government authorities and the scientists and engineers concerned. The flow diagram on the right of Figure I “Planning for the Mitigation of Earthquake Disasters” shows the steps involved in meeting the practical objective of calculating seismic hazard. The steps are in boxes numbered 1 to 12 and comments on some of them are set out below: Step 1: The basic data required for this step are of two types. The first consists of historical reports on earthquake damage (non instrumental, macro-seismic) from which the epi- centre location and the size of the earthquake in terms of macroseismic intensity, I, are estimated. (Evidently, earthquakes off the coast or in unpopulated areas may escape the record partly or totally). The second type consists of data on earthquake parameters 13 based on the analysis of seismograms. However, reliable locations on a world wide scale are not available before 1964, and earlier determinations of epicentre co-ordinates may be in error by 50 - 150 km, depending on the number and position of seismic stations. Historical records are urgently needed but they, as we11 as instrumental determinations prior to 1964, must be carefully checked before being processed. For the sake of re- liability and consistency of statistical treatment, the principle of homogeneity in space, time and magnitude should be adhered to. Step 2: In catalogues and in seismic maps the differential accuracy of earthquake parameters must be indicated. Step 3: Active tectonics are indicative of increased seismic risk. The activity of a region may be denoted by recent and continuing vertical and horizontal movements, uplifting of coast lines and by large strains. Step 4: Potential source areas are identified by means of the clusGering of known epicentres and/or the location of faults active during the neotectonic era. The most difficult prob- 
**Analysis**
The text appears to be discussing the process of calculating seismic hazard and mitigating earthquake disasters, which suggests a focus on natural phenomena and potential risks to human populations and infrastructure. The language used is technical and refers to specific concepts in seismology, such as epicentres, macroseismic intensity, and fault lines. This suggests that the text is related to the field of science and technology.

**Category**
Science and technology