JPH029717B

PURPOSE:To detect time difference without error by defining delay time in the range corresponding to the distance information when the mutual correlation of the detection data is computed while the distance information between detection points of a sensor is stored into a memory. CONSTITUTION:A detection data from the reference point is inputted into a terminal 1 while the detection data from other observation points are inputted into the terminal 2. When the generation of a seismic wave is detected with a level identification circuit 3, a data intake control circuit 5 is started. The circuit 5 applies data at the reference point and other observation points into an intake mutual correlation computing circuit 7 to compute the mutual correlation. The maximum of the relative delay time of the detection data is difined by the distance information stored in a memory 6. The signal of the maximum value detection circuit 8 and delay time information from the circuit 7 are inputted into a time difference output circuit 9, the delay time when the maximum value detection signal was applied is outputted as time difference information.