Chile Earthquake: ‘A Complicated Fracture’
‘A jumping rupture process’
The Chilean M8.8 megaquake that struck offshore Maule region on 27 February, was a “complicated rupture process” scientists at the GFZ German Research Center for Geosciences say.
Quakes of this magnitude break the entire Earth’s crust, they said. “After closer analysis of the seismic waves radiated by this earthquake during the first 134 seconds after start of the rupture, the researchers came to the conclusion that only the region around the actual epicenter was active during the first minutes. In the second minute the active zone moved north towards Santiago. After that the region south of Concepción became active for a short time. This rupturing trend agrees well with the distribution of the aftershocks during the following three days, as observed by the GEOFON-measuring network of the GFZ up to 03.03.2010.”
Rupture Propagation After Southern Chile’s Maule Earthquake. © GFZ. Click Image to Enlarge.
In 1960, the largest ever instrumentally-recorded earthquake, which measured magnitude 9.5, originated at Valdivia, south of the Maule region. “The quake of 27 February connects directly to the rupture process of Valdivia,” said Professor Jochen Zschau, Director of Earthquake Risk and Early Warning Section at the GFZ. “With this, one of the last two seismic gaps along the west coast of South America might now be closed. With the exception of one last section, found in North Chile, the entire earth crust before the west coast of South America has been ruptured within the last 150 years.”
The Nazca plate which forms a part of the Pacific Ocean Floor moves eastwards at about 70mm per year, subducting the South American plate. Thus producing very powerful earthquakes in the region. “In the course of about one century, the Earth’s ruptures completely in a number of strong quakes from Patagonia in the South to Panama in the North. Even Darwin reported, in his diary, of the strong earthquake in Concepción on 20 February 1835 and the resulting Tsunami.”
Chile Earthquake History. © GFZ. Click Image to Enlarge.
GFZ researchers have reportedly studied the collision of the Nazca plate and the South American Plate since 1994. “As a result of numerous expeditions and measuring campaigns in this area this Potsdam Helmholtz Centre avails of the probably the most dense data record on such a subduction zone. “Within the framework of the DFG Priority Programme “Deformation processes in the Andes”, and with the Geotechnology Project TIPTEQ we have just been able to collect a unique data record for the southern part of the Andes” says Professor Onno Oncken, Director of the Department Geodynamics and Geomaterials at the GFZ, and leader of these studies. The current quake puts us in the position to precisely compare the tectonics before and afterwards, a unique situation both internationally and in Earth science.”
GFZ is operating the Plate Boundary Observatory (PBO) in northern Chile, which they’ll hand over to Chilean researchers on 15 March 15, 2010.
Related Links:
Fire Earth 