The Japan Meteorological Agency announced starting Aug. 11 that it will implement improvements to boost the accuracy of its emergency earthquake alert system, which notifies the public beforehand of major tremors.
The Japan Meteorological Agency announced starting Aug. 11 that it will implement improvements to boost the accuracy of its emergency earthquake alert system, which notifies the public beforehand of major tremors.
The accuracy rates, which have been slightly above 30 percent after the March 11 earthquake, should improve to more than 60 percent with the improvements.
As a rule, meteorologists issue earthquake alerts to areas that are projected to experience an intensity of 4 or more in an earthquake with an estimated maximum intensity of lower 5 or more at its epicenter.
According to the agency, it has issued 87 alerts from March 11-Aug. 1 over a wide area, prompted by aftershocks of the Great East Japan Earthquake and unrelated temblors.
Of the 87 alerts, 56 were issued to areas including those that were later found to record an intensity of 2 or less. In 40 cases, the agency treated several quakes as one temblor, resulting in an overestimation of the intensity.
After the March 11 disaster, the agency revised the system's settings to differentiate a quake occurring in one area from one in another region.
The latest revision will allow the system to exclude quakes of below magnitude 3.5 because that level of earthquake is too minor to alert the general public.
The agency said it confirmed that had the new system been in place before March 11, 25 of the 40 overestimated cases would have been accurately predicted.
Akihiko Wakayama, an official with the agency's management division, said the agency will make improving the system its highest priority, and when an alert is issued, it wants people to protect themselves against an expected earthquake.