Preparing for the Unexpected

Living in California means living with earthquakes. During the last decade alone we have experienced several damaging earthquakes, some of which have come as big surprises. We were surprised by earthquakes without surface break, surface break without much seismic radiation, and a south-dipping fault in an area of primarily north-dipping structures. Why were we taken by surprise? We were surprised primarily because the duration of our data base is so short compared with the time scale of earthquake recurrence that our knowledge is very limited. Since the time is very limited today, let me focus our attention on Los Angeles.