1.Institute of Geophysical and Geochemical Exploration,CAGS,Langfang 065000,China; 2.National Modern Geological Exploration Technology Research Center,Langfang 065000,China
Abstract：It is an attempt to detect natural gas hydrate by using shallow seismic technology in permafrost regions of the Tibetan plateau.When the vibrator encounters the locally undulating surface,the ground surface cannot be effectively coupled with the vibrator's excitation plate,and the excitation effect becomes worse.Conducting an empty vibration before the data acquisition of each physical point is helpful to improving the coupling degree between the surface and the seismic vibrator.On the other hand,the interface between the shallow surface low velocity melting layer in summer and the lower high velocity layer is a strong reflection interface.The reflective interface produces so-called energy shielding problem.In winter,the problem of energy shielding can be avoided,but the shallow surface high speed permafrost often causes the vibrator excitation resonance.The harmonic interference in seismic records seriously reduces the quality of seismic acquisition.Under the condition that the surface is close to the "half rigidity",the source excitation not only avoids the energy shield formed by the melting of the low velocity layer on the surface but also avoids the harmonic interference caused by the high velocity layer.The corresponding denoising technique can effectively suppress the various kinds of interference on seismic record and increase signal-to-noise ratio of seismic record.
