  We consider a modified Burridge-Knopoff model with a view to understand
results of acoustic emission (AE) relevant to earthquakes by adding a
dissipative term which mimics bursts of acoustic signals. Interestingly, we
find a precursor effect in the cumulative energy dissipated which allows
identification of a large slip event. Further, the AE activity for several
large slip events follows a universal stretched exponential behavior with
corrections in terms of time-to-failure. We find that many features of the
statistics of AE signals such as their amplitudes, durations and the intervals
between successive AE bursts obey power laws consistent with recent
experimental results. Large magnitude events have different power law from that
of the small ones, the latter being sensitive to the pulling speed.
