Midterm colloquium by Line Pinna – Niels Bohr Institute - University of Copenhagen

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Midterm colloquium by Line Pinna






 
Seismological Receiver functions and Earth structure below Greenland

Studying earthquakes is one of the primary methods to unravel the hidden structure of the solid Earth. The energy released during an earthquake will propagate away from its source in the shape of seismic waves. Since the velocity of the wave depends on the material in which it travels, the wave, when arriving at the surface, brings valuable information of the planet below us.

One method which is especially useful for studying interfaces of abrupt velocity change is the Receiver Function (RF) analysis. When a compressional wave (P-wave) crosses an interface in the Earth, part of its energy is converted into a shear wave (S-wave). The S-wave is thus the result of the local structure beneath the station. By studying the difference in arrival time between the P-wave and the converted S-wave one can thus determine the depth of the interface.

The Earth can be roughly be separated into the crust, the mantle and the core. The Moho marks the boundary between the crust and the mantle, while inside the mantle two boundaries, the 410 km discontinuity and the 660 km discontinuity, mark the transition between the upper and lower mantle.

These three interfaces can successfully be examined by the RF technique.

Examples of this method will be presented for exactly these three interfaces below the west coast of Greenland. Since the presence of the ice sheet makes earthquake monitoring in Greenland difficult the majority of monitoring stations are restricted to the coast. Therefore, the RF method provides good results for especially this region.