采用重力异常的导纳理论推估海底地形

Bathymetry Prediction Based on the Admittance Theory of Gravity Anomalies

系统探讨了采用重力异常的导纳理论推估海底地形的方法.在频率域内对海底地形和重力异常的相关性进行了分析,确定在20-300km 波段内两者相关系数最高,适合通过重力异常反演.以皇帝海山链为例,分别采用未补偿导纳模型和顾及挠曲补偿的导纳模型开展研究,其中涉及的地壳厚度和有效弹性厚度等参数通过均衡响应函数法得到.引入余弦低通滤波器,有效地解决了向下延拓过程中产生的高频震荡问题.算例结果表明,采用重力异常的导纳理论能够有效地反演海底地形,结果真实可靠,反演模型的相对精度在6%左右,与ETOPO1模型相当,且能够刻画出ETOPO1模型中未显现的地形细节.由于地形变化剧烈,反演模型在海山链沿线附近精度不甚理想.

Based on the admittance theory of gravity anomalies,the method of bathymetry prediction was studied in detail in this paper.In frequency domains,the correlation between gravity anomalies and bathymetry was analyzed,which suggests that the wavelength band correlated strongly was in a range of 20—300 km,this band was appropriated to inverse bathymetry by gravity anomalies.Took the Emperor Chain as an example,the uncompensated admittance model and flexural isostatic admittance model were used for researching,respectively,the included parameter of crust thickness and effective elastic thickness were calculated by the isostatic response function.As the down continuation factor was unstable,a high-cut filter was proposed in the inversion procedure to ensure convergence of series.The results showed that,the admittance theory of gravity anomalies can be used effectively in the bathymetry prediction,the predicted result was real and reliable,the relative precision was approximately 6%,which was equal to ETOPO1 model,and the detailed feature of sea floor which was not showed in ETOPO1 model can also be depicted;the precisions were not so well in areas of ocean mountains intensively distributed because of the complexion of the sea floor.