The horizontal records of ocean-bottom seismometers (OBS) are usually highly noisy, generally due to ocean-bottom currents tilting the instrument, which greatly limits their practical usage in ocean-bottom seismology. In shallow water, water waves with energy concentration around 0.07 Hz induce additional noise on OBSs. Such noise is not well understood. In this article, we propose a noise model to explain the horizontal noise around 0.07 Hz. The noise model consists of three types of noise, that is, water-wave-induced noise, current noise with a relatively constant orientation, and background random noise. The wave-induced horizontal acceleration is theoretically shown to be proportional to the time derivative of ocean-bottom pressure. We validate the noise model and related theories using realistic observations. Results are potentially applicable to determine the propagation direction of water waves nearshore, and also provide constraints on the underlying Earth structure. The results can also be applied to the removal of wave-induced noise, achieving a typical maximum improvement in the signal-to-noise ratio of 10–20 dB for time periods with strong wave noise.

中文翻译：

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水波引起的 OBS 噪声：理论、观察和潜在应用

海底地震仪（OBS）的水平记录通常噪声很大，这通常是由于海底洋流使仪器倾斜造成的，这极大地限制了它们在海底地震学中的实际应用。在浅水中，能量集中在 0.07 Hz 左右的水波会对 OBS 产生额外的噪声。这种噪音尚不清楚。在本文中，我们提出了一个噪声模型来解释 0.07 Hz 左右的水平噪声。噪声模型由水波诱发噪声、方向相对恒定的水流噪声和背景随机噪声三类噪声组成。理论上，波浪引起的水平加速度与海底压力的时间导数成正比。我们使用实际观察来验证噪声模型和相关理论。结果可能适用于确定近岸水波的传播方向，并且还提供对底层地球结构的约束。结果还可以应用于消除波浪引起的噪声，在波浪噪声较强的时间段内，信噪比典型地最大提高了 10-20 dB。