HR: 09:45h
AN: T11F-08 INVITED [Abstracts]
TI: Structure of the San Andreas Fault Zone and SAFOD Drill Site as Revealed by Surface Geologic Mapping
and Seismic Profiling Near Parkfield, California
AU: * Rymer, M J
EM: mrymer@usgs.gov
AF: U. S. Geological Survey, 345 Middlefield Rd. MS 977, Menlo Park, CA 94025
United States
AU: Catchings, R D
AF: U. S. Geological Survey, 345 Middlefield Rd. MS 977, Menlo Park, CA 94025
United States
AU: Thayer, M
EM: maurits_thayer@hotmail.com
AF: Dept. of Geology, Arizona State University, Tempe, AZ 85287
United States
AU: Arrowsmith, J R
EM: ramon.arrowsmith@asu.edu
AF: Dept. of Geology, Arizona State University, Tempe, AZ 85287
United States
AB:
New geologic mapping, combined with high-resolution seismic reflection and refraction profiling, in the vicinity of the San
Andreas Fault Observatory at Depth (SAFOD) deep bore hole near Parkfield, California indicates a wide and structurally
complex San Andreas fault zone. The geologic and geophysical techniques both indicate the location and orientation of
previously unmapped faults. The San Andreas fault zone near the SAFOD site is at least 5 km wide and is dominated by faults
oriented subparallel to the surface trace of the San Andreas fault. Subsurface orientation of faults indicate that the San
Andreas fault zone is composed of at least two flower structures in the upper 3 km, with the main trace approximately
centered on the more easterly of these structures. The SAFOD drill site is located near the center of the other flower
structure. A third flower structure may lie farther to the southwest of our studies. The flower structures likely merge at
depth, but at least in the upper 3 to 4 km (the target depth of the SAFOD main hole), they are distinct features. Based on
inferred ages of rock types juxtaposed across faults and geomorphic evidence along faults, it appears that the plate boundary
(San Andreas fault zone) near the SAFOD site has migrated eastward during the past approximately 20 million years by forming
new flower structures.
DE: 8000 STRUCTURAL GEOLOGY (New field, replaces single entry 8165)
DE: 8005 Folds and folding
DE: 8010 Fractures and faults
DE: 8015 Local crustal structure
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting