ON ANDEAN STRUCTURE, PART I I: EARTHQUAKE R ISK IN CHILE

The problem of earthquake risk in Chile is discussed in terms of seismic history, geotectonic provinces and regional variations in earthquake incidence. Seismic zoning is impractical be-cause all of Chile above Parallel 42 ° South has been within the epicentral area of some destruc-tive earthquake. The probability concept of earthquake risk is discussed in reference to the seismieity of Santiago. It is found that the earthquake risk at Santiago for an acceleration of0.1 g is 62.5% in any 10-year period. For the same interval, the risk of a "destructive " earthquake (intensity 8) is of the order of 20%. INTRODTJCTION The structural features of the South Andean region have been outlined in a