An 8.9 Richter Scale earthquake followed by a tsunami rocked Japan on March 11, 2011. The epicenter was 130 km off the east coast of Sendai City, or 400 km northeast of Tokyo at a depth of 24.4 km. "This earthquake caused devastating tsunami wave as high as 10 m around Sendai. We are concerned with this incident. However, from this incident we can learn a lot how the Japanese Government and its citizens deal with earthquake disaster management," said Dr. Subagyo Pramumijoyo at UGM on Thursday (17/3), responding to the disaster in Japan.
Based on information from Japan Meteorological Agency in Jakarta recently, Subagyo said that wave P which came first in the seismometer record can actually be used for early warning, though only a few seconds before the earthquake had rocked the place where the seismometer was. The wave was then damaged during the earthquake due to wave S that came later after wave P.
Subagyo said that from a distance of 130 km from the epicenter, Sendai City will receive the signal of wave P at approximately 6 km/ sec speed after 21.6 seconds and wave S with 4 km/ sec speed and destructive will be arriving after 32.5 seconds. So, actually there is difference of 10.9 seconds to remind the public that there will come a devastating earthquake. Meanwhile, Tokyo, 400 km from the epicenter still has a difference of P and S wave arrivals for 33.4 seconds. "Therefore, the population of Sendai actually still have a few minutes to escape from the upcoming tsunami that swept the coastal areas," he said.
The Lecturer of Department of Geology Faculty of Engineering UGM conveyed data that in Sendai about twenty thousand homes were damaged and twenty thousand people died. The Japanese government deployed fifty thousand martial troops, while NHK also directly performed coverage in areas hit by the tsunami with a helicopter. "Because the best hierarchical organization in Japan is the organization of soldiers," said Subagyo Pramumijoyo.
From various information and television shows, Subagyo assessed that Japanese society has earthquake awareness and disaster preparedness. Because the country is in earthquake-prone region, people have been given earthquake socialization. "They search for the nearest shelter, under a desk or where they feel safe. People seemed to be much trained with the earthquakes," he added.
Subagyo assessed that high discipline and honesty had a contribution in the way the community faced the disaster. "I think without high discipline, people will not be calm during the earthquake. Also, they are queuing in an orderly manner to obtain aid after the earthquake occurred. Prices in Tokyo are stable, too. In contrast to the experience of the earthquake in Yogyakarta, 2006, the price of a box of instant noodles had tripled," said Subagyo.
Similarly, the handling of nuclear reactors in Fukushima, the Japanese government responded immediately by declaring a nuclear emergency. The government had to evacuate 200,000 people away from a radius of 20 km from the reactors. "We certainly can learn how to build a nuclear reactor, but also how to equip nuclear managers with high discipline," he explained.
The reactors currently handled by experts, the current radiation level had reached 160 times of normal radiation level. In fact, four days after the destruction of the Fukushima reactor, Tokyo people which is over 250-km distance had been advised to stay indoors because of fears of nuclear dust. "Again, we can learn from this incident. Even if there is a desire to build a nuclear reactor, we can choose the most secure place during disasters, especially earthquakes. With a variety of economic considerations, we are expected to have a nuclear reactor, but it needs to be considered where the waste will be disposed of," he concluded.