Abstract: A seismic triggered seismograph (10) has a transducer (12) that measures particle vibration along three orthogonal axes and a microphone (14) which measures atmospheric overpressure. The four parameters measured produce signals which are passed through delay circuits (58, 60, 62, 90) and then connected for recording on magnetic tape (21). The seismic signals are examined before being input to the delay circuits (58, 60, 62) and when any of the signals exceeds a predetermined threshold, a tape transport (154) and recording mechanism are activated so that the signals are recorded when they emerge from the delay circuits. Both the delay circuits (58, 60, 62, 90) and the magnetic recording are implemented with analog format. At the end of a predetermined time interval following a seismic event, a calibration signal is applied to the magnetic recording. Following the calibration signal, the transducer (12) is activated by a standard amplitude signal for indicating calibration of the transducer (12).