Haar Wavelet Transform for Arrival Time Identification in Bender Element Tests

Abstract

The determination of shear wave velocity (V-s) using bender elements can be affected by the near-field effect. This phenomenon hinders the identification of the S-wave arrival time of an output signal. Multiple alternatives have been presented to counteract these effects, including the use of wavelet transforms during the last decade. In this article, the Haar wavelet is used because of the simplicity and speed of calculation. The determination of S-wave arrival time in signals influenced by the near-field effect is performed by setting an explicit event with a high value of energy at a specific time, in relation to the scale average energy in different levels of multiresolution analysis. The results show that regardless of the input frequency, the S-wave arrival time values are very similar, and the near-field effect is not observed when wavelet approach is used to determine the S-wave arrival times, unlike when applying other traditional interpretation approaches.