Temporal change of near-surface shear wave velocity associated with rainfall in Northeast Honshu, Japan

Abstract

We apply seismic interferometry to earthquake records to investigate temporal change of near-surface shear wave velocity associated with rainfall in Northeast Honshu, Japan. We observe there exists a threshold (around 100 mm of 24 h rainfall total) of the temporal influence of rainfall on near-surface shear wave velocity. The velocity does not change significantly under low-intensity rainfall, while it is reduced by 1–3% with one exception of 10% when the rainfall intensity exceeds the threshold. Compared with the travel time of no rain, the travel time increment of low-intensity rainfall is no more than 3 × 10−4 s, while that of high-intensity rainfall ranges between 10−3 and 10−2 s. Based on the results of observation, we propose a one-dimensional model to compute the travel time increment, which can give a preliminary estimation of the temporal influence of rainfall on near-surface shear wave velocity.