Marta Tárraga

Monitoring the reawakening of Canary Islands' Teide Volcano

Following more than 30 years of seismic and volcanic quiescence, the Canary Islands region located off the northwestern coast of Africa started to show signs of seismovolcanic activity at the end of 2003 (Figure 1). In spring 2004, there was a significant increase in the number of seismic events (a mixture of volcano-tectonic events and regional earthquakes with pure volcanic events such as tremors and long-period signals) located inland on Tenerife Island. The increase ofactivity in 2004 coincided with an increase of fumarolic activity at the Teide volcano on Tenerife Island, an increase in the emission of carbon dioxide in the northwestern part of the island, and changes in the gravimetric field on the northern flank of the volcano. After several seismic events had been felt by the population, the first alert level was declared by the civil protection division of the local government.This apparent reawakening of Teide, which last erupted in 1909, provides an opportunity to study from the initial stages the reactivation of this volcanic area and its related phenomena.

Applying Fractal Dimensions and Energy-Budget Analysis to Characterize Fracturing Processes During Magma Migration and Eruption: 2011–2012 El Hierro (Canary Islands) Submarine Eruption

The impossibility of observing magma migration inside the crust obliges us to rely on geophysical data and mathematical modelling to interpret precursors and to forecast volcanic eruptions. Of the geophysical signals that may be recorded before and during an eruption, deformation and seismicity are two of the most relevant as they are directly related to its dynamic. The final phase of the unrest episode that preceded the 2011–2012 eruption on El Hierro (Canary Islands) was characterized by local and accelerated deformation and seismic energy release indicating an increasing fracturing and a migration of the magma. Application of time varying fractal analysis to the seismic data and the characterization of the seismicity pattern and the strain and the stress rates allow us to identify different stages in the source mechanism and to infer the geometry of the path used by the magma and associated fluids to reach the Earth’s surface. The results obtained illustrate the relevance of such studies to understanding volcanic unrest and the causes that govern the initiation of volcanic eruptions.

Chapter 13 The Failure Forecast Method: Review and Application for the Real-Time Detection of Precursory Patterns at Reawakening Volcanoes

Abstract This paper sets out to assess the failure forecast method (FFM) and its application to volcanology. After first reviewing the history of its development and the published literature, a special focus will be given to the possible use of FFM in the analysis of reawakening volcanoes and caldera unrest. We present results from its application to the recent episode of unrest at the Las Canadas caldera, Tenerife (Spain). Here the FFM procedure was automated, solving the problem of subjectivity in the application of FFM.

Chapter 14 Perspectives on the Application of the Geostatistical Approach to Volcano Forecasting at Different Time Scales

Abstract In the problem of forecasting a volcanic eruptive scenario, empirical or observational time series must be examined in order to look for precursory behaviour. A key concept in this respect is that of memory or persistence of a given time series. A time series that does not keep some memory of its past cannot, in fact, provide information about the future of the evolving volcanic process, i.e. it cannot help to forecast an eruption. The geostatistical approach aims to identify this memory, if it exists, quantify its duration and exploit its potential in forecasting, and can be applied not only in the time but also in the space domain. In this paper, a review is presented of the state of the art, and an application to the case of a possible reawakening of a caldera is presented.

Dynamical parameter analysis of continuous seismic signals of Popocatépetl volcano (Central Mexico): A case of tectonic earthquakes influencing volcanic activity

The continuous background seismic activity contains information on the internal state of a volcanic system. Here, we report the influence of major regional tectonic earthquakes (M > 5 in most cases) on such state, reflected as changes in the spectral and dynamical parameters of the volcano continuous seismic data. Although changes do not always occur, analysis of five cases of earthquake-induced variations in the signals recorded at Popocatépetl volcano in central México reveal significant fluctuations following the tectonic earthquakes. External visible volcanic activity, such as small to moderate explosions and ash emissions, were related to those fluctuations. We briefly discuss possible causes of the variations. We conclude that recognition of fluctuations in the dynamical parameters in volcano monitoring seismic signals after tectonic earthquakes, even those located in the far field, hundreds of kilometers away, may provide an additional criterion for eruption forecasting, and for decision making in the definition of volcanic alert levels.

Geodetic Research on Deception Island

Deception Island (62.93° S, 60.57°W) is one of the few active volcanoes in the Antarctica, whose most recent eruptions took place in 1842, 1967, 1969 and 1970. In the following paper geodetic investigations carried out in this area during the last years are described. During the continuous Spanish campaigns in Antarctica, several scientific groups have developed different projects in order to control deformation the island suffers as a result of its volcanic activity. With this purpose, a geodetic network has been designed and improved. Nowadays, the network consists of twelve stations around Port Foster which are provided with WGS-84 geodetic coordinates with respect to the ITRF2000, and another station at the Spanish Base Juan Carlos I on Livingston Island. Time analysis of these coordinates will lead us to get the horizontal deformation model. On the other hand, a levelling network has been designed to obtain the vertical deformation model. This network is denser in those areas where the volcanic activity is stronger, as at Fumarole Bay and the Hill of Obsidians. GPS, levelling and gravimetric measurements have also been collected in secondary points to obtain an experimental geoid model which makes possible an adequate reference frame for physical applications.

SANARIS Project: A Satellite Network for Natural Risk Monitoring

A new satellite communication system specificallydesigned for low-rate data applications has beendeveloped and prototyped. A validation project isproposed to install a pilot network to be operated for6 months. One of the target markets related tovolcanoes, has been selected, so that a group of usersis integrated in the project. A specific applicationfor this market will be developed regarding dataacquisition, processing, storage and dissemination todistant users. The feasibility of using the newsatellite system to provide a new Eutelsat service forlow-rate data applications, will be evaluated from theperformance of the pilot network. The system ofautomatic acquisition, field storage and communicationwith the local control center is already functioning,as well as the circulation of information viaInternet. The development of the application andtransmission via satellite to distant users is stillin an evaluation phase for the volcanoes of Timanfaya(Lanzarote, Canary Island), Vesuvius (Naples) and SeteCidades Caldera (Sao Miguel, Azores Islands).