Influence of tidal level on quantifying the probability of nearshore tsunami hazard

Abstract

Nearshore tsunami hazard can be greatly affected by the tidal level, especially when large tsunami waves meet the high tidal level. This study aims to quantify the probability of the peak nearshore tsunami elevation (PNTE) caused by seismic tsunamis considering the randomness of event occurrence time and the variation of tidal level. The coast around the Pearl River Estuary has been chosen as the study area to show the influence of tidal level on the probability of nearshore tsunami hazard. Two approaches are proposed to calculate the PNTE considering the effect of tide in a probabilistic tsunami assessment framework. One approach is a linear superposition of tsunami wave upon the tidal level, and the other considering the influence of tidal level on tsunami nearshore amplification. The probability of the PNTE along the concern coast is obtained. The results considering the effect of tide show that the PNTE corresponding to short return period is obviously larger than that based on the mean sea level, but no obvious difference in the case of long return period. Moreover, in the study area, the two approaches considering the effect of tide show only slight difference in estimating the probability of PNTE, which suggests the applicability of the linear superposition method in nearshore tsunami hazard assessments.