The new tiltmetric network of Tenerife: technical and scientific issues

2020 ◽  
Author(s):  
José Barrancos ◽  
Monika Przeor ◽  
Luca D'Auria ◽  
Iván Cabrera ◽  
Ana Carolina Montañez ◽  
...  
Keyword(s):  
Ground Deformation ◽  
High Sensitivity ◽  
High Gain ◽  
Web Page ◽  
Differential Gps ◽  
Volcanic System ◽  
Gps Network ◽  
Tenerife Island ◽  
Worm Gears ◽  
Tilt Change

<p>Since 2004, the Instituto Tecnológico y de Energías Renovables (ITER) in collaboration, since 2011, with the Instituto Volcanológico de Canarias (INVOLCAN), are monitoring Canary Islands archipelago with a network of more than 30 differential GPS stations. Specifically, in Tenerife island alone there are 12 permanent GPS receivers. Data are processed automatically using Bernese software, constituting an important tool for the geodetic monitoring of Tenerife.</p><p>Since 2016, the volcanic system of Tenerife is experiencing a hydrothermal unrest, with a marked increase of the diffuse CO<sub>2</sub> flux from the crater of Mt. Teide, the major volcanic edifice of the island. This increased flux is likely to be related to the injection of fluids of magmatic origin within the hydrothermal system of Tenerife. The subsequent pressurization of this system is reflected also by the increase in the background microseismicity observed since July 2017. Until now, the GPS network has not recorded significant ground deformation above the instrumental error.</p><p>With the aim of improving the geodetic monitoring of Tenerife, detecting possible small ground deformation below the sensitivity of the GPS network, INVOLCAN has recently started deploying, since June 2019, high-gain tiltmeters (Jewell Instruments A603-C) in the surrounding of Mt. Teide. Currently the tiltmetric network consists of 3 tiltmeters, located close to existing seismic or GPS stations. Data are automatically downloaded via UMTS connection and processed daily.</p><p>The nominal sensitivity of such instruments is less than 2.5 nradians, hence their installation and calibration require very careful operations. The sensors are equipped with leveling worm-gear feet to guarantee a perfect levelling. However, the high sensitivity of the instrumentation makes adjustments made manually totally useless. The tilt change caused by the weight of the human operator during the levelling is enough to drive the instrument out of scale. For this reason, INVOLCAN developed a robotic system to perform the required adjustments from remote. The system is based on Arduino Mega 2560, driving two servomotors to adjust the leveling worm-gears. Another servomotor allows switching the gain level. The system can be accessed and operated through an internal web page, which allows driving the servomotors and checking the leveling of the tiltmeter platform by using an Arduino Ethernet.</p>

scholarly journals Tilt and strain change during the explosion at Minami-dake, Sakurajima, on November 13, 2017

2021 ◽  
Author(s):  
Kohei Hotta ◽  
Masato Iguchi
Keyword(s):  
Ground Deformation ◽  
Large Strain ◽  
Phase 1 ◽  
Small Strain ◽  
Phase 2 ◽  
The North ◽  
Strombolian Eruption ◽  
Strain Change ◽  
Tilt Change

Abstract We herein propose an alternative model for deformation caused by an eruption at Sakurajima, which have been previously interpreted as being due to a Mogi-type spherical point source beneath Minami-dake. On November 13, 2017, a large explosion with a plume height of 4,200 m occurred at Minami-dake. During the three minutes following the onset of the explosion (November 13, 2017, 22:07–22:10 (Japan standard time (UTC+9); the same hereinafter), phase 1, a large strain change was detected at the Arimura observation tunnel (AVOT) located approximately 2.1 km southeast from the Minami-dake crater. After the peak of the explosion (November 13, 2017, 22:10–24:00), phase 2, a large deflation was detected at every monitoring station due to the continuous Strombolian eruption. Subsidence toward Minami-dake was detected at five out of six stations whereas subsidence toward the north of Sakurajima was detected at the newly installed Komen observation tunnel (KMT), located approximately 4.0 km northeast from the Minami-dake crater. The large strain change at AVOT as well as small tilt changes of all stations and small strain changes at HVOT and KMT during phase 1 can be explained by a very shallow deflation source beneath Minami-dake at 0.1 km below sea level (bsl). For phase 2, a deeper deflation source beneath Minami-dake at a depth of 3.3 km bsl was found in addition to the shallow source beneath Minami-dake which turned inflation after the deflation obtained during phase 1. However, this model cannot explain the tilt change of KMT. Adding a spherical deflation source beneath Kita-dake at a depth of 3.2 km bsl can explain the tilt and strain change at KMT and the other stations. The Kita-dake source was also found in a previous study of long-term ground deformation. Not only the deeper Minami-dake source MD but also the Kita-dake source deflated due to the Minami-dake explosion.

