Abstract: This invention relates to an integrated acoustic network system to provide warning of impending groundfall in underground mines. The system includes a plurality of geophones which derive acoustic signals by which the source of seismic disturbances is located, and an array of high frequency piezoelectric sensors which pick up signals from small ground disturbances which precede groundfall. A warning system is provided both at the scene of mining operations and at a central location of impending groundfall and of the location of its occurrence.