Danger from New Type of Seismic Activity in Japan

Researchers have discovered a specific type of seismic movement occurred in the Magnitude 7.3 earthquake that hit Kumamoto in April.

    They say long-period ground motion was as strong as ever observed during an inland earthquake caused by faults slipping. The scientists say the movement was strong enough to topple a high-rise building, Japan's broadcaster (NHK World) reported.

    Professor Yoshiaki Hisada of Kogakuin University ran a simulation with the premise a 29-story building in Tokyo was hit by this type of action. The 150-meter high building appears to heave when it is shaken by the long-period ground motion as powerful as that observed in Kumamoto. 

    The simulation he conducted on the skyscraper showed the uppermost floor could sway as much as 3.5 meters. The building would remain tilted even after the tremors subside.

    Hisada says the long-period ground motion was 3 times as powerful as planned for by construction firms erecting high-rise buildings. This means many structures may not withstand such violent tremors.

Experts say government officials need to step up earthquake safety measures for urban areas near active faults.

Soruce ; QNA