Abstract: A physical model for collinear fault with an unconnected area has been designed and con-ceptually been used to simulate the barrier or strong area concerning the earthqua ke preparation. Biaxi-al compressional experiments on middle -size rock sample w ith this model have been done and more than4600 A E events have been located accurately. Farther more, the statistical characteristics of A E spatio-temporal distribution h ave been studied preliminarily. Due to the influence of strong locked area, it re-veals a clear evolvement process of gaps around the unconnected area before the 98% of peak strength,which gradually develops in time and contracts in space. During the w eakening stage after the peakstrength, larger AE events are crowded together in passive lower wall and smaller A E events distributeddispersively in active hanging wall. Comparing with the elastic stage, the main aea of AE activity mi-grated from active hanging wall to the passive lower wall during the weakening stage. And the frequen-cy of larger AE events and the AE releasing strain energy increased obv iously during the weakeningstage. The A ER reached the highest value at the moment before the fracture of unconnected area. Thevariation of b values reviewed a typical feature that b value reduced gradually in the prophase for along time, and then rises back quickly before the instability. Results also show that the fracture insta-bility has more evident and more abundant microfracture precursors than that of stick -slip.

Key words: Acoustic emission, Rock sample for collinear fault with an unconnected area, Differential stress, Spatio-temporal evolvement of AE