Catastrophe in Chile

Abstract

A S ALL the world now knows, one of the worst catastrophes in seismic history struck southern Chile in May, 1960. A series of severe earthquakes, beginning on the morning of the twenty-first, devastated the country for a distance of a thousand miles. Ten days of terror left some iooo persons dead and 350,000 homeless; 65,000 dwellings were destroyed, and 8o,ooo were damaged.' The first shock lasted barely 3 5 seconds, yet nearly one-third of the buildings in the city of Concepcion are said to have collapsed. The ground movements that followed on May 22 toppled buildings in the cities of Valdivia, Puerto Montt, and Temuco. On the same day the maremotos (seismic sea waves, or tsunamis) that accompanied the earthquake hit the coastal areas south of Concepcion and swept into the sea many fishing settlements on both the mainland and the islands. On the island of Chiloe the waves destroyed four-fifths of the buildings of Ancud; Castro was heavily damaged by fire. Communications south of Santiago were disrupted, and even as this account is in proof, some two months later, little is known of the fate of smaller communities on Chiloe and the islands to the south. Navigation on the channels forming Chile's inland waterway south of Puerto Montt was prohibited because islands had disappeared and new islands had appeared. The Chilean government is faced with the necessity of revising completely its navigation charts for some 8oo miles of maritime canals from Chiloe to the Strait of Magellan. Part of what remained of the city of Valdivia had to be evacuated because of the threat of floods from the Rio San Pedro, the outlet of Lago Riniihue, with its large watershed in the cordillera. Displacement of earth at three places along the river had dammed the waters at the outlet of the lake. The lowest of the three slides contained at least fifty million tons of material, mostly clay and glacial debris intermingled with enormous amounts of vegetation. An increasing head of water behind these obstructions would sooner or later break through, and the resulting flood would wipe out everything on its way to the sea. In a race against the rising waters, swollen by heavy rains, Chilean engineers and workmen began construction of bypassing canals around the three slides. They also blasted down the walls of the canyon immediately below the lowest slide to reinforce it; the two upper slides, which were smaller, were leveled off and faced with wire cable and timber, being in effect made into dams. On July 7 the spillway canals were put in operation, and the water level in Lago Riniihue, which by this time had risen some 65 feet, began to fall. It was the hope and expectation that the level in the lake would drop rapidly enough so that even if the three slides became saturated and gave way, the damage below would not be great.