Study Of Reflection Wave Travel Time Tomography Inversion Method

In western area with complex geological conditions,the acquisition of seismic data is very seriously affected,which makes the signal to noise ratio of original seismic record relatively low and increases the difficulty of data processing.In order to solve problems such as static correction,migration and amplitude recovery,we must figure out the underground strata structure in complex terrain area.The first application of tomography occurred in medical field.Since it was introduced into geoscience in 1970 s and 1980 s,it has evolved into a mature technology,which is increasingly used in the field of geophysical exploration.Tomographic imaging method uses obtained data outside the object to invert and construct the internal structure.As the travel time of seismic wave is related to underground velocity,we can obtain velocity structure underground by inverting the travel time of received seismic wave data.Seismic travel time tomography imaging method based on high-frequency approximation ray tracing theory can obtain observed travel time clearly,as the travel time of seismic wave has high signal-to-noise ratio.Because this method mainly studies the kinematic characteristics of seismic wave,it can calculate speed fast has the advantages.Due to its relatively early development,it is very mature right now and becomes the main method of seismic tomography.In this paper,we first reviewed the development history of seismic tomography,and then stated the development status of reflected wave ray tracing and inversion method.We build speed model and use it to carry out forward modeling and inverting calculation,obtain the reflection interface through stack section and pick up reflection travel time in common midpoint gathers.As to the ray tracing method we use the shortest path ray tracing method with linear difference in partitioned multi-step.Then we use orthogonal decomposition least square method(LSQR)with regularization to perform inversion the inversion process.The results show that the method can obtain better inversion results,which indicates that the method has certain value.