Aaliya Shaikh

Aaliya Shaikh

2011 Tohoku earthquake

Table of Contents

Abstract

The consequences of the 2011 Mw9.0 Tohoku earthquake were studied through various reconnaissance and in-depth investigations. The focus of the research was to determine the earthquake early warning system and how it affected the population along with the previous understanding of disasters without EEW. There is also a link between earthquake & tsunami tragedies to wave phenomena in the following study. Furthermore, it explains the coastal defences in Japan and how they played a role during the 2011 Tohoku earthquake. One of the major concerns was the disaster’s long-term consequences on the local population and hence to overcome that, how earthquake safety prevention drills are already being instilled into young students in elementary and primary schools, are all discussed in this paper. The report finishes with a list of recommendations for avoiding future natural disasters of this nature.

Introduction

Background:

The Tohoku earthquake on March 11, 2011, occurred in the Japan Trench, where the Pacific Plate’s lithosphere subducted beneath the Okhotsk Plate. The lithosphere rupture was around 500 km long and 200 km wide (Ammon et al., 2011). The earthquake caused a massive tsunami in several sites along the Tohoku coast, causing damage to over 900,000 buildings in the prefectures of Iwate, Miyagi, Fukushima, and Ibaraki (NPA, 2012). In comparison, the earthquake shook around 95,000 structures (MLIT, 2011). The Japan National Police Agency confirmed 15,852 deaths, 6,011 injuries, and 3,287 individuals missing as of February 20, 2012. (NPA, 2012).

How is the topic related to waves?

Tsunamis are continuous oceanic gravity waves that are most commonly triggered by underwater earthquakes. They transmit at rates similar to shallow-water wave speeds (200 m/s) because their horizontal wavelengths are much longer than the ocean depth (4 km for the Pacific Ocean). Furthermore, because their characteristic scales (tens of minutes and hundreds of kilometres) are within the spectrum of small and medium atmospheric gravity waves, the coupling with both tsunamis and atmospheric gravity waves are expected to be strong, implying that a tsunami could be an effective source of atmospheric gravitational waves. (Hines, 1974)

Objectives:

To discuss the Earthquake early warning system

To understand the various coastal defences

To discuss the Earthquake Disaster Education For Primary/Secondary Students

Methodology

Qualitative research methodology has been used in the following paper. The paper will include three essential points that are related to tsunami and earthquakes and how the wave phenomenon has been correlated with these natural disasters. The three points are; to discuss the Earthquake early warning system, to understand the various coastal defences, and to discuss the earthquake disaster education for primary/secondary students. An in-depth understanding of all the above-mentioned points will be studied by using books, tsunami warning official website data, and certain scientific journals along with online Japanese news material.

Earthquake Early Warning System

Since October 2007, Japan has had a well-advanced public earthquake early warning (EEW) system. Several types of nationwide seismic networks are operated by the Japan Meteorological Agency (JMA) and Japan’s National Institute for Earth Science and Disaster Prevention (NIED).

Only the Hi-net and the JMA’s Tsunami and Earthquake Observation and Monitoring system transfers information in real-time among the four networks. The current EEW system is based on these two networks, which has a total of about 1,000 sites spaced at approximately 25 km mesh intervals (NIED 2012). Several million people near the epicentre of the 2011 Tohoku-oki earthquake and tsunami (also known as 3.11) received the EEW roughly 15 to 20 seconds before the most violent shaking began, and many more people in adjacent regions had a longer lead time until less intense shaking began. 

The EEW System’s Conduct Before Tohoku-oki Earthquake & Tsunami

There are two methods for identifying an earthquake: one is focused on seismic data from a single site, and the other is dependent on seismic data from two or more locations. The lead times of the EEW system (the time it takes from the detection of an earthquake to the production of an EEWg alert) have ranged from 1 to 11 seconds. When one-site data is used, the average elapsed time is 5.4 seconds, and when multiple-site data is used, the average elapsed time is 6.4 seconds. Another assessment parameter is the system’s predicted shaking strength vs the experienced shaking strength; this statistic is relevant to the EEWg situation.

In 45% of cases, the predicted and observed shaking strength were in agreement, and in 91% of cases, the gap was less than 1 on the JMA scale. It is recommended that users of the EEW system consider these constraints.

