Cement-treated ground often possesses significant spatial variation in strength and stiffness. Studies on the detection and stiffness measurement of weak zones in cement-treated ground using seismic geophysical methods remain limited to date. The work examines the feasibility of using seismic travel time tomography to detect and measure the stiffness of weak zones in cement-treated ground, through 1-g modelling of a cross-hole setup with weak zones of prescribed sizes and stiffnesses. Using bender elements as transmitters and receivers, shear wave velocity profiles across the weak zones are mapped. Sizes, locations, and stiffnesses of the weak inclusions are also inferred from shear wave travel times using GeoTomCG. The results indicate that although the sizes and locations of weak zones can be reliably detected using first-arrival time-picking, the stiffnesses is significantly over-estimated. The latter is due to the arrival of the diffracted waves around the weak zone masking the arrival of the transmitted waves. A modified time-picking method, using the wavelet transform, is developed and is shown to give more reliable stiffness measurements of the weak zone, but not the shape. Combining direct and wavelet time-picking allows the sizes, shapes, locations, and stiffnesses of the weak zones to be more reliably resolved.