@article {zhang_water-wave-induced_2024,
	title = {Water-Wave-Induced OBS Noise: Theories, Observations, and Potential Applications},
	journal = {Journal of Geophysical Research: Solid Earth},
	volume = {129},
	number = {4},
	year = {2024},
	note = {_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2023JB027787},
	month = {04/2024},
	pages = {e2023JB027787},
	abstract = {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{\textendash}20 dB for time periods with strong wave noise.},
	keywords = {infragravity waves, OBS noise, ocean-bottom pressure, tilt noise},
	issn = {2169-9356},
	doi = {10.1029/2023JB027787},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2023JB027787},
	author = {Zhang, Chun and An, Chao}
}
@article {deng_theoretical_2022,
	title = {Theoretical Solution and Applications of Ocean Bottom Pressure Induced by Seismic Waves at High Frequencies},
	journal = {Geophysical Research Letters},
	volume = {49},
	number = {9},
	year = {2022},
	note = {_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2021GL096952},
	pages = {e2021GL096952},
	abstract = {Previous studies have demonstrated that the ocean-bottom pressure associated with seismic seafloor motion is linearly proportional to the vertical seafloor acceleration, for frequencies much lower than the resonance frequency of water layer (c0/4h, c0 water sound speed, h water depth). In this article, we use realistic observations to verify a theoretical relation between the ocean-bottom pressure and vertical acceleration up to the water resonance frequency. We then show two applications of the theoretical relation. First, the pressure amplitude recorded by differential pressure gauges is calibrated, and the calibration coefficient is found to vary by frequency. Second, Rayleigh wave phase velocity near the water resonance frequency can be calculated from recordings of pressure and vertical seafloor acceleration at a single station, which is useful to constrain the shallow Earth structure.},
	issn = {1944-8007},
	doi = {10.1029/2021GL096952},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2021GL096952},
	author = {Deng, Han and An, Chao and Cai, Chen and Ren, Hengxin}
}
@article {an_characteristics_2021,
	title = {Characteristics of Low-Frequency Horizontal Noise of Ocean-Bottom Seismic Data},
	journal = {Seismological Research Letters},
	volume = {93},
	number = {1},
	year = {2021},
	pages = {257{\textendash}267},
	abstract = {Horizontal records of ocean-bottom seismographs are usually noisy at low frequencies (\&lt; 0.1~Hz). The noise source is believed to be associated with ocean-bottom currents that may tilt the instrument. Currently horizontal records are mainly used to remove the coherent noise in vertical records, and there has been little literature that quantitatively discusses the mechanism and characteristics of low-frequency horizontal noise. In this article, we analyze in situ ocean-bottom measurements by rotating the data horizontally and evaluating the coherency between different channels. Results suggest that the horizontal noise consists of two components, random noise and principle noise whose direction barely changes in time. The amplitude and the direction of the latter are possibly related to the intensity and direction of ocean-bottom currents. Rotating the horizontal records to the direction of the principle noise can largely suppress the principle noise in the orthogonal horizontal channel. In addition, the horizontal noise is incoherent with pressure, indicating that the noise source is not ocean surface water waves (infragravity waves). At some stations in shallow waters (\&lt;300~m), horizontal noise around 0.07~Hz is found to be linearly proportional to the temporal derivative of pressure, which is explained by forces of added mass due to infragravity waves.},
	issn = {0895-0695},
	doi = {10.1785/0220200349},
	url = {https://doi.org/10.1785/0220200349},
	author = {An, Chao and Cai, Chen and Zhou, Lei and Yang, Ting}
}
@article {An2017,
	title = {Theoretical Solution and Applications of Ocean Bottom Pressure Induced by Seismic Seafloor Motion},
	journal = {Geophysical Research Letters},
	volume = {44},
	number = {20},
	year = {2017},
	month = {oct},
	pages = {10,272{\textendash}10,281},
	issn = {00948276},
	doi = {10.1002/2017GL075137},
	url = {http://doi.wiley.com/10.1002/2017GL075137},
	author = {An, Chao and Cai, Chen and Zheng, Yong and Meng, Lingsen and Liu, Philip}
}
