* Dozens believed trapped in rubble after quake
* Cost of damage could run to several billion dollars
* No irregularities reported at nuclear plants
* Sony, Toyota, Honda operations affected (Adds more than 470 quakes on Japanese island since Thursday; quote from chief cabinet secretary; details of Ecuador quake)
By Kaori Kaneko and Thomas Wilson
TOKYO, April 17 (Reuters) - Japanese rescue teams on Sunday scoured the splintered remains of buildings destroyed by a series of deadly earthquakes in southern Japan as time ran out for finding survivors and as major Japanese manufacturers face production losses from supply chain disruptions.
A 7.3 magnitude tremor struck early on Saturday, killing at least 32 people, injuring about a thousand and causing widespread damage to houses, roads and bridges, with at least one mountain highway severed in two, concrete tumbling into the valley below.
In the village of Minamiaso, 11 people were “out of contact”, said public broadcaster NHK. Rescuers pulled 10 students out of a collapsed university apartment in the same settlement on Saturday.
“In Minamiaso, where the damage is concentrated, there may still be people trapped under collapsed buildings, so we are focusing our attention and rescue and search efforts in this area,” Chief Cabinet Secretary Yoshihide Suga told reporters.
It was the second major quake to hit Kumamoto province on the island of Kyushu in just over 24 hours. The first, late on Thursday, killed nine people. Of more than 470 quakes hitting Kyushu since Thursday, 78 have been at least a four on Japan’s intensity scale, strong enough to shake buildings.
Quakes are common in Japan, part of the seismically active “Ring of Fire” which sweeps from the South Pacific islands, up through Indonesia, Japan, across to Alaska and down the west coast of the United States and Central and South America.
At the other end of the ring this weekend, Ecuador’s biggest earthquake in decades killed at least 77 people, caused devastation in coastal towns and left an unknown number trapped in ruins. A 6.1 magnitude quake also struck southeast of the Pacific island nation of Tonga, with no immediate reports of damage.
Three nuclear plants in the southern Japanese region were unaffected by the second quake, but the Nuclear Regulation Authority said it will hold an extraordinary meeting on Monday to discuss the disaster.
A massive 9 magnitude quake and tsunami in northern Japan in March 2011 caused the worst nuclear crisis since Chernobyl in 1986, shutting down the nuclear industry for safety checks and sending radiation spewing across the countryside. The first reactor to restart was Kyushu Electric’s Sendai No. 1, which is at one of the plants in the region hit on Saturday.
Nearly 20,000 people were killed in the 2011 tsunami.
The Kumamoto region is an important manufacturing hub.
Toyota Motor Corp said it would suspend production at plants across Japan after the quakes disrupted its supply chain.
Electronics giant Sony Corp said its Kumamoto image sensors plant would remain suspended. One of the company’s major customers for the sensors is Apple. Meanwhile, Honda Motor Co. said production at its motorcycle plant in southern Japan would remain suspended through Friday.
Suga said the government may seek a supplementary budget to cover the cost of the quakes.
“We will do all that we can,” Kyodo News quoted Suga as telling a press briefing.
All commercial flights to the damaged Kumamoto airport were cancelled and Japan’s bullet train to the region suspended. Expressways are closed in wide areas because of landslides and cracks in road surfaces, hindering efforts to get supplies of water and food to survivors.
Overnight, rescuers digging with their bare hands dragged some elderly survivors, still in their pyjamas, out of the rubble and onto makeshift stretchers made of tatami mats.
Prime Minister Shinzo Abe said he would boost the number of troops helping to 25,000 and had accepted a U.S offer of help with air transportation.
Heavy rains fuelled worries of more landslides and with hundreds of aftershocks and fears of more quakes, thousands spent the night in evacuation centres.
“It’s full in there. There’s not a inch to sleep or even walk about in there. It’s impossible in there,” a resident of Mashiki town said outside an evacuation centre.
Firefighters handed out tarpaulins to residents so they could cover damaged roofs, but many homes were simply deserted.
Around 62,700 households were without electricity, water supplies had been disrupted to more than 300,000 homes and some areas had lost their gas supply, said NHK.
More than 110,000 people have been evacuated from the Kumamoto area, said Kyodo.
Troops set up tents for evacuees and water trucks were being sent to the area while television footage showed people stranded after the fall of a bridge being rescued by helicopters.
Police said 32 people had been confirmed dead in Saturday’s quake. The government said about 190 of the injured were in a serious condition.
The epicentre of Saturday’s quake was near the city of Kumamoto and measured at a shallow depth of 10 km (six miles), the United States Geological Survey (USGS) said. The shallower a quake, the more likely it is to cause damage.
The city’s 400-year-old Kumamoto Castle was badly damaged, with its walls breached after having withstood bombardment and fire in its four centuries of existence.
The USGS, a science organisation that provides information on ecosystems and the environment, estimated there was a 72 percent likelihood of economic damage exceeding $10 billion, adding that it was too early to be specific. Major insurers are yet to release estimates.
Additional reporting by Linda Sieg, Elaine Lies, William Mallard, Shinichi Soashiro, Chris Gallagher, Kiyoshi Takenaka, Miniami Funakoshi and Tim Kelly; Writing by Michael Perry and Nick Macfie; Editing by Lincoln Feast and Martin Howell