptococcus pneumoniae. Severity of 20% of patients with pneumonia in 2011 was mild, but required hospitalization. Proportion of mild inpatients in 2011 was doubled compared to those in 2010 and 2012 The duration of hospitalization after the earthquake was prolonged. CONCLUSIONS: From the results of this study, even from the time of the acute phase after a natural disaster including an earthquake, not only life-saving medical care but also prevention measures against pneumonia are necessary. Also, after an earthquake, there would be a greater need to ensure sufficient hospital beds and to improve the function of discharge planning at the base disaster hospitals.

Strong Ground Motion in the 2011 Tohoku Earthquake: A One-Directional Three-Component Modeling

Local wave amplification due to strong seismic motions in surficial multilayered soil is influenced by several parameters such as the wavefield polarization and the dynamic properties and impedance contrast between soil layers. The present research aims at investigating seismic motion amplification in the 2011 Tohoku earthquake through a one-directional three-component (1D-3C) wave propagation model. A 3D nonlinear constitutive relation for dry soils under cyclic loading is implemented in a quadratic line finite element model. The soil rheology is modeled by mean of a multi-surface cyclic plasticity model of the Masing-Prandtl-Ishlinskii-Iwan (MPII) type. Its major advantage is that the rheology is characterized by few commonly measured parameters. Ground motions are computed at the surface of soil profiles in the Tohoku area (Japan) by propagating 3C signals recorded at rock outcrops, during the 2011 Tohoku earthquake. Computed surface ground motions are compared to the Tohoku earthquake records at alluvial sites and the reliability of the 1D-3C model is corroborated. The 1D-3C approach is compared with the combination of three separate one-directional analyses of one motion component propagated independently (1D-1C approach). The 3D loading path due to the 3C-polarization leads to multiaxial stress interaction that reduces soil strength and increases nonlinear effects. Time histories and spectral amplitudes, for the Tohoku earthquake, are numerically reproduced. The 1D-3C approach allows the evaluation of various parameters of the 3C motion and 3D stress and strain evolution all over the soil profile.

Tohoku Earthquake: A Surprise?

Abstract We consider three questions related to the 2011 Tohoku mega‐earthquake: (1) Why was the event size so grossly underestimated by Japan’s national hazard map? (2) How should we evaluate the chances of giant earthquakes in subduction zones? (3) What is the repeat time for magnitude 9 earthquakes off the Tohoku coast? The maximum earthquake size is often guessed from the available history of earthquakes, a method known for its significant downward bias. We show that historical magnitudes systematically underestimate this maximum size of future events, but the discrepancy shrinks with time. There are two quantitative methods for estimating the corner magnitude in any region: a statistical analysis of the available earthquake record and the moment conservation principle. However, for individual zones the statistical method is usually ineffective in estimating the maximum magnitude; only the lower limit can be evaluated. The moment conservation technique, which we prefer, matches the tectonic deformation rate to that predicted by earthquakes with a truncated or tapered magnitude–frequency distribution. For subduction zones, the seismic or historical record is insufficient to constrain either the maximum or corner magnitude. However, the moment conservation principle yields consistent estimates: for all the subduction zones the corner magnitude is of the order 9.0–9.7. Moreover, moment conservation indicates that variations in estimated corner magnitude among subduction zones are not statistically significant. Another moment conservation method, applied at a point on a major fault or plate boundary, also suggests that magnitude 9 events are required to explain observed displacement rates at least for the Tohoku area. The global rate of magnitude 9 earthquakes in subduction zones, predicted from statistical analysis of seismicity as well as from moment conservation, is about five per century; five actually happened.

東北地方のベニヒカゲを概観する(元気です!東北)

東北地方のベニヒカゲを概観する(元気です!東北)

Ground design of a 3 GeV accelerator-complex for the synchrotron light in Tohoku, Japan (SLiT-J)

A conceptual design of 3 GeV accelerator complex for synchrotron radiation facility in Tohoku area, Japan (SLiT-J) is described. The complex is consisted with a 3 GeV low emittance storage ring and a C-band full-energy injector linac. Circumference of the ring should not be exceeded 300 m because of compactness (saving cost and power consumption). Nevertheless target emittance of the ring is less than 2 nmrad, which will be really competitive with newly constructed 3rd generation light sources. Tentatively designed lattice offers a low emittance of 1.8 nmrad with reasonably wide dynamic aperture. Presuming 4 typical undulators to cover the wide spectral range such as 10 eV to 20keV, the brightness is expected from 1017 – 1021 phs/mm2/mrad2/s/0.1%b.w./300mA. For the hard x-ray region, considerable photon flux may be provided by using multipole mini-wiggler with high magnetic field, which is inserted into the middle of cell. Though realistic prospect of the project is not predictable at present, we anticipate that the facility will be open in 2016.

