Chapter 18 Tectonic and volcanic deformation at São Miguel Island, Azores, observed by continuous GPS analysis 2008–13

Okada, Jun; Sigmundsson, Freysteinn; Ófeigsson, Benedíkt G.; Ferreira, Teresa; Rodrigues, R.

doi:10.1144/m44.18

Cited by 8 publications

(13 citation statements)

References 89 publications

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“…Despite the almost complete absence of volcanic activity, the CFVS represents one of the more active seismic zones in the archipelago in which episodes of volcanic deformation (Trota 2008;Okada et al 2015) are taking place. Just two eruptions have occurred in the Lagoa do Congro area.…”

Section: Discussionmentioning

confidence: 99%

Chapter 10 Distribution and significance of basaltic eruptive centres: São Miguel, Azores

Ferreira

Gomes

Gaspar

et al. 2015

Memoirs

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Basaltic volcanism occurs at all the active volcanic systems of São Miguel. For the last 30 ka, the eruption of basaltic magma has been particularly significant in the areas between the three polygenetic volcanoes -Sete Cidades, Fogo and Furnas -and two basaltic fields have developed: the Picos Fissural Volcanic System (PFVS) and the Congro Fissural Volcanic System (CFVS). About 5 ka ago volcanic activity at CFVS ended abruptly and since then almost all basaltic activity has been concentrated at the PFVS, where about 30 eruptions have taken place. Despite the absence of eruptive activity, the Congro system represents one of the most active seismic areas in the archipelago. It shows episodes of volcanic deformation that are indicative of magma ascent, which halted beneath the volcanic system. Two historical eruptions are associated with the PFVS. The 1563 eruption at Pico do Sapateiro was of basaltic composition, whereas that of the 1652 eruption was, for almost two centuries, also considered to be basaltic. This event had, however, a Vulcanian style and involved the production of large amounts of fine ash and the growth of three trachyte domes with associated coulées. It was accurately described in contemporary historical accounts. † Deceased 19 May 2012.

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Section: Discussionmentioning

confidence: 99%

Chapter 10 Distribution and significance of basaltic eruptive centres: São Miguel, Azores

Ferreira

Gomes

Gaspar

et al. 2015

Memoirs

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“…A common observation for all the anomalous periods is that they occur during winter periods, when the gas flux data are more scattered and thus more challenging for the statistical approaches applied. GPS data are only available in the literature for the period from 2010 to May 2013 (Okada et al, 2015). Those authors highlighted deformation on the Fogo Volcano edifice for the period September 2011 to August 2012, associated with some of the recorded seismic swarms.…”

Section: Discussionmentioning

confidence: 99%

“…Nowadays the volcanic activity in the area is characterized not only by seismic swarms (Silva et al, 2012), but also by episodes of ground deformation (Okada et al, 2015) and the presence of secondary manifestations of volcanism, such as three main hydrothermal fumarolic fields (Caldeira Velha, Caldeiras da Ribeira Grande and Pico Vermelho), thermal and cold CO 2 -rich springs, as well as, several diffuse degassing areas (Ferreira et al, 2005;Caliro et al, 2015;Viveiros et al, 2015b). These manifestations are essentially found out in the north flank of the volcano, and seem to be tectonically controlled by the graben faults.…”

Section: Characterization Of the Study Areamentioning

confidence: 99%

Automatic Filtering of Soil CO2 Flux Data; Different Statistical Approaches Applied to Long Time Series

et al. 2018

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Monitoring soil CO 2 diffuse degassing areas has become more relevant in the last decades to understand seismic and/or volcanic activity. These studies are specially valuable for volcanic areas without visible manifestations of volcanism, such as fumaroles or thermal springs. The development and installation of permanent soil CO 2 flux instruments has allowed to acquire long time series in different volcanic environments, and the results obtained highlight the influence of environmental variables on the gas flux variations. Filtering the influence of these external variables on the gas flux is crucial to understand deep processes on the volcanic system. This study focuses on the discussion of different statistical approaches applied to the long time series recorded in a diffuse degassing area of the Azores archipelago, mainly on the application of stepwise multivariate regression analysis, wavelets and Fast Fourier transforms to understand the CO 2 flux variations and to detect eventual anomalous periods that can represent deep changes in the volcano feeding reservoirs. A permanent soil CO 2 flux station is installed at Caldeiras da Ribeira Grande area since June 2010. This degassing site is located at Fogo Volcano, a polygenetic volcano at S. Miguel Island. The station performs measurements based on the accumulation chamber method and has coupled several environmental sensors. Average soil CO 2 flux and soil temperature values around 1,165 gm −2 d −1 and 33 • C, respectively, were measured in this site between June 2010 and June 2017. Multivariate regression analysis shows that about 47% of the soil CO 2 flux variations are explained by the effect of the soil and air temperature, wind speed, and soil water content. Spectral analysis highlights the existence of 24 h cycles in the soil CO 2 flux time series, mainly during the summer period. The filtered time series showed some anomalous periods and a correlation with the geophysical data recorded on the area was carried out. The models proposed have been applied on a near real-time automatic monitoring system and implementation of these approaches will be profitable in any volcano observatory of the world since it allows a fast understanding of the degassing processes and contribute to recognize unrest periods.

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“…7). The island experienced events of volcanic unrest in the Fogo-Congro area (Trota 2009;Okada et al 2015) and these changes in trends are a reflex of the adjustment of the stations to inflation-deflation processes (PDEL is not affected, as it is located farther away from these active volcanic systems). In the last 2 yr the trends for FRNS and VFDC are varying at a rate of ∼0.3 mm yr −1 and ∼0.7 mm yr −1 , respectively.…”

Section: Azores Archipelagomentioning

confidence: 99%

Vertical land motion and sea level change in Macaronesia

Mendes¹,

Barbosa

Romero

et al. 2017

Geophysical Journal International

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This study addresses long-term sea level variability in Macaronesia from a holistic perspective using all available instrumental records in the region, including a dense network of GPS continuous stations, tide gauges and satellite observations. A detailed assessment of vertical movement from GPS time series underlines the influence of the complex volcano-tectonic setting of the Macaronesian islands in local uplift/subsidence. Relative sea level for the region is spatially highly variable, ranging from −1.1 to 5.1 mm yr −1. Absolute sea level from satellite altimetry exhibits consistent trends in the Macaronesia, with a mean value of 3.0 ± 0.5 mm yr −1. Typically, sea level trends from tide gauge records corrected for vertical movement using the estimates from GPS time series are lower than uncorrected estimates. The agreement between satellite altimetry and tide gauge trends corrected for vertical land varies substantially from island to island. Trends derived from the combination of GPS and tide gauge observations differ by less than 1 mm yr −1 with respect to absolute sea level trends from satellite altimetry for 56 per cent of the stations, despite the heterogeneity in length of both GPS and tide gauge series, and the influence of volcanic-tectonic processes affecting the position of some GPS stations.

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Chapter 18 Tectonic and volcanic deformation at São Miguel Island, Azores, observed by continuous GPS analysis 2008–13

Cited by 8 publications

References 89 publications

Chapter 10 Distribution and significance of basaltic eruptive centres: São Miguel, Azores

Chapter 10 Distribution and significance of basaltic eruptive centres: São Miguel, Azores

Automatic Filtering of Soil CO2 Flux Data; Different Statistical Approaches Applied to Long Time Series

Vertical land motion and sea level change in Macaronesia

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