What Controls Effective Elastic Thickness of the Lithosphere in the Pacific Ocean?

摘要

The effective elastic thickness (Te) of the lithosphere is a proxy for mechanical strength and can be used to constrain lithospheric rheology and understand how surface deformation relates to deep Earth processes. Here, we map Te variations over the Pacific Ocean from the inversion of the admittance between free-air gravity anomaly and bathymetry data calculated using a continuous wavelet transform, taking both surface and subsurface loads into account. The Pacific lithosphere show Te ranging between 0 and 80 km with a mean of 13.5 km and a standard deviation of 12.3 km. We find that Te is generally poorly correlated with plate loading age, crustal age, heat flow and Curie point depth, except for relatively young (<60 Ma) and warm lithospheres. Most oceanic plateaus and seamounts show Te <= 10 km, with the lowest values (<5 km) around active spreading centers. The highest Te estimates (>30 km) are found along subduction zones and around the Hawaiian-Emperor Seamount Chain (HESC). Taken together, these results support a temperature control on Te for small loads and warm lithosphere through steady-state creep processes, but strain hardening operating at large plastic strain and low temperature could explain high Te associated with large-amplitude and long-wavelength loads (subduction zones and the HESC) and should be incorporated in yield strength models of oceanic Te.