Validation of a New Velocity Structure Inversion Method Based on Horizontal-to-Vertical (H/V) Spectral Ratios of Earthquake Motions in the Tohoku Area, Japan

The earthquake motion generated by the multiple scattering due to the complexity of the underneath soil structure can be referred to as a diffuse wave field. Under the assumption of the well‐diffused wave field it is accepted that the average autocorrelation of a single receiver is proportional to the imaginary part of the Green’s function when both source and receiver are located at the same point. In this study we focus on sites where the site effect can be described using a 1D model. Previous studies show that the imaginary part of the Green’s function at the free surface is proportional to the square of the absolute value of the corresponding transfer function for a plane, vertically incident wave with unit amplitude. It is then possible to carry out an inversion of the 1D velocity structure using the relationship between the horizontal‐to‐vertical (H/V) spectral ratio and the ratio of horizontal and vertical transfer functions. We verify that the average H/V spectral ratio computed with a sufficiently large number of earthquake data depends only on the underneath geological structure and not on the set of data used to compute it. We then carry out inversions of the velocity structures for 10 sites of the K‐NET and KiK‐net networks in the Tohoku area, Japan, following the proposed theory for earthquake H/V spectral ratios. We verify that there is a good match between the observed H/V spectral ratios and the theoretical ones corresponding to the proposed velocity structures for the 10 target sites studied in the present work. Online Material: Figures showing variations of H/V spectral ratios and results of the inversions and tables of inversion parameters.

A Unit Commitment Model with Demand Response and Electric Storage Device for the Integration of Variable Renewable Energies

This paper describes development of a unit commitment model with demand response and electric storage device for the integration of variable renewable energies by considering forecast outputs and errors for photovoltaic and wind power generations. We analyze operation plans for power systems in Tokyo area and Tohoku area where a large amount of variable renewable energies are introduced in 2030. We estimate curtailment of wind power for Tohoku area in 2030 because the power system in Tohoku area can not integrate wind power generation planned to be installed in 2030. Then this paper shows that the integrated operation of the two power systems can integrate both photovoltaic and wind power generations planned to be installed in 2030. Finally we evaluate economic efficiency for the integrated operation of the two power systems.

The Activities after the Award of JSEE-The Recovery from Great Earthquake of East Japan and the Education of Colleges of Technology in Tohoku Area-

The Activities after the Award of JSEE-The Recovery from Great Earthquake of East Japan and the Education of Colleges of Technology in Tohoku Area-

仙台平野沿岸に植栽された海岸保安林の歴史と東北地方太平洋沖地震津波に対する効果

The Great East Japan Earthquake occurred on March 11, 2011 and the coastal zones along the Pacific Ocean in Tohoku area have received severe damage by tsunami. Most of coastal forestations have been severely damaged or swept away due to a gigantic tsunami. In this paper, historical background of coastal forestation was studied by detailed literature surveys. An instructive formula was developed between damage level of houses and a distance from coastal forestation by field investigations at the coast of Sendai plain. Furthermore, damage level of houses was clarified as a function of inundation depth of tsunami with influence of a housing code.

地域型復興住宅の生産者グループにおける木造住宅の生産体制に関する統計的把握

The greater earthquake occurred in Tohoku area, northern Japan, March 11, 2011, called Tohoku earthquake (March 11, 2011). This induced not only big quake over eastern Japan, but also gigantic tsunami attacking on the Pacific coast of Tohoku area, where it was caused considerable damages. Over the disaster area, we start various activities for restoration houses. In this report, the authors indicate about the tendency on the organization of local housing groups for supplying wooden restoration houses, according to the result of statistical analysis we examined.

