Investigating volcanic hazard in Cape Verde Islands through geophysical monitoring: network description and first results

Abstract. We describe a new geophysical network deployed in the Cape Verde Archipelago for the assessment and monitoring of volcanic hazards as well as the first results from the network. Across the archipelago, the ages of volcanic activity range from ca. 20 Ma to present. In general, older islands are in the east and younger ones are in the west, but there is no clear age progression of eruptive activity as widely separated islands have erupted contemporaneously on geological timescales. The overall magmatic rate is low, and there are indications that eruptive activity is episodic, with intervals between episodes of intense activity ranging from 1 to 4 Ma. Although only Fogo Island has experienced eruptions (mainly effusive) in the historic period (last 550 yr), Brava and Santo Antão have experienced numerous geologically recent eruptions, including violent explosive eruptions, and show felt seismic activity and geothermal activity. Evidence for recent volcanism in the other islands is more limited and the emphasis has therefore been on monitoring of the three critical islands of Fogo, Brava and Santo Antão, where volcanic hazard levels are highest. Geophysical monitoring of all three islands is now in operation. The first results show that on Fogo, the seismic activity is dominated by hydrothermal events and volcano-tectonic events that may be related to settling of the edifice after the 1995 eruption; in Brava by volcano-tectonic events (mostly offshore), and in Santo Antão by volcano-tectonic events, medium-frequency events and harmonic tremor. Both in Brava and in Santo Antão, the recorded seismicity indicates that relatively shallow magmatic systems are present and causing deformation of the edifices that may include episodes of dike intrusion.

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Investigating volcanic hazard in Cape Verde Islands through geophysical monitoring: network description and first results

Natural Hazards and Earth System Sciences Discussions ◽

10.5194/nhessd-1-4997-2013 ◽

2013 ◽

Vol 1 (5) ◽

pp. 4997-5032 ◽

Cited By ~ 2

Author(s):

B. Faria ◽

J. F. B. D. Fonseca

Keyword(s):

Seismic Activity ◽

Volcanic Hazard ◽

Monitoring Network ◽

Cape Verde ◽

Geological Time ◽

Geophysical Monitoring ◽

Age Progression ◽

Tectonic Events ◽

Geothermal Activity ◽

First Results

Abstract. We describe a new geophysical network deployed in the Cape Verde archipelago for the assessment and monitoring of volcanic hazards, and the first results from the network. Across the archipelago, the ages of volcanic activity range from ca. 20 Ma to present. In general, older islands are in the east and younger ones are in the west, but there is no clear age progression and widely-separated islands have erupted contemporaneously on geological time scales. The overall magmatic rate is low, and there are indications that eruptive activity is episodic, with intervals between episodes of intense activity ranging from 1 to 4 Ma. Although only Fogo island has experienced eruptions (mainly effusive) in the historic period (last 550 yr), Brava and Santo Antão have experienced numerous geologically recent eruptions including violent explosive eruptions, and show felt seismic activity and geothermal activity. Evidence for recent volcanism in the other islands is more limited and the emphasis has therefore been on monitoring of the three critical islands of Fogo, Brava and Santo Antão, where volcanic hazard levels are highest. Geophysical monitoring of all three islands is now in operation. The first results show that in Fogo the seismic activity is dominated by hydrothermal events and volcano-tectonic events that may be related to settling of the edifice after the 1995 eruption; in Brava by volcano-tectonic events (mostly offshore), and in Santo Antão by volcano-tectonic events, medium frequency events and harmonic tremor. Both in Brava and in Santo Antão, the recorded seismicity indicates that relatively shallow magmatic systems are present and causing deformation of the edifices that may include episodes of dike intrusion.

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Multiparametric monitoring of the ongoing eruption of Sangay volcano, Ecuador

10.5194/egusphere-egu21-10300 ◽

2021 ◽

Author(s):

Francisco Javier Vasconez ◽

Silvana Hidalgo ◽

Stephen Hernández ◽

Josué Salgado ◽

Sébastien Valade ◽

...

Keyword(s):