scholarly journals A 35-GHz Polarimetric Doppler Radar for Long-Term Observations of Cloud Parameters—Description of System and Data Processing

2015 ◽  
Vol 32 (4) ◽  
pp. 675-690 ◽  
Author(s):  
Ulrich Görsdorf ◽  
Volker Lehmann ◽  
Matthias Bauer-Pfundstein ◽  
Gerhard Peters ◽  
Dmytro Vavriv ◽  
...  
Keyword(s):  
Doppler Radar ◽  
High Sensitivity ◽  
High Gain ◽  
Cloud Parameters ◽  
Satellite Validation ◽  
Meteorological Observatory ◽  
Averaging Time ◽  
Ice Water ◽  
Water Contents

AbstractA 35-GHz radar has been operating at the Meteorological Observatory Lindenberg (Germany) since 2004, measuring cloud parameters continuously. The radar is equipped with a powerful magnetron transmitter and a high-gain antenna resulting in a high sensitivity of −55 dBZ at 5-km height for a 10-s averaging time. The main purpose of the radar is to provide long-term datasets of cloud parameters for model evaluation, satellite validation, and climatological studies. Therefore, the system operates with largely unchanged parameter settings and a vertically pointing antenna. The accuracy of the internal calibration (budget calibration) has been appraised to be 1.3 dB. Cloud parameters are derived by two different approaches: macrophysical parameters have been deduced for the complete period of operation through combination with ceilometer measurements; a more enhanced target classification and the calculation of liquid and ice water contents are realized by algorithms developed in the framework of the European CloudNet project.

Crustal viscosity and its control on volcanic ground deformation patterns

2020 ◽  
Author(s):  
Matthew Head ◽  
James Hickey ◽  
Jo Gottsmann ◽  
Nico Fournier
Keyword(s):  
Volume Change ◽  
Ground Deformation ◽  
Geothermal Gradient ◽  
Time Dependent ◽  
Temperature Dependent Viscosity ◽  
Volcanic System ◽  
Change Models ◽  
Dependent Viscosity ◽  
Deformation Patterns ◽  
Underlying Processes

<p>Episodes of ground deformation, relating to the unrest of a volcanic system, are often readily identifiable within geodetic timeseries (e.g. GPS, InSAR). However, the underlying processes facilitating this deformation are more enigmatic. By modelling the observed deformation signals, the ultimate aim is to infer characteristics of the deforming reservoir; namely the size and time-dependent evolution of the system and, potentially, the fluxes of magma involved. These parameters can be estimated using simple elastic models, but the presence of shallow or long-lived magmatic systems can significantly perturb the local geothermal gradient and invalidate the elastic approximation. Inelastic rheological effects are increasingly utilised to account for these elevated thermal regimes, where a component of viscous (time-dependent) behaviour is expected to characterise the observed deformation field.</p><p>Here, our investigations are concentrated on Taupō volcano, New Zealand, the site of several catastrophic caldera-forming eruptions. We use 3D thermomechanical models of the Lake Taupō region, featuring thermal constraints and heterogeneous crustal properties, to compare the commonly-used Maxwell and Standard Linear Solid (SLS) viscoelastic configurations under contrasting deformation mechanisms; a pressure condition (stress-based) and a volume-change (strain-based). By referring to models allocated a single viscosity value, we investigate the influence of a temperature-dependent viscosity distribution on the predicted spatiotemporal deformation patterns. Comparisons of the overpressure models highlights the influence of the crustal viscosity structure on deformation timescales, by enabling the SLS rheology to account for both abrupt and long-term deformation signals. For the Maxwell rheology, we show that the viscosity distribution results in unexpected deformation patterns, both spatially and temporally, and so query the suitability of this rheology in other model setups. Further to this, the deformation patterns in volume-change models are governed by the resulting stress response, and the effect of the viscosity structure on its propagation. Ultimately, we demonstrate that variations in crustal viscosity greatly influence spatiotemporal deformation patterns, more so than heterogeneous mechanical parameters alone, and consequently have a large impact on the inferences of the underlying processes and their time-dependent evolution. The inclusion of a crustal viscosity structure is therefore an important consideration when modelling volcanic deformation signals.</p>

