The array arrangement of receivers was studied to improve the resolution of LOTEM (long offset transient electromagnetics) survey. To eliminate the effect of underground structure from a source to a receiving point, continuous array arrangement from a source site is desirable. The survey at the Yufuin fault was carried out by arranging TEM receivers at intervals of 100m from the source. Since the synchronization between transmitting and receiving points by high-precision clock is essential, an amplifier for a flux gate magnetometer capable of measuring at four points at the same time was used. In the south plateau of the Yufuin basin, a relatively high resistivity stratum more than several tens ohm m exists at depth less than several hundreds meter, and a low resistivity stratum less than 10 ohm m exists under that. Those boundary depth increases toward the north up to 950m, and the depth subsequently decreases toward the north until the low resistivity stratum disappears. In addition, the uniform stratum of 1000m deep continues toward the north. Such precise resistivity structure around the fault was obtained by dense arrangement of measuring points. 4 refs., 7 figs.