On November 15, 2017, an event related to the disappearance of the Argentine military submarine ARA San Juan was detected by two hydrophone triplet stations of the IMS network, established to enforce the nuclear test ban treaty (CTBT). From the two direct hydroacoustic arrivals recorded at 6000 and 8000 km from the localized wreckage, calculated location based on hydroacoustic data only is poorly constrained, and the associated uncertainties are large. In an attempt to interpret the recorded signals, an air dropped calibration grenade was conducted by the Argentine Navy two weeks later, on December 1, 2017, near the last known position of the submarine. From the comparison of temporal and spectral features of both events, we confirm the impulsive nature of the San Juan event. Array processing was performed with a progressive multi-channel correlation method (PMCC). Fine propagation details of direct arrivals are very well resolved in time-frequency space and thirteen secondary arrivals are revealed for the San Juan event, within the fifteen minutes following direct arrivals. The detections presented in this paper were calculated with DTK-PMCC software embedded in the NDC-In-A-Box virtual machine, and can be reproduced by any CTBTO principal user (Member State user which can access raw waveform data and data bulletins). All the identified late arrivals are associated to reflections or refractions from seamounts, islands and the South American continental Slope. The accurate identification of all the reflectors allows to significantly improve the source location accuracy: 95% confidence ellipse area has been reduced by a factor of 100 compared to location obtained from direct arrivals only, and the estimated location is 3.5 km from the known location of the wreckage. The originality of the relocation method is that it is based on the joint inversion of both San Juan and calibration events unknown parameters, and from the selection of only a well-chosen subset of secondary arrivals. Its calculation did not require either the need of advanced oceanographic specifications, or sophisticated methods requiring heavy computational means. Finally, a detailed cepstral analysis of the direct and secondary arrivals has allowed to detect the existence of a second impulse (doublet) in the signals associated to both San Juan and calibration events. Unlike the calibration event, the anisotropic character of the delays measured from the San Juan cepstra suggests that the 15 November signal was generated by two impulsive acoustic sources closely separated in space and time over scales comparable to the size of the submarine. This study demonstrates the capability of the hydroacoustic component of the IMS network to accomplish its mission of Comprehensive Nuclear-Test-Ban Treaty monitoring.

中文翻译：

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与阿根廷 ARA San Juan 潜艇损失相关的水声信号分析

2017 年 11 月 15 日，IMS 网络的两个水听器三重站检测到与阿根廷军用潜艇 ARA San Juan 失踪有关的事件，IMS 网络旨在执行禁止核试验条约 (CTBT)。从距局部残骸 6000 和 8000 公里处记录的两次直接水声波到，仅基于水声数据的计算位置约束很差，相关的不确定性很大。为了解释记录的信号，两周后，即 2017 年 12 月 1 日，阿根廷海军在潜艇最后一个已知位置附近进行了空投校准手榴弹。通过比较两个事件的时间和光谱特征，我们确认了圣胡安事件的冲动性。使用渐进式多通道相关方法 (PMCC) 进行阵列处理。直接到达的精细传播细节在时频空间中得到了很好的解析，并且在直接到达后的 15 分钟内为圣胡安事件揭示了 13 次二次到达。本文中提出的检测结果是使用 NDC-In-A-Box 虚拟机中嵌入的 DTK-PMCC 软件计算得出的，任何禁核试条约主要用户（可以访问原始波形数据和数据公告的成员国用户）都可以复制。所有确定的迟到都与海山、岛屿和南美大陆坡的反射或折射有关。准确识别所有反射体可以显着提高源定位精度：与仅从直接到达获得的位置相比，95% 置信椭圆区域减少了 100 倍，估计位置距离残骸已知位置 3.5 公里。重定位方法的独创性在于它基于圣胡安和校准事件未知参数的联合反演，并且仅选择了精心挑选的二次到达子集。它的计算既不需要先进的海洋学规范，也不需要需要大量计算手段的复杂方法。最后，对直接和二次到达的详细倒谱分析允许检测与圣胡安和校准事件相关的信号中是否存在第二个脉冲（双峰）。与校准事件不同，从圣胡安倒谱测量的延迟的各向异性特征表明，11 月 15 日的信号是由两个在空间和时间上紧密分离的脉冲声源产生的，其尺度与潜艇的大小相当。这项研究展示了 IMS 网络的水声组件完成其全面禁止核试验条约监测任务的能力。