retariat of the World Meteorological Organization. English, 87 pages, Price 20 SFr. 12 VI. EARTHQUAKES 6.1 Seismic aspects Seismic hazard is defined as the probability F(Y) that a certain ground motion parameter will be exceeded in a period of (T)years. It is essential that the users of primary seismological data, or of hazard figures, should be aware of the inaccuracies inherent in the data and of possible errors in the determination of individual parameters. Users should always ask seismologists and geologists for an assessment of the accuracy and confidence in the information and advice which they provide. The procedures which provide probabilistic values of seismic hazard cannot always be followed in practice. Simple approaches may be used if the data required are not available, OK if a rough estimate of hazard would be acceptable. In many countries, the largest macroseismic intensities that have been observed so far are regarded as defining the level of the hazard and, using this technique, maps can be constructed. However, such an approach may result in danger- ous gaps since earthquakes may occur in places where no activity had previously been reported. Efforts are therefore being made, using geotectonic evidence, to improve the maps by extending the zones ,of largest macroseismic intensity, (1 max.). 6.1.1 Calculation of seismic hazard Figure I shows in the form of diagrams the sequence of actions to be taken by government authorities on the one hand, and by earth scientists and earthquake engineers on the other hand, in order to draw up and implement plans for the mitigation of earthquake disasters. In this way, facilities, data and techniques may be made available for the calculation of seismic hazard. At alI stages in the implementation of the plan there would, of course, be full decision between the 
**Analysis**
The text appears to be a technical report related to earthquakes and seismic hazard, providing information on the calculation of seismic hazard, the importance of accuracy and confidence in data, and the implementation of plans for mitigating earthquake disasters. The language used is specialized and assumes a certain level of background knowledge in seismology and geology. The text does not mention economic, social, or cultural aspects, which suggests that it is primarily focused on a scientific or technical topic.

**Category**
Science and technology