Séminaire IPGS le Mardi 14 Novembre à 13h45.
Intervenant : Aurélien Mordret, MIT (
sites.google.com/site/aurelienmordretswebpage
).Titre : Toward a 3D thermo-mechanical model of the Greenland lithosphere from ambient noise tomography
Abstract :
During the past 120 million years, the Greenland craton
drifted over the Iceland hotspot; however, uncertainties in geodynamic
modeling and a lack of geophysical evidence prevent an accurate
reconstruction of the hotspot track. I image the Greenland lithosphere
down to 200 km depth with seismic noise tomography. The 3D shear-wave
velocity model obtained using 4-5 years of continuous records from the
GLISN seismic network is well resolved for most of the Greenland main
island. The crustal part of the model clearly shows different tectonic
units. The hotspot track is observed as a linear high-velocity anomaly
in the middle and lower crust, most probably associated with magmatic
intrusions. In the upper mantle, a pronounced low-velocity anomaly
below the East coast might be due to the remnant effect of the Iceland
hotspot when it was at its maximum intensity. Thermo-mechanical
modeling suggests that this area has higher temperature and lower
viscosity than the surrounding cratonic areas and experiences a higher
than average surface heat flow. This new detailed picture of the
Greenland lithosphere will drive more accurate geodynamic
reconstructions of tectonic plate motions and help to better
understand the North Atlantic tectonic history. Models of Greenland
glacial isostatic adjustment will benefit from the 3D upper mantle
viscosity model, which in turn will enable more precise estimations of
the Greenland ice-sheet mass balance.