Considering the fact that seismic waves do not vertically propagate near the surface especially under near field earthquakes, a simplified model is deduced to analyze the seismic response under obliquely incident waves based on the propagation theory in elastic half-space. It is considered the incident waves are harmonic, reflected at the free surface. The seismic stresses at arbitrary depth and the corresponding dynamic stress paths are estimated to investigate the effect of the incident angle of input waves. Under the single incidence of P-waves or SV-waves, it is shown that in the coordinate plane (/2，), the stress path will be a fluctuating ellipse, the angular between X axis and the long axis of the ellipse, and the ratio of long axis to short axis of the ellipse are related to the incident angle, frequency, wave velocity, etc. Moreover, preliminary discussion is also made on the way to simulate such a dynamic stress path in laboratory tests.
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