Breakthroughs in understanding the structure and dynamics of our planet will strongly depend upon instrumenting deep oceans. Progress has been made these last decades in ocean-bottom seismic observations, but ocean-bottom seismometer (OBS) temporary deployments are still challenging and face setup limitations. Launched from oceanographic vessels, OBSs fall freely and may slightly drift laterally, dragged by currents. Therefore, their actual orientation and location on the landing sites are hard to assess precisely. Numerous techniques have been developed to retrieve this key information, but most of them are costly, time-consuming or inaccurate. In this work, we show how ship noise can be used as an acoustic source of opportunity to retrieve both the orientation and the location of OBSs on the ocean floor. To retrieve the OBS orientation, we developed a first method based on a combination of seismic and pressure data through the use of the acoustic intensity. This latter can be used to quantify the OBS orientation from the ship noise direction of arrival (DOA), which can then be compared with known ship trajectories obtained from the automatic identification system (AIS). To accurately relocate OBSs, we also developed a second method based on the hydrophone data which computes distances of acoustical sources by measuring time differences of arrival (TDOA) between direct and reverberated phases. The OBS location is then retrieved by fitting measured ship distances with known ship trajectories. In this study, a full network of OBSs deployed in the SW Indian Ocean was reoriented and a test station was relocated. We demonstrate that our new methods may quantify the OBS orientation with an accuracy of about one degree, and its location with an accuracy of a few tens of metres, depending on the number of ships used in the analysis.

中文翻译：

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从船舶噪声分析中定位和定位海底地震仪

在理解我们星球的结构和动力学方面的突破将在很大程度上取决于深海仪器。过去几十年海底地震观测取得了进展，但海底地震仪 (OBS) 的临时部署仍然具有挑战性，并面临设置限制。从海洋学船只发射，OBSs 自由下落，可能会轻微横向漂移，被洋流拖曳。因此，它们在着陆点上的实际方向和位置很难准确评估。已经开发了许多技术来检索此关键信息，但其中大多数技术成本高昂、耗时或不准确。在这项工作中，我们展示了如何将船舶噪声用作机会的声源来检索 OBS 在海底的方向和位置。要检索 OBS 方向，我们开发了第一种方法，该方法基于通过使用声强度结合地震和压力数据。后者可用于根据船舶噪声到达方向 (DOA) 量化 OBS 方向，然后可以将其与从自动识别系统 (AIS) 获得的已知船舶轨迹进行比较。为了准确重新定位 OBS，我们还开发了基于水听器数据的第二种方法，该方法通过测量直接相位和混响相位之间的到达时间差 (TDOA) 来计算声源的距离。然后通过将测量的船舶距离与已知的船舶轨迹进行拟合来检索 OBS 位置。在这项研究中，部署在西南印度洋的完整 OBS 网络进行了重新定向，并重新安置了一个测试站。