Table Of ContentFURTHER TITLES IN THIS SERIES
1. F.A. VENING MEINESZ
THE EARTH'S CRUST AND MANTLE
2. T. RIKITAKE
ELECTROMAGNETISM AND THE EARTH'S INTERIOR
3. D.W. COLLINSON, K.M. CREER and.S.K. RUNCORN
METHODS IN PALAEOMAGNETISM
4. M. BATH
MATHEMATICAL ASPECTS OF SEISMOLOGY
5. F.D. STACEYand S.K. BANERJEE
THE PHYSICAL PRINCIPLES OF ROCK MAGNETISM
Developments in Solid Earth Geophysics .
6
PHYSICAL VOLCANOLOGY
Edited by
L. CIVETTA1, P. GASPARINI12, G. LUONGO2
and
A. RAPOLLA
^-Institute of Geology and Geophysics, University of Naples, Naples, Italy
% Vesuvius Observatory, Ercolano, Naples, Italy
ELSEVIER SCIENTIFIC PUBLISHING COMPANY
Amsterdam — Oxford — New York 1974
ELSEVIER SCIENTIFIC PUBLISHING COMPANY
335 JAN VAN GALENSTRAAT
P.O. BOX 211, AMSTERDAM, THE NETHERLANDS
AMERICAN ELSEVIER PUBLISHING COMPANY, INC.
52 VANDERBILT AVENUE
NEW YORK, NEW YORK 10017
LIBRARY OF CONGRESS CARD NUMBER: 73-78249
ISBN 0-444-41141-0
WITH 186 ILLUSTRATIONS AND 22 TABLES
COPYRIGHT © 1974 BY ELSEVIER SCIENTIFIC PUBLISHING COMPANY,
AMSTERDAM
ALL RIGHTS RESERVED. NO PART OF THIS PUBLICATION MAY BE
REPRODUCED* STORED IN A RETRIEVAL SYSTEM, OR TRANSMITTED IN ANY
FORM OR BY ANY MEANS, ELECTRONIC, MECHANICAL, PHOTOCOPYING,
RECORDING, OR OTHERWISE, WITHOUT THE PRIOR WRITTEN PERMISSION OF
THE PUBLISHER,
ELSEVIER SCIENTIFIC PUBLISHING COMPANY, JAN VAN GALENSTRAAT 335,
AMSTERDAM
PRINTED IN THE NETHERLANDS
To
Professor Giuseppe Imbo,
Professor of Earth Physics at the
University of Naples and
Director of the Vesuvius Observatory,
in the occasion of his retirement
PREFACE
The earth sciences have many fields of direct concern to man. Research
aiming at the prediction or prevention of great natural disasters — such as
earthquakes, floods, volcanic eruptions, etc. — have gradually gained interest
because of the increased populations and economic development in
potentially dangerous areas.
Unfortunately, progress in the branch of geophysics and geochemistry
applied to the surveillance of volcanoes and prediction of volcanic eruptions
has not proceeded on a worldwide scale. Observatories exist only on some
volcanoes in Japan, Hawaii, New Zealand, Kamchatka, Italy and few other
countries. Most data come from research and continuous observations
carried out on these volcanoes, which represent only a small fraction of the
volcanoes of the world. At present we have practically no knowledge of the
relationship between geophysical phenomena (seismicity, electric and
magnetic fields, ground deformation, etc.) and activity of most volcanoes.
For this reason, a book devoted to physical volcahology gathers the
experience relative to far too few volcanoes, which must be considered as
"test-sites".
Furthermore, even for these volcanoes, the most recent advances in
surveillance have not gone far beyond statistical models relating some geo-
physical phenomena which are forerunners to eruptions (e.g., frequency of
shallow microearthquakes, characteristics of microtremors, ground deforma-
tions, etc.). Although these models may be of practical use for predicting
the activity of the single volcano to which they refer, progress toward a
deterministic approach based on a worldwide theory of volcanism is
hindered by unsufficient understanding of the causes of many observed geo-
physical phenomena. Any further advance in this direction is strictly
related to a better understanding of such problems as: magma generation
processes, mechanisms of the uprise of magmas, evolution of the gas phase
within the magmatic solution, etc. Geochemistry and experimental petrology
are probably the most promising branches for restricting the number of
possible solutions to these problems. Volcano geophysicists should be aware
of the contributions these methodologies can give to such fundamental
problems. This is why some articles, which are not strictly "physical", but
rather "chemical" volcanology, have been considered pertinent to the
subject of this book.
This book presents a collection of fourteen original papers written in
1971 in honour of Prof. Giuseppe Imbo, former Director of the Vesuvius
Observatory and Professor of Earth Physics at the University of Naples, on
the occasion of his retirement. It is certainly not a text book, nor does it
viii PREFACE
cover all the aspects of this science. It joins together specialized articles on
the state of the art in the main branches in this field.
The subject this book deals with are: the application of geophysical
methods to the surveillance of active volcanoes (seismology, ground deforma-
tion, electromagnetism, infrared radiometry) and to the study of the
structures of volcanic areas, some physical properties of volcanic rocks
(electrical and magnetic), and geochemistry of magmatic gases, an example
of the kind of information that geochemical methods can contribute to
volcanology and some general themes of physical volcanology.
These articles do not cover all the main themes fundamental to the study
of volcanoes; such basic subjects as the origin of magmas, the energetics of
eruption, viscosity of magmas, etc., are unfortunately not dealt with.
On the other hand, although volcanology is at present a science of
concern not only to geologists and petrographers but also to geophysicists,
geochemists and experimental petrologists, most books on volcanology deal
mainly with classical and descriptive subjects.
In the editors' opinion this book finds its justification in its attempt to
fill, at least in part, the lack of books devoted to the geophysical aspects of
volcanology.