河川における外来植物の使用実態とその逸出リスクの地域差

Many plants, including alien plants, are introduced to cover embankments or to plant in riverbed park zones during the course of river management. However, many alien plants have escaped and established in riparian environments. Some alien plants have negative effects on nature conservation and river management. Therefore, estimations of the risk of escape and establishment are needed for the ecologically safe use of useful alien plants. In order to clarify regional differences in the escape risk of alien plants, we conducted a questionnaire investigation to assess the amount of alien plants introduced by river management, and we compared the occurrence of alien plants in the riparian environment using the dataset of a national survey on river environments. The results showed that many species of alien horticultural plants were used. In contrast, only a small number of alien revegetation plant species were used; however, these were used in huge amounts. On the basis of the regional differences in occurrence and introduction amount, we clarified the risk of 39 alien species as follows: species having a high escape risk nationwide; species having a high escape risk in the Hokkaido and Tohoku areas, but with a low escape risk in warmer regions; and species having low escape risk in riparian environments nationwide.

海岸丘と海岸林の複合作用が津波に及ぼす影響に関する研究

After the 3.11-Tsunami in the Tohoku Region of Japan in 2011, many comprehensive field observations on tsunami damages were done. The coastline areas of Tohoku had coastal dunes and forests could have acted as a barrier against the tsunami. But surveys have shown that almost all of the coastal forest was swept away with its roots by the tsunami, and houses behind these forests were not spared and were completely destroyed and washed way. However, some houses and manmade structures were able to withstand the strength of the tsunami waves. These houses were located behind both coastal dunes and forests, which efficiently acted as a barrier against the tsunami. In this paper, the effects of the dunes and the forest on tsunami currents are studied through hydraulic experiments, and the coupled effect of the dunes and forests as coastal barriers are also studied.

The Ionospheric Precursor to the 2011 March 11 Earthquake Based upon Observations Obtained from the Japan-Pacific Subionospheric VLF/LF Network

By using network observation of subionospheric VLF (very low frequency)/LF (low frequency) signals in Japan and in Russia, we have found a significant ionospheric perturbation prior to the recent 2011 March 11 Japan earthquake (EQ) which occurred at sea proximate to the Tohoku area on the main island (Honshu) of Japan was an exceptionally huge plate-type EQ. A remarkable anomaly (with a decrease in the nighttime amplitude and also with enhancement in dispersion) was detected on March 5 and 6 along the propagation path from the NLK (Seattle, USA) transmitter to Chofu (together with Kochi and Kasugai). We also have observed the corresponding VLF anomaly during a prolonged period of March 1 - 6, with minima in the nighttime amplitude on March 3 and 4 along the path from JJI (Miyazaki, Kyushu) to Kamchatka, Russia. This ionospheric perturbation has been discussed extensively with respect to its reliability. (1) How abnormal is this VLF/LF propagation anomaly? (2) What was the temporal evolution of terminator times? (3) Were there any solar-terrestrial effects (especially the effect from geomagnetic storms) on the VLF/LF propagation anomaly? (4) The effect of any other EQs and foreshock activities on the VLF/LF anomaly? (5) Were there any correlations with other related phenomena? Finally, (6) are there any other examples of a VLF/LF propagation anomaly for oceanic EQs? We then compared the temporal properties of ionospheric perturbations for this EQ with those of a huge number of inland EQs and compared the corresponding spatial scale with the former result of the same oceanic 2004 Sumatra EQ with nearly the same magnitude. Finally, the generation mechanism of those seismo-ionospheric perturbations is briefly discussed.

東北版「食道胃静脈瘤治療の標準化」作成の試み

東北版「食道胃静脈瘤治療の標準化」作成の試み

Numerical Analysis of Liquefaction in a River Levee on Soft Cohesive Ground

During the 2011 off the Pacific coast of Tohoku earthquake, liquefaction at the bottom of embankments extensively damaged river levees in the Tohoku and Kanto areas. This study presents preliminary numerical simulation of liquefaction in a river levee on soft cohesive ground along the Eai River during the earthquake. Static analysis reproduced the initial state of stress and moisture in such an embankment before the earthquake. Static analysis showed a decrease in mean effective stress and an increase in water content at the bottom of the embankment due to the settlement of soft cohesive ground. The effect of initial stress and moisture conditions on the seismic responses of the river levee are discussed through dynamic threephase coupled analysis with an initially deformed configuration and moisture distribution. Numerical results showed that stress relaxation in the embankment caused an increase in settlement at the crest of embankment.