NHK has learned that most of the people who survived last year's deadly mudslides triggered by a powerful earthquake in Hokkaido were on the second floor of their homes.

The quake struck the Japanese northern prefecture in the predawn hours of September 6, 2018.

Thirty-six people were killed by massive landslides in the town of Atsuma.

NHK found there were 16 people who survived but lost family members in the mudslides that struck their houses.

It turned out that at least 14 of the 16 survivors were sleeping on the second floor of the homes at the time.

Tadao Nakamura lost his 76-year-old mother when a mudslide hit their house in the town. She was on the first floor when the disaster hit, while Nakamura escaped death by staying upstairs.

Nakamura said a wave of mud inundated only the first floor of his house. He said his mother would have been saved if she had been on the second floor.

In Japan, people are advised to go upstairs when they have no other choice in cases of heavy rains and flooding.

An expert says similar tactics could work in the event of an earthquake.

Professor Hiroaki Takahashi of Hokkaido University recommends that people locate their bedroom on the second floor and away from slopes if their houses stand in landslide-prone areas.

He urges authorities when preparing for earthquake-triggered disasters to draw up prevention measures with the dangers of steep slopes in mind.