An 8.8 Magnitude E.Q. Shook Offshore Maule, Chile on Feb 27, 2010
An 8.8 Magnitude earthquake hit the offshore Maule, Chile on Feb. 27, 2010. The epicenter of the earthquake was located 95 kilometers from Chillan, the nearest major city of Chile. This earthquake took place at the boundary between the Nazca and South American tectonic plates at a depth of 35 kilometers [USGC fact sheet]. The two plates are converging at a rate of 70 mm per year. The death toll has exceeded 800 so far but the total fatality number is not clear yet. At least 1.5 million houses were damaged by the earthquake-tiggered tsunami in the Concepcion-Valparaiso area. Minor damage to boats and a dock in the San Diego area, California were caused by a Pacific-wide tsunami. The earthquake was felt in most parts of Chile, Argentina and some parts of Bolivia, southern Brazil, Paraguay, Peru and Uruguay. More than 90 aftershocks have been recorded, ranging from 4.9 to 6.9 in magnitude. A 6.2-magnitude aftershock was recorded near the earthquake’s epicenter on Feb 28.
The Feb 27, 2010 earthquake occurred 230 kilometers north of the 9.5 magnitude event that took place in May of 1960, the largest earthquake worldwide recorded by instrumental seismology. The Canadian Association for Earthquake Engineering is sending a reconnaissance team on March 8 and March 9, 2010 to investigate the effects of the earthquake on physical infrastructure.
The initial report received from Professor Ruben Boroschek of University of Chile indicates that, at two locations measured in Santiago, the peak horizontal ground accelerations were 0.17g and 0.24g, with corresponding peak vertical ground accelerations of 0.14g and 0.13g, respectively. The peak spectral accelerations at these two locations are 0.56g and 0.66g, respectively. The soil conditions at these locations are unclear. Comparisons with Chilean Code requirements indicate that the recorded spectral accelerations were generally in agreement with code recommended design values, with lower values within the short period range, and exceeding design values slightly in the high period range (beyond T = 1.0 sec). Similar comparisons were made with the same two records by John Adams of the Geological Survey Canada against the Uniform Hazard Spectra for Victoria, B.C., using firm soil conditions and the National Building Code of Canada (NBCC-05). The comparisons indicates that the NBCC-2005 values provide a good envelop for the spectra of these two records, with slightly higher values at 0.2 sec.
CNN photos of earthquake aftermath
Haiti – Struck by Devastating 7.0 Magnitude E.Q on Jan 12, 2010
A devastating earthquake with a magnitude of 7.0 on the Richter scale hit the Caribbean nation of Haiti. The epicenter of the earthquake was located 25 kilometers South West of the capital Port-au-Prince, causing extensive damage and structural failures. The earthquake occurred in the boundary region separating the Caribbean plate from the North America plate at a depth of 13 km [USGC fact sheet]. The tectonic structure of the region is highly complex, consisting of tangle of faults near the intersection of the Caribbean and North American crustal plates. The quake struck on a 50 to 60 km stretch of approximately 500 km long Enriquillo-Plantain Garden Fault.Close proximity of the epicentre and the shallow nature of the earthquake resulted in total destruction of Port-au-Prince and nearby towns.
The Canadian Association for Earthquake Engineering sent a reconnaissance team to Haiti. Professors Patrick Paultre and Jean Proulx of the University of Sherbrooke contacted reconnaissance studies between February 28 and March 13, 2010.
The main shock was followed by two strong aftershocks of 5.9 and 5.5 magnitude shortly thereafter. The death toll is estimated in excess of 100,000. Government alone has discovered over 20,000 bodies during the first few days of the disaster.
The earthquake wrecked the presidential palace, U.N. Headquarters and many other government buildings. The destruction is believed to be at a larger scale than that observed after the 2004 South East Asian Earthquake and Tsunami.
The construction appears to be of poor quality, with little or no seismic design practices. The predominant type of construction is non-ductile reinforced concrete frames and concrete masonry block walls.