After the twenty-first century, the Global Navigation Satellite System-Acoustic ranging (GNSS-A) technique detected geodetic events such as co- and postseismic effects following the 2011 Tohoku-oki earthquake and slip-deficit rate distributions along the Nankai Trough subduction zone. Although these are extremely important discoveries in geodesy and seismology, more accurate observation that can capture temporal and spatial changes are required for future earthquake disaster prevention. In order to upgrade the accuracy of the GNSS-A technique, it is necessary to understand disturbances in undersea sound speed structures, which are major error sources. In particular, detailed temporal and spatial variations are difficult to observe accurately, and their effect was not sufficiently extracted in previous studies. In the present paper, we reconstruct an inversion scheme for extracting the effect from GNSS-A data and experimentally apply this scheme to the seafloor sites around the Kuroshio. The extracted gradient effects are believed to represent not only a broad sound speed structure but also a more detailed structure generated in the unsteady disturbance. The accuracy of the seafloor positioning was also improved by this new method. The obtained results demonstrate the feasibility of using the GNSS-A technique to detect a seafloor crustal deformation for oceanography research.

中文翻译：

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从GNSS-A海洋学中提取的海底声速结构的梯度场

二十一世纪后，全球导航卫星系统声测距（GNSS-A）技术检测到了大地事件，例如2011年东北冲地震后的同震和后地震影响以及南海海槽俯冲带的滑坡率分布。 。尽管这些是大地测量学和地震学中极其重要的发现，但对于未来的地震灾难预防，仍需要进行更精确的观测以捕获时空变化。为了提高GNSS-A技术的准确性，有必要了解海底声速结构中的干扰，海底声速结构是主要的误差源。特别是，详细的时间和空间变化很难准确观察到，并且在以前的研究中还没有充分提取它们的作用。在本文中，我们重建了一个反演方案，以从GNSS-A数据中提取效果，并将该方案实验性地应用于黑潮附近的海底站点。提取的梯度效应被认为不仅代表了较宽的声速结构，而且还代表了非稳态扰动中产生的更详细的结构。这种新方法还提高了海床定位的准确性。获得的结果证明了使用GNSS-A技术检测海底地壳变形以进行海洋学研究的可行性。提取的梯度效应被认为不仅代表了较宽的声速结构，而且还代表了非稳态扰动中产生的更详细的结构。这种新方法还提高了海床定位的准确性。获得的结果证明了使用GNSS-A技术检测海底地壳变形以进行海洋学研究的可行性。提取的梯度效应被认为不仅代表了较宽的声速结构，而且还代表了非稳态扰动中产生的更详细的结构。这种新方法还提高了海床定位的准确性。获得的结果证明了使用GNSS-A技术检测海底地壳变形以进行海洋学研究的可行性。