Raw output units of instrument – contraction positive
1.2 x 106
1.0 x 106
0.8 x 106
0.6 x 106
0.4 x 106
0.2 x 106
0
-0.2 x 106
A. Raw data
Bad Data Flag
8 x 104
6 x 104
4 x 104
2 x 104
0
-2 x 104
1.6 x 105
B. Edited
C. Offsets corrected
Exponential fit for
contraction due
to grout curing
1.4 x 105
1.2 x 105
1.0 x 105
Start of useable data
0.8 x 105
3000
D. Grout-curing curve
2000
subtracted
1000
0
-1000
-2000
-3000
Sept. 1
Nov. 1
Jan. 1
Mar. 1
1999
May 1
July 1
2000
VOLCANO DEFORMATION–
Geodetic Monitoring Techniques
By Daniel Dzurisin
U.S. Geological Survey graphics