Early Arrival Waveform Tomography: 3D Case Study
Early arrival waveform tomography is a high-end near surface imaging solutions to handle a variety of near-surface problems, especially if large topography variations and strong velocity contrasts are common. The waveform tomography can further improve the near surface velocity model, which shows greater vertical and lateral resolution and reveals a high velocity layer, than travel time tomography. Near surface imaging affects the result of static correction in preprocessing stage. More accurate near surface velocity model, more satisfied the result of static correction.
A high resolution seismic imaging technique, Full waveform inversion (FWI), by using time domain early arrival acoustic waveform inversion is applied to 3D seismic land data in Saudi Arabia for the purpose of constructing a near-surface velocity model. This picture below shows the comparison of oblique views of the 3D traveltime tomography model (a) and the waveform tomography model (b). The waveform inversion produces a velocity model which shows greater vertical and lateral resolution of karst features and reveals a high velocity layer not present in the traveltime inversion model.
Compare a near-surface model derived from 3D acoustic early arrival waveform inversion to a model derived by 3D traveltime tomography for a 3D seismic land survey in Saudi Arabia. The waveform inversion produces a velocity model which shows greater vertical and lateral resolution of karst features and reveals a high velocity layer not present in the traveltime inversion model.
Full Waveform Inversion was developed for solving complex near-surface statics and velocity problems in areas where karst, low velocity layers, outcropping refractors, and strong velocity contrasts exist. Other near-surface solutions such as Delay-Time, GLI, and Traveltime techniques may fail in these complex environments.