AIR Analyzes Chile Quake: No Tsunami; Minimal Damages Reported

March 27, 2012

Catastrophe modeling firm AIR Worldwide’s report on the earthquake that struck central Chile on Sunday night concludes that, although the quake was a strong tremor – magnitude 7.1 – minimal damages are expected, and no significant loss of life has so far been reported.

“The earthquake occurred on the subduction zone that was partially ruptured by the 2010 earthquake; it can therefore be considered another aftershock of the 2010 earthquake,” explained Dr. Tao Lai, principal engineer at AIR Worldwide. “It is located in the epicentral area of the 1928 M7.5 earthquake.”

AIR noted that officials had taken precautionary measures, evacuating approximately 25,000 coastal residents in the Bio Bio and Maule regions, “as original estimates placed the epicenter offshore in the Pacific Ocean. This same region was affected by the devastating M8.8 Maule quake in 2010, which generated a massive tsunami that wiped out parts of the coast, according to AIR. Later analysis placed yesterday’s quake onshore, which prompted Chile’s emergency officials to cancel the tsunami warning.”

The USGS estimated that more than 800,000 people “experienced strong shaking (Modified Mercalli Index of VI) and 9000 people experienced very strong shaking (MMI of VII) in the Maule region. Moderate shaking was felt in Chile’s capital of Santiago (more than 200 kilometers [125 miles] north of the epicenter), where buildings swayed from side to side for some 20 seconds.”

AIR said that “no major damage has been reported in the affected area, including near the epicenter. Falling debris has caused a few minor injuries and there are reports of traffic accidents and landslides. The quake caused massive power outages and disruptions to mobile communications.”

According to AIR, reported building damage “has typically been nonstructural in nature, mostly to roofs and ceilings.

AIR also pointed out that “Chile’s long history of damaging earthquakes has resulted in a strict building code, which is generally well enforced in cities. However, many buildings in rural locations and historic town centers are older structures constructed of adobe.

“These are widespread in the epicentral region and typically do not adhere to the country’s building code; they are characterized by poorer seismic performance than modern buildings. However, because of earthquake awareness, these adobe structures were typically built with very thick walls embedded with wood rods and straw and generally show more seismic resistance than similar construction in other regions of the world.”

AIR did explain that in 2010, “the Maule earthquake off Chile’s coast caused significant damage to thousands of older adobe structures. Damage to adobe structures was not reported yesterday, however, in part due to the weaker magnitude of yesterday’s quake.”

AIR concluded that it “does not expect significant insured losses from this event.”

Source: AIR Worldwide

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