A demonstration of time-lapse imaging using ultra-high-frequency seismic reflection data

Time-lapse seismic imaging has improved our capability to measure and understand dynamic processes in the subsurface. However, there are very few examples using ultra-high-frequency (kHz-range) seismic data. Exacting requirements for navigation can be prohibitive for acquiring coherent, true-3D volumes and residual errors manifest as noise in time-lapse differences making it challenging to interpret real subsurface changes. By updating the acquisition and processing workflows for the 3D Chirp, an ultra-high-frequency sub-bottom profiler, initial results illustrate high amplitude and navigation repeatability. Post-processing was used to improve the capability and performance of real-time kinematic GPS, coupled with high-accuracy inertial measurements to yield centimetre-level absolute positioning in a range of operating conditions. A comparison of seismic reflection volumes acquired over the same area at high and low tide reveals a normalized RMS difference of 16.1% and demonstrates the capability for direct quantitative monitoring of the shallow subsurface at decimeter-resolution.