FIGURE 6.13.-Distribution of large and small earthquakes along the San Andreas fault system. In general, modern instrumental data (C; see chap. 5) portray same pattern of activity seen in large earthquakes from preinstrumental (A) and instrumental (B) eras. Some areas characterized by high levels of microearthquakes, such as well-defined faults east of northern section of the San Andreas fault (red line), have not produced significant earthquakes in historical time and so are considered probable sites of future activity.