@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 {chaudhuri_widespread_2022,
	title = {Widespread Very Low Frequency Earthquakes (VLFEs) Activity Offshore Cascadia},
	journal = {Geophysical Research Letters},
	volume = {49},
	number = {13},
	year = {2022},
	note = {_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2022GL097962},
	pages = {e2022GL097962},
	abstract = {A significant amount of stress in the Cascadia subduction zone (CSZ) is released by different forms of slow earthquakes including tremors, low-frequency earthquakes, and very low-frequency earthquakes (VLFEs){\textemdash}all occurring onshore at the deeper part of the transition zone. Their activity offshore, however, remains elusive. We discover widespread occurrence of discrete VLFEs offshore Cascadia using ocean-bottom seismometers. Barring occasional regular fast earthquakes, VLFEs are the only seismic stress indicators offshore. Using centroid moment tensor inversion and matched filtering, we detect sequences of 12 distinct families of VLFEs. The VLFEs in northern CSZ have focal mechanisms consistent with the area{\textquoteright}s subduction zone deformation. Interestingly, the VLFEs in the southern part of CSZ show strike-slip faulting, attributed to offshore faults, sediment consolidation, subduction bending, and transpressional regimes created by complex plate tectonics. It challenges a canonical view of the seismogenic zone in Cascadia characterized by a frictionally homogeneous fault segment producing only regular fast earthquakes.},
	issn = {1944-8007},
	doi = {10.1029/2022GL097962},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2022GL097962},
	author = {Chaudhuri, Kuntal and Ghosh, Abhijit}
}
@article {Cai2018,
	title = {Water input into the Mariana subduction zone estimated from ocean-bottom seismic data},
	journal = {Nature},
	volume = {563},
	number = {7731},
	year = {2018},
	month = {nov},
	pages = {389{\textendash}392},
	issn = {0028-0836},
	doi = {10.1038/s41586-018-0655-4},
	url = {http://www.nature.com/articles/s41586-018-0655-4},
	author = {Cai, Chen and Wiens, Douglas A. and Shen, Weisen and Eimer, Melody}
}
@article {bostock_wavefield_2012,
	title = {Wave-Field Decomposition of Ocean Bottom Seismograms},
	journal = {Bulletin of the Seismological Society of America},
	volume = {102},
	number = {4},
	year = {2012},
	month = {aug},
	pages = {1681{\textendash}1692},
	abstract = {Seismograms recorded on the seafloor are affected by reverberations in the overlying ocean layer. We examine the feasibility of removing these reverberations through a 1D wave-field decomposition based on a reflection{\textendash}transmission formulation of the problem. Two decomposition schemes are presented. The first scheme involves a simple manipulation of the fundamental matrix relating stress and displacement of plane harmonic waves to upgoing and downgoing wavevector coefficients and requires measurement of both ocean bottom displacement and pressure. The second approach involves only displacement recordings and knowledge of the water column depth. This latter quantity will generally be known a priori from deployment logs, or, alternatively, it may be estimated using vertical displacement and pressure seismograms in a preprocessing step. Both approaches require prior information on seabed properties. In the case of P-wave incidence, the decomposition depends primarily on the seabed S velocity β0. This quantity can be determined by examining trial decompositions over a range of β0{\textquoteright}s and selecting the value that minimizes the energy of the upgoing S-wave component at the arrival time of the incident wave. We apply this approach to synthetic seismograms for a simple Earth structure and to recordings of two large events from the Central Oregon Locked Zone Array (COLZA) on the continental margin of Oregon. The real data indicate that the wave-field decompositions are largely successful at lower frequencies (\&lt;0.1  Hz) but that 3D scattering, likely originating near the sediment{\textendash}basement contact, is manifested at higher frequencies.},
	issn = {0037-1106},
	doi = {10.1785/0120110162},
	url = {https://doi.org/10.1785/0120110162},
	author = {Bostock, M. G. and Trehu, A. M.}
}
