A method is presented for identification of local soft ground position based on measurement of the angle between arrival wave and a vibration source. Vertical ground motion is measured using a circular array of six sensors. The angle between the arrival wave and the source can be determined, based on F-k spectrum analysis of the data. To examine the validity of the proposed method, field investigations were performed. It is shown that (1) The arrival wave angles tend to fluctuate wildly in case that local soft ground locates between the sensor array and the source and the wavelength is about 1.5 times the soft ground depth; (2) The arrival wave angles tend to point in the direction of the source in case that ground between the sensor array and the source is uniform.