Lava Flow ◽

Seismic Activity ◽

Ground Deformation ◽

Monitoring Network ◽

Deformation Pattern ◽

Density Currents ◽

Eruptive Activity ◽

Data Set ◽

Eruptive Style ◽

Eruptive Episode

During the last two decades, Sangay has been one of the most active Ecuadorian volcanoes. However, because of its remote location and logistically difficult access, monitoring Sangay is a challenging task. The IG-EPN tackled this problem by expanding its terrestrial monitoring network and complementing it with the available satellite data. On 7th May 2019, the most recent and ongoing eruptive episode commenced. Compared to the previously monitored and observed eruptive activity at Sangay since the 2000&#8217;s, this episode is by far the most intense and the first to affect populated areas due to ash fallouts and numerous lahars. Surface activity is generally characterized by frequent low-to-moderate magnitude ash emissions and a semi-continuous viscous lava flow extrusion. This activity is punctuated by occasional lava flow collapse events, probably associated with pulses of high lava extrusion and that produced long-runout pyroclastic density currents towards the southeastern flank.Here, we present the most complete data set of long-term instrumental observations performed at Sangay. SO2&#160;degassing, seismic activity, ground deformation, ash emissions and thermal anomalies are depicted as a multiparametric sequence to better understand the link between these parameters and the dynamism and eruptive style of this isolated volcano. &#160;Correlations between the depicted parameters are not straight-forward, making it hard to identify patterns that might lead to enhanced eruptive activity. High values of SO2&#160;recorded by the DOAS instruments as well as the TROPOMI satellite sensor seem to coincide with periods of increased eruption rate. Nevertheless, increases in SO2 flux do not occur systematically before or after these episodes. Seismic activity, characterized by daily counts of individual seismic events, does not demonstrated a clear precursory pattern either. These results indicate that none of the available monitoring parameters currently allow for a timely forecast of the largest and potentially most dangerous eruptions. However, looking at the entire time series we are able to distinguish a slightly but progressive change in the ground deformation displacement associated with a higher number of earthquakes per day prior to the 20 September 2020 paroxysmic event. This eruption produced regional ash fallout which affected significant swaths of farming lands and livestock. Since then, a different ground deformation pattern has taken hold, and coincides with a step decrease in the number of daily earthquakes and a significant increase in the SO2&#160;mass measured by TROPOMI.This behavior matches an open-vent system, where punctual increases in eruptive activity show few precursory signals. The observed increase in all the parameters compared to previous eruptions before 2019 allows us to propose that this eruptive phase is fed by batches of deep and volatile-rich magma which rise to the surface at high ascent rates. The interpretations presented here are an important step towards a better understanding of the dynamism and eruptive style of this very active and isolated volcano. Moreover, the various monitoring parameters from terrestrial to satellite provide a better picture of the behavior of Sangay that could be applied to other remote and open-system volcanoes.

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Geochemical and geophysical monitoring of thermal waters in Sloveniain relation to seismic activity

Annals of Geophysics ◽

10.4401/ag-3181 ◽

2009 ◽

Vol 48 (1) ◽

Author(s):

A. Popit ◽

J. Vaupotic ◽

T. Dolenec

Keyword(s):

Seismic Activity ◽

Thermal Waters ◽

Geophysical Monitoring

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Atmospheric electric field in the Atlantic marine boundary layer: first results from the SAIL project

10.5194/egusphere-egu2020-18767 ◽

2020 ◽

Author(s):

Susana Barbosa ◽

Mauricio Camilo ◽

Carlos Almeida ◽

José Almeida ◽

Guilherme Amaral ◽

...

Keyword(s):

Boundary Layer ◽

Electric Field ◽

Marine Boundary Layer ◽

Weather Conditions ◽

Cape Verde ◽

The Other ◽

Atmospheric Electric Field ◽

Fair Weather ◽

Near Surface ◽

First Results

The study of the electrical properties of the atmospheric marine boundary layer is important as the effect of natural radioactivity in driving near surface ionisation is significantly reduced over the ocean, and the concentration of aerosols is also typically lower than over continental areas, allowing a clearer examination of space-atmosphere interactions. Furthermore, cloud cover over the ocean is dominated by low-level clouds and most of the atmospheric charge lies near the earth surface, at low altitude cloud tops. The relevance of electric field observations in the marine boundary layer is enhanced by the the fact that the electrical conductivity of the ocean air is clearly linked to global atmospheric pollution and aerosol content. The increase in aerosol pollution since the original observations made in the early 20th century by the survey ship Carnegie is a pressing and timely motivation for modern measurements of the atmospheric electric field in the marine boundary layer. Project SAIL (Space-Atmosphere-Ocean Interactions in the marine boundary Layer) addresses this challenge by means of an unique monitoring campaign on board the ship-rigged sailing ship NRP Sagres during its 2020 circumnavigation expedition. The Portuguese Navy ship NRP Sagres departed from Lisbon on January 5th in a journey around the globe that will take 371 days. Two identical field mill sensors (CS110, Campbell Scientific) are installed on the mizzen mast, one at a height of 22 m, and the other at a height of 5 meters. A visibility sensor (SWS050, Biral) was also set-up on the same mast in order to have measurements of the extinction coefficient of the atmosphere and assess fair-weather conditions. Further observations include gamma radiation measured with a NaI(Tl) scintillator from 475 keV to 3 MeV, cosmic radiation up to 17 MeV, and atmospheric ionisation from a cluster ion counter (Airel). The 1 Hz measurements of the atmospheric electric field and from all the other sensors are linked to the same rigorous temporal reference frame and precise positioning through kinematic GNSS observations. Here the first results of the SAIL project will be presented, focusing on fair-weather electric field over the Atlantic. The observations obtained in the first three sections of the circumnavigation journey, including Lisbon (Portugal) - Tenerife (Spain), from 5 to 10 January, Tenerife - Praia (Cape Verde) from 13 to 19 January, and across the Atlantic from Cape Verde to Rio de Janeiro (Brasil), from January 22nd to February 14th, will be presented and discussed.

