In recent years,it has been demonstrated that thelow-level jet streams(LLJs)developed in thesouth of the Meiyu(Baiu)front play a critical role inthe overseas migrations of the planthoppers intoJapan and Korea. However...In recent years,it has been demonstrated that thelow-level jet streams(LLJs)developed in thesouth of the Meiyu(Baiu)front play a critical role inthe overseas migrations of the planthoppers intoJapan and Korea. However, the involement of theLLJs during the process of sequential displacements展开更多
Because of the combination of optimization algorithms and full wave equations, full-waveform inversion(FWI) has become the frontier of the study of seismic exploration and is gradually becoming one of the essential to...Because of the combination of optimization algorithms and full wave equations, full-waveform inversion(FWI) has become the frontier of the study of seismic exploration and is gradually becoming one of the essential tools for obtaining the Earth interior information. However, the application of conventional FWI to pure reflection data in the absence of a highly accurate starting velocity model is difficult. Compared to other types of seismic waves, reflections carry the information of the deep part of the subsurface. Reflection FWI, therefore, is able to improve the accuracy of imaging the Earth interior further. Here, we demonstrate a means of achieving this successfully by interleaving least-squares RTM with a version of reflection FWI in which the tomographic gradient that is required to update the background macro-model is separated from the reflectivity gradient using the Born approximation during forward modeling. This provides a good update to the macro-model. This approach is then followed by conventional FWI to obtain a final high-fidelity high-resolution result from a poor starting model using only reflection data.Further analysis reveals the high-resolution result is achieved due to a deconvolution imaging condition implicitly used by FWI.展开更多
文摘In recent years,it has been demonstrated that thelow-level jet streams(LLJs)developed in thesouth of the Meiyu(Baiu)front play a critical role inthe overseas migrations of the planthoppers intoJapan and Korea. However, the involement of theLLJs during the process of sequential displacements
基金supported by the National Natural Science Foundation of China(Grant No.41504106&41274099)the Science Foundation of China University of Petroleum(Beijing)(Grant No.2462015YJRC012)State Laboratory of Petroleum Resource and Prospecting(Grant No.PRP/indep-3-1508)
文摘Because of the combination of optimization algorithms and full wave equations, full-waveform inversion(FWI) has become the frontier of the study of seismic exploration and is gradually becoming one of the essential tools for obtaining the Earth interior information. However, the application of conventional FWI to pure reflection data in the absence of a highly accurate starting velocity model is difficult. Compared to other types of seismic waves, reflections carry the information of the deep part of the subsurface. Reflection FWI, therefore, is able to improve the accuracy of imaging the Earth interior further. Here, we demonstrate a means of achieving this successfully by interleaving least-squares RTM with a version of reflection FWI in which the tomographic gradient that is required to update the background macro-model is separated from the reflectivity gradient using the Born approximation during forward modeling. This provides a good update to the macro-model. This approach is then followed by conventional FWI to obtain a final high-fidelity high-resolution result from a poor starting model using only reflection data.Further analysis reveals the high-resolution result is achieved due to a deconvolution imaging condition implicitly used by FWI.
