( CNN ) -- Tokyo faces the possibility of being hit by a massive earthquake within the next four years , according to Japanese researchers . The University of Tokyo 's Earthquake Research Institute predicts there is a 70 % probability that the capital 's metropolitan area will experience a magnitude-7 quake within four years and a 98 % probability within the next 30 years . Nearly one year ago , a magnitude 9.0 quake struck off Japan 's central Pacific coast , triggering a devastating tsunami and aftershocks that left more than 15,700 dead , according to a government report in December on Japan 's recovery from the catastrophe . About 4,500 were listed as missing . Nearly 700 aftershocks registering magnitude 5 or greater followed last year 's quake , the government report said . The March 11 earthquake -- dubbed `` Tohoku '' after the region in which it occurred -- also damaged the Fukushima Dai-ichi nuclear power station , where three reactors experienced full meltdowns , creating a nuclear crisis for a country already grappling with disaster . The research institute cited for its findings the Gutenberg Richter Law , which states that an increase in small tremors will likely increase the number of larger earthquakes . According to another paper published in September , the institute concluded that the quake ruptured a fault area nearly 500 kilometers in length and 200 kilometers wide offshore . The fourth strongest quake recorded in history , Tohoku caused abrupt stress changes in the upper plate and triggered widespread seismic activity throughout the Japanese island . The northern part of Ibaraki Prefecture , in particular , saw a significant increase of shallow seismicity after the quake compared with the extremely low rate eight years prior , the researchers said . Should Tokyo 's inhabitants be worried ? The research institute 's findings carry great consequences for the 42 million people who live in the Tokyo metropolitan area . The Central Disaster Management Council has estimated that a large-scale earthquake in the next few decades could result in 11,000 deaths and an economic loss of 112 trillion yen ( US $ 1.5 trillion ) . Its goal is to halve the estimated death toll and reduce the estimated economic loss . How precise are seismic forecasts ? Gary Gibson , a seismologist at Australia 's Seismology Research Centre , called the Earthquake Research Institute 's findings `` not at all unexpected , '' given the level of seismic activity and their model . `` Seismologists can not predict with certainty when , where and how large the next big earthquake will be , '' he wrote in an e-mail to CNN . `` However , it is possible to forecast the probability of an earthquake in a particular time range ( e.g . the next four years ) , location area ( e.g . the Tokyo region ) , and magnitude range ( e.g . greater than magnitude 7.0 ) . `` Long-term forecasts use average activity levels from all known past earthquakes , geological data from fault displacements , and data about plate movement and deformation from very precise GPS measurements and other methods to determine these probabilities . '' What is the government saying ? The government 's Headquarters for Earthquake Research Promotion had put a 70 % probability of a magnitude-7 quake in Kanto region , which encompasses Tokyo and Yokohama , within 30 years , based on long-term seismicity and hazard studies . Scientists have already dubbed as `` Tokai '' an expected 8.0 quake near Suruga Bay , where large quakes have historically struck every 100-150 years , according to the Japan Meteorological Agency . The last one , a magnitude-8.4 quake , occurred in 1854 -- nearly 160 years ago . According to Gibson , the seismologist , the enhanced seismicity in the area affected by the Tohoku quake may fall towards normal levels and could affect the research institute 's findings . Results for the six-month period after the quake would become available after this coming March 11 , the quake 's anniversary , he noted . Why is Japan so prone to earthquakes ? The Japanese archipelago and neighboring areas rest on or around four tectonic plates -- the Pacific , Philippine Sea , North American and Eurasian plates -- whose movements account for one of the most seismically active places on earth . Can Tokyo withstand a 7.0 quake ? Gibson said that while the area is a very active one seismically , building standards are high , therefore reducing the damage caused by earthquakes . Buildings in Tokyo held up well in the face of the `` Tohoku '' quake . Reinforced concrete and anti-seismic systems in buildings are among features that have helped absorb shocks when earthquakes occur . Watch Tokyo 's quake-proof communities . `` A magnitude 7.0 earthquake is very much smaller than the magnitude 9.0 Tohoku earthquake , '' he wrote . `` It would need 1,000 magnitude-7.0 earthquakes to release as much strain energy as the magnitude 9.0 . The fault rupture size is tens of kilometers , rather than hundreds of kilometers , and the fault displacement two to three meters rather than 20 to 30 meters . '' Serious damage could be limited , if it occurs offshore , he added . And the shallower the quake , such as within 10 kilometers of the surface , the more localized the damage . CNN 's Junko Ogura contributed to this report .
Forty-two million people live in Tokyo metropolitan area . Institute : Tokyo faces 70 % probability of M-7 quake within four years , 98 % chance within 30 years . Government puts 70 % probability of magnitude-7 quake in region within 30 years . March 11 quake and tsunami left more than 15,700 dead , government says .