Tidal drag and westward drift of the lithosphere  

作　　者：Vincenzo Nesi Oscar Bruno Davide Zaccagnino Corrado Mascia Carlo Doglioni 

机构地区：[1]Dipartimento di Matematica Guido Castelnuovo,Piazzale Aldo Moro,5,Roma 00185,Italy [2]Istituto Nazionale di Geofisica e Vulcanologia,Via di Vigna Murata,605,Roma 00143,Italy [3]Computing and Mathematical Sciences Department,Caltech,1200 E.California Blvd.,MC 305-16,Pasadena 91125,CA,USA [4]Dipartimento di Scienze della Terra,Piazzale Aldo Moro,5,Roma 00185,Italy

出　　处：《Geoscience Frontiers》2023年第6期102-116,共15页地学前缘(英文版)

基　　金：support from Progetto di Ricerca 2020,Progetto di Ricerca di Ateneo 2021,“Equazioni differenziali ellit-tiche e paraboliche non lineari”Sapienza n.RM120172B8F74615;Oscar Bruno gratefully acknowledges support from NSF under con-tract DMS-2109831,from AFOSR under contract FA9550-21-1-0373;from the NSSEFF Vannevar Bush Fellowship under ONR contract number N00014-16-1-2808;The research was also sup-ported by ESA grant 4000133529/20/NL/GP(Doglioni).

摘　　要：Tidal forces are generally neglected in the discussion about the mechanisms driving plate tectonics despite a worldwide geodynamic asymmetry also observed at subduction and rift zones.The tidal drag could theoretically explain the westerly shift of the lithosphere relative to the underlying mantle.Notwithstanding,viscosity in the asthenosphere is apparently too high to allow mechanical decoupling produced by tidal forces.Here,we propose a model for global scale geodynamics accompanied by numerical simulations of the tidal interaction of the Earth with the Moon and the Sun.We provide for the first time a theoretical proof that the tidal drag can produce a westerly motion of the lithosphere,also compatible with the slowing of the Earth’s rotational spin.Our results suggest a westerly rotation of the lithosphere with a lower bound ofω≈(0.1-0.2)°/Myr in the presence of a basal effective shear viscosityη≈10^(16)Pa-s,but it may rise toω>1°/Myr with a viscosity ofη≈≤3×10^(14)Pa-s within the Low-Velocity Zone(LVZ)atop the asthenosphere.This faster velocity would be more compatible with the mainstream of plate motion and the global asymmetry at plate boundaries.Based on these computations,we suggest that the super-adiabatic asthenosphere,being vigorously convecting,may further reduce the viscous coupling within the LVZ Therefore,the combination of solid Earth tides,ultra-low viscosity LVZ and asthenospheric polarized small-scale convection may mechanically satisfy the large-scale decoupling of the lithosphere relative to the underlying mantle.Relative plate motions are explained because of lateral viscosity heterogeneities at the base of the lithosphere,which determine variable lithosphere-asthenosphere decoupling and plate interactions,hence plate tectonics.

关 键 词：Tidal drag Plate motions Polarized plate tectonics Lithosphere-asthenosphere interaction 

分 类 号：P542[天文地球—构造地质学]