Many past works report the role of edge flames in the stabilization of lifted turbulent jet diffusion flames, where a steep fuel concentration gradient exists. Gentle concentration gradients are smeared by turbulence, making it interesting to study the edge flame structure and the stabilization mechanism. In the present work, we investigate two CH4-air flames stabilized in a splitter plate burner with controlled concentration gradient. One flame faces a relatively gentle concentration gradient and another, a steep concentration gradient. Fuel-rich and fuel-lean streams on either side of the splitter plate mix downstream of the splitter plate tip to form the concentration gradient. The level of premixedness is controlled by varying the equivalence ratios of the rich and lean streams. The turbulence is generated by a passive grid with intensity ~8%. The flame is anchored by a recirculation zone at one end in the spanwise direction. Planar laser diagnostics is performed at mid-span, away from the stabilization location. Particle image velocimetry (PIV) and OH planar laser induced fluorescence (PLIF) are simultaneously performed to investigate the flow field around these flames. The flow velocity decreases upstream of the flame, and the instantaneous velocity profile resembles that of a laminar triple flame. The local flame speed of unburned reactants just upstream of the flame leading edge is evaluated by measuring the mean flow velocity measured at the flame base, averaged over instantaneous velocity fields in a flame fixed frame of reference. The flame front is deduced from the velocity jump across the flame, which is reflected in a streamwise strain field. Mean tangential strain (strain component of flame stretch) along the flame front is evaluated from the deduced flame front and the velocity filed. The strain peaks at the flame leading edge and progressively reduces on either side of the leading edge. The peak strain value is higher for the flame with the steep concentration gradient, which is correlated with a lower flame speed. Whereas, the lower strain in flame with the gentle concentration gradient facilitates its flame speed being higher. The mean tangential strain profile along the flame front resembles that of a laminar triple flame, but with higher values. This could be due to the turbulence effect apart from the higher mean velocity than for a corresponding laminar flame. The results suggest that the partially premixed turbulent flame stabilizes through triple flame structure, even at relatively gentle concentration gradient within the range tested.