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421 - The resilience of the Chilean coast after the earthquake of 2010
January 2013
In February 2010, a violent earthquake struck Chile, causing a tsunami 10 m in height. Affecting millions of people, the earthquake and giant wave also transformed the appearance of the coastline: the dunes and sandbars were flattened, and the coast subsided in places by up to 1 m. But although the inhabitants are still affected for the long term, the shore system quickly rebuilt itself. A team from IRD and its Chilean partners( 1) showed that in less than a year, the sedimentary structures had reformed. The Chilean coast therefore represented a unique “natural laboratory” for studying coastal formation processes. The subsidence of the coast also revealed the effects of rising sea levels on shores.
405 - The new face of El Niño
May 2012
El Niño is changing. This climatic troublemaker is increasingly appearing in a form known as Modoki, Japanese for 'similar but different'. The heart of the phenomenon is moved from the eastern tropical Pacific towards the centre of the Pacific basin. New research conducted by the IRD and its partners from the Legos( 1) laboratory details the biological aspects of Modoki in the equatorial zone. Such events reduce the levels of phytoplankton in the central Pacific area: Satellite images analysed between 1997 and 2010 show the ocean to be less green during the events of 2002-2007 and 2009-2010. This colouring demonstrates reduced levels of surface marine algae, synonymous with a low level of biological activity.
Another study conducted with Peruvian( 2) researchers and those from the Locean( 3) laboratory has revealed that Modoki, inversely to its larger cousin, might be responsible for upwelling( 4) the length of the South-American coastline. A high resolution oceanic model, linked to satellite and historic data from Imarpe( 5), indicates that recent episodes have seen an increase in this rising cold water, rich in nutrients. The predicted increase in frequency of Modoki( 6) events could thus influence fishing in the zone.
402 - Exiled ‘brains’ under-employed
April 2012
Who are the Latino-American migrants? What do they do in their host country? The new MICAL observatory( 1), led by IRD researchers, enables the day-to-day study of the movements of this diaspora across the world. Thanks to this data, sociologists are able to describe the massive exile of ‘brains’ that took place in the first half of the 2000s in Latin America. Between 2000 and 2006, the number of expatriate graduates doubled, and today has reached over 3 million. It’s a loss that may be damaging in the country of origin, but can also represent a generalised loss of knowledge: these exiles very often end up under-employed. The percentage of engineers, researchers and other high grades working at an under-qualified level has greatly increased as a result. This was the case in 2006, for example, for three quarters of Bolivian and Ecuadorian migrants
Today the crisis that is currently affecting Spain is modifying or even inverting the migratory trends. A return to the new Latin-American eldorados is increasingly being observed. The consequences of this on the graduates' situation should be monitored closely.
387 - In search of lost water under glaciers
October 2011
Over 99 % of the Earth’s fresh water exists in ice formations or underground. IRD geophysicists, aiming to find ways of detecting this resource, are at the spearhead in the development of an innovatory method based on nuclear magnetic resonance. To date, it is the only technique applicable for detecting liquid water underground or under a glacier from the surface and for estimating the volume.
This method recently found an original application as an aid for warning of glacier hazard. It successfully detected the presence of an immense water pocket of 55 000 m3 sitting under the Tête Rousse glacier in Haute-Savoie. This posed a flooding threat to people living in the valley below. Warning was given and the local authorities conducted a draining operation.
This technique is adaptable to glacier risk management, but it can also help for water supply provision. It can benefit both tropical mountain areas, such as the Andes or the Himalaya where glacial water can be a major threat, given the context of climate change, and semi-arid regions where water resources lie stored deep underground.
355 - Chile: the earth shook and the coast rose up
September 2010
On 27 February 2010, a huge earthquake, with magnitude 8.8, shook Chile. It left 500 dead and 13 million Chileans were affected, amounting to nearly 80 % of the country’s population. The event was one of the six most powerful earthquakes since the beginning of the 20th Century. Coast uplift has been proved by research scientists from Chile, France, and Germany( 1). This rise reached as high as 2.5 m and resulted in an advance of the shoreline of as much as 500 m towards the sea in places. Conversely, in the hinterland, the ground subsided by nearly 1 metre.
Since 1835, date of the previous strong earthquake in this zone, the equivalent to 12 m of deformation of the earth’s crust, resulting from tectonic block convergence, had been stored at the contact zone between the Nazca Plate and the South-American Plate. On 27 February 2010, rupture of the lithosphere( 3), along a 500 km long fault segment, released most of this mechanical energy in a single abrupt shock.
This study helps better understand the seismic cycle, with the long-term objective of finding ways of predicting and preventing the seismic risk.
