A new approach in moving target bearing estimation based on time differences of arrival of seismic signals received at a four-sensor square array is proposed.The weak correlation between propagation speed of signals and bearing estimation under such sensor layout is exploited in theory

simple and explicit expressions of bearing margins as well as the maximum bearing estimation band range are deduced.Influence of signal propagation speed and time delay measurement errors on precision of bearing estimation is discussed according to simulation computation.It is eventually demonstrated through field experiment that this technique has a smaller bearing estimation error than the commonly used three-axis geophones and it has certain application value.