State of the Art in Volcanic Seismology

Abstract

The ultimate goal of a volcanic seismologist is to predict a volcanic eruption using seismological observations.

Towards that goal, seismologists have worked on both conventional and unconventional approaches to the understanding of structure and processes inside a volcano. The structure inside a volcano is, probably, the most complex subject seismologists have ever encountered on Earth. It is extremely heterogeneous, anisotropic and absorptive with irregular interfaces and topography including cracks of all sizes and orientation. The source processes are also much more complicated than usual tectonic earthquakes, because they involve additional dynamics of gas and fluid magma in generating seismic signals, to be deciphered by seismologists.

In the present work, the author presents a personal view of various seismological methods currently used in studying structure and processes in volcanic areas, and recommends a unique design of experiment tailored to each volcanic area. With regard to the prediction of volcanic eruption, he advocates a combined monitoring of coda Q⁻¹ and volcanic (harmonic) tremor. The study of volcanic tremor requires a new breed of seismologists who can deal with the dynamics of fluid and gas coupled to the seismic radiation. Non-linearity of dynamics, at the source of volcanic tremor, may be much stronger than that at an earthquake source. Older seismologists trained in linear solid dynamics, however, may still find a great deal of work to do in delineating the detailed internal structure of a volcano, and in accurately separating the source, path and site effects in the complicated seismograms observed in a volcanic area.