摘要
OBS(Ocean Bottom Seismometer,海底地震仪)在布放到海底之后,其方位指向通常是随机的;由于海流等因素的影响,其实际位置通常也会偏离投放位置,因此需要对其位置及方位进行重定位定向.针对目前的定位和定向方法大多基于走时计算,本文首先讨论了利用海底地震仪的水波初至偏振方位进行海底地震仪水平位置及方位重定位定向的线性反演方法和非线性反演方法,给出了线性反演的近似公式,并分析了近似公式的误差;然后,通过大量理论模型试验对比了两种方法的误差及稳定性;最后,对我国南海某地的5台OBS实测数据进行了反演处理.理论模型试验结果表明,在一些特殊情况下,线性反演存在不收敛的情况,而非线性方法则具有较好的稳定性和较高的精度.非线性反演方法采用差分演化算法,对比了直接优化方位角残差目标函数和双差法,结果表明,对于理论模型和实际数据两种方法得到的结果几乎完全相同,但迭代收敛情况双差法明显好于前者,双差法经600余次迭代达到最优稳定状态,而前者在迭代1 000多次之后才达到稳定最优状态.
Abstract
The OBS(ocean bottom seismometer)orientation is generally randomly directed when released to the ocean bottom,and needs to be redirected by the polarization azimuth.The OBS location is also need to be relocated.In this paper,we discuss both linear and non—linear methods using polarization azimuth of water break for inverting the OBS location and orientation simultaneously.We present an approximate formula for linear inversion and ana-lyzed error of the formula.We conduct a series of numerical experiments to test the accuracy and robustness of the two methods.Five OBS deployed in South China Sea are processed u-sing both methods.The result of numerical experiments shows that linear method is not con-vergence under some circumstances,while non-linear method has better robustness and high-er precession.We use differential evolution(DE)algorithms for non—linear method,compa-ring the cases of optimizing azimuth residuals and optimizing the difference of azimuth residu-als(double difference),the result indicates that the solutions are almost identical while the double difference scheme has a better convergence status,the DD scheme convergence at a-bout 600 iterations,where the former one convergence at about 1 000 iterations.
NETL
NSTL
维普
万方数据