INTRODUCTION TO VOLCANIC SEISMOLOGY

Transcription

1 INTRODUCTION TO VOLCANIC SEISMOLOGY V.M. Zobin Observatorio Vulcanologico, Colima, Mexico ELSEVIER Amsterdam - Boston - Heidelberg - London - New York - Oxford Paris - San Diego - San Francisco - Singapore - Sydney - Tokyo

2 vii Contents Chapter 1 1 Introduction 1.1. Terms and definitions Volcanic terms Tectonic terms Seismological terms Subject of the book Acknowledgements 7 Chapter 2 9 Seismicity at Volcanoes 2.1. History of seismic monitoring of volcanic activity Classification of volcanic earthquakes Sequences of volcanic earthquakes Sequences of volcano-tectonic earthquakes Sequences of eruption earthquakes 28 Chapter 3 31 Origin of Volcano-tectonic Earthquakes 3.1. Magma and its physical and chemical properties Volcanism and tectonics Models of volcano-tectonic earthquake sequences 42 Chapter 4 47 Origin of Eruption Earthquakes 4.1. Processes of the outlet of eruption products from volcanic 47 crater Fragmentation of magma Volcanic "fall-and-flow" processes Seismic modeling of eruption earthquakes Model of seismic signals produced by an eruption Models based on the vibration of magma body Models based on degassing process of magma Modeling of seismic signals generated by pyroclastic 64 flows and rockfalls

3 viii Contents Chapter 5 67 Volcano-tectonic Earthquakes at Basaltic Volcanoes 5.1. Volcano-tectonic earthquakes associated with shield 67 volcanoes Kilauea volcano, Hawaii Mt. Etna, Sicily Volcano-tectonic earthquakes associated with 77 stratovolcanoes Oshima volcano, Izu islands, Japan Klyuchevskoy volcano, Kamchatka, Russia Volcano-tectonic earthquakes associated with fissure New Tolbachik Volcanoes, Kamchatka, Russia Volcano-tectonic earthquakes associated with caldera 86 collapse Fernandina volcano, Galapagos Isl Volcano-tectonic earthquakes associated with submarine Teishi-Knoll volcano, Izu Islands, Japan 89 Chapter 6 93 Volcano-tectonic Earthquakes at Andesitic Volcanoes 6.1. Volcano-tectonic earthquakes associated with volcanic 93 "directed blasts" Bezymianny volcano, Kamchatka, Russia Sheveluch volcano, Kamchatka, Russia Volcano-tectonic earthquakes associated with phreatic and 100 phreato-magmatic explosions El Chichon volcano, Mexico Volcan de Colima, Mexico Soufriere Hills volcano, Montserrat Volcano-tectonic earthquakes associated with lava 110 extrusions Volcan de Colima, Mexico Volcano-tectonic earthquakes associated with flank 113 eruption Sakurajima volcano, Japan 113 Chapter Volcano-tectonic Earthquakes at Dacitic Volcanoes 7.1. Volcano-tectonic earthquakes associated with central Mt. St. Helens, Cascades, U.S.A Usu volcano, Hokkaido, Japan 119

4 ix Unzen volcano, Kyushu, Japan A. Pinatubo volcano, Philippines Volcano-tectonic earthquakes associated with flank 129 Chapter General Properties of Volcano-tectonic Earthquake Swarms 8.1. Properties of volcano-tectonic earthquake swarms inferred 133 from the data of Chapters 5 to Temporal variations Spatial distributions Post-eruption seismic activity Duration of seismic activity before volcanic event Position of a volcanic event according to the stage of 138 volcano-tectonic earthquake swarm 8.2. Additional data about volcano-tectonic earthquake swarm 139 properties Size of volcano-tectonic earthquake swarm area Earthquake swarm duration Magnitude-frequency relations of events in volcano- 141 tectonic earthquake swarms Chapter Source Properties of Volcano-tectonic Earthquakes 9.1. Focal mechanisms of volcano-tectonic earthquakes: double 145 couple and non-double couple models Double couple model Non-double couple model Spectral characteristics of volcano-tectonic earthquakes Spectra of total records of volcano-tectonic 157 earthquakes Spectral source characteristics of volcano-tectonic 158 earthquakes and their relationship with the type of volcanic activity Temporal variations of spectral source characteristics 161 of volcano-tectonic earthquakes in the course of volcanic activity 9.3. Seismo-tectonic deformations in volcanic region 165 Chapter Significant Volcano-tectonic Earthquakes and their Role in Volcanic Processes Selection of significant volcano-tectonic earthquakes that 172

5 occurred in the XXth century Focal rupturing of significant volcano-tectonic 175 earthquakes and its role in volcanic processes Rupturing of the magnitude Mw 5.2 earthquake 176 preceding the 1989 Teishi Knoll submarine eruption Rupturing of the magnitude Mw 7.1 earthquake 178 preceding the 1996 Akademia Nauk volcano subaqual eruption Rupturing of the magnitude Mw 5.6 earthquake 181 preceding the 1996 Grimsvotn volcano subglacial eruption The magnitude 7 volcano-tectonic earthquakes in volcanic 183 processes Event No 2, Katmai, Alaska Event No 3, Sakurajima, Japan Seismic hazard of significant volcano-tectonic earthquakes Maximum magnitude Mmax Attenuation of intensity with distance for volcanic 192 earthquakes Recurrence time Estimation of seismic hazard of volcanic activity of 196 Colima volcano, Mexico Chapter Volcanic Tremor Seismograms and spectra Location of volcanic tremor Oshima volcano, Izu islands Kilauea volcano, Hawai Volcanic tremors in eruptive process Etna volcano, Italy Pavlof volcano, Alaska Kilauea volcano, Hawai Relationships between the intensity of seismic signals and 202 volcanic events Special cases of volcanic tremors Isolated tremors Deep tremor Long-period tremor 210 Chapter' Earthquakes Related to Pyroclastic Flows and Rockfalls Occurrences of "fall-and-flow" earthquakes Relationship between the "fall-and-flow'' earthquakes and 215 seismo-volcanic activity during lava emission Quantification of "fall-and-flow" earthquakes 217

6 xi Quantification of "fall-and-flow" earthquakes 217 recorded by short-period instruments at Volcan de Colima, Mexico Relationship between the amplitude of the long- 222 period records of "fall-and-flow" earthquakes and the volume of pyroclastic flows Location pyroclastic flows using amplitude signals of "fall- 224 and-flow" earthquakes Chapter Explosion Earthquakes Waveforms of explosion earthquakes Occurrences of explosion earthquakes and their location Explosion earthquakes in the eruptive process Size of explosion earthquakes 233 Chapter Seismic Monitoring of Volcanic Activity and Prediction of Volcanic Eruptions Methodology of seismic monitoring of volcanic activity Applications of volcanic seismicity in the prediction of 241 volcanic Methods based on the statistical variations in the 243 parameters of volcano-tectonic earthquakes Methods based on a study of the variations in 249 complex behavior of different types of volcanic earthquakes Seismic precursors to small explosions 250 Chapter Some Remarks About Unresolved Problems Variety of low-frequency volcanic earthquakes Low-frequency volcano-tectonic earthquakes Low-frequency eruption earthquake s Seismic activity at dormant volcanic structures: 258 A problem of possible eruption Matsushiro swarms Long Valley swarms Campi Flegrei swarms 261 References 265 Index of Volcanic Events 285