“…A number of receiver functions (RFs) studies also find a strong, sharp discontinuity beneath the oceanic plates (Akuhara et al, 2021;Hannemann et al, 2017;Kawakatsu et al, 2009;Kumar & Kawakatsu, 2011;Mark et al, 2021;Reeves et al, 2015;Rychert & Shearer, 2011;Rychert et al, 2018aRychert et al, , 2018bRychert et al, , 2021Schmerr, 2012;Tonegawa et al, 2019;Zhang & Olugboji, 2021). Active source imaging find unexpected sharp discontinuities associated with channels (Mehouachi & Singh, 2018;Qin et al, 2020;Stern et al, 2015). Magnetotelluric imaging also finds a low resistivity channels that are also not explained by thermal models (Naif et al, 2013).…”