The San Andreas Fault Observatory at Depth (SAFOD) project was established in 1998 with the aim to improve our understanding of the San Andreas Fault. It has succeeded as the first borehole to intercept regions of seismicity at depth along a plate-boundary fault, with near complete recovery of material from two active fault strands.
This application can be used to find information about each core section and explore available samples.
Last updated: January 2026
Drilling of the SAFOD core was conducted in one pilot phase and three main phases:
1. Pilot Hole (2002): A 2.2 km vertical hole drilled near the planned SAFOD drill site.
2. Phase 1 (2004) & Phase 2 (2005): The main hole was drilled vertically for the first 1.5 km and then at an angle of approx. 60 degrees from the vertical in order to intercept the full width of the San Andreas Fault near where microearthquakes were clustered (Hole C).
3. Phase 3 (2007): Three lateral sidetracks (Holes E and G) were drilled to intercept actively deforming zones of the San Andreas Fault.