The EEW System During Tohoku-oki Earthquake & Tsunami

90% of these persons were proactive instead of reactive in time to preserve their own lives and the lives of their family members, or to take additional activities as planned. Some decisions were made based on gut reactions to the alerts. This high percentage of effectiveness is almost certainly due to EEW system education, both in schools and in society at large. Despite numerous flaws, the efficiency of EEW has prompted Japan to expand its already vast seismic and tsunami surveillance networks offshore, east of the Japan island arc, to 150 locations, and to establish a unique terminal for advanced EEW uses in schools with over 53,000 students.

The success of the EEW systems is determined first and foremost by how far its warnings are disseminated and how many people would benefit from earthquake warnings. From a survey conducted by the JMA, the majority of respondents (87 per cent) said they were familiar with the EEW system. This high percentage is assumed to be attributable to the respondents’ previous experiences with 10 EEWg alerts in the three years leading up to the Tohoku-oki earthquake. However, it’s worth noting that 13% of the population is unaware of the EEW.

Fig 1: The offshore earthquake epicentre is displayed as a red star on two maps of the March 11, 2011 M9.0 Tohoku-oki, Japan earthquake region. Using the JMA (Japan Meteorological Agency) Intensity Scale, the map on the left depicts the observed shaking intensity. The earliest EEW warning times are depicted as concentric circles on the map to the right.

Coastal Defences

Japan does indeed have a high proportion of coastline to the land surface and has heavily relied on a small quantity of flat coastal productive land, with 70% of its assets concentrated in the 10% of total surface area that is flat coastal plain (Kokusai Kogyo Group, 2011). Four cities (Miyako, Kamaishi, Ofunato, and Ishinomaki) are recognized as “major ports” in the zone impacted by the Great East Japan tsunami, and Sendai-Shiogama is one of Japan’s 23 “specially designated significant ports” serving worldwide maritime networks. The ports are hubs of production and import/export, passenger transportation centres, and provide economic activities, lodging, and recreation, so tsunami devastation to ports has an impact far beyond the surrounding area. In addition to the value of coastal land and infrastructure, the occurrence of typhoons, storm surges, and tsunamis has led to the creation of some of the world’s most comprehensive coastal defences in Japan. 

 On March 11th, a sum of 8,500 m of breakwaters crumbled (Yagyu 2011), along with the recently built tsunami breakwater in Kamaishi City, which was made to resist a 5–6 m tsunami. The Meiji Sanriku tsunami, which was far smaller than the Great East Japan 2011 disaster, was used to create many coastal safety systems along the Sanriku coast. As a result, they were ineffective at preventing overtopping waves, and in many cases, they failed catastrophically. Takahashi et al. (2011b) proposed that, rather than creating bigger structures in the future, coastal defences should stay the same size, but with special care paid to their stability so that they can withstand even a massive tsunami despite being overtopped. The logic behind this is that a defence that is overpowered but endures is preferable to none at all. 

Vertical Evacuation Structures

According to The Japan Times (2011), Japan has over 70,000 designated tsunami evacuation sites, which are made up of regions of land or buildings that are either on high ground or far enough inland to prevent inundation. Other structures are designated as vertical evacuation configurations, which are situated in the anticipated tsunami upwelling zone but are designed to withstand tsunami loading and have enough vertical height that can provide safe refuge above the approximate tsunami inundation level, according to government guidelines (Cabinet Office Government of Japan, 2005). The importance of vertical evacuation facilities in offering refuge in the flood zone has been demonstrated by observations from the March 11th, 2011, tsunami. At least 9,700 individuals in five towns on the Sendai Plain were saved by escaping to the higher floors of RC buildings during the tsunami.

Fig 2: Vertical Evacuation Structure in Japan. 

Fig 3: In Kaifu, Japan, this concrete structure serves as a vertical evacuation structure. Structures like this are simple to get to, travel within, and give protection from tsunamis’ devastating forces.

Earthquake Disaster Education For Primary/Secondary Students

Disaster education is taught in Japan’s daycare centres, primary, junior high, and high schools, as well as universities, to help students prepare for disasters. On September 1, the Great Kanto Earthquake struck, and that day was declared Disaster Prevention Day. As a result, a Disaster Prevention Week was established in the fall, and adults working at businesses, in addition to schoolchildren, participate in evacuation instruction regularly. More natural disasters have occurred in recent years, such as the Tohoku earthquake and tsunami in 2011, which was the most destructive earthquake ever recorded in Japan and resulted in a massive tsunami as we learned above. Toyota City, in Aichi Prefecture, is about in the middle of Tokyo and Osaka. Motoshiro Elementary School in this city holds an annual evacuation drill to plan for fires and earthquakes. People learn evacuation procedures and then walk them to the neighbourhood junior high school, or they go to an evacuation shelter on the roof of a local shopping centre with daycare children. This elementary school is also affiliated with a university, and it uses GPS to track the time it takes to evacuate.