Correlation between submerged and continental infill at Campi Flegrei caldera: insights on the volcano-tectonic events of the last 15 kyr

2020 ◽  
Author(s):  
Jacopo Natale ◽  
Stefano Vitale ◽  
Roberto Isaia ◽  
Francesco D'Assisi Tramparulo ◽  
Luigi Ferranti ◽  
...  
Keyword(s):  
Ground Deformation ◽  
Relevant Information ◽  
Seismic Facies ◽  
Campi Flegrei ◽  
Sea Level Changes ◽  
Volcanic System ◽  
Campi Flegrei Caldera ◽  
Reflection Seismic ◽  
Continental Deposits ◽  
Seismic Facies Analysis

<p>The Campi Flegrei caldera (southern Italy) is characterized by over one-third of its extension lying below the sea. In the last 15 ka the caldera floor has suffered hundreds of meters of ground deformation alternating uplift and subsidence episodes in response to the activity of the volcanic system. The evidence of significant uplifts is witnessed by the occurrence of marine sequences exposed on land, both along a 30 m high La Starza cliff and in numerous well logs. However, most of these sediments are currently hidden below the sea. This work aims to reconstruct the marine counterpart of the infill by using large multiscale reflection seismic data (>100 profiles) and an accurate seismic facies analysis. The latter consisted in the study and<br>comparison of seismic attributes, scaled to the resolution of the different datasets, to their geological analogs on land. Furthermore, by observing the changes in the pattern of on-lap terminations, thickness, amplitude, and distribution of erosive features of different horizons, we tentatively ascribed these sequences to the well-known continental deposits. The study of the whole sequence above the Neapolitan Yellow Tuff (15 ka) allowed us to gather relevant information about the relationships between stratigraphic record, ground deformation and sea-level changes. In particular, the reconstruction of buried surfaces gave us hints on the evolution of the volcanic system including the role of faults in terms of estimation of displacement and relationships with the different epoch of major eruptive activity.</p>

Photodetection Technology Based on Laser Coding Emission

2011 ◽  
Vol 189-193 ◽  
pp. 3745-3749 ◽  
Author(s):  
Jing Guo ◽  
He Zhang ◽  
Xiang Jin Zhang ◽  
Xiao Feng Wang
Keyword(s):  
High Sensitivity ◽  
Avalanche Photodiode ◽  
High Gain ◽  
Low Noise ◽  
High Signal ◽  
Weak Signal ◽  
Echo Signal ◽  
Long Distance ◽  
The Poor ◽  
Theory And Experiment

For the extremely weak echo signal and the poor anti-interference ability of the long-distance laser fuze, the high signal noise ratio (SNR) receiving system based on laser coding mode was designed. In order to improve the weak signal receiving ability, the avalanche photodiode (APD) with high sensitivity, low noise and high gain was adopted. And the optimum multiplication factor of APD when the system obtains the highest SNR was analyzed and calculated. Then, the amplifying circuit optimum matching with APD and the decoding circuit were designed, and validated by the experiments. The theory and experiment results indicate that the design is efficiency and capable to the long distance laser fuze, the system can exactly decode the weak laser coding signals received and export the ignition signal.

scholarly journals Caldera’s Breathing: Poroelastic Ground Deformation at Campi Flegrei (Italy)

2021 ◽  
Vol 9 ◽  
Author(s):  
Micol Todesco
Keyword(s):  
Pore Pressure ◽  
Ground Deformation ◽  
Campi Flegrei ◽  
Driving Mechanism ◽  
Extensive Literature ◽  
Magma Intrusion ◽  
Volcanic System ◽  
Scientific Debate ◽  
Fluid Content ◽  
History Of

