August 16, 2007

scientists respond to Peru Earthquake

The earthquake was the largest to hit Peru in over six years.

Zygi Lubkowski, Associate Director at Arup, said:

“Yesterday’s earthquake is the largest event to hit this earthquake ravaged country since the 23 June 2001 (see http://www.eeri.org/lfe/peru.html). It has clearly caused damage and destruction over a wide area and it is indeed fortunate that the epicentre of the earthquake was not closer to Lima. Despite relatively modern building codes, many people in Peru reside in older and unregulated housing, which are more susceptible to earthquake shaking.”

Seismologist Dr Roger Musson of the British Geological Survey, said:

“This earthquake is on an adjacent section of the plate boundary to the earthquake of 23 June 2001, magnitude 8.4 Mw, which killed around 150 people. This earthquake fills a seismic gap between Peru and Chile, which was last active in 1877, to this extent a great earthquake in this location was expected at some point.

“Last night’s earthquake was located approximately 550 km south of a magnitude 7.9 Mw earthquake, on 31 May 1970, which killed around 50,000 people.”

Edmund Booth Consulting Engineer and expert in earthquake resistant design, said:

“This was a big earthquake, but huge events caused by movements between the tectonic plates that meet along the west coast of South America are to be expected. So this one was not in the least unusual, and there was a similar sized event at almost the same location 50 years ago. Worldwide, around half a dozen events of this sort of size occur in a typical year, but of course they only lead to devastation if they are in populated areas.

“A death toll of over 300 people is of course a tragedy but big earthquakes near centres of population, like this one, can cause very much larger loss of life. There are very few details so far on the types of building construction that fared worst; there will be scientific investigations in due course, but no surprises have emerged to date, and most likely it will be found that the usual culprits — poorly built construction not incorporating well know techniques of earthquake resistant design — have fared the worst.”

A spokesperson for he British Geological Survey, said:

“The British Geological Survey has recorded an earthquake with a magnitude of 7.9 Mw at 23:40 GMT on the 15th of August 2007. This earthquake is located near the coast of Peru, approximately 150 km SSE of Lima. A state of emergency has been declared in the coastal town of Ica, which appears to be the worst affected area. Latest reports suggest that at least 330 people have been killed in Ica, where buildings were destroyed and power supplies have been cut. The earthquake was felt strongly in the capital Lima, where buildings shook and people ran onto the street.

“A precautionary tsunami alert was issued by the Pacific Tsunami Warning Centre in Hawaii but was then withdrawn after analysis of tide-gauges.”

Dr David Rothery, Senior Lecturer In Earth Sciences, who chairs the Open University’s new course ‘Volcanoes, earthquakes and tsunamis’, said:

“Last night’s (15 August 23:40 GMT, 16 August 00:40 BST) 7.9 earthquake just off the coast of Peru was one of the largest that can be expected anywhere in the world in an average year, and caused extensive damage. This one was caused by the Nazca Plate (the floor of the Pacific Ocean) being dragged below the South American Plate. The quake was under the sea and happened at a relatively shallow depth (about 30 km or 18 miles), about the same depth as the larger Sunda Trench earthquake that caused the Boxing Day tsunami in the Indian Ocean (2004). In this case a tsunami was also caused by the sudden movement of the sea-bed, measured offshore with a height of about 30 cm locally, and reaching a tsunami-monitoring buoy 2500 miles southeast of Hawaii with a deep-water height of about 4 cm five hours later. Tsunamis are dangerous when the wave-height increases as they move into shallow water.”

Prof Bill McGuire, Director Benfield Hazard Research Centre, said: