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Multiple-input multiple-output (MIMO) technique has been progressing in communication systems and radars. However, exploration of underground, especially earth’s crust structure is a frontier of MIMO sensing. The authors develop periodic orthogonal pseudo-noise codes with zero-correlation zone (ZCZ) and investigate their application to underground elastic wave reflection model. The codes are constructed by the convolution between periodic real-valued orthogonal pseudo-noise sequences and a common periodic real-valued pseudo-noise sequence which are inserted by zeroes, respectively. The constructed codes take the low-magnitude value below 2, consisting of all non-overlapping product of elements in two sequences, and their whole period given by the product of two sequence periods leads to the process gain of noise suppression, and their ZCZ is decided by the period of the common sequence. The auto-correlation function of a code is impulsive in the whole period and the cross-correlation functions between codes are zero over ZCZ. In the MIMO sensing simulation, two codes of period 635 and maximum value 1.74 constructed by two orthogonal sequences of period 5 and a sequence of period 127 are transmitted simultaneously and reach a receiver through short and long paths in the presence of noise, and are detected without crosstalk as the improved signal-to-noise ratios by correlation processing. The family number of orthogonal set, the periods of the orthogonal sequence and the common sequence are selectable for the applications. The developed codes are applicable to radar, sonar and LiDAR.