A powerful 8.8 magnitude earthquake on the Richter scale has struck south-central Chile. The quake, the third strongest in the past 100 years, was centered in the VIII Administrative District of Chile also known as the Bío-Bío near the city of Concepción, Chile’s second largest city with just under 900,000 inhabitants. The quake struck at approximately 3:30 AM local time when most residents were sleeping and was felt as far north as Santiago and as far east as Mendoza, Argentina.
The quake, which was centered 22 miles deep in the Earth, set off a tsunami with warnings spanning the Pacific including ones for Hawaii and southern California. Tsunami warnings are in effect for 53 countries across the Pacific Basin. Waves hit the Juan Fernández Islands (the setting for Robinson Crusoe) wiping out half of the small town. The coastal areas of Easter Island were evacuated as a precaution. A tsunami wave travels at about 600 miles per hour, about as fast as a jet, and it can be expected to cross the Pacific and hit Japan 21 hours after the quake hit.
The loss of life so far stands at 147 but is expected to rise as Chileans awake to the devastation and sift through the rubble. This was a deep quake though it was 101.8 times more powerful than the 7.0 quake that struck Port-au-Prince back on January 12, 2010. However, the Haiti quake was shallower and Haiti’s infrastructure wasn’t built to withstand quakes. Chile has much more experience with earthquakes and much more stringent building codes. Nonetheless, the damage to infrastructure especially in Concepción seems vast. The city was founded in 1550 and one can expected buildings from the colonial era to have suffered immensely.
The Bío-Bío is one of the world’s richest fisheries. That small region accounts for some 5 percent of world seafood production. The region is a major producer of sea bass, farmed salmon (Chile’s second largest export), mackerel, hake, sardines and anchovies. The Bío-Bío is also, not surprisingly, a major shipbuilding center. The area is also a major forestry products producer and a tourist gateway to the lake district in Patagonia. The region is named after the Bío-Bío river, one of the most rugged rivers in the world and a major whitewater rafting destination. Finally, the region is a major hydroelectric power producer.
The quake comes at an odd time for Chile as the country is in the midst of a Presidential transition and a change of power from one party to another. Sebastián Piñera, the first right of center candidate to be elected President in Chile since 1958 and the first conservative since the end of the Pinochet dictatorship, is to assume the oath of office on March 11th. Outgoing President Michelle Bachelet has declared a “state of catastrophe.”
Chile’s Seismic History
The magnitude-8.8 earthquake that struck off the coast of Chile early Saturday morning occurred along the same fault responsible for the biggest quake ever measured, a 1960 tremor that killed thousands in Chile and hundreds more across the Pacific.
Both earthquakes took place along a fault line where the Nazca tectonic plate, the section of the earth’s crust that lies under much of the Eastern Pacific Ocean south of the Equator, is sliding beneath another section, the South American plate. The two are converging at a rate of about three and a half inches per year.
Earthquake experts said the strains built up by that movement, plus the stresses added along the fault line by the 1960 quake and smaller ones in the intervening years, led to the rupture on Saturday along what is estimated to be about 400 miles of the fault. The quake generated a tsunami, with wave heights of about 5 feet recorded along the Chilean coast and larger waves forecast for Hawaii and elsewhere in the Pacific.
The quake was centered about 140 miles north of the center of the 1960 earthquake, which ruptured more than 650 miles of the fault and was measured at magnitude 9.5. The fault is a thrust fault, in which most of the ground motion during a quake is vertical.
Experts said the earthquake appeared to have no connection to a magnitude 6.9 quake that struck off the southern coast of Japan on Saturday. The Chilean event also had no connection to the magnitude-7.0 quake that occurred in Haiti on Jan. 12.
That quake, which is believed to have killed more than 200,000 people, occurred along a strike-slip fault, in which most of the ground motion is lateral.
Paul Caruso, a geophysicist with the U.S. Geological Survey in Golden, Colo., said the quake on Saturday generated about 500 times more energy than the Haitian quake, which was measured at magnitude-7.0. “But even though this quake is larger, it’s probably not going to wreak the devastation that the Haitian quake did,” at least on land, Caruso said.
For one thing, he noted, the quality of building construction is better in Chile than in Haiti. And the fact that the quake occurred offshore should also help limit the destruction. In Haiti, the rupture occurred only a few miles from the capital, Port-au-Prince. The rupture on Saturday was centered about 200 miles southwest of the Chilean capital, Santiago, and 60 miles from the nearest town, Chillan.
In some respects, the Chilean quake is similar to the Indonesian earthquake of Dec. 26, 2004. That quake, which also occurred along a thrust fault, generated a tsunami that killed more than 200,000 people around the Indian Ocean.
When they occur underwater, thrust-fault earthquakes are far more likely to create tsunamis than tremors on strike-slip faults, said David Schwartz, an earthquake geologist with the geological survey in Menlo Park, Calif. “When they slip, the fault that causes the earthquake breaks the surface, and pushes the water up,” he said. “It pushes an awful lot of water. And that water has to go somewhere.”
That is what occurred in 1960. A tsunami generated by that quake devastated Hilo, Hawaii, with waves as high as 35 feet, killing 61 people. The tsunami reached as far as Japan, reaching northern parts of the main island, Honshu, about a day after the quake and killing 185 people and destroying more than 1,600 homes.
The New York Times has a full account as does The Independent. The UK Guardian has some great coverage of the tsunami impact.
If you understand Spanish, you can watch Chilean television at TV de Chile on Ustream.