Claimed lower-crustal and upper-mantle earthquakes in Tibet and California: Where are they really?

Much attention has been given to claims of sub-Moho earthquakes in the continental mantle. How many of these earthquakes are truly below the Moho has been questioned based on uncertainty of hypocentral locations and vague speculation whether new methods such as Sn/Lg ratios may give erroneous sub-Moho locations in complex crustal structures. Perhaps the clearest demonstration of location relative to the Moho is when a local near-Moho earthquake has an S-minus-P time comparable to the Ps time of a teleseismic receiver-function Moho conversion with a piercing point close to the local event. This method has shown sub-Moho tectonic earthquakes in the Himalaya and sub-Moho magmatic earthquakes in Saudi Arabia, but the requirement for Ps piercing point coincidence with the local earthquake requires local epicenters less than ~half the crustal thickness from the recording station, a constraint very rarely satisfied. We examined two catalogs with nominally near Moho events: a regional catalog of tectonic earthquakes in western Tibet created using TomoDD (Dey et al., Seismica, 2025), and a local suite of magmatic earthquakes near the Nevada-California border relocated using NonLinLoc and an adjoint-simulation 3D velocity model and topographic corrections (Trugman, SRL, 2024). In western Tibet, nine earthquakes were nominally located at depths 47–74 km with epicenters