Actualité scientifique
Scientific news
N° 421
January 2013
Actualidad cientifica
The resilience of the Chilean coast
after the earthquake of 2010
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
© IRD/R-M Ojeda
sandbars were flattened,
and the coast subsided in
places by up to 1 m. But
although the inhabitants are
still affected for the long
The earthquake of February 2010 did extensive damage in Chile (here in the city of Curicó).
term, the shore system
Worth knowing
quickly rebuilt itself. A team
from IRD and its Chilean
On 27 February 2010, a mega-earthquake of a magnitude of 8.8 off the coast of Chile and the tsunami 10 m
high which followed, caused more than 600 victims, and affected millions of Chileans. Collapsed buildings and
bridges, power and telephone lines cut… the losses were evaluated at more than 15 billion dollars.
partners1 showed that in
It was one of the six most powerful earthquakes ever recorded on the planet. The Earth’s crust broke over 500 km,
along an ocean fault situated just 6 km off the Chilean coast.
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.
In addition to the material and human damage, the
consequences of the earthquake and tsunami on
the coastline biology and appearance were very
severe. For lack of previous observations, it was the
first time that a scientific team, bringing together
IRD researchers and their Chilean partners1, have
been able to describe the geomorphological impact
of such a catastrophe.
on 800 km of coast. The topographical and GPS
surveys showed that the tsunami acted like a bulldozer, destroying existing structures: dunes, underwater sandbars, beaches, etc. This “reset” made
the Chilean coast a unique case for the scientists to
understand the formation of these geomorphological structures.
High resilience of the shore
The tsunami wiped the slate clean
Less than a week after the event, the international
team had been formed and was making observations, at first on a spot basis, to evaluate the impact
A twice-monthly follow-up of the natural reconstruction of the coastline was then conducted by means
of topographical surveys, satellite imaging and georeferenced photos. They found that the shore had
FOR MORE INFORMATION
Contacts
Rafael Almar, researcher at IRD
rafael.almar@ird.fr
Tel: +33 (0)5 61 33 30 06
responded quickly to the disaster. After a few
months, most of the sandy coastal structures had
rebuilt themselves – but with a different morphology.
Unexpectedly, within one year the sediment system
had found a new equilibrium 2, different to that
preceding the earthquake.
Global warming live
The earthquake lifted the offshore bar south of the
epicentre, whereas for around 100 km to the north,
it sunk by tens of centimetres to one metre. This
subsidence reproduced within a few minutes the
effects that the rise in sea level predicted over the
coming decades would have 3. This makes the
Chilean coastline a unique natural “laboratory” to
better anticipate the impacts of global warming on
coasts. Until now, models based their projections on
a simple equation, known as the “Bruun equation”4.
Thanks to their observations, the researchers have
just shown that reality appears to be more complex
than predicted5.
UMR LEGOS (CNRS/IRD/CNES/
Université de Toulouse)
In December 2012, a joint mission with the Chilean
partners allowed a permanent observation system
for continuously tracking the dynamic of the shore to
be created. The recent creation of the Centro
Nacional de Investigación para la Gestión Integrada
de Desastres Naturales, responsible for this tracking,
will make for improved risk management for the local
fishing communities which, for their part, were
affected for the long term by the catastrophe of 2010.
Rodrigo Racienfuegos, assistant
professor and co-director of
Cigiden
racienfu@ing.puc.cl
Address
14, Av. Edouard Belin
31400 Toulouse
References
Villagran M., Cienfuegos R., Almar
Rafael , Catalan P., Camano A. Tsunami
du Chili 2010 : destruction du système
littoral et retour vers un équilibre
sédimentaire ?. Nantes : Paralia, 2012,
p. 541-548. Journées Nationales Génie
Côtier - Génie Civil, 12. 2012/06/12-14,
Cherbourg. fdi:010056158
Dic – Gaëlle Courcoux
Fritz, H.M., Petroff, C.M., Catalan, P.A.,
Cienfuegos, R., Winckler, P., Kalligeris,
N.,Weiss, R., Barrientos, S.E., Meneses,
G., Valderas-Bermejo, C., Almar Rafael,
Dominguez, J.C. and Synolakis, C.E.
2011. Runup variability of the 27
February 2010 Chile tsunami. Journal
of Pure and Applied Geophysics . 1-22.
DOI 10.1007/s00024-011-0283-5
1. Catholic University of Chile, Federico Santa Maria Technology University, the company Arauco.
2. i.e. stabilised with the strain exerted by the ocean currents, waves, storms, etc.
3. Global warming is melting ice and expanding surface water. The oceans will thus rise by around 1 m by 2100, according to the
latest projections.
4. Bruun’s equation says that the retreat of the coastline will be proportional to the rise in sea level.
5. The team compared two bays where the ground level had subsided by 80 cm. In Duao Bay, the beach had eroded by 200 m
in one year, while the beach at the mouth of río Mataquito had expanded by hundreds of metres.
Keywords
Chile, Earthquake, Coast, Tsunami
*Did you know?
The redistribution of the land masses due to this earthquake slightly reduced the planet’s moment
of inertia, i.e. its resistance to rotation, thereby shortening the length of the day by 1.26
millionths of a second.
Coordination
Gaëlle Courcoux
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© IRD/DIC, Novembre 2012 - Conception et réalisation graphique : L. CORSINI
On the left, the epicenter of the earthquake. In the center, permanent video monitoring system installed in December 2012. On the right, fishing communities
have been permanently impacted.
© IRD/ R-M Ojeda
© PUC / L. Suarez
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