German research team deploys to Chile's quake region

With a magnitude of 9.5, the Chilean earthquake that struck on February 27 was the strongest earthquake ever measured since that in Valdivia in 1960, just south of the starting point of the currently affected region. Scientists from the German Research Centre for Geosciences (GFZ) are building a monitoring network in Chile to alert the public of such severe earthquakes.

Installation of a Creepmeter of the Plate-Boundary Observatory Chile, ©GFZ

Quakes of such strength effectively penetrate the entirety of the earth’s crust. In examining the seismic waves caused by the quake during the first 134 seconds after the rupture began, the researchers discovered that only the region around the epicenter was active in the first minute. In the second minute, the active zone moved north to Santiago.

After that, the region south of Concepción was active for just a short time. The fracture is in line with the distribution of the aftershocks that occurred over the following three days, as measured by GRZ through March 3. 

Tectonic action from Patagonia to Panama

“The earthquake on February 27 joins the break from Valdivia,” explains Jochen Zschau, director of the GRZ Earthquake Risk and Early Warning Department. “With it, one of the last two seismic gaps along the west coast of South America can now be closed. With the exception of the last section located in northern Chile, the entirety of the earth’s crust along the west coast of South America has broken.”

The underlying tectonic plate phenomenon is that the Nazca Plate, as part of the Pacific Ocean Floor, moves at around 70 millimeters per year eastwards, colliding with the South American Plate. As it does, it pushes under the continent.

The resulting earthquakes are thus among the world’s strongest. In the course of about a century, the earth’s crust has broken from Patagonia in the south all the way to Panama in the north from a series of earthquakes. Even Charles Darwin wrote of a strong earthquake in Concepción on February 20, 1835 and the resulting tsunami.

Data shows the tectonics before and after the quake

To investigate the aftershock activity in the latest seismic gaps, GFZ researchers are set to travel to Chile March 13.  Together with the Chilean seismological service, they’ll build a seismological-geodetic network in the area of Concepción – Santiago. The GRZ team will be joined by German partners from the IFM Geomar in Kiel and the Freie Universität Berlin. The researchers will be deployed for around three months with the goal of developing better insight into the mechanisms of these breaks in the earth’s crust.

GFZ researchers have been investigating the collision of the Nazca Plate and the South American Plate since 1994. The Potsdam Helmholtz Center has one of the most comprehensive records of such a zone from its many expeditions and campaigns. “In the DFG collaborative research center, we’ve collected a unique record of information relating to the southern part of the Andes,” says Onno Oncken, Director of the GFZ Department of Geodynamics and Geomaterials which is leading the study. This allows for a precise comparison of tectonics before and after the quake, a unique situation in science.

Currently, the GFZ operates a Plate Boundary Observatory in northern Chile, the last remaining seismic gap in Chile. The observatory will be given over to its Chilean colleagues in a ceremony on March 15 in connection with the earthquake service cooperation. The integrated field experiment will be accompanied by the new Berlin-Brandenburg research platform Geo.X.

www.gfz-potsdam.de