Ground deformation at Campi Flegrei has fuelled a long-term scientific debate about its driving mechanism and its significance in hazard assessment. In an active volcanic system hosting a wide hydrothermal circulation, both magmatic and hydrothermal fluids could be responsible, to variable degrees, for the observed ground displacement. Fast and large uplifts are commonly interpreted in terms of pressure or volume changes associated with magma intrusion, while minor, slower displacement can be related to shallower sources. This work focuses on the deformation history of the last 35 years and shows that ground deformation measured at Campi Flegrei since 1985 is consistent with a poroelastic response of a shallow hydrothermal system to changes in pore pressure and fluid content. The extensive literature available for Campi Flegrei allows constraining system geometry, properties, and conditions. Changes in pore pressure and fluid content necessary to cause the observed deformation can then be calculated based on the linear theory of poroelasticity. The predicted pore pressure evolution and fluid fluxes are plausible and consistent with available measurements and independent estimates.

The application of geodetic observations for near-real time monitoring of Icelandic volcanoes

2021 ◽  
Author(s):  
Michelle Parks ◽  
Benedikt Ófeigsson ◽  
Halldór Geirsson ◽  
Vincent Drouin ◽  
Freysteinn Sigmundsson ◽  
...  
Keyword(s):  
Real Time ◽  
Ground Deformation ◽  
Current Status ◽  
Caldera Collapse ◽  
Real Time Monitoring ◽  
Volcanic System ◽  
Magmatic Intrusions ◽  
Reykjanes Peninsula ◽  
Magma Migration ◽  
Active Volcanoes

<p>Ground deformation is frequently one of the first detectable precursors alerting scientists to changes in behavior or the onset of unrest at active volcanoes. GNSS, InSAR, strain and tilt measurements are routinely used by volcano observatories for monitoring pre-eruptive, co-eruptive and post-eruptive deformation. In addition to monitoring signals related to magma migration, deformation observations are used as an input into geodetic modeling to determine the location and rate of magma accumulation and help define the structure of magma plumbing systems beneath active volcanoes.</p><p>This presentation will provide an update of how geodetic observations are being used in conjunction with seismicity and gas measurements, for the near-real time monitoring of key Icelandic volcanoes; to determine their current status, identify the onset and likely cause of unrest, locate magmatic intrusions, determine magma volumes and supply rates and assess the likelihood of eruption. An overview of the current status of the following active volcanoes will be provided: Hekla, Bárðarbunga and Grímsvötn, along with an update of the recent volcano-tectonic unrest on the Reykjanes Peninsula.</p><p>Hekla is one of the most active and dangerous volcanoes in Iceland with approximately 18 eruptions since 1104. Over the past few decades, Hekla erupted at almost regular ~10 year intervals, with the last four eruptions occurring in 1970, 1980–1981, 1991 and 2000. Previous geodetic studies have suggested magma storage at depths of 12-25 km directly beneath the volcanic edifice. However, recent InSAR analysis has detected a localized inflation signal to the west of the volcano. A regional borehole strain meter network has proven instrumental for real-time eruption forecasting at Hekla.</p><p>In the Bárðarbunga volcanic system, the six-month long effusive 2014-2015 Holuhraun eruption was accompanied by gradual caldera collapse of up to 65 m and was preceded by a two-week period of 48 km long lateral dyke propagation with extensive seismicity and deformation. Geodetic observations indicate that Bárðarbunga began to slowly inflate in July 2015. This may be explained by a combination of renewed magma inflow and viscoelastic readjustment of the volcano.</p><p>The Grímsvötn subglacial volcano is the most frequently erupting volcano in Iceland, with eruptions in 1998, 2004 and 2011. A GPS station shows a prominent inflation cycle prior to eruptions. Observations during the 2011 eruption suggest a pressure drop at a surprisingly shallow level (about 2 km depth) during the eruption, in a similar location as in previous eruptions. Deformation at this volcano has now surpassed that observed prior to historic eruptions and its aviation color code is currently elevated to yellow.</p><p>In December 2019, the Reykjanes Peninsula entered a phase of volcano-tectonic unrest characterized by seismic swarms, followed in late January 2020 by inflation detected in near-real time by GNSS and InSAR observations. At the time of writing (mid-January 2021) there have been three magmatic intrusions in the vicinity of Svartsengi, an intrusion beneath Krýsuvík and indications of magma migration at depth along the entirety of the Peninsula.</p>

Can high rates of passive volcanic gas emissions induce reservoir depressurization at Ambrym volcano (Vanuatu)?