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Study of self potential anomalous fluctuations in a seismic active zone of Lucano Apennine (southern Italy): recent results

Natural Hazards and Earth System Science ◽

10.5194/nhess-8-1099-2008 ◽

2008 ◽

Vol 8 (5) ◽

pp. 1099-1104 ◽

Cited By ~ 1

Author(s):

G. Colangelo ◽

V. Lapenna ◽

L. Telesca

Keyword(s):

Active Zone ◽

Seismic Activity ◽

Southern Italy ◽

Complex Nature ◽

Stress And Strain ◽

Geophysical Monitoring ◽

Time Period ◽

Long Time ◽

Self Potential ◽

Apennine Chain

Abstract. Geoelectrical fluctuations measured in seismic areas have been attributed to stress and strain changes, associated with earthquakes. The complex nature of this problem has suggested the development of monitoring stations in order to perform geophysical monitoring for a long time period and with a high sample rate. In this paper, anomalous geoelectrical fluctuations of SP signals recorded in the S. Loja basin, Lucano Apennine chain by Tito and Picerno stations, and linked with seismic activity, are analyzed and discussed.

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Analysis of microseismicity in the Hengill Geothermal Area, SW Iceland

10.5194/egusphere-egu2020-8704 ◽

2020 ◽

Author(s):

Camilla Rossi ◽

Francesco Grigoli ◽

Simone Cesca ◽

Sebastian Heimann ◽

Paolo Gasperini ◽

...

Keyword(s):

Clustering Analysis ◽

Power Plants ◽

Electrical Power ◽

Monitoring Network ◽

Earthquake Location ◽

Seismic Zone ◽

Geothermal Systems ◽

Moment Tensors ◽

Geothermal Activity ◽

Location Clustering

Geothermal systems in the vicinity of the Hengill volcano, SW Iceland, started to be exploited for electrical power and heat production since the late 1960s, and today the two largest operating geothermal power plants are located at the Nesjavellir and the Hellisheidi. This area is a complex tectonic and geothermal site, being located at the triple junction between the Reykjanes Peninsula (RP), the Western Volcanic Zone (WVZ), and the South Iceland Seismic Zone (SISZ). The region is seismically highly active with several thousand earthquakes located yearly. The origin of such earthquakes may be either natural or anthropogenic. The analysis of microseismicity can provide useful information on natural active processes in tectonic, geothermal and volcanic environments as well as on physical mechanisms governing induced events. Here, we investigate the microseismicity occurring in Hengill area to understand physical source mechanisms and the origin of these microseismic events. We use a very dense broadband monitoring network deployed since November 2018 with support of the GEOTHERMICA project COSEISMIQ and apply robust and full-waveform based methods for earthquake location, clustering analysis and source mechanism determination. Our dataset consists of about 637 events with ML ranging between 0.8 and 4.7 from December 2018 to January 2019. We use this rich and large dataset for testing a workflow for automated processing. Earthquake location and clustering analysis show that seismicity is spatially clustered, with shallower events at the center of geothermal site in proximity to geothermal plants, and deeper earthquakes in the southern part of the study area. Most of our moment tensors can suggest the influence of geothermal activity and geothermal energy exploitation operations on the subsurface. This work is supported by the COSEISMIQ project of the EU GEOTHERMICA program .

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Measurements of Night Sky Brightness in the Veneto Region of Italy: Sky Quality Meter Network Results and Differential Photometry by Digital Single Lens Reflex

Journal of Imaging ◽

10.3390/jimaging5050056 ◽

2019 ◽

Vol 5 (5) ◽

pp. 56 ◽

Cited By ~ 7

Author(s):

Andrea Bertolo ◽

Renata Binotto ◽

Sergio Ortolani ◽

Simone Sapienza

Keyword(s):

Environmental Protection Agency ◽

Monitoring Network ◽

Light Pollution ◽

Veneto Region ◽

First Results ◽

Differential Photometry ◽

Sky Brightness ◽

Night Sky ◽

The University ◽

Night Sky Brightness

In this paper, we present the implementation of a monitoring network for artificial light at night (ALAN), based on Sky Quality Meter devices (SQM) installed in seven locations of the Veneto region. The system is coordinated by the Regional Environmental Protection Agency (ARPA-Veneto) and the Department of Physics and Astronomy of the University of Padova, in collaboration with a local dark-sky association, Venetostellato. A new centralized database containing zenith night sky brightness (NSB) data was implemented to collect data from all SQM stations of the regional territory, not only in real time (since 2017), but in some stations since 2011. We now have a dataset to determine how light pollution is affecting astronomical observatories. A WEB portal was created to offer different downloads from these NSB data. We present the results of some elaborations for the 2018 dataset (statistics, histograms, annual and cumulative plots) for seven monitoring sites. For Ekar and Pennar sites, we also present the NSB monthly trend from 2014 until the time of the study. We purchased a reflex camera with a fish eye lens, appropriately calibrated with the software (SW) Sky Quality Camera, which allowed us to study ALAN using differential photometry. Here, we present our first results obtained by studying the night evolution of light pollution in the urban location of Padova.

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