Articles | Volume 5, issue 1
Solid Earth, 5, 327–337, 2014

Special issue: The Lithosphere-Asthenosphere Boundary (LAB) Dilemma

Solid Earth, 5, 327–337, 2014

Research article 19 May 2014

Research article | 19 May 2014

Seismic structure of the lithosphere and upper mantle beneath the ocean islands near mid-oceanic ridges

C. Haldar, P. Kumar, and M. Ravi Kumar C. Haldar et al.
  • National Geophysical Research Institute (CSIR), Uppal Road, Hyderabad-500007, India

Abstract. Deciphering the seismic character of the young lithosphere near mid-oceanic ridges (MORs) is a challenging endeavor. In this study, we determine the seismic structure of the oceanic plate near the MORs using the P-to-S conversions isolated from quality data recorded at five broadband seismological stations situated on ocean islands in their vicinity. Estimates of the crustal and lithospheric thickness values from waveform inversion of the P-receiver function stacks at individual stations reveal that the Moho depth varies between ~ 10 ± 1 km and ~ 20 ± 1 km with the depths of the lithosphere–asthenosphere boundary (LAB) varying between ~ 40 ± 4 and ~ 65 ± 7 km. We found evidence for an additional low-velocity layer below the expected LAB depths at stations on Ascension, São Jorge and Easter islands. The layer probably relates to the presence of a hot spot corresponding to a magma chamber. Further, thinning of the upper mantle transition zone suggests a hotter mantle transition zone due to the possible presence of plumes in the mantle beneath the stations.