Seabed seismometers planned to improve prediction
The Education, Science and Technology Ministry is to install 400 seismometers on the seabed in areas close to the expected epicenters of the anticipated Tokai, Tonankai and Nankai earthquakes in a five-year project starting from April next year. The sensors are intended to help predict the occurrence and scale of the quakes, which experts expect to be massive magnitude-8 events on the open-ended Richter scale. According to the government's Earthquake Research Committee, there is an 87 percent possibility of a major quake in the Tokai region within the next 30 years. The Tonankai earthquake is between 60 and 70 percent likely, while there is a 50 percent of the Nankai quake occurring. The committee also estimated that a quake could hit magnitude-8.5 if the Tonankai and Nankai earthquakes occurred simultaneously. If all three earthquakes occur simultaneously, the committee predicts that there would be about 25,000 casualties. Despite such alarming predictions, research on the areas of the seabed anticipated to be near the epicenters of the Tokai, Tonankai and Nankai earthquakes is still at an early stage. This is because of the relatively high cost of installing sensors on the seabed compared with installing them on land. The five-year project will cover an area from SagamiBay to the KiiPeninsula, as well as the one from Shikoku to the Sea of Hyuga. In both areas, seismometers will be placed 10 to 20 kilometers apart. Hydraulic gauges will be also installed in these areas to observe seismic activity and crustal movements. The sub-seafloor structure of the areas will be closely examined using data from the drilling vessel Chikyu (Earth) of the Japan Agency for Marine-Earth Science and Technology. The studies help prediction of the places most likely to be hit by large earthquakes, as well as their probable scale of the likelihood of following tsunami.