The Snake River Plain Experiment revisited. Relationships between a Farallon plate fragment and the transition zone

Éric Beucler (1) , Sébastien Chevrot (2) , Jean-Paul Montagner (3)

1 LPG - Laboratoire de Planétologie et Géodynamique [UMR 6112]
2 GET - Géosciences Environnement Toulouse
3 IPGP (UMR_7154) - Institut de Physique du Globe de Paris

We reconsider the analysis of the 93 PASSCAL-OREGON SRP experiment data. The techniques applied to the processing of Pds waves, which are P to $ conversions at seismic discontinuities at depth d in the receiver region, differ from those employed by Ducker & S/•ee/•an [1997]. We perform global moveout corrections and migration, taking advantage of the alignment of seismicity along the great circle described by the array (South America, and the Kuril and Aleutians islands). We do not detect a deep signature of a mantle plume. The 410 km discontinuity exhibits a fragmented aspect, which prevents us from reliably estimating the transition zone thickness. The 660 km discontinuity is clearly more visible, and largely deflected in a large part of the profile. We associate this anomalous behaviour and the noisy aspect of the discontinuities with the presence of a Farallon plate fragment. 660 have been reported on a regional scale study using an array of 20 broadband stations in the Yellowstone-Snake River Plain (YSRP) complex [Ducker & S/•ee-/•an, 1997]. The array configuration was a 510 km NW-SE trending line crossing the YSRP (Fig. 1), which is assumed to be the Yellowstone hotspot track [Smith & Braile, 1994]. Indeed, while a part of the magmatic material is trapped in the lithosphere under the actual Yellowstone caldera, producing high siliceous lavas, the plume is sheared by the North-American plate motion. We analyze the data produced by the 93 PASSCAL-OREGON SR.

Domaines: Géophysique [physics.geo-ph]

Éric Beucler, Sébastien Chevrot, Jean-Paul Montagner. The Snake River Plain Experiment revisited. Relationships between a Farallon plate fragment and the transition zone. Geophysical Research Letters, 1999, 26 (17), pp.2673-2676. ⟨10.1029/1999GL008345⟩. ⟨hal-03196234⟩