Min Xu


The focus of my research is on the seismic structure of oceanic crust created at fast and slow-spreading mid-ocean ridges (MORs) and the variability of this structure, related both to spreading rate and to temporal and spatial changes in magma delivery from the mantle.  

The first part focuses on the fast-spreading MOR segment (East Pacific Rise, EPR 9°50'N).  Specifically, I use partial-offset P- and S-wave stacking to qualitatively estimate melt-rich and melt-poor sections of the axial magma chamber (AMC), and relate these results with hydrothermal venting systems present on the seafloor and recent eruptive processes, and use the 2D time domain finite-difference (TDFD) method for the full anelastic wave equation to forward model the origin of crustal reflectivity observed at EPR 9°50'N (particuarly sub-AMC events).  These models will also be key tools to assess the offset extent, if any, of S-wave energy in our recordings, a necessary step before conducting P- and S-wave stacking. Furthermore, 1D waveform modeling of the AMC using along-axis data will be employed to obtain seismic properties (e.g., P- and S-wave velocity, density, Poisson’s ratio) that are proxies for the porosity and fluid content of the magma body.  

The second part focuses on the slow-spreading MOR segment (Mid-Atlantic Ridge, MAR 23°30’N). I used refracted arrivals recorded along a 6-km-long hydrophone streamer during a MCS survey to constrain the shallow seismic velocity structure of the Kane Oceanic Core Complex (OCC), and based on the lithological interpretation of the velocity models we did some interpretations on the temporal and spatial evolution of melt supply at the Kane OCC. In addition, I did a complementary project about the magnetic polarity reversal of the Kane OCC.  We analyzed a series of magnetic profiles collected by submersible Nautile vertically up the southern wall of the Kane fracture zone and used the calculated magnetization structure to determine the geometry of a magnetic polarity reversal boundary exposed in cross-section on the northern boundary of Kane Megamullion (KMM) on the flanks of the MAR near 23°40’N.