“…Since the first discovery by Revenaugh and Sipkin (1994) from multiple‐ScS reverberation mapping in northeast Asia, a seismic low velocity layer (LVL) above the mantle transition zone (MTZ) has been observed with a thickness ranging from 20 to 90 km in a number of tectonic settings, including convergent oceanic margins, plume, and continental collision zones (Tauzin et al., 2010; Vinnik & Farra, 2007; Wei & Shearer, 2017). Seismological methods used to detect such a LVL range from multiple‐ScS reverberations (Bagley et al., 2009; Courtier & Revenaugh, 2007; Revenaugh & Sipkin, 1994), receiver functions (Liu et al., 2016; Tauzin et al., 2010, 2017; Vinnik & Farra, 2002, 2007), SS precursors (Wei & Shearer, 2017), body wave triplications (Gao et al., 2006; Han et al., 2021; Song et al., 2004), and seismic tomography (Obayashi et al., 2006). Marked by a sharp interface with the overlying mantle and a 2%–6% reduction in shear wave velocity, the LVL is generally recognized as a chemical, rather than thermal, anomaly.…”