SOME THOUGHTS ON FAULT MATURITY AND EARTHQUAKE FORECASTING

Plate boundary migration induces the formation of new faults. These faults evolve over time, starting out as numerous short-segment faults with variable strike within a complex plate boundary zone, eventually simplifying into a few longer segment faults better aligned with the direction of plate motion. The process is best observed in arid continental regions, where sparse vegetation cover and a dry atmosphere facilitate geologic mapping and high precision geodetic measurements. We will discuss some examples from the western US portion of the Pacific-North America plate boundary zone, a good natural laboratory for studies of fault evolution. Here, the Eastern California shear zone – Walker Lane system formed or accelerated in the last 5-10 million years, associated with the inland jump of the southern portion of the plate boundary to form the Gulf of California. Some implications for earthquake forecasting will also be briefly discussed.