Near-surface observations of submesoscale circulations play a crucial role in understanding physical/biological processes in the upper open oceans, but current Eulerian observational platforms such as satellite altimetry and HR radar have limitations in resolution and coverage area. In this work, we introduce a way of studying submesoscale turbulence over an area of few hundred kilometers using Eulerian velocity observations. Geostationary satellite-based observations have extended the spatiotemporal scales down to submesoscales, at which local dispersion, ageostrophic circulation, vertical transport, and physical/biological interaction strongly occur. The movement of Chlorophyll-a distributions taken from theGeostationary Ocean Color Imager (GOCI) was processed by the method of Particle Image Velocimetry (PIV), from which we generated a submesoscale-permitting Eulerian velocity field around the Korea peninsula. The observations in the East/Japan Sea in April indicated two spectral regimes following k^-3 and k^-5/3 at scales larger and smaller than 50km, respectively. The spectral kink may represent a superposition of quasi-geostrophic (GQ) turbulence and surface quasi-geostrophic turbulence in an additive way, indicating a phase of increasing dominance of a QG flow in April.