2021 ◽  
Author(s):  
Tara Shreve ◽  
Raphaël Grandin ◽  
Marie Boichu
Keyword(s):  
Ground Deformation ◽  
Lumped Parameter Model ◽  
Magma Ascent ◽  
Large Reservoir ◽  
Gas Emissions ◽  
Volcanic System ◽  
Lumped Parameter ◽  
Gas Geochemistry ◽  
The Impact

<p>Satellite-based UV spectrometers can constrain sulphur dioxide (SO<sub>2</sub>) fluxes at passively degassing volcanoes over decadal time scales. From 2005 to 2015, more than 15 volcanoes had mean passive SO<sub>2 </sub>fluxes greater than 1 kiloton per day. Although the processes responsible for such high emission rates are not clearly established, this study aims to investigate the impact of strong degassing on the pressurization state of volcanic systems and the resulting ground deformation. One possible result of high degassing rates is the depressurization of the region where the melt releasing gas is stored, which may result in subsidence at the Earth’s surface. Passive degassing may depressurize pathways between deep and shallow magma storage regions, resulting in magma ascent and possibly eruption.</p><p>A lumped-parameter model developed by Girona et al., 2014 couples the mass loss by passive degassing with reservoir depressurization in an open volcanic system. However, this model has yet to be tested using real measurements of gas emissions and ground deformation. In our study, we focus on Ambrym volcano, the past decade’s top passive emitter of volcanic SO<sub>2</sub>, which exhibits intriguing long-term subsidence patterns and no obvious pressurization preceding eruptive periods. We compare subsidence rates measured by InSAR to the system’s average daily SO<sub>2</sub> flux, focusing on a subsidence episode spanning 2015 to 2017 that is not clearly linked to magma removal from the system. Using realistic input parameters for Ambrym’s system constrained by petrology and gas geochemistry, a range of reservoir volumes and conduit radii are explored. Large reservoir volumes (greater than 30 km<sup>3</sup>) and large conduit radii (greater than 300 m) are consistent with depressurization rates obtained from geodetic modelling of InSAR measurements using the Boundary Element method. By comparing these values of reservoir volume and conduit radius with those estimated from geodesy, gas geochemistry, and seismology, we test the applicability and discuss uncertainties of the aforementioned lumped-parameter physical model to interpret the long-term subsidence at Ambrym volcano as a result of sustained passive degassing.</p>

scholarly journals MiniFAST: A sensitive and fast miniaturized microscope for in vivo neural recording

2020 ◽  
Author(s):  
Jill Juneau ◽  
Guillaume Duret ◽  
Joshua P. Chu ◽  
Alexander V. Rodriguez ◽  
Savva Morozov ◽  
...  
Keyword(s):  
Open Source ◽  
High Speed ◽  
High Sensitivity ◽  
High Gain ◽  
Image Sensor ◽  
High Speed Imaging ◽  
Light Power ◽  
Excitation Light

AbstractObserving the activity of large populations of neurons in vivo is critical for understanding brain function and dysfunction. The use of fluorescent genetically-encoded calcium indicators (GECIs) in conjunction with miniaturized microscopes is an exciting emerging toolset for recording neural activity in unrestrained animals. Despite their potential, current miniaturized microscope designs are limited by using image sensors with low frame rates, sensitivity, and resolution. Beyond GECIs, there are many neuroscience applications which would benefit from the use of other emerging neural indicators, such as fluorescent genetically-encoded voltage indicators (GEVIs) that have faster temporal resolution to match neuron spiking, yet, require imaging at high speeds to properly sample the activity-dependent signals. We integrated an advanced CMOS image sensor into a popular open-source miniaturized microscope platform. MiniFAST is a fast and sensitive miniaturized microscope capable of 1080p video, 1.5 µm resolution, frame rates up to 500 Hz and high gain ability (up to 70 dB) to image in extremely low light conditions. We report results of high speed 500 Hz in vitro imaging of a GEVI and ∼300 Hz in vivo imaging of transgenic Thy1-GCaMP6f mice. Finally, we show the potential for a reduction in photobleaching by using high gain imaging with ultra-low excitation light power (0.05 mW) at 60 Hz frame rates while still resolving Ca2+ spiking activity. Our results extend miniaturized microscope capabilities in high-speed imaging, high sensitivity and increased resolution opening the door for the open-source community to use fast and dim neural indicators.

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