Positions and orientations of geophones in the SAFOD Pilot Hole
from Volker Oye

Notes from Rufus:

Positions east and north are in meters relative to the SAFOD Pilot Hole wellhead, which is located at (in WGS84 reference frame):

SAFOD Pilot Hole Lat. = 35.97425794 deg
SAFOD Pilot Hole Long. = -120.55210714 deg

Depths are in meters above mean sea level (MSL), and were determined by reference to ground elevation at the Pilot Hole wellhead. The ground elevation at the wellhead is 660.5 m MSL, which was obtained by adding the depth of the geoid below the reference ellipsoid (33.2 m, from the National Geodetic Survey's Geodetic Toolkit and their GEOID03 model, see www.ngs.noaa.gov) to the WGS84 ground height above ellipsoid determined by the USGS (627.3 m).

Positions are rounded to the nearest 0.5 m for the E/N position and to the nearest 1 m for the depth.

The deviation of the borehole was obtained by gyroscopic survey (azimuth and incidence of well path). Orientations were estimated comparing explosion and earthquake data recorded at the downhole geophones with theoretical data obtained from 3D ray tracing (Thurber et al. model). The deviation of the borehole was included. Three rotations are needed to end up with E, N, Z (positive up) components for the recorded geophone channels ch3, ch2, ch1.

• assign ch1 → Z (positive down), ch2 → N, ch3 → E
• multiply Z component by -1
• clockwise rotation of α_c + α_w around the Z-axis (now positive up)
• clockwise rotation of γ_w to remove the dip of the well path along E-component, which is now perpendicular to the well path azimuth.
• counter clockwise rotation of α_w to put N-component back to global North.

geophone#, E[m], N[m], Z[m] rel. to sea level, calibration azimuth 
α_c, well path azimuth α_w, well path incidence γ_w
1, 6, -26, -1436, 264, 345, 2.5
2, 6.5, -27.5, -1396, n.a., 160, 2.6
3, 6, -29, -1356, 120, 8, 2.6
4, 5.5, -31, -1316, 193, 30, 1.6
5, 5, -31.5, -1276, 284, 51, 1.3
6, 4.5, -32, -1236, 180, 57, 1.4
7, 3.5, -32, -1196, 43, 80, 1.4
8, 2.5, -32.5, -1156, 21, 120, 1.2
9, 2.5, -32, -1116, 210, 170, 1.5
10, 2.5, -31, -1075, 299, 190, 1.8
11, 3, -28.5, -1036, 182, 208, 2.7
12, 4, -27, -996, 283, 207, 3.3
13, 5, -25, -956, 338, 202, 3.2
14, 6, -23, -915, 140, 200, 2.3
15, 6, -22, -876, 76, 210, 2
16, 7, -21, -836, n.a., 220, 2
17, 8, -20, -796, 149, 260, 1.9
18, 9, -20, -756, 125, 269, 2.7
19, 12, -20, -716, 39, 266, 3.4
20, 14, -20, -676, n.a., 252, 4
21, 16, -18.5, -636, 255, 242, 3.6
22, 19, -17, -596, 248, 236, 2.8
23, 20, -16.5, -556, 41, 225, 2.8
24, 21, -14, -516, 325, 194, 3.5
25, 21, -11, -475, 131, 172, 5.9
26, 20.5, -8, -436, n.a., 172, 5.5
27, 20, -3, -396, 215, 168, 5
28, 19, -0.5, -356, 228, 157, 4
29, 18, 1, -316, 252, 146, 3.3
30, 17, 2.5, -276, 11, 130, 2.5
31, 15.5, 3.5, -236, 92, 117, 2.2
32, 14, 4, -196, 309, 116, 1.9