How Can We Prepare for the Tokyo Inland Earthquake?
October 30, 2019
Mr. Naoshi Hirata
Professor, Earthquake Research Institute,
University of Tokyo
As we look back at recent earthquakes that caused significant damage, a magnitude-6.7 earthquake occurred off Yamagata Prefecture three months ago and caused major damage to buildings. Fortunately, there were no casualties, although Murakami City in Niigata Prefecture experienced strong shaking of seismic intensity 6-upper and Tsuruoka City in Yamagata Prefecture recorded 6-lower. Hokkaido was hit by an earthquake of the same magnitude last year that claimed more than 40 lives. Hokkaido Eastern Iburi Earthquake caused the shutdown of key thermal power plants and blackout across the entire island for a few days, making us realize the profound impact inflicted on current electricity-dependent society. It took a heavy toll on dairy farming which is the island’s major industry. It also triggered life-threatening crisis especially for patients using electrical medical devices including artificial respirators.
Another earthquake of magnitude 6.1 and seismic intensity 6-lower hit northern Osaka last year and caused 6 deaths, including one elderly woman who died of medical complications exacerbated by a natural disaster. The northern Osaka Prefecture Earthquake had its own issues and challenges as it struck a densely populated urban area during the morning rush hours as well as numerous passengers were affected by consequent traffic disruptions that continued for several days.
As we focus on earthquakes of magnitude 6 and stronger, there were 12 in the past one year. A database of the Japan Meteorological Agency has tracked 1,800 major earthquakes since 1923, revealing on average 18 to 19 earthquakes hit our country each year. These records prove that major earthquakes have not increased in recent years but there is at least one earthquake as powerful as the one that hit northern Osaka every month somewhere in Japan. Many precious lives will be lost should a powerful earthquake hit big cities. Kumamoto Earthquakes (magnitude 7.3) claimed 273 lives in 2016, of which over 200 died of indirect causes linked to the disaster. If the same scale of earthquake hits Metropolitan Tokyo, it will cause catastrophic damage due to high population density coupled with a large number of fragile housings that still remain. “Exposure” is one component of disaster risk, referring to what is affected by natural disasters, such as people and property.
Based on the current seismic analysis of the strength of rocks and locations of tectonic plates, we can predict the area where earthquakes are likely to occur and also calculate the intensity of shaking depending on different locations. Should a magnitude-7.3 earthquake occur directly beneath the southern part of Metropolitan Tokyo, approximately 30% of Tokyo as well as 3 Prefectures (Kanagawa, Chiba and Saitama) are expected to experience seismic intensity level 6-lower or higher. According to the report issued by the Central Disaster Management Council, the maximum number of fatalities is estimated to reach 23,000 while as many as 610,000 buildings are estimated to be completely destroyed or burned by fire. Massive power outage will upend our daily life, roads will be severely congested and extensive railway networks will halt for at least a month. The overall economic damage is estimated to total 95.3 trillion yen which is equivalent to our annual national budget.
The Council published these figures as a basis to set quantitative disaster mitigation goals with specific deadlines. The Tokyo Metropolitan Government stipulated its Urban Development Plan for Disaster Resistance and identified measures to take for areas with “close-set” wooden houses that can suffer particularly great damages in the event of a disaster. The Plan identifies 28 priority zones and provides subsidies to promote the construction of fireproof and earthquake-resistant structures that can prevent spread of fire and enhance urban fireproof functions. It also advances road construction to enable the passage of emergency vehicles and smooth implementation of firefighting, rescue activities and evacuation.
I would also like to highlight the importance of disaster risk reduction literacy at various levels, sectors and organizations of society, but most importantly starting from each individual. It consists of awareness creation and basic knowledge to empower each person to comprehend the nature of disaster and make better decisions in the event of a disaster. It will play an instrumental role in “taking proactive actions for a better society and life based on essential disaster countermeasures”. Tokyo Fire Department has set the “10 Tips for Earthquake Safety” and disseminated safety suggestions which call on to “protect yourself first” and then “make sure you have ways out: open doors and windows”. Children get such information and trainings at school. Another useful tool is the “National Earthquake Forecast Map” to get correct understanding of the hazard vulnerability depending on where you are. The Headquarters for Earthquake Research Promotion operates the Earthquake Hazard Station website which compiles the probability of earthquakes with severity of shaking. As you put the exact address into the website, it will provide information on the probability of hazard for each location.
As I close my speech, let me highlight the importance of seismic design and retrofitting to avoid an astronomical amount of economic damage as well as high number of casualties caused by earthquakes. By taking advantage of the latest scientific findings and technology, we must work to build a robust community and society based on comprehensive disaster risk reduction literacy.