Fig 4 & 5 : Disaster training to students (Photos provided by Motoshiro Elementary School, Toyota City)

Disaster prevention events for parents and children are held in the Shinagawa Disaster Prevention Experience Hall. The event is set up in such a way that you can get experience while having a good time with recognizable objects. Every child in Japan learns this famous phrase “don’t push, don’t run, don’t speak, and don’t go back” when it comes to disaster prevention. In addition to this term, certain school’s guidelines include the phrase “don’t go near,” which means that pupils should avoid unsafe locations.

Conclusion & Recommendation

Ressilient Infrastructure: Sendai’s water supply was disrupted for up to 500,000 people, and the city’s water treatment plan was totally submerged by Tohoku.  Sendai City used the disaster as a learning opportunity to improve the resilience of these infrastructures, including retrofitting existing systems with seismic resilience upgrades, improving business continuity planning for sanitation systems, and developing a geographic information system (GIS)-based wealth management system that would allow for easy recognition and restoration pf pipes and other assets.

Conducting Regular Simulation Drills: The Central Disaster Management Council updates the Comprehensive Disaster Management Drill Framework every year. In the affected region and throughout Japan, the Tohoku resulted in new and enhanced drill protocols. For example, in 2015, the Tokyo metropolitan region hosted the 35th Joint Disaster Simulation Drill to address issues recognised during the Tohoku, such as improving mutual assistance systems among inhabitants, government agencies, and organisations, verifying disaster management plans, and improving federal agencies’ disaster response capabilities.

Effective Communication between various Stakeholders: This entails involving and empowering a wide range of stakeholders, including women, the elderly, youngsters, children and the private sector. Building trust and social bonds has been shown to lessen catastrophe impacts; a study conducted after the Tohoku earthquake revealed that towns with high social capital lost fewer residents to the tsunami. Following the disaster, the elders of Ofunato established the Ibasho Cafe, a community place dedicated to fostering social capital among the elderly.

References

  • Ammon, C. J., Lay, T., Kanamori, H., & Cleveland, M. (2011). A rupture model of 2011 off the Pacific coast of Tohoku Earthquake. Earth, Planets and Space, 63(7), 693-696. doi:10.5047/eps.2011.05.015
  • Damage Situation and Police Countermeasure, (2012, February 20), National Police Agency of Japan, NPA. Retrieved from: https://reliefweb.int/report/japan/japan-damage-situation-and-police-countermeasures-associated-2011tohoku-district
  • Ports and Harbours in Japan, (2006), Ministry of Land, Infrastructure, Transport, and Tourism, MLIT (2006). Retrieved from: http://www.mlit.go.jp/english/2006/k_port_and_harbors_bureau/17_p_and_h/index.html
  • Einaudi, F., & Hines, C. O. (1974). WKB approximation in application to acoustic-gravity waves. The Upper Atmosphere in Motion Geophysical Monograph Series, 508-530. doi:10.1029/gm018p0508
  • Japan Meteorological Agency (JMA, 2009), Announcement of emergency earthquake situation, Retrieved from: https://www.jma.go.jp/jma/en/Emergency_Warning/ew_index.html
  • Kokusai Kogyo Group (2011) Characteristics of Japan’s DRR: a perspective from the spatial information sector. UN ISDR, Third session of the Global Platform for disaster risk reduction. Geneva, Switzerland
  • Yagyu T (2011) Thank you very much for your messages of sympathy regarding the Great East Japan Earthquake of March 11, 2011—a message from the secretary of PIANC Japan. Sailing ahead (PIANC ENewsletter), 8. Retrieved from http://www.pianc.org/downloads/sailingahead/SailingAheadApril2011/ JapanEarthquake.pdf
  • Fig 1:  Wald, D.J., 2020. Practical limitations of earthquake early warning. Earthquake Spectra, 36(3), pp.1412–1447. 
  • Fig 2 & 3: Ewing, Lesley & Goltz, James & Holmes, William & Petty, Ervin & Priest, George & Turner, Althea & Walsh, Timothy, (2009). Vertical Evacuation from Tsunamis: A Guide for Community Officials. 

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