Seismic Anisotropy Beneath Ruapehu Volcano: A Possible Eruption Forecasting Tool
Alexander Gerst1,2*
and
Martha K. Savage1
The orientation of crustal seismic anisotropy changed at least
twice by up to 80° because of volcanic eruptions at Ruapehu
Volcano, New Zealand. These changes provide the basis for a
new monitoring technique and possibly for future midterm eruption
forecasting at volcanoes. The fast anisotropic direction was
measured during three seismometer deployments in 1994, 1998,
and 2002, providing an in situ measurement of the stress in
the crust under the volcano. The stress direction changed because
of an eruption in 1995–1996. Our 2002 measurements revealed
a partial return to the pre-eruption stress state. These changes
were probably caused by repeated filling and depressurizing
of a magmatic dike system.
2 University of Karlsruhe, Germany.
* Present address: Institute of Geophysics, University of Hamburg, Bundesstrasse 55, 20146 Hamburg, Germany.
To whom correspondence should be addressed. E-mail: publications{at}planet3.de
