Imaging of subsurface faults using refraction migration with fault flooding

Abstract

We propose a novel method for imaging shallow faults by migration of transmitted refraction arrivals. The assumption is that there is a significant velocity contrast across the fault boundary that is underlain by a refracting interface. This procedure, denoted as refraction migration with fault flooding, largely overcomes the difficulty in imaging shallow faults with seismic surveys. Numerical results successfully validate this method on three synthetic examples and two field-data sets. The first field-data set is next to the Gulf of Aqaba and the second example is from a seismic profile recorded in Arizona. The faults detected by refraction migration in the Gulf of Aqaba data were in agreement with those indicated in a P-velocity tomogram. However, a new fault is detected at the end of the migration image that is not clearly seen in the traveltime tomogram. This result is similar to that for the Arizona data where the refraction image showed faults consistent with those seen in the P-velocity tomogram, except it also detected an antithetic fault at the end of the line. This fault cannot be clearly seen in the traveltime tomogram due to the limited ray coverage. Highlights A novel algorithm is presented for imaging a near-surface fault boundary by migrating recorded and virtual refractions to their points of intersection. The virtual refractions are created by continuing the incident refractions across the fault after flooding it with the velocity of the incident medium. The key assumptions are that one side of the fault has a much faster velocity than the other side, and there is an underlying refractor interface. Tests with synthetic data and recorded refraction data validate the efficacy of this method.

Role of Seismic Refraction Tomography (SRT) in bedrock mapping; case study from industrial zone, Ain-Sokhna area, Egypt

“…Nevertheless, refraction tomography is not subject to these constraints (Thurber and Ritsema, 2007;Whiteley et al, 2020). Therefore, it is able to resolve velocity gradients and lateral velocity changes and can be applied in geological conditions where conventional refraction techniques fail, such as areas of compaction, karst, and fault zones (Hiltunen and Cramer, 2008;Metwally et al, 2017;Brixová et al, 2018;Akingboye and Ogunyele, 2019;Herlambang and Riyanto, 2021). Several studies (White, 1989;Nurhandoko et al, 1999;Leucci et al, 2007;Azwin et al, 2013;Bery, 2013) prove the high applicability of the SRT technique in subsurface velocity modelling and ground exploration.…”

Application of Noise Attenuation on 2D Shallow Offshore Seismic Reflection Data: A Case Study from the Baltic Sea

“…The most common geophysical method, seismic reflection, studies subsurface structures. Geophysicists are interested in interpreting the travel times of the seismic waves [3,4]. This leads geophysicists to pay special attention to seismic data processing, particularly for the removal of various unwanted signals, because the quality of the subsurface imaging is largely determined by the accuracy of the processed data.…”