Hunting for oceanic island Moho

S U M M A R Y The structure of the oceanic crust conforms in general to a very simple model. However, fine-scale variations of this structure in anomalous regions (such as beneath oceanic islands) remain poorly resolved. Here we examine teleseismic receiver functions (RFs) computed at four permanent broadband seismic stations on islands in the Pacific region. The RF method is ideal for examining the fine structure of the crust because it is sensitive to the interfaces between layers, though less sensitive to average wave speed. RFs at these oceanic island stations are characterized by a train of Ps conversions from shallow depths, rather than the isolated Moho conversion typically seen at continental stations. We find that a simple three-layer structure (the old oceanic crust sandwiched between an extruded volcanic layer and an underplated layer) explains the main features of the RFs. Our data indicate that oceanic islands share a common structure, a principal feature of which is crustal underplating, with a total crustal thickness of 11–20 km.