Correct Understanding of Probability that an Earthquake of M. 7 Class Occurred Underneath Tokyo Metropolitan Region

KATO Takaaki

doi:10.11188/seisankenkyu.64.429

Bibliographic Information

Other Title

「首都直下地震の発生確率」の適切な読み方
「シュトチョッカジシンノハッセイカクリツ」ノテキセツナヨミカタ

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Description

In 2012 Jan, a newspaper reported that “an inner-plate earthquake of M. 7 class will occur with probability 70% in 4 years, according scientific findings”. Other mass media followed the news, but they put an inner-plate earthquake as a specific earthquake whose epicenter is located under Tokyo Bay. The latter information was incorrect.<br> An inner-plate earthquake in the first news was not specific one. That means one which can occur anywhere in Tokyo metropolitan region. In general, strong shaking area by an inner-plate earthquake is limited to inside area of a circle with radius 20km at maximum. Therefore, in case of an earthquake enough far away from a specific point, there will be no damage. Probability 70% in 4 years includes all earthquakes. It is different from probability on the earthquake under Tokyo Bay and from probability which a specific point shakes. This series of reports can be said to make social awareness of disaster higher, and to contribute to promote disaster countermeasures.<br> At the same time, I can point out that it has negative effect. The correct scientific knowledge was not diffused to society. The contribution is not a reason of discharge. Ideally the situation to promote disaster prevention measures by correct scientific knowledge should be realized.<br> In this paper, I explain the difference of two probabilities from the original and information by the following mass media and demonstrate the relation of probabilities of “occurrence of an inner-plate earthquake” and “shaking of a specific point in Tokyo metropolitan region” mathematically. Finally I discuss how the information should be published.[This abstract is not included in the PDF]

Journal

SEISAN KENKYU

SEISAN KENKYU 64 (4), 429-432, 2012

Institute of Industrial Science The University of Tokyo