【5】 Characteristics of the Next Nankai Earthquake

1) Strong Shaking

   The next Nankai Earthquake is expected to be around magnitude 8.4 (about 4 times the size of the 1946 occurrence). Most areas of the prefecture will experience strong tremors of seismic intensity strong 5 to strong 6 (some areas will be 7). These tremors should continue for around 100 seconds.

2) Land Subsidence and Inundation by Seawater

   The earthquake may cause the land in some areas to sink, leading to inundation with seawater prior to the arrival of the tsunami. In 1946, the land around Cape Muroto and Cape Ashizuri was upraised, and the central region around Kochi City sank.

3) Landslides

   Landslides caused by earthquakes can give rise to a phenomenon called Mountain-Tsunami. This occurs when a landslide blocks a river, forming a temporary dam that holds back a lake. When this unstable dam breaks, water and debris rush down the valley, forming a tsunami from above. This may also occur after heavy rains, not just after earthquakes. It is particularly concerning if an earthquake strikes during a time of heavy rain. Be particularly careful if the river exhibits any changes after an earthquake (eg. a change in water-level, or the river suddenly goes murky)

4) Large Tsunami

   The next Nankai Earthquake will give rise to large tsunami over 3m high. These will hit coastal areas very soon after the earthquake.

5) Predicted Damage

   The Predicted Damage to Property and People from the Next Nankai Earthquake
   (Assuming the earthquake hits in the early morning when most people are asleep.)

(2nd Kochi Basic Earthquake Management Study, March 2004)
Number of buildings destroyed (Excludes partly destroyed/ damaged) Total By tremors By tsunami By landslide By fire By land liquefaction
Approx. 81,600 (15.4% of all 530,000 buildings within the prefecture) Approx. 31,200 Approx. 35,700 Approx. 9,900 Approx. 2,700 Approx. 2,100
Killed and Injured Total Total Killed Total Injured
Approx. 20,390 (2.5% of the 810,000 people in Kochi – from 2000 Census) Approx. 9,630 (1,800 by building collapse, 7,000 by tsunami, 680 by landslide and 150 by fire) Approx. 10,760(9,340 by building collapse, 850 by landslide and 570 by fire)