Mapping Crustal Thickness Variation and Relative Plate-Hotspot Motion for the Pacific Ocean using Satellite Gravity Inversion

We determine crustal thickness for the Pacific Ocean, between 80oN to 80oS and 140oE to 295oE, using a gravity inversion method which incorporates a lithosphere thermal gravity anomaly correction (Greenhalgh & Kusznir, 2007; Chappell & Kusznir, 2008). Superposition of illuminated satellite gravity anomaly data onto crustal thickness maps from gravity inversion provides improved determination of sea-floor spreading trajectories, hot spot tracks and their inter-relationship. Data used in the gravity inversion are bathymetry, free-air gravity anomaly and sediment thickness from Sandwell and Smith (2008), Smith and Sandwell (2009) and Laske and Masters (1997) respectively. The gravity inversion method, which is carried out in the 3D spectral domain and predicts Moho depth, incorporates a lithosphere thermal gravity anomaly correction. Lithosphere thermal model re-equilibration (cooling) times, used to calculate the lithosphere thermal gravity anomaly correction, are conditioned by ocean isochron information (Mueller et al. 2008), and continental margin breakup ages. The lithosphere thinning distribution, used to define the initial thermal model temperature perturbation, may be defined using ocean isochron information or derived from the gravity inversion using no a priori isochron information. The resulting maps of crustal thickness with superimposed illuminated satellite gravity data show plate boundaries, micro-plates, micro-continents, oceanic plateaus and volcanic seamounts trails. The physical significance of the mapped parameter (i.e. crustal thickness) combined with its high resolution and broad scale allows observational links to be made between plate and hot-spot motion both present and past. Crustal thickness variation predicted by gravity inversion also shows intriguing relationships with tectonic fabric and roughness within oceanic lithosphere indicated by illuminated satellite free-air gravity data.