Sébastien Valade

Universidad Nacional Autónoma de México

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Maurizio Ripepe

University of Florence

Diego Coppola

University of Turin

Giorgio Lacanna

University of Florence

Marco Laiolo

University of Turin

D. Legrand

Universidad Nacional Autónoma de México

Franck Donnadieu

Laboratoire Magmas et Volcans

Dario Delle Donne

Istituto Nazionale di Geofisica e Vulcanologia

Riccardo Genco

University of Florence

Andrew Harris

Centre National de la Recherche Scientifique

Francesco Massimetti

University of Turin

Cooperative Institutions

Centre National de la Recherche Scientifique

Istituto Nazionale di Geofisica e Vulcanologia

Laboratoire Magmas et Volcans

Institut de Recherche pour le Développement

Université Clermont Auvergne

Instituto Geofísico de la Escuela Politécnica Nacional

Observatoire Volcanologique de Goma

University of Florence

Observatoire de Physique du Globe de Clermont-Ferrand

Clermont Université

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Process of small explosion at Stromboli volcano as inferred from analyses of broad-band seismic waveforms recorded at very-near-field stations

Japan Geoscience Union (2020)

Shunsuke Sugimura Takeshi Nishimura Maurizio Ripepe Giorgio Lacanna D. Legrand

Volcanology

Source

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Citations (0)

Complex hazard cascade culminating in the Anak Krakatau sector collapse

Nature Communications (2019)

Thomas R. Walter Mahmud Haghshenas Haghighi Felix Schneider Diego Coppola Mahdi Motagh

Abstract Flank instability and sector collapses, which pose major threats, are common on volcanic islands. On 22 Dec 2018, a sector collapse event occurred at Anak Krakatau volcano in the Sunda Strait, triggering a deadly tsunami. Here we use multiparametric ground-based and space-borne data to show that prior to its collapse, the volcano exhibited an elevated state of activity, including precursory thermal anomalies, an increase in the island’s surface area, and a gradual seaward motion of its southwestern flank on a dipping décollement. Two minutes after a small earthquake, seismic signals characterize the collapse of the volcano’s flank at 13:55 UTC. This sector collapse decapitated the cone-shaped edifice and triggered a tsunami that caused 430 fatalities. We discuss the nature of the precursor processes underpinning the collapse that culminated in a complex hazard cascade with important implications for the early detection of potential flank instability at other volcanoes.

Flank

10.1038/s41467-019-12284-5

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Citations (281)

Magma pressure discharge induces very long period seismicity

Scientific Reports (2021)

Maurizio Ripepe Dario Delle Donne D. Legrand Sébastien Valade Giorgio Lacanna

Volcano seismicity is one of the key parameters to understand magma dynamics of erupting volcanoes. However, the physical process at the origin of the resulting complex and broadband seismic signals remains unclear. Syn-eruptive very long period (VLP) seismic signals have been explained in terms of the sudden expansion of gas pockets rising in the liquid melt. Their origin is linked to a magma dynamics which triggers the explosive process occurring before the explosive onset. We provide evidence based on acoustic, thermal, and ground deformation data to demonstrate that VLP signals at Stromboli are generated at the top of the magma column mainly after the explosion onset. We show that VLP amplitude and duration scale with the eruptive flux which induces a decompression of 103-104 Pa involving the uppermost ~ 250 m of the feeding conduit. The seismic VLP source represents the final stage of a ~ 200 s long charge and discharge mechanism the magma column has to release excess gas accumulated at the base of a denser and degassed magma mush. The position of the VLP seismic source coincides with the centroid of the shallow mush plug and tracks elevation changes of the magma free surface.

Magma chamber

10.1038/s41598-021-99513-4

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Seismic Source Migration During Strombolian Eruptions Inferred by Very‐Near‐Field Broadband Seismic Network

Journal of Geophysical Research Solid Earth (2021)

Shunsuke Sugimura Takeshi Nishimura Giorgio Lacanna D. Legrand Sébastien Valade

Abstract We analyze seismic waves excited by small Strombolian explosions to understand the source process of volcanic explosions. We deployed five broadband seismometers at only 100–300 m away from the active craters of Stromboli volcano, Italy. Moment tensor inversion of the entire seismic signals in the 0.05–0.2 Hz band locates the source at a depth of 170 and 150–200 m west/southwest of the crater where acoustic waves are excited. Contrary, the sources of seismic waves in the 0.2–0.5 and 0.5–1.0 Hz bands are excited almost at the explosion onset and are located close to the crater. We show for the first time that explosions are preceded of about 10–20 s by a small amplitude seismic phase. Semblance analysis shows that this phase is radiated from a depth of 170 m beneath the western part of the crater area. Our analysis indicates that the source moves about 50 m toward the active crater 10–20 s before the explosion occurs at the surface. At the explosion onset, the source moves back to the same location of the small preceding phase. These lateral migrations of the seismic source are estimated by moment tensor inversion and semblance analysis. We suggest that migration reflects the bending of the shallow feeding system toward northeast. Seismic waves are thus reflecting the history pressure generated by the rising of a gas‐rich pocket in the very shallow portion of a magma mush and by the following restoring force occurring after the explosion.

