Deadly Japanese earthquake: What we know so far

More than 40 people are believed to have died after a powerful earthquake struck southern Japan on Saturday, the second quake in days.

Here's what we know so far about the disaster.

  • What happened?

A 7.3 magnitude earthquake hit southern Japan at 1.25 am local time (4.25pm GMT).

The epicenter of the quake was near the city of Kumamoto on the southern island of Kyushu and measured at a shallow depth of 10 kms (6 miles), the United States Geological Survey said.

A tsunami warning was issued, but this has since been lifted.

  • How many people have died?

According to local media, at least 40 people have been killed as a result of the earthquake.

It is also thought that more than 1,000 people have been injured.

A woman stands in front of a destroyed house. Credit: Reuters

Others remain trapped in collapsed buildings, with chief cabinet secretary Yoshihide Suga saying nearly 80 people were believed trapped or buried in rubble.

Local media said 11 people were trapped in a university apartment in the town of Minami Aso as well as in a nursing home in the town of Mashiki.

Up to 20,000 troops are expected to be helping with rescue efforts by Sunday, in addition to police, firefighters and medics.

Prime Minister Shinzo Abe said: "Nothing is more important than human life and it's a race against time. I want rescue activities to continue with the utmost effort."

  • How much damage has been done?

Television footage of the area showed fires, power outages, collapsed bridges and gaping holes in the earth.

Residents near a dam were told to leave because of fears it might crumble, while the 400-year-old Kumamoto Castle was badly damaged.

Around 170,000 homes were without power and 385,000 without water, Suga said.

No irregularities were reported at three nuclear power plants in the area, a senior government official said.

Factories producing vehicle parts and tech components for companies including Sony and Honda halted production as they assessed the damage.

The region's transport network suffered considerable damage with one tunnel caved in, a highway bridge damaged, roads blocked by landslips and train services halted.

Kumamoto airport was also closed.

  • Is there a danger of another earthquake?

There are plenty of reasons for people to be concerned about another big quake.

Saturday's earthquake followed a 6.5 magnitude quake which left nine people dead on Thursday.

Since then there have been more than 230 aftershocks of at least level one on the Japanese scale, Japan's meteorological agency said.

Many people have been evacuated from their homes. Credit: RTV

Aftershocks from Saturday's earthquake have hindered rescue efforts and fueled fears of more powerful quakes.

John Bellini, a geophysicist at the USGS, said: "We have already seen of several of the mid to upper five plus magnitude range, and over the next several days and weeks, we would not be surprised to see more earthquakes of this size."

  • Why is Japan so susceptible to earthquakes?

Japan is on the seismically active "ring of fire" around the Pacific Ocean on the edge of several continental and oceanic tectonic plates.

This area of high seismic and volcanic activity runs from New Zealand, through Japan and across to Alaska.

As a result, Japan experiences frequent earthquakes and has many volcanoes.