Abstract
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.
Highlights
Mid-oceanic ridges (MORs) are the largest sources of magma on the earth
We interpret the shallower LVLs as conversions from the lithosphere–asthenosphere boundary (LAB), since they are consistent with previous receiver function studies (Li et al, 2003; Heit et al, 2007; Rychert and Shearer, 2009 etc.)
For stations PSCM and ROSA, our conversion point plots show that the data sample a similar upper mantle region (Fig. 7) and the upper mantle transition zone is normal compared to the global average value
Summary
Mid-oceanic ridges (MORs) are the largest sources of magma on the earth. Being the locus of new lithosphere generation and accretion to the existing ones, their study assumes importance in understanding the dynamics of plate tectonics. Most of the seismological knowledge of the oceanic plates, near the ridges, comes from highresolution 3-D seismic tomography studies using active source data (Evangelidis et al, 2004). Seismic reflection/refraction studies have been carried out near the ridges (Bjarnson and Menke, 1993; Evangelidis et al, 2004; Rodgers and Harben, 1999) in and around the Atlantic All these studies reveal a highly variable crustal structure. We attempt to investigate the seismic structure using the available data from five seismological stations situated on the islands located close to the mid-oceanic ridges. The crustal structure may not truly represent the nature of the oceanic plate due to possible influence of the islands, the deeper structure is devoid of such effects
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
