Figure 8

A) Geologic map of the Parkfield site, showing the locations of magnetotelluric (MT) profiles across the San Andreas fault at both the primary ("proposed") and alternate drill sites. Also shown are the locations of a the high-resolution seismic reflection/refraction profile to be conducted across the primary site in the Fall of 1998 and seismic reflection lines conducted 1-2 km south of the alternate site (P. Malin, pers. comm., 1996). B) Cross section along A-A', schematically showing the drill hole (note that this cross section is for the alternate drill site; see text). The contact between Tertiary marine sediments (Tsm) and the underlying grantitic basement (gr) was determined from the seismic survey conducted by P. Malin (pers. comm., 1996). The Franciscan melange is denoted by Kjf. The hachured region shows a low-resistivity zone associated with the San Andreas fault, as imaged by the MT profile across the alternate site (Unsworth et al., 1997).