Lithospheric flexural modelling of the seaward and trenchward of the subducting oceanic plates

摘要

Based on a two-segment plate flexural modelling, we investigated the effective elastic thickness of global subducting oceanic lithosphere. Our results show that for the plate age of 0 to 50 Ma, the seaward effective elastic thicknessT(e)(M)values are located between 600 and 900 degrees C isotherms, and do not track any isotherm, while the majority of the trenchward effective elastic thicknessT(e)(m)values are located between 300 and 600 degrees C isotherms. For the plate age older than 50 Ma,T(e)(M)values basically matches the 600 degrees C isotherm with some fluctuations for the age older than 110 Ma, whileT(e)(m)values mainly fall between 200 and 400 degrees C isotherms. The reduction in effective elastic thickness (T-e(M)-T-e(m)) varies from 2.6 to 30.1 km, or 11-68% of seawardT(e)(M). Thus, the absolute value of the decrease in the effective elastic thicknesses (T-e(M)-T-e(m)) increases with the plate age, while the percentage reduction in the effective elastic thickness (1-T-e(m)/T-e(M)) has no obvious relationship with the age, but more related to the curvature of bending plate. Almost all bending-related earthquakes occurred above theT(e)(M)line, but many normal-faulting earthquakes are deeper than theT(e)(M)-T(e)(m)line, implying that the plate may still retain some thickness of an elastic property core in the areas (depth) where earthquakes occur.