In New Zealand, Civil Defence exists because many natural hazards and man-made accidents can create disasters of dimensions that could not be dealt with by the normal emergency services. The destructive earthquake without warning is probably the most difficult and dangerous threat to public safety for Civil Defence to contend with. Most other causes of disaster either have some degree of warning or are relatively localised compared with the sudden and widespread effects of a major earthquake. Civil Defence planning is, in a sense, already based upon a vague and imprecise prediction of earthquakes known to be more likely to occur in some areas than in others and accepted as likely to happen at any time. The effect on Civil Defence of
 better earthquake prediction will depend
 on the probability, accuracy (in time, location and magnitude) of such prediction and how soon before the event it can be made.