49 Setting up the prototype seismic vault that will house the equipment for some of the seismic stations of the future permanent RESIF broadband array. Very Large-Scale Research Infrastructure to probe the Earth’s interior Dedicated to the study of the Earth’s interior, the French seismological and geodetic network (RESIF) is taking shape. With an array of 750 seismological and geodetic instruments throughout France (plus an additional 150 by 2020), it will provide more refined data about ground deformation. This Very Large-Scale Research Infrastructure, a significant French contribution to the European infrastructure project EPOS (European Plate Observing System), will be used not only for fundamental research but also to shed light on the hazards related to ground motion, especially earthquakes, and improve management of natural resources. What happens when Earth’s magnetic field flips Researchers have broken new ground in understanding the Earth’s magnetic field reversals. By combining on a common timescale data from ten sequences of overlying volcanic flows that had recorded the direction of the field, researchers were able to construct a model in three phases: a precursory event, the north-south (or south-north) polarity switch, followed by a rebound. The switch between the two polarities appears to be very rapid, lasting no longer than 1,000 years. This model challenges a number of ideas about the processes involved during such reversals. Nature October 2012 Using seismic noise to probe the deep Earth -------------------------------------------------------------------------------------------------------------------------------------------------------- For the first time, seismologists in Grenoble have succeeded in using the seismic noise generated by ocean swell to probe the deep Earth. Researchers have long used seismic waves to determine the structure, temperature and composition of the Earth’s interior. However, they had to wait for an earthquake to occur in order to do so. Although a more recent method using surface waves generated by ocean swell (seismic noise) made it possible to overcome this problem, it could only image the Earth’s surface layers. Now, for the first time, seismologists in Grenoble have succeeded in using the body waves in the seismic noise, which penetrate to greater depth, to locate the boundaries of the transition zone separating the upper and lower mantle at a depth of between 410 and 660 kilometers. To do this, they used an array of 42 seismic stations located in Finland. The advantage of the method is that it can be implemented at any time, independently of the occurrence of earthquakes. Science November 2012 Left: current distribution of seismic stations making up the permanent broadband array. Right: planned configuration of RESIF’s permanent broadband antenna. Class A stations Class B stations operational planned planned 2012 A year at CNRS
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