Attenuation tomography of the upper mantle

Alice Adenis (1) , Eric Debayle (1) , Yanick Ricard (1)

1 LGL-TPE - Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement

We present QsADR17, a global shear wave attenuation model of the upper mantle. Synthetic tests confirm that large-scale shear attenuation anomalies are resolved in the whole upper mantle with limited vertical smearing (≤50 km). QsADR17 shows strong correlation with surface tectonics down to 200 km depth, with low attenuation beneath continents and high attenuation beneath oceans. The attenuation signal near 250 km depth is dominated by a high-quality factor along subduction zones. Attenuating anomalies are found beneath mid-ocean ridges down to 150 km and under most Pacific hot spots from the lithosphere down to the transition zone. The presence of broad attenuating anomalies at 150 km depth in the Pacific Ocean suggests that several thermal plumes pond in the asthenosphere. Evidence for compositional heterogeneities is found in the lithosphere at the base of cratons and in a number of active regions.

Keywords: tomography; attenuation; surface wave; Pacific Ocean; mantle; shear wave; tomography

Domains: Sciences of the Universe [physics]; Earth Sciences

Alice Adenis, Eric Debayle, Yanick Ricard. Attenuation tomography of the upper mantle. Geophysical Research Letters, 2017, 44, pp.7715-7724. ⟨10.1002/2017GL073751⟩. ⟨insu-03710108⟩