Theory of largest values applied to earthquake magnitudes

The theory of largest values [see 1, 2, of “References” at end of paper] requiring data on only the largest event in each of a number of equal time‐intervals, recommended itself to the author as a possible way of describing the earthquake activity of a region. A preliminary analysis using the calendar month as the interval having demonstrated the applicability of the theory in this field, the author has investigated the feasibility of using still shorter Intervals [3]. In the present paper the interval used is one‐third of a month—the first day through the tenth, the eleventh through the twentieth, and the twenty‐first to the end of the month. This interval therefore corresponds to that of one year used in flood‐analyses. A compensating change has been made in the return‐period scale (Fig. 2). Incomplete results of further analysis indicate that it is feasible to use a time‐interval as short as five days.