A Japanese research team recently said that they have detected annual seafloor subsidence — or gradual caving — near the Nankai Trough off the country's Pacific coast for the first time.

The team used water pressure gauges of the Donet underwater earthquake and tsunami observation network to detect the changes in two locations off the Kii Peninsula in central Japan.

Long-term observations at multiple sites could aid in assessing the risk of major earthquakes and tsunamis.