Experts reviewing the impact of "long-period ground motion" on tall structures such as high-rises following the March 11 earthquake are calling for creating a new system that would enhance warnings in the event of a major temblor and subsequent aftershocks.
Unlike the direct impact of an earthquake, long-period ground motion can at times be amplified by geographical conditions and other factors. Such slow-cycle tremors can impact a much greater area and cause serious damage, especially to large structures such as oil tanks and tall buildings.
The experts, operating under the Meteorological Agency since November, revealed Tuesday that people in skyscrapers in Tokyo, 400 km from the epicenter, felt intense shaking compared with people at ground level.