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| | Abstract | | Pore pressure that controls earthquake activities temporally changes with surface perturbations. Hence, an interpretation of pore pressure changes associated with the natural phenomenon is important. Seismic velocity monitoring can be used to evaluate temporal variations in pore pressure. Presently, the effect of the sea has not been discussed in detail. Thus, identifying the imprint of the sea-level in the seismic velocity becomes our interest. We analyzed the seismic velocity changes and sea-level in Chugoku-Shikoku, Japan. We first applied a bandpass filter in various frequency bands and calculated the correlation between the filtered data. Next, we constructed a linear model between the absolute correlations and the station proximity to the coast. The significance of the model was evaluated by considering its probability value. For a specific frequency band, the absolute correlation of seismic velocity changes, and sea-level tends to decrease with the increasing distance from the coast. This trend may infer the possibility of crustal deformation by ocean loading. Such deformation could cause pore pressure to increase or decrease at a few kilometers from the coast. We conclude that seismic velocity monitoring is useful to evaluate the pore pressure changes due to the natural loadings, such as from seawater mass. |
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