Great Sumatra Earthquake Registers on Electrostatic Sensor

Strong electrical signals that correspond to
the Mw = 9.3 earthquake of 26 December 2004,
which occurred at 0058:50.7 UTC
off the west coast of northern Sumatra, Indonesia,
were recorded by an electrostatic sensor
(a device that detects short-term variations in
Earth’s electrostatic fi eld) at a seismic station
in Italy, which had been installed to study the
infl uence of local earthquakes on a new landslide
monitoring system.
Electrical signals arrived at the station practically
instantaneously and were detected up
to several hours before the onset of the Sumatra
earthquake (Figure 1) as well as before
local quakes. The corresponding seismic signals
(p-waves) arrived 740 seconds after the
start of the earthquake. Because the electrical
signals travel at the speed of light, electrical
monitoring for the global detection of very
strong earthquakes could be an important
tool in signifi cantly increasing the hazard
alert window.

Röder, H., R. Büttner, and B. Zimanowski (2002),
Seismo-electrical effects: Experiments and field
measurements, Appl. Phys. Lett., 80, 334 336.