Estimating the lithospheric flexure of a plate with non-uniform flexural rigidity: a quantitative modelling approach

Ming-Ju Xu,Chun-Feng Li,Jin-Yao Gao,Fei Ji,Zhao-Cai Wu,Ai-Guo Ruan

doi:10.1186/s40623-021-01497-y

Abstract

Lithospheric deformation is a fundamental process in plate tectonics. It is, therefore, critical to determine how the lithosphere responds to geological loads to better understand tectonic processes. The lithosphere can be modelled as the flexure of a thin, elastic plate over long-term (> 105 yr) geological timescales. The partial differential equation for the flexure of an orthotropic plate is used indirectly to calculate theoretical admittance and coherence, which are then compared against the observed admittance and coherence to invert for the non-uniform flexural rigidity (or effective elastic thickness, Te) of the plate. However, the process for accurately recovering variable lithospheric flexure remains unresolved, as the classical lithospheric model may overestimate the deflection of the plate. Here we adopt the classic lithospheric model with applied external and internal loads at the surface and Moho, respectively, and assume that the compensation material is denser than the mantle material beneath the Moho. The lithospheric flexure errors are derived mainly from the Te and Moho recovery errors in this lithospheric model. Synthetic modelling is then performed to analyse the influence of the Te and Moho errors. The analysis of synthetic modelling shows that: (1) the Te error-induced flexure errors exhibit a rippling pattern, and the rippling pattern is broader in high Te regions; (2) the Moho error-induced flexure errors mainly occur in the low Te regions, and applying Airy isostasy theory in low Te regions may still greatly overestimate the lithospheric deformation amplitude; and (3) the lithospheric flexure errors are dominated by the Te and Moho errors in the high and low Te regions, respectively.

Highlights

IntroductionThe lithospheric strength of tectonic plates reflects their resistance to vertical deformation in response to geological loads over long-term (> 105 yr) geological timescales (Watts and Burov 2003)
As Te is a periphrastical parameter for understanding lithospheric rheology and deformation, directly modelling lithospheric flexure should provide key insights into the nature of tectonic evolution and dynamics
Here, we employed the classic lithospheric model with an applied external load at the surface and internal load at the Moho, and assumed that the compensation material was denser than the mantle material beneath the Moho, in an attempt to estimate lithospheric flexure

Summary

Introduction

The lithospheric strength of tectonic plates reflects their resistance to vertical deformation in response to geological loads over long-term (> 105 yr) geological timescales (Watts and Burov 2003) This assumption allows the lithosphere to be modelled as the flexure of. Numerous studies have used Te to analyse lithospheric rheology and deformation (Pérez-Gussinyé et al 2009; Chen et al 2015; Ji et al 2017, 2020; Lu et al 2020) This idealised term does not refer to an existing thickness or physical layer within the Earth, but instead corresponds to the thickness of an ideal elastic plate that undergoes the same deformation as the lithosphere under the same loads (Watts 2001). As Te is a periphrastical parameter for understanding lithospheric rheology and deformation, directly modelling lithospheric flexure should provide key insights into the nature of tectonic evolution and dynamics

Methods

Conclusion