By Ivan Alvarado
COPIAPO, Chile (Reuters) - Two small tremors shook northern Chile early on Wednesday but did not disrupt efforts to rescue 33 miners trapped deep underground 20 days after a cave-in, as the men sent heartwarming messages to relatives on the surface.
Engineers are working to install a big drill to dig out the miners, found alive on Sunday. They face an up-to-four-month wait for rescue in a hot, humid tunnel half a mile deep, a wait they have yet to be told about.
Witnesses at the mine head said the tremors were not felt at ground level. It was unclear if the miners, who are 4.5 miles (7 km) inside the winding mine, 2,300 ft (700 meters) vertically down, were jolted.
The nation is still recovering from a devastating February 27 quake -- one of the biggest ever recorded -- and ensuing tsunamis, which killed more than 500 people and ravaged cities, roads and industries in south central Chile.
Miners and their relatives are exchanging letters via a narrow shaft the width of a softball, a crucial part of maintaining their mental health.
"You have no idea how much my soul aches to have been underground and unable to tell you I was alive," trapped miner Edison Pena said in a letter to his family.
"The hardest thing is not being able to see you."
Fellow miner Esteban Rojas promised his wife he would finally buy her a wedding dress as soon as he gets out, and hold a church marriage ceremony, 25 years after they wed in a registry office.
Officials are vetting letters sent by relatives, to avoid any shocks. Some disagree with the method.
"It's very important for the miners' mental health that they communicate openly with their families, and without filters, either by letter or by phone," said Claudio Barrales, a clinical psychologist at the Universidad Central in Santiago.
LIFE GOES ON
Trapped miners' relatives, who have been living in plastic tents at the mine head in a makeshift settlement dubbed Camp Hope, are gradually returning to their normal lives, but some are drawing up rosters to take turns being at the mine.
Rescue crews are sending hydration gel, soup and medication through the narrow bore hole to keep the miners alive during the long rescue effort.
An intercom has been set up, and mini entertainment devices may be sent down the hole to help ease the pressure.
To avoid hurting morale, officials have not yet told the miners how much longer they will likely be underground.
But many people think they deserve to know.
"It's always good to know," Commodore Ronald von der Weth Fischer, head of Chile's submarine fleet, told Reuters from aboard a submarine in the port city of Valparaiso late on Tuesday.
"I'd recommend keeping communication flowing, so that they are connected to the outside world. They should hear the news, know what's going on with their favourite soccer teams, to create a feeling of normalcy."
Engineers hope to start drilling the escape shaft by the weekend. They are building a concrete platform on which to erect the drill, which will bore a vertical shaft around 2 feet (62 cm) in diameter. The plan is to use a pulley and cage to evacuate the miners one at a time once the shaft is complete.
Chile's government has turned both to navy submariners and to NASA for survival tips, and wants to send the men high-nutrient, space mission-like rations.
The miners have lost around 22 pounds (10 kg) each after surviving on half a glass of milk and two mouthfuls of canned tuna every 48 hours until supplies ran out.
The men have sent samples of water from underground tanks that have helped them to survive to the surface for testing, and rescuers are sending down fortified mineral water.
The miners are in remarkable health, and have stripped off their shirts to deal with the heat.
Officials are looking for ways to help ease psychological pressure, and plan to set up special lighting in the tunnel to mimic night and day, with dull red lights to help the miners sleep. They are also going to send down games like cards.
The accident in the small gold and copper mine has turned a spotlight on mine safety in Chile, the world's No. 1 copper producer, although accidents are rare at major mines. The incident is not seen having a significant impact on Chile's output.
President Sebastian Pinera has fired officials of Chile's mining regulator and vowed to overhaul the agency.
Analysts say the feel-good factor of finding the miners alive, coupled with the government's hands-on approach, could help Pinera as he tries to push through changes to mining royalties the centre-left opposition had shot down.
(Additional reporting by Antonio de la Jara, Maria Jose Latorre and Molly Rosbach; Writing by Simon Gardner; Editing by Jerry Norton)
