Comparing two interpolation methods based on POCS for determining EM wave velocity from sparse CMP data

Abstract

As an array antenna ground penetrating radar (GPR) system electronically and sequentially switches among predefined antenna combinations after ten and several milliseconds with minimal effort, multi-offset gather data, such as common mid-point (CMP) data, can be acquired almost seamlessly by fixing antenna location. The array GPR system has been used to collect time-lapse multi-offset GPR data, such as CMP data, during the field infiltration experiment (Iwasaki et al., 2016). However, the CMP data obtained by the array GPR may be too sparse to estimate reliable EM velocity using a standard velocity analysis, such as semblance. We then attempted to interpolate the sparse CMP data based on projection onto convex sets (POCS) algorithm (Yi et al., 2016) coupled with NMO correction to determine EM wave velocities. The main objective of this study was to compare two methods based on POCS to interpolate sparse CMP data. Specifically, the effect of applying NMO correction prior to interpolation was investigated. The two methods were applied to the sparse CMP data collected during the field infiltration test with the array GPR. The results show that the NMO correction prior to the interpolation may improve the accuracy of the final velocity estimation.