Oceanic Residual Depth Measurements, the Plate Cooling Model and Global Dynamic Topography

摘要: Convective circulation of the mantle causes deflections Earth's surface that vary as a function space and time. Accurate measurements this dynamic topography are complicated by need to isolate remove other sources elevation, arising from flexure lithospheric isostasy. The complex architecture continental lithosphere means measurement present-day is more straightforward in oceanic realm. Here, we present an updated methodology for calculating residual bathymetry, which proxy topography. Corrections applied account effects sedimentary loading compaction, anomalous crustal thickness variations, subsidence age, non-hydrostatic geoid height variations. Errors formally propagated estimate uncertainties. We apply global database 1,936 seismic surveys located on crust generate 2,297 spot topography, including 1,161 with corrections. resultant anomalies have amplitudes ±1 km wavelengths ∼1,000 km. Spectral analysis our using cross-validation demonstrates spherical harmonics up degree 30 (i.e. down 1,300 km) required accurately represent these observations. Truncation expansion at lower maximum erroneously increases amplitude inferred long-wavelength There strong correlation between observations free-air gravity anomalies, magmatism, ridge seismicity, vertical motions adjacent rifted margins, tomographic models. infer shorter wavelength components observed pattern may be attributable presence thermal within shallow asthenospheric mantle.