Japan's major electronics companies had found no serious damage to their facilities after a series of powerful earthquakes shook Niigata prefecture, northwest of Tokyo.
The first earthquake struck at 5.56pm on 23 October and had a magnitude of 6.8, according to the Japan Meteorological Agency. Ten strong aftershocks measuring between magnitude 4.4 and 6.5 and shook the prefecture and a wide region of Japan in the two hours following the main quake.
More than 300 earthquakes strong enough to be felt rattled the area between 23 October and 25 October at 9am, including one that registered magnitude 5.6. Like the other strong quakes, it could be felt across a wide area and shook buildings in Tokyo, which is about 250km away.
Sanyo Electric and Matsushita Electric Industrial both have factories in Ojiya city, which is closest to the epicenter of the string of earthquakes. Sanyo's factory produces chips for audio-visual products and the Matsushita factory is part of the company's digital copier and fax business.
"At this point, they haven't been able to get inside the building," said Ryan Watson, a spokesman for Sanyo Electric. The company has blocked employees entering as a safety measure but there has been no fire or major structural collapse, he said. "As far as equipment damage, they are not sure."
Matsushita said production at its Ojiya factory and a second factory in Niigata prefecture that produces semiconductors is currently suspended while the company checks equipment for damage.
Production was stopped and employees were evacuated on Saturday at a Sharp factory in Niigata that produces components but production has been restarted, said Miyuki Nakayama, a spokeswoman for the company.
The earthquakes also stopped production at NEC Electronics' semiconductor factory in Yamagata, said Sophie Yamamoto, a spokeswoman for the company. Production at the facility, which is one of Japan's most advanced chip factories, was suspended after the initial series of earthquakes and resumed on 24 October. It was stopped again on 25 October after another powerful earthquake, she said.
Fujitsu, Hitachi, Mitsubishi Electric, NEC, Sony and Toshiba all reported no major disruption to their operations.
The earthquakes have also put strain on the telecommunications network with major carriers reporting trouble.
NTT East reported several thousand phones lines are out of order as a result of the quakes. On 23 October it put into action its disaster messaging service that acts as a central voice mailbox and allows subscribers to leave recorded messages for people trying to reach them. As of 11pm on 24 October, the system had handled several hundred thousand messages.
NTT DoCoMo reported the first set of quakes knocked out 47 base stations and as of 12 noon 25 October 32 of these remained offline. The base stations cover 10 areas of the prefecture and in those areas 87.5% of customers cannot use their cell phones, said Takumi Suzuki, a spokesman for the carrier. Over 59,000 people posted messages on DoCoMo's I-mode disaster message board.
Vodafone KK had seven 2G (second-generation) and eight 3G (third-generation) mobile base stations out of service as of 8am on 25 October, the majority as a result of power outages in the area, said Matthew Nicholson, a company spokesman. The carrier currently has no estimate for when full service will be restored. "The government has forbidden both Tohoku Electric and the carriers from going in because it has been designated a dangerous area," he said.
KDDI's Au unit said its service is out in five areas of Niigata and its network is congested in several other parts of the prefecture.
At least 24 people were killed and 2,200 injured by the earthquakes, according to Japanese public broadcaster Nippon Hoso Kyokai. Houses collapsed, roads buckled and a Shinkansen bullet train was derailed by the quakes, which are the deadliest Japan has seen for a decade.
Martyn Williams writes for IDG News Service