Study: Tokyo quake could register 7
A major earthquake a government panel presumes could occur centered under northern Tokyo Bay could register 7--the strongest on the Japanese seismic intensity scale--in central Tokyo, a ministry study has found.
The new prediction came as a result of underground structure research by the Education, Culture, Sports, Science and Technology Ministry that showed an area of a plate boundary beneath Tokyo Bay is about 10 kilometers shallower than previously thought. With the new findings, the ministry said it plans to begin a review next fiscal year on current earthquake damage estimates as well as measures against the quake.
This is one of 18 major quakes the government's Central Disaster Prevention Council has calculated may occur with an epicenter beneath the Tokyo metropolitan area. The council has assumed the epicenter of the quake below northern Tokyo Bay would be at the boundary of a land plate and the Philippine Sea Plate, which subducts below the land plate. The quake's projected magnitude is 7.3.
The panel predicted in 2004 a quake would register a seismic intensity in the upper 6 range.
The ministry's research team, made up of experts from universities and research institutions, placed seismographs at about 300 locations in the Tokyo metropolitan area between fiscal 2007 and 2011. The new data contradicted the panel's previous calculations that estimated the boundary was 30 kilometers to 40 kilometers below the seabed.
Based on the new research results, the team reestimated the possible seismic intensity of a quake after revising such data as the point where the plates would collide along the plate boundary.
According to a new map that shows the estimated seismic intensity in the Tokyo area, the quake is now predicted to register an intensity of 7 in some areas, including central Tokyo, the eastern and southern parts of Tokyo's 23 wards, Kawasaki and Yokohama. The area registering an intensity of upper 6 would also be larger than the council previously assumed. Because such calculations change according to ground characteristics and other conditions, the research team intends to validate the findings and create a final quake intensity distribution map, the ministry said.
According to the panel's current damage estimates, if the predicted quake occurred below northern Tokyo Bay, 11,000 people would be killed and about 850,000 buildings would collapse or be burned down in the worst-case scenario.
If the panel revises the quake's highest intensity to 7, its estimated damage of the quake would expand.
As quake predictions involve many uncertainties, this calculation of a plate-boundary quake is simply a possibility. However, in the wake of the March 11 Great East Japan Earthquake, which has given the nation a lesson in preparing for the worst, the government has been urged to thoroughly check whether its disaster preparedness for the capital is sufficient. An apparent urgent task for the government is making social infrastructure, such as utilities, and buildings resistant to earthquakes. If structures meet the current quake-resistance requirements, they are unlikely to collapse even in the event of a quake with an intensity of 7. But if the requirements are not met, even reinforced concrete structures could collapse.
A destructive tsunami has not been predicted to strike the Tokyo metropolitan area, but water gates and dikes might be broken after the presumed quake. In light of this, the government also apparently needs to take steps to prevent subway systems and low-lying coastal areas from being flooded.
Región de Kanto. 

El Gobierno de Japón informó que las posibilidades de un gran terremoto en la región de Kantō, específicamente en la metrópolis de Tokio, podría ser peor de lo que se espera, según revelaron nuevos estudios geológicos.

Los nuevos datos revelaron que la placa continental tectónica y la placa filipina cuya parte se encuentra por debajo de Tokio se encuentra a una profundidad mucho menor a los 40 kilómetros que se creían, los nuevos datos la localizaron a tan solo 10 kilómetros, lo que generaría temblores mucho más fuertes a 7,3 grados en la escala de Richter.

Esa magnitud es capaz de alcanzar el grado 7 Shindo, (escala sísmica japonesa donde siete es la intensidad máxima) en más de 23 barrios de Tokio, así como en Kawasaki y Yokohama. El gobierno nipón reveló que el terremoto mataría a 11.000 personas y destruiría a 850.000 edificios en la zona metropolitana.

Sin embargo, este es solo uno de los 17 grandes sismos que el Centro de Prevención de Desastres del Gobierno de Japón prevé en la gran metrópoli. A pesar de la cercanía de Tokio al mar, no se prevé que el sismo genere un tsunami, pero sí que cause severos daños en represas generando inundaciones en las zonas bajas de la ciudad.

Japón tiene un eficiente sistema de alerta temprana de sismos, que alerta con segundos o incluso minutos de anticipación la ocurrencia de un fuerte movimiento,  tal y como fue el caso del 11 de marzo de 2011.