Figure 5

Schematic illustration of the fault zone monitoring string that we are proposing to use in the 4-km-deep Parkfield drill hole (see text). Although not shown here, we are also investigating the possibility of incorporating sensors for continuous monitoring of borehole deformation and/or tilt into the instrument package. The monitoring string is designed so that it can be removed for instrument repair and maintenance and so that the cased hole can be repeatedly logged for deformation induced by ongoing fault creep and/or earthquakes.