São Miguel - Test Page for Apache - Universidad de Granada

346 Pages·2007·14.93 MB·Spanish

University of Granada
Andalusian Institute of Geophysics

Passive and Active Seismic Tomography of Volcanic Islands
São Miguel (Portugal) and Deception (Antarctica)

DISSERTATION
for the degree of
Doctor of Earth Sciences

presented by
Daria Zandomeneghi

on the recommendation of
Prof. Dr. Jesús M. Ibañez Godoy, examiner
Dr. Fco. Javier Almendros Gonzalez, co-examiner

University of Granada, 2007
Editor: Editorial de la Universidad de Granada
Autor: Daria Zandomeneghi
D.L.: Gr. 1712 - 2007
ISBN: 978-84-338-4413-2
Universidad de Granada
Doctorado en Ciencias de la Tierra
Instituto Andaluz de Geofísica

Tomografía Sísmica Activa y Pasiva en las Islas Volcánicas
São Miguel (Portugal) y Decepción (Antártida)

MEMORIA
para optar al grado de Doctor en Ciencias de la Tierra

presentada por
Daria Zandomeneghi

Fdo. Daria Zandomeneghi

V°B° de Director V°B° del Director

Fdo. Dr. Jesús Ibañez Godoy Fdo. Javier Almendros
Universidad de Granada, 2007
Index
Spanish Extended Abstract 1
Esta Tesis 1
Tomografía y Volcanes 3
Tomografía Activa y Pasiva 4
Isla Decepción 6
Introducción 6
Experimento Sísmico 7
Resultados y Discusión 9
Conclusiones 10
São Miguel 11
Introducción 11
El experimento sísmico 12
Resultados y discusión 14
Conclusiones 15
Conclusiones Generales 16
1.Tomography and Volcanoes 24
1.1. . Seismic Tomography 24
1.2. Tomography and Volcanoes 25
1.2.1. Importance of Tomographic Models 26
1.2.2. General Interpretation of Vp and Vs Anomalies in Volcanoes 28
1.2.3. Active and passive seismic tomography 33
1.2.4. An example 35
Campi Flegrei 37
1.3. References 42
2.Theory and Principles 46
2.1. . Locating Earthquakes 47
2.2. Velocity Model 50
2.2.1. Theory Fundamentals 51
2.2.1.1. Representation of Structure 51
2.2.1.2. Traveltime Determination 52
2.2.1.3. Inverse Problem 56
2.2.1.4. Analysis of Solution Quality 61
2.2.2. 1D Models 66
2.2.3. 3D Model 69
2.2.3.1. Benz’s Method 69
2.2.3.2. Toomey’s Method 71
References 75
3.Central São Miguel 78
Abstract 78
Extended Abstract 80
Introduction 80
Seismic Experiment 81
Results and Discussion 83
Conclusions 84
3.1. The Question 85
3.2. Tectonic Overview 86
3.3. Previous Studies 88
3.3.1. Geology 88
3.3.2. Hydrothermal and Geothermal Activity 93
3.3.3. Geochemistry 95
3.3.4. Gravimetry 95
3.3.5. Geodesy 100
3.3.6. Tectonics and Seismology 102
3.3.7. Resuming the ‘State of the Art’ 107
3.4. . Seismic experiment 109
3.4.1. Objectives 109
3.4.2. Institutions 109
3.4.3. Experiment Design 110
3.4.4. Station Types 112
3.4.4.1. Lennartz Marslite 112
3.4.4.2. MalIAG 113
3.4.4.3. Local network 114
3.4.5. Data processing 116
3.4.5.1. Data Formats and Software 116
3.4.5.2. P and S Arrival Time Determination 116
3.4.5.3. Data Quality 118
3.4.6. Previous Results from the Experiment 119
3.4.6.1. Seismic data 119
3.4.6.2. Minimum 1D Velocity Model and High Precision Locations 122
3.5. 1-D Velocity Model 123
3.5.1. Method 123
3.5.2. Input Data 123
3.5.3. Tests 126
3.5.4. Results 130
3.6. Initial Locations 136
3.6.1. Method 136
3.6.2. Input Data 136
3.6.3. Results 138
3.7. 3-D Velocity Model 142
3.7.1. Method 142
3.7.2. Input Data 142
3.7.2.1. Data selection 143
3.7.2.2. Grid definition and parameter selection 143
3.7.2.3. Initial Model 146
3.7.3. Vp/Vs Ratio 146
3.7.4. Error 146
3.7.5. Resolution analysis and input tests 148
3.7.5.1. Checkerboard Test 148
3.7.5.2. Impulse Response Test 156
3.7.5.3. Reconstruction Test 157
3.7.5.4. Starting Models 159
3.7.5.5. Jackknife Test 160
3.7.6. Results 161
3.8. Discussion of Results and Conclusions 169
3.8.1. Low velocity regions 170
3.8.2. High velocity regions 171
3.9. Conclusions 175
References 177
4.Deception Island 180
Abstract 180
Extended Abstract 182
Introduction 182
Seismic Experiment 183
Results and Discussion 185
Conclusions 186
4.1. The Question 187
4.2. Tectonic Overview 188
4.3. Previous Studies on Deception 192
4.3.1. Geology and Volcanology 193
4.3.2. Structural Geology and Geodynamics 199
4.3.3. Gravimetry and Magnetics 201
4.3.4. Seismicity 204
4.3.5. Seismic Structure 209
4.3.6. Resuming the ‘State of the Art’ 212
4.4. Seismic Experiment 214
4.4.1. Objectives 214
4.4.2. Institutions 215
4.4.3. Experiment Design 215
4.4.3.1. Air-gun Shooting Configuration 217
4.4.3.2. Source Generation 221
4.4.3.3. Signal Characteristics 223
4.4.4. Station Types 224
4.4.4.1. Lennartz Marslite 225
4.4.4.2. Lennartz M24 225
4.4.4.3. malIAG 226
4.4.4.4. OBS 227
4.4.5. Data Processing 228
4.4.5.1. Data Formats and Software 228
4.4.5.2. Data Quality 229
4.4.5.3. P Arrival Time Determination 232
4.4.5.4. Input Format 235
4.4.6. Other Results from the Experiment 235
4.4.6.1. Gravimetry 236
4.4.6.2. Magnetics 236
4.4.6.3. Bathymetry 236
4.4.6.4. Water Measurements 239
4.5. 3D Tomography 240
4.5.1. Method 240
4.5.2. Input 241
4.5.2.1. Grids Definition and Parameters Selection 241
4.5.2.2. Data Selection 245
4.5.2.3. Initial Model 245
4.5.2.4. Bathymetry 246
4.5.3. Error Definition 251
4.5.4. Resolution Analysis 259
4.5.4.1. DWS Definition 260
4.5.4.2. Checkerboard Test 263
4.5.4.3. Impulse Response Test 275
4.5.4.4. Reconstruction Test 281
4.5.4.5. Spike on Reconstructed Image 283
4.5.4.6. Shifted Grid Test 285
4.5.5. Starting Model 286
4.6. Results 291
4.6.1. Description of Results 291
4.6.2. More about the Result Quality 300
4.6.2.1. 2D Profiles 300
4.6.2.2. Bathymetry 303
4.6.3. Discussion of Results 305
4.6.3.1. A1 305
4.6.3.2. A2 307
4.6.3.3. A3 307