The Meteorological Agency plans to add alerts for long and slow seismic movements that affect skyscrapers to its emergency earthquake warning system for TVs and mobile phones, officials said Monday.

The new feature, which the agency hopes to put into operation as early as fiscal 2018, will inform the public of areas expected to experience so-called long-period ground motion.

High-rises are particularly susceptible to such motion. When large quakes produce it, tall buildings tend to sway for sustained periods, with the impact being greater on the upper floors.

Ground motion during the Great East Japan Earthquake in March 2011 off the coast of Tohoku broke a fire-proof door at a building in the city of Osaka — about 700 km from the epicenter.

That quake, which had a massive magnitude of 9.0, hit the maximum of 7 on the Japanese seismic intensity scale.

The Meteorological Agency currently issues early warnings via TV and mobile phone when it thinks a quake with an intensity of 5 or higher is about to strike.

Officials say areas projected to experience quakes of 4 or higher on the intensity scale are likely to overlap areas that will be seriously affected by long-period ground motion. But it is not unusual for distant locations to be affected by such quakes.

The agency uses a four-point scale to rate protracted ground motion. It plans to issue warnings for levels 3 and 4, when the swaying is strong enough to make standing difficult.

Development work on the project will begin in April, the officials said.

The agency has published data on long-period ground motion on its website since March 2013.

Level 4 ground motion was observed for the first time during the earthquakes that damaged Kumamoto Prefecture last April.