Strombolian eruption

Seismometer

Microseism

Seismic moment

10.1029/2021jb022623

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Near-source Doppler radar monitoring of tephra plumes at Etna

Journal of Volcanology and Geothermal Research (2016)

Franck Donnadieu Patrick Fréville C. Hervier M. Coltelli Simona Scollo

Volcanic hazards

10.1016/j.jvolgeores.2016.01.009

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Sangay volcano (Ecuador): the opening of two new vents, a drumbeat seismic sequence and a new lava flow in late 2021

Volcanica (2022)

Silvana Hidalgo Francisco J. Vasconez Jean Battaglia Benjamin Bernard Pedro Espín

On 2 December, 2021 we recorded a sequence of drumbeat seismic events at Sangay volcano. This sequence lasted several hours and resulted in two explosive emissions whose eruptive columns reached 9 km above crater. Unexpectedly, these explosions did not produce any ash fallout in the inhabited areas around the volcano. This drumbeat sequence was produced after a series of morphological changes, including the opening of two new vents (W and N) and a landslide. These occurred during an enhanced period of ground deformation and degassing. Further analysis of satellite images allowed us to determine that this sequence was associated with the widening of the recently open vent north of the main crater, and the extrusion of a new lava flow. Timely communication of this event to the authorities and the population was ensured by the IG-EPN by following internal protocols. The corresponding short reports reached more than 300,000 people.

Sequence (biology)

10.30909/vol.05.02.295311

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Volcanic Hot-Spot Detection Using SENTINEL-2: A Comparison with MODIS–MIROVA Thermal Data Series

Remote Sensing (2020)

Francesco Massimetti Diego Coppola Marco Laiolo Sébastien Valade Corrado Cigolini

In the satellite thermal remote sensing, the new generation of sensors with high-spatial resolution SWIR data open the door to an improved constraining of thermal phenomena related to volcanic processes, with strong implications for monitoring applications. In this paper, we describe a new hot-spot detection algorithm developed for SENTINEL-2/MSI data that combines spectral indices on the SWIR bands 8a-11-12 (with a 20-meter resolution) with a spatial and statistical analysis on clusters of alerted pixels. The algorithm is able to detect hot-spot-contaminated pixels (S2Pix) in a wide range of environments and for several types of volcanic activities, showing high accuracy performances of about 1% and 94% in averaged omission and commission rates, respectively, underlining a strong reliability on a global scale. The S2-derived thermal trends, retrieved at eight key-case volcanoes, are then compared with the Volcanic Radiative Power (VRP) derived from MODIS (Moderate Resolution Imaging Spectroradiometer) and processed by the MIROVA (Middle InfraRed Observation of Volcanic Activity) system during an almost four-year-long period, January 2016 to October 2019. The presented data indicate an overall excellent correlation between the two thermal signals, enhancing the higher sensitivity of SENTINEL-2 to detect subtle, low-temperature thermal signals. Moreover, for each case we explore the specific relationship between S2Pix and VRP showing how different volcanic processes (i.e., lava flows, domes, lakes and open-vent activity) produce a distinct pattern in terms of size and intensity of the thermal anomaly. These promising results indicate how the algorithm here presented could be applicable for volcanic monitoring purposes and integrated into operational systems. Moreover, the combination of high-resolution (S2/MSI) and moderate-resolution (MODIS) thermal timeseries constitutes a breakthrough for future multi-sensor hot-spot detection systems, with increased monitoring capabilities that are useful for communities which interact with active volcanoes.

Moderate-resolution imaging spectroradiometer

Spectroradiometer

10.3390/rs12050820

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Citations (42)

OSARIS, the “Open Source SAR Investigation System” for Automatized Parallel InSAR Processing of Sentinel-1 Time Series Data With Special Emphasis on Cryosphere Applications

Frontiers in Earth Science (2019)