CONTRIBUTORS
R. CASSINIS Laboratorio per la Geofisica della Litosfera, Milan,
Italy
H.C. CLARK Department of Geology, Rice University, Houston,
Texas, U.S.A.
R. DIBBLE Department of Geology, Victoria University of
Wellington, Wellington, New Zealand
G.S. GORSHKOV Institute of Physics of the Earth, Academy of
Sciences, Moscow, U.S.S.R.
H. ISHIKAWA Department of Geology, Kagoshima University,
Kagoshima, Japan
D.B. JACKSON United States Geological Survey, Denver, Colorado,
U.S.A.
G.V. KELLER Department of Geophysics, Colorado School of
Mines, Golden, Colorado, U.S.A.
W.T. KINOSHITA United States Geological Survey, Menlo Park,
California, U.S.A.
A. KUBOTERA Aso Volcanological Laboratory, Kyoto University,
Kyoto, Japan
G.M. LECHI Laboratorio per la Geofisica della Litosfera, Milan,
Italy
F. MACHADO Junta de Investigacoes do Ultromar, Lisbon, Portugal
T. MINAKAMI Earthquake Research Institute, University of Tokyo,
Tokyo, Japan
CD. OLLIER Canberra College of Advanced Education, Canberra,
Australia
A. RAPOLLA Istituto di Geologia e Geofisica, University of Naples,
Naples, Italy
D.A. SWANSON United States Geological Survey, Menlo Park,
California, U.S.A.
G.E. SIGVALDASON Science Institute, University of Iceland, Reykjavik,
Iceland
I. YOKOYAMA Department of Geophysics, Faculty of Science,
Hokkaido University, Sapporo, Japan
Chapter 1
SEISMOLOGY OF VOLCANOES IN JAPAN
TAKESHI MINAKAMI
Earthquake Research Institute, University of Tokyo, Tokyo (Japan)
INTRODUCTION
The numerous volcanoes in Japan occupy a part of the northern volcan-
ic belt in the circum-Pacific seismic and volcanic zone. Forty-five of these
volcanoes have records of eruptions in historical time. Consequently,
Japan has experienced many disasters caused by eruptions, such as the
1707 Huzi explosive eruption, the 1783 Asama eruption and the 1953
Myozin-syo submarine eruption, etc. (Fig.l). It is also well known that the
islands of Japan and the adjacent regions have suffered frequently from a
Fig.l. Geographical locations of some Japanese volcanoes referred to in this chapter.
2 T. ΜΙΝΑΚΑΜΙ
series of catastrophic earthquakes of tectonic origin, including the 1854
Nankaido, the 1923 Kwanto and the 1933 Sanriku-oki earthquakes. Such
disasters as those mentioned above have promoted the development of
seismology and volcanology in Japan, in order to protect people living in
such environments from the catastrophies caused by violent earthquakes
and volcanic eruptions.
In order to distinguish earthquakes of volcanic origin, it is necessary to
discover whether or not any difference exists between earthquakes of
volcanic and those of tectonic origin. According to the results of seismic
observations made at various points on the Earth's surface, it is most
characteristic that the volcanic earthquakes are not only limited in their
magnitude as compared with the tectonic or ordinary earthquakes, but
also originate at shallower depths than tectonic earthquakes, as is shown
in Fig.2. Moreover, a particular distribution of initial motions in earth-
A type
/ Volcano USU Volcano HAKONE Volcano KILAUEA
Volcanic tremor (Harmonic tremor)
Volcano KILAUEA Volcano 00 SIMA
Explosion quake
Volcano ASAMA Volcano 00 SIMA
Fig. 2. Seismograms of earthquakes and tremors originating in volcanoes.
SEISMOLOGY OF VOLCANOES IN JAPAN 3
quakes of volcanic origin suggests a special mechanism of production of
seismic waves, which is different from the mechanism of tectonic earth-
quakes. Different features also exist in the patterns of development in
seismic activity of volcanic and tectonic origin, and in the relationship
between magnitudes and seismic frequencies for earthquakes of different
origins.
In this chapter, the author deals in condensed form with the nature of
volcanic earthquakes, according to research carried out in Japan.
GENERAL DESCRIPTION OF VOLCANIC EARTHQUAKES
Firstly, it is appropriate to classify earthquakes of volcanic origin accor-
ding to the location of their foci, their relationship to eruptions and the
nature of the earthquake motions, in order to understand the outline of
the general features of this type of earthquake.
According to the location of their foci and the nature of earthquake
motion, earthquakes of volcanic origin are classified into four types
(Fig.2):
(1) A-type volcanic quakes.
(2) B-type volcanic quakes.
(3) Explosion-quakes or earthquakes followed by explosive eruption.
(4) Volcanic tremors or volcanic pulsations.
It is necessary to define the characteristics of these four types of
volcanic earthquakes, and for this purpose they are explained briefly in
the following sections.
A-type volcanic earthquakes
A-type earthquakes take place in and beneath volcanoes at places
deeper than 1 km, generally in a range from 1 km to 20 km. Although the
A-type quakes include a series of strong quakes as in the cases of the
1968—1969 Ebino earthquake swarm, the 1914 Sakura-zima and the
1943—1944 Usu swarm, etc., they are generally less than 6 in magnitude.
The pattern of development of seismic activity or the seismic frequency of
the Α-quake is classified as swarm type, as are those of the B-type and
explosion-quakes, and is quite different from the development pattern of
seismic activity of tectonic origin. On examining the seismograms, the
nature of earthquake motions of the A-type quakes is similar to those of
the shallow tectonic quakes.
B-type volcanic earthquakes
The B-type earthquakes originate usually in and adjacent to active
craters at extremely shallow depths, e.g., the summit crater of Mt. Asama,
