Finetuning ground penetrating radar velocity analysis from hyperbola fitting using migration

Abstract

The widely used tool, ground penetrating radar (GPR), has proven to be an excellent research method for glaciological studies. The total ice thickness and englacial structures can be studied, and the method can give information on the temperature regime within the ice. Good velocity profiles are needed to convert measured two-way travel time to depth information. In addition, a good velocity analysis can be used to improve data processing. A number of methods can be used to find the GPR wave velocity, which are briefly described. This study used hyperbola fitting to estimate the velocity in a glaciological study. In addition, Kirchhoff's migration was used to fine-tune this velocity estimate. Within the Longyearbreen glacier, situated next to Longyearbyen on Spitsbergen, Svalbard archipelago, objects in the ice act as scattering points that create hyperbolas. Using the hyperbola-fitting method, a GPR wave velocity equal to 0.170 ± 0.005 m/ns was estimated. By doing Kirchhoff's migration and studying the collapse of hyperbolas with variations of the migration velocity, a more accurate velocity estimate can be achieved; 0.172 ± 0.002 m/ns. A more accurate velocity estimate like this opens possibilities for better characterization of the ice body and ice thickness variations, as well as the variation of these as a function of time. In March 2022, the maximum ice thickness in the investigated area was calculated to be 88 ± 1 m.

Calibration of the Radio Neutrino Observatory - Greenland (RNO-G)

“…If the depth of a reflector in the ice is known, the average index of refraction of the ice above it can simply be calculated from the timing of the radar echo. If the target depth is not known, the index of refraction can be measured using the radar echo time as the horizontal distance from the target is increased [10]. Useful targets for this are the antennas of an RNO-G station (which will also help with the antenna position calibration).…”

GPR velocity correction method in transversely heterogeneous media based on CMP data

“…The GPR data acquired based on the above methods can be used for velocity estimation; especially CMP data is widely used. For CO data, hyperbola fitting is often used to obtain velocity information (Cui et al., 2018; Dou et al., 2017; Lei et al., 2019; Li & Zhang, 2021; Rønning, 2023; Zhou et al., 2018). Although this method is efficient and simple, it relies on the presence of diffracted waves in the data.…”