Canal Hamamatsu | Top Page > Disaster Prevention > What is an Earthquake?
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更新日:2022年4月2日
The surface of the Earth is made up of tens of hard, flat blocks known as plates. The points at which different plates are connected sometimes hit each other or are pushed under one another due to slight movements caused by the movement of the mantle found beneath them. This has led to the formation of mountain ranges and sea trenches, and also leads to earthquakes and volcanic activity.
The Philippine Sea Plate, located in the seabed to the south of Shizuoka Prefecture, has been moving from the south, levering itself under the Continental Eurasia Plate and dragging the tip of the Eurasia Plate down with it. When the strain caused by this reaches its limit, the Eurasia Plate will bounce back causing an earthquake. This will be the Tokai Earthquake.
The Tokai Earthquake Theory was announced in 1976. The last occurrence, the Ansei Tokai Earthquake, was in 1854. If you consider that large earthquakes tend to occur in the same locations in cycles of 100 to 150 years, the "next biggie" is without doubt on its way.
Seismic Intensity Scale | How humans are affected | Situation inside structures | Situation outside of structures |
---|---|---|---|
0 | The human body cannot sense tremors of this size, but they can be detected with sensitive seismic measurement devices | ||
1 | Some people at rest in a quiet indoor environment might sense slight tremors. | ||
2 | Most people at rest in a quiet indoor environment will sense tremors. Some sleeping people might be awakened by it. | Ceiling lamps and other hanging objects will sway slightly. | |
3 | Almost all people in indoor environments will feel tremors and some walking people may even feel them. Most sleeping people will be awakened by the tremors. | Dishware, etc., on shelves will make a rattling sound. | Outdoor power lines will sway some. |
4 | Most people will experience some degree of alarm. Most people walking at the time of the earthquake will feel tremors. Most sleeping people will be awakened by the tremors. | Ceiling lamps and other hanging objects will sway noticeably and dishware, etc., on shelves will make a rattling sound. Some standing objects not firmly grounded may be toppled. | Outdoor power lines will sway noticeably, and some people riding bicycles may feel tremors. |
5 Weak | Most people will experience extreme alarm and will have an urge to grab onto something stable. | Ceiling lamps and other hanging objects will sway violently. Dishware, books or other objects on shelves may fall. Most standing objects not firmly grounded will be toppled. Household furniture not fixed in place may shift around and/or be toppled. | There may be falling glass from broken windows. Utility poles will sway noticeably. Road surfaces may be damaged. |
5 Strong | Most people will not be able to walk without grabbing onto something stable. Physical movement will be impaired. | Many objects on shelves such as dishware, books, etc., will fall. Televisions may fall from their stands. Household furniture not fixed in place may be toppled. | There may be falling glass from broken windows. Non-reinforced concrete block walls may collapse. Vending machines not securely fastened may topple. Riding a bicycle will become difficult, and many cars may come to a stop. |
6 Weak | It will be difficult to remain standing. | Most household furniture items not fixed in place will be shifted around and/or be toppled. Some doors may not be able to be opened. | Wall tiles and window glass may shatter and fall. |
6 Strong | It becomes impossible to remain standing, and movement is restricted to crawling. The tremors may be so intense that people will be unable to move at all, and might actually be physically tossed about. | Almost all household furniture items not fixed in place will be shifted around and/or toppled. | Window glass and wall tiles on many structures will shatter and fall. Nearly all non-reinforced concrete walls will collapse. |
7 | Almost all household furniture items not fixed in place will be shifted around violently and/or toppled. | Window glass and wall tiles on almost all structures will shatter and fall. Nearly all non-reinforced concrete walls will collapse. |
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