6- to 9-inch (15 – 23 cm)
hole drilled 450 – 800 feet
(137 – 244 m) below
ground surface
Satellite
telemetry
Electronics
enclosures
OR
6 x 6 x 8 foot
(2 x 2 x 2.4 meter)
above ground
Cement and/or
bentonite grout
7 x 8 foot
(2.1 x 2.4 meter)
below ground
Tiltmeter
400 – 800 feet
(122 – 244 meters)
DRAWING NOT TO SCALE
(Dimensions are approximate)
Seismometer
(3C-Vel and 3C-Acc)
100 – 150 feet
(30 – 45 meters)
20 – 40 feet
(6 – 12 meters)
Pore pressure monitor
Heat flow monitor
Aquifer
Expansive grout
Strainmeter
VOLCANO DEFORMATION–Geodetic Monitoring Techniques
By Daniel Dzurisin
U.S. Geological Survey graphics