David Loibl Bodo Bookhagen Sébastien Valade Christoph Schneider

With the advent of the two Sentinel-1 (S1) satellites, Synthetic Aperture Radar (SAR) data with high temporal and spatial resolution is freely available. This provides a promising framework to facilitate detailed investigations of surface instabilities and movements on large scales with high temporal resolution, but also poses substantial processing challenges because of storage and computation requirements. Here we present OSARIS, the 'Open Source SAR Investigation System', as a framework to process large stacks of S1 data on High-Performance Computing (HPC) clusters. Based on GMTSAR, shell scripts, and the workload manager Slurm, OSARIS provides an open and modular framework combining parallelization of high-performance C programs, flexibility of processing schemes, convenient configuration, and generation of geocoded stacks of analysis-ready base data, including amplitude, phase, coherence, and unwrapped interferograms. Time series analyses can be conducted by applying automated modules to the data stacks. The capabilities of OSARIS are demonstrated in a case study from the northwestern Tien Shan, Central Asia. After merging of slices, a total of 65 scene pairs were processed from 150 total input scenes. OSARIS processing yields a comprehensive set of interferometric data for each pair, including amplitude, coherence, unwrapped interferometric phase, and line-of-sight displacement (LOSD). The coherence time series exhibits pronounced seasonal variability, with relatively high coherence values prevailing during the summer months in the nival zone. As an example of a time series analysis module, we present OSARIS' 'Unstable Coherence Metric' (UCM) which identifies pixels affected by significant drops from high to low coherence values. Surface changes along moraine ridges, steep slopes, and several gullies during July and August were observed. Measurements of motion provided by LOSD measurements require careful evaluation because interferometric phase unwrapping is prone to errors. Here, OSARIS provides a series of modules to detect and mask unwrapping errors, correct for atmospheric disturbances, and remove large-scale trends. Wall clock processing time for the case study (area ~9,000 km²) was ~9h:47m on a machine with 320 cores and 1536 GB RAM. In total, ~11d:08h:28m were saved through parallelization. OSARIS thus allows to implement S1-based region-wide investigations of surface movement events over multiple years.

10.3389/feart.2019.00172

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Citations (16)

Sangay volcano (Ecuador): multiparametric analysis of the December 2021 eruptive activity including the opening of new vents, a drumbeat seismic sequence and a new lava flow

Silvana Hidalgo Francisco J. Vasconez Jean Battaglia Benjamin Bernard Pedro Espín

Sangay is a 5286 m high stratovolcano located in the southern part of the Ecuadorian Andes, about 200 km south of the capital city of Quito. Sangay is the last active volcano to the south of the Northern Andes, and has been characterized by an almost constant and continuous activity with variable periods of quiescence. During historical times, the written reports describe at least 9 major eruptions since 1628. Sangay has been instrumentally monitored by the Instituto Geofísico of the Escuela Politécnica Nacional (IG-EPN) since 2013. In May 2019, Sangay began a new eruptive period, which is still ongoing and has been categorized as the most intense in the last six decades. The main phenomena produced during this period are small explosions, ash and gas emissions, lava fountaining, lava flows and associated pyroclastic currents and secondary lahars.On 1 December 2021, from around 19:20 UTC, the seismic recordings of SAGA station began to show transient events occurring regularly. These events persisted for the next 13 hours with an irregularly accelerating rate of occurrence and increasing amplitude before merging into tremor at around 08:20 on 2 December. This sequence was rapidly followed by two explosive emissions, which were observed by the GOES-16 satellite, the first one at 09:02 and the second at 09:13. The emissions produced a 14.5 km-high gas-rich, ash-depleted eruptive column without any associated regional fallout reported. This drumbeat sequence was produced after a series of morphological changes observed through satellite images (Planet and Sentinel 2). Specifically, during the short time period considered in this study: 1) two new vents opened; 2) a landslide affected the northern flank of the volcano; 3) the first drumbeat sequence was recorded at Sangay; and 4) a new lava flow was emitted through the new northern vent. The drumbeat sequence is interpreted as being caused by the forced extrusion of this new lava flow through the new opening northern vent. Timely communication of this kind of volcanic events is favored by the creation and strict following of internal protocols within volcano observatories and the appropriate use of social networks allowing thousands of people to be reached in very short time period. The corresponding short report produced by the IG-EPN reached more than 300.000 people.

Stratovolcano

Lahar

Sequence (biology)

10.5194/egusphere-egu23-9354

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Modulation of Popocatépetl’s activity by regional and worldwide earthquakes

Bulletin of Volcanology (2022)

Thomas Boulesteix D. Legrand Noémie Taquet Diego Coppola Marco Laiolo

Abstract Volcanoes switching from quiescence to eruption shortly after catastrophic earthquakes have raised interest for volcanic triggering and the influence of earthquakes on volcanic activity. Its influence on already active systems and especially at open-vent volcanoes is more difficult to apprehend. A number of recent observations suggest an influence of tectonic earthquakes on Popocatépetl’s activity, the importance of which remains unknown. To further investigate this, we introduce an index, based on the near-field concept, identifying the earthquakes with the highest potential to promote volcanic activity (hereafter termed “significant earthquakes”). The time series of significant earthquakes is compared with the intensity of the volcanic activity, as characterized by the number and energy of volcano-tectonic earthquakes, the number of dome extrusions, the intensity of thermal and degassing fluxes, and ash production. Three main periods with contrasting activity stand out showing that Popocatépetl presents intense activity when significant tectonic earthquakes are frequent. Enhanced extrusion apparently follows significant earthquakes quickly with pulses of dome extrusion that peak after 1.3 ± 0.3 years. Conversely, extrusive activity vanishes when significant seismicity disappears, as during the period 2003–2011, which coincides with a 12-year-long significant seismicity gap. Hence, we propose that the 1994–2022 open-vent activity at Popocatépetl is in part modulated by the repetitive occurrence of significant earthquakes that periodically promote volcanic activity.

Extrusive

10.1007/s00445-022-01584-2

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Citations (9)