浅海中球形声源诱发的海底地震波快速预报方法研究

On fast prediction method of seabed seismic wave induced by spherical sound source in shallow water

针对浅海中球形声源诱发的海底地震波预报问题,提出了一种基于等效源-有限元联合法的快速预报方法。首先,基于波叠加原理,将球形声源的辐射声场等效为其对称轴上若干等效点源辐射声场的线性叠加,根据与球形声源表面上等效点源数量一致的场点振速匹配原则,确定等效点源的强度;然后,采用有限元法建立球形声源、浅海环境、边界条件的耦合动力学模型,计算相应源强下每个等效点源诱发的海底地震波场,并将其线性叠加快速求得球形声源诱发的海底地震波场;最后,从计算精度和效率两个方面,分别采用上述方法和有限元法,给出不同频率、不同海底底质时海水-海底界面上的法向应力级衰减曲线。结果表明:所提方法具有建模简洁、计算精度和效率高等特点,可用于快速预报浅海中球形声源诱发的海底地震波场。

Aiming at the problem of seabed seismic wave prediction induced by spherical sound source in shallow water,a fast prediction method based on wave superposition-finite element coupling method was proposed.According to equivalent source principle,the radiated sound field of the spherical sound source was equivalent to the linear superposition of some equivalent point sources on its symmetry axis.The strength of the equivalent point source was determined by using vibration velocity matching principle of same number as that of the equivalent point source,which was on surface of the spherical sound source.The coupling dynamic model including the spherical sound source,shallow water environment and boundary conditions was established by finite element method(FEM),and seabed seismic wave field induced by each equivalent point source with the corresponding source intensity was linearly superimposed,and thus seabed seismic wave field induced by spherical sound source was given quickly.From the points of calculation accuracy and efficiency,attenuation curves of vertical stress level on water-seabed interface at different frequencies and under seabed sediments were given by using FEM and the proposed method.The results show that the method is characterized by simple modeling,high calculation accuracy and efficiency,and can be used to quickly predict seabed seismic wave field induced by spherical sound sources in shallow water.