The Mini-Sosie is a digital seismic system developed by Barbier and Viallix. The source is a 130- or 220-pound (59 or 99 Kg) tamper identical with those used for earth compaction. By acting on the throttle, the operator obtains a series of random impulses at an average rate of 10 per second. The digital recorder is connected to a normal 12- or 24-trace seismic reflection array and to a sensor set up on the tamper base plate. Each pulse from the sensor activates a register for each trace; thus, each repeatable seismic event corresponding to the impact which created the pulse is stored in the registers at a constant time interval after the activation of the register. Therefore, seismic events occurring at a constant time interval after the surface impulse will add up when t e contents of a group of registers are stacked. Other events due to preceding or subsequent impulses behave as random noise and their sum decreases as more register contents are stacked. The operation amounts to a real-time correlation between the series of random pulses and the input from the geophones. The Mini-Sosie method is in fact a product of the microprocessor revolution. For two-way times of 1 second, decoding in

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real time multiplies the stacking rate by more than 10 if the Mini-Sosie method is compared to an ordinary impulse-by-impulse stacking method such as weight dropping. The method resists moderate external noise well and the source can be used almost everywhere, and is particularly useful in populated areas.

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