Officials acknowledged that multiple seismometers had failed several months ago, and hadn't been repaired since.
The quake produced powerful tremors along parts of Japan's eastern coast, and was felt strongly in Tokyo, however, no tsunami alert was issued
Strong earthquake of 6.4 magnitude rocks Japan; advisory tsunami warning lifted as no major damages reported
A strong 6.4-magnitude earthquake rocked Japan, sparking a tsunami advisory that was later lifted with no reports, on Wednesday
About 2,500 people remain in evacuation centres in Japan's Hokkaido after landslides buried houses and rain at the weekend loosened the soil in a further threat to unstable houses.
Japan earthquake toll rises to 30 as rescuers dig through landslides; 9 still unaccounted for in worst-hit Atsuma town
The toll from an earthquake that rocked Japan's northernmost main island of Hokkaido rose to 30 on Saturday, and 9 others remained unaccounted for in rural town Atsuma after an entire mountainside collapsed on their homes
Japanese authorities on Tuesday issued landslide alerts in Osaka, after a strong earthquake a day earlier measuring 6.1 on the Richter scale left four dead and 381 injured
Japan earthquake: Toll rises to four after 81-year-old woman found dead in Takatsuki; flight, train services hit in Osaka
Residents in western Japan were cleaning up debris on Monday evening after a powerful earthquake hit the area around Osaka killing four people.
FIFA World Cup 2018: Japanese footballers worried about family after earthquake, send condolences to those affected
The Japan football team has sent its condolences to those affected by the earthquake in Osaka, with some players worried about family living in the area.
Powerful quake of 6.1 magnitude jolts Japan's Osaka: Three killed, 91 injured, tremors destroy walls and start fires
Japan's Osaka was hit by an earthquake that measures 6.1 on the Richter Scale. It killed three, injured 91, knocked over walls and disrupted the city's activities.
Japan's nuclear regulator says a nuclear power plant in the area suspended operations while it checked for any problems
Searchers found a man's body Wednesday in a landslide-hit area in southern Japan, bringing the death toll to 48 from two powerful earthquakes last week. Three people remain missing.
Rescuers in southern Japan where twin earthquakes triggered landslides found another body on Tuesday, raising the likely death toll to 45.
A magnitude-7.8 earthquake shook Ecuador's central coast on Saturday. Here is a list of some of the world's strongest earthquakes since 1900:
The death toll in a strong earthquake measuring 7.3 on the Richter Scale that struck the island of Kyushu in southwestern Japan has risen to 41.
Electronics giant Sony Corp on Sunday said production at its image sensor plant in Kumamoto, southern Japan, remained suspended as it assessed damage from a powerful earthquake.
Electronics giant Sony Corp said a factory producing image sensors for Apple Inc and other smartphone makers will remain closed while it assesses the damage from two deadly earthquakes which hit southern Japan.
Japan has been rocked by yet another earthquake, the second such quake in two days in the archipelago. The earthquake on Friday measured 7.0 on the Richter scale.
A baby girl was rescued from a collapsed house early on Friday, more than six hours after a powerful earthquake rocked Japan, leaving nine people dead.