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Although geodetic monitoring techniques have been widely used in areas of seismic or volcanic activity, the difficulty inherent to their discrete nature means that they must be deployed carefully to ensure the best possible detection or sensitivity of these points (see e. g. , BALDI and UNGUENDOLI, 1987; JOHNSON and WYATT, 1994; SEGALL and MATTHEWS, 1997; Yu et al. , 2000). In many cases, a more global monitoring method, is required yet at the same time one that offers the highest level of sensitivity which enables detection of the phenomenon. Interferometry radar (InSAR) techniques have been shown to play an important role in seismic and volcanic monitoring because they cover large areas (100 x 100 km) and can be easily systematized in monitoring (see e. g. , MASSONNET and FEIGL, 1998; BDRGMANN et al. , 2000; MASSONNET and SIGMUNDSON, 2000; HANSSEN, 2001). The limitations inherent to the GPS and InSAR techniques (mainly observations at discrete surface points in the case of GPS and existence of non-coherent areas and the fact that, at present, the three displacement components cannot be obtained in SAR interferometry) can be overcome by using them together or other techniques (e. g. , PUGLISI and COLTELLI, 2001; RODRiGUEZ-VELASCO et al. , 2002; FERNANDEZ et al. , 2003).
List of contents
Stress Changes Modelled for the Sequence of Strong Earthquakes in the South Iceland Seismic Zone since 1706.- 3-D Modelling of Campi Flegrei Ground Deformations: Role of Caldera Boundary Discontinuities.- Comparison of Integrated Geodetic Data Models and Satellite Radar Interferograms to Infer Magma Storage During the 1991-1993 Mt. Etna Eruption.- GPS Monitoring in the N-W Part of the Volcanic Island of Tenerife, Canaries, Spain: Strategy and Results.- Far-field Gravity and Tilt Signals by Large Earthquakes: Real or Instrumental Effects?.- Study of Volcanic Sources at Long Valley Caldera, California, Using Gravity Data and a Genetic Algorithm Inversion Technique.- Gravity Changes and Internal Processes: Some Results Obtained from Observations at Three Volcanoes.- New Results at Mayon, Philippines, from a Joint Inversion of Gravity and Deformation Measurements.- The Interpretation of Gravity Changes and Crustal Deformation in Active Volcanic Areas.- Intrusive Mechanisms at Mt. Etna Forerunning the July-August 2001 Eruption from Seismic and Ground Deformation Data.- Methods for Evaluation of Geodetic Data and Seismicity Developed with Numerical Simulations: Review and Applications.- A Free Boundary Problem Related to the Location of Volcanic Gas Sources.- High CO2 Levels in Boreholes at El Teide Volcano Complex (Tenerife, Canary Islands): Implications for Volcanic Activity Monitoring.- Simulation of the Seismic Response of Sedimentary Basins with Vertical Constant-Gradient Velocity for Incident SH Waves.- The Use of Ambient Seismic Noise Measurements for the Estimation of Surface Soil Effects: The Motril City Case (Southern Spain).- Results of Analysis of the Data of Microseismic Survey at Lanzarote Island, Canary, Spain.- Microtremor Analyses at Teide Volcano (CanaryIslands, Spain): Assessment of Natural Frequencies of Vibration Using Time-dependent Horizontal-tovertical Spectral Ratios.- Tilt Observations in the Normal Mode Frequency Band at the Geodynamic Observatory Cueva de los Verdes, Lanzarote.
Summary
The topics included in this issue deal with many aspects of volcanic and seismic activity, two of the natural hazards of geological origin that have the greatest impact and pose the predominant risk to society. This book comprises eighteen papers, most of which were presented at an international seminar organized and held at the Complutense University of Madrid in October 2001. The papers address geodetic, geophysical and geochemical effects caused by seismic and volcanic activity; monitoring of volcanic and seismic processes using space and terrestrial techniques; complementarity of these techniques; theoretical modelling of volcanic and seismic processes; inverse problem; interpretation of observations; hazards; seismicity patterns and application.
