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Tianze Liu, PhD Student at Stanford, presents “Post-critical SsPmp and its application in Virtual Deep Seismic Sounding (VDSS)” at the MIT Earth Resources Laboratory.
Live video of this talk will be available on our Youtube Channel.
“In recent years, Virtual Deep Seismic Sounding (VDSS) has emerged as a novel method to image the Moho. However, the nature of post-critical SsPmp, the seismic phase used in VDSS, is not well understood. Here, inspired by Yu et al., (2012), a study conducted at MIT showing significant discrepancy between VDSS and receiver-function (RF) Moho depths in North China, we explore the sensitivity of SsPmp phase shift, amplitude and travel time to lithospheric structures. Our findings are (1) SsPmp phase shift is sensitive to upper-mantle and lower-crustal Vp, (2) SsPmp amplitude is insensitive to Moho sharpness, but is reduced when sedimentary basin is present at the virtual source, and (3) SsPmp travel time is not only sensitive to crustal properties, but also lateral heterogeneity in the lithosphere. We then apply VDSS to data collected by the Yellowknife array in SW Slave Province, which shows a crustal thickness of 38 ± 4 km, an average crustal Vp of 6.6 ± 0.2 km, and an upper-mantle Vp of 8.0–8.1 km/s, which agree reasonably well with results given by active-source studies. In addition, with a VDSS-RF joint analysis, we estimate the average crustal Vp/Vs ratio to be 1.76 ± 0.06, in good agreement with traditional H-k stacking results. Furthermore, the joint distribution of our average crustal Vp and Vp/Vs ratio indicates an intermediate average crustal composition. This intermediate crustal composition, together with the Neoarchean age of SW Slave province, may imply the change of crust-forming mechanism from plume tectonics to plate tectonics during late Archean.”