西北太平洋岩石圈有效弹性厚度及其构造意义  

The lithosphere effective elastic thickness and its tectonic implications in the Northwestern Pacific

作　　者：胡敏章[1,2] 李建成[2] 李辉[1] 徐新禹[2] 申重阳[1] 邢乐林[1,2] 

机构地区：[1]中国地震局地震研究所,地震大地测量重点实验室,武汉430071 [2]武汉大学测绘学院,武汉430079

出　　处：《地球物理学报》2015年第2期542-555,共14页Chinese Journal of Geophysics

基　　金：中国地震局地震研究所所长基金重点项目(IS201326125);国家自然科学基金(41204019;41304003)资助

摘　　要：本文引入滑动窗口导纳技术（MWAT）,计算西北太平洋岩石圈有效弹性厚度（Te）.首先,基于SIO V15.1海底地形模型,模拟研究了MWAT法计算Te的精度,表明当Te〈5km时,误差在±1km以内,当Te≥5km时,相对误差在10%以内.分别采用GEBCO、SIO V15.1和BAT_VGG海底地形模型,构建了西北太平洋Te,通过对获得的洋壳密度参数和实测导纳与模型导纳之差的均方根进行分析,结果表明,BAT_VGG模型更适用于Te计算.西北太平洋Te均值为13.2km,标准差为6.9km,以板块冷却模型为参考,主要分布在150℃～450℃等温线深度范围内.白垩纪和侏罗纪时期岩石圈Te分布在150℃～300℃等温线深度范围内,且未随海山加载时岩石圈年龄增大而增大,说明海山加载时岩石圈年龄不是影响其强度的唯一因素.南太平洋超级海隆活动,以及研究区域广泛存在的断裂带构造,都曾对本区域岩石圈演化产生过重要影响,可能是本地区岩石圈Te较小的构造原因.A variety of methods have been applied to estimate lithospheric effective elastic thickness（Te）.Scientists have calculated Te of the lithosphere under various features,but there are contradictory results among them.In this paper,accuracy of Te calculated by MWAT（Moving Window Admittance Technique）was analyzed synthetically based on SIO（Scripps Institute of Oceanography）V15.1bathymetry model and a simple lithospheric flexure isostatic model.The Te model of the Northwestern Pacific（15°S—45°N,145°E—215°E）is re-evaluated.We discussed the tectonic setting of the lithosphere in the studied area based on Te and age samples of the seafloor.The theoretical basis for Te estimating is the flexural isostatic model.Te can be established by minimizing the RMS misfit between the observed and theoretical admittance. The theoretical admittance is calculated based on flexural isostatic model.The observed admittance is calculated based on cross-spectral analysis of bathymetry and gravity model.We can calculate Te in twosteps.First,at 20～50km wave bands,the uncompensated theoretical admittance is calculated with differentρc（2300～2900kg·cm^3）and d（mean model depth ±500m）.The value ofρcand dcan be recovered area by area by fitting the theoretical and observed admittance.Secondly,at wave lengths longer than 50 km,with the recoveredρcand d,the theoretical admittance can be computed for different Te.We can obtain an optimal Te when the RMS misfit between the theoretical and observed admittance is minimized.With the MWAT method,six windows range from 400km×400km to 1400km×1400km are used to estimate Te,using 3Dspectral analysis technique.The final Te is weighted mean of these six results.For comparison,three kinds of bathymetry model are used.They are GEBCO,SIO V15.1and BAT_VGG.BAT_VGG is a bathymetry model formed with ship soundings and vertical gravity gradient anomalies. In our simulations,Te centered on（21°N,157°E）is recovered for different inputted Te（1～50km）.The effects of cru

关 键 词：岩石圈有效弹性厚度 挠曲均衡模型 海底地形 重力异常 三维导纳分析 

分 类 号：P736[天文地球—海洋地质] P312[天文地球—海洋科学]