Analyse Of The Impulse Response Of Kirchhoff-type True-amplitude Demigration

The seismic imaging is a technique which is based on the wave theory and connects with the finally aim of seismic exploration, we can see that the seismic imaging is the kernel content of reflect seismology. Nowadays, the most extensive imaging technique is the seisimic migration imaging, there is a lack of one that can transcend it.The seismic exploration has been developed with the geological assignment, there are a lot of usefull information in the seismic reflect signal, especially the amplitude of reflect wave, is an object which is worthiness to disquisitive . So, in the following project, people work hard to preserve the comparatively amplitude. Today in the"Three High"of seismic exploration, there is a specific one that is high preserve amplitude.In a raw seismic field record the amplitude is called true if the data is unprocessed. In any other seismic time section, e.g., after preprocessing or demigration, the true-amplitude signal is represented by the source wavelet divided by a factor which accounts for the geometrical spreading effects pertaining to the actual ray path and multiplied with the reflection coefficient. Kirchhoff-type true–amplitude migration and demigration are published in the 90s of the 20th century a group of seismic reflect imaging technique, the basic aim is to get true-amplitude reflection signal,using the classical diffraction stack migration reform. For migration, true-amplitude signal is defined as the first reflection without geometrical spreading factor and the transmission loss ; For demigration, true-amplitude signal is defined as demigrationfield with the correct geometrical spreading factor and reflection coefficient.With the classical Kirchhoff migration, the Kirchhoff-type true-amplitude migration and the wave equation is not directly linked. In fact, the process of the establishment of Kirchhoff-type migrationd and demigration theory, their starting point is a weighted diffraction stack integral, rather than any wave equation. Therefore, it can be understanded and accepted as a justice. In the past 10 years, the true-amplitude weight function has been the focus of integral migration and inversion. The weight function is important factor that impacts the energy distribution of demigration pulse response. Based on the references of Tygel and Hubral, for the Study of the pulse response of true-amplitude demigration,we derivated the weight function detailed, and we discussed the geometrical spreading factor as well as the reflection angle that related to the reflect energy. Around the true-amplitude weight function of demigration, we proceed the study with the geometrical features of isochrones, because of its geometrical shape and curvature for the local are very important to the calculation of Kirchhoff-type ture-amplitude demigration weight function and imaging impact. we calculate the isochrones in in homogeneous and gradient media,analyse the geometrical features of isochrones in homogeneous and gradient media.On this basis, analyse the true-amplitude demigration weight function in both homogeneous and level layers media, Study of the weight function changes with the depth ,the offset and the time expansion in homogeneous media. According to China's complex characteristics of topography and geological conditions, as an example of two-dimensional tilt interface,we derivate the true-amplitude under the conditions of undulating surface simply. Finally, basis on the study of true-amplitude demigration and weight function, we calculate the demigration impulse response in homogeneous media, build a seismic geological model,write a procedure, realize the process of true-amplitude demigration.