Journal of Volcanology and Geothermal Research最新文献

{"title":"Experimental verification for self-organization process on the spatial distribution and edifice size of rootless cone","authors":"Rina Noguchi,&nbsp;Wataru Nakagawa","doi":"10.1016/j.jvolgeores.2024.108221","DOIUrl":"10.1016/j.jvolgeores.2024.108221","url":null,"abstract":"<div><div>We discuss the decision factor of the spatial distribution of rootless eruption, continuous explosions caused by interactions between lava and water. Signs of these eruptions are found on both Earth and Mars, and their spatial distribution is believed to be self-organized due to the scramble for available volatile substances, such as water. An analog experiment of rootless eruptions was conducted to verify this self-organization process using syrup and baking soda. This study focused on “failed conduits” disturbed by surrounding conduits and could not form stable paths to the surface. Through the experiments, we found that the self-organization process is driven by the competition for both available volatile substances and conduits. Candidates of such failed conduits could be found in nature where high-temperature lava and shallow groundwater were met. The role of the conduit-merge effect is deemed important in determining the spatial distribution pattern and edifice size of rootless cones on Earth and other planetary bodies.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"458 ","pages":"Article 108221"},"PeriodicalIF":2.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143180893","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Variations in pore structure in subaerial lava flows at Nishinoshima, Japan, inferred from physical properties","authors":"Yuya Akamatsu ,&nbsp;Takeshi Suzuki ,&nbsp;Noriko Tada ,&nbsp;Kazuki Sawayama ,&nbsp;Hiroshi Ichihara ,&nbsp;Ikuo Katayama ,&nbsp;Genya Sakamoto ,&nbsp;Yuhji Yamamoto ,&nbsp;Fukashi Maeno ,&nbsp;Kenta Yoshida","doi":"10.1016/j.jvolgeores.2024.108262","DOIUrl":"10.1016/j.jvolgeores.2024.108262","url":null,"abstract":"<div><div>Nishinoshima, a volcanic island in the Izu–Ogasawara arc, Japan, has erupted intermittently since activity restarted in 2013, alternating primarily between effusive lava flows and explosive eruptions. An understanding of pore structure in lava flow clues to the volcanic processes that accompany eruption, including the physical conditions during effusion, the efficiency of gas escape, and seawater circulation within the edifice. We investigated the relationships between various physical properties of the lava flows on Nishinoshima to characterize their internal pore structure. Laboratory measurements of porosity, density, permeability, electrical resistivity, and P-wave velocity were conducted at ambient temperature and atmospheric pressure on andesitic lava blocks collected by land-based surveys conducted in 2016, 2019, and 2021. The measured resistivities and P-wave velocities vary with porosity, although the trends are different in different lithofacies (vesicular, dense, and foliated blocks). By comparing these variations with theoretical models, they can be attributed to differences in connectivity and geometry of pore space in the different lithofacies. These lithofacies-dependent pore structures contribute to the observed variations in permeability, which can vary by as much as five orders of magnitude for a given porosity. The differences in pore structure and permeability may be related to post-eruption processes, where shear deformation during lava flow emplacement flattened and elongated the bubbles, leading to low aspect ratios, smaller apertures, and higher connectivity in the foliated lavas. Our data and interpretations could assist in estimating the internal pore structures at Nishinoshima through geophysical surveys, although further investigation incorporating submarine samples is necessary.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"458 ","pages":"Article 108262"},"PeriodicalIF":2.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143180870","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Trace element transport by volcanic gases at Vulcano (Sicily, Italy) – Speciation, deposition and fluxes","authors":"Celine L. Mandon ,&nbsp;Hanna Kaasalainen ,&nbsp;Sergio Calabrese ,&nbsp;Everett L. Shock ,&nbsp;Panjai Prapaipong ,&nbsp;Franco Tassi ,&nbsp;Ingvi Gunnarsson ,&nbsp;Jóhann Gunnarsson-Robin ,&nbsp;Andri Stefánsson","doi":"10.1016/j.jvolgeores.2024.108235","DOIUrl":"10.1016/j.jvolgeores.2024.108235","url":null,"abstract":"<div><div>The geochemistry of trace elements in volcanic gas emissions at Vulcano (Sicily, Italy) was investigated. Trace element concentrations in 94–412 °C fumarole gases span over 10 orders of magnitude, from ∼0.01 pmol/mol to ∼300 μmol/mol, with some metalloids (B, Si) being the most abundant, followed by alkali, alkaline earth, and certain transition metals, and rare earth elements typically displaying the lowest concentrations. Thermodynamic modeling predicts most trace elements to be transported as chloride, hydroxide, and mixed hydroxy-chloro gas species (LiCl, KCl, NaCl, RbCl and CsCl, Be(OH)₂, Mg(OH)₂, MgCl₂, CaCl₂, SrCl₂, CaCl(OH), TiOCl₂, VOCl, VOCl₂, VOCl₃, NbOCl₃, Cr(OH)₃, CrCl₃, Fe(OH)₂, FeCl₂ Co(OH)₂, CoCl₂, Ni(OH)₂ to NiCl₂, Cd(OH)₂, CdCl_2, Re(OH)₃, ReCl₃, ZnCl₂, AgCl, WO₂(OH)₂, Al(OH)₃, Si(OH)₄, B(OH)₄, TlO, GaCl₃, SbCl, MnCl₂, CuCl). Sulfide, hydrate, and elemental gas species are also important for some elements (Cd, AuS, Hg, PbS₂, BiS, Bi, AsS, As₂S₃, TeS, SeH, SeS). However, for many trace elements, speciation remains uncertain or unknown due to a lack of thermodynamic data. Upon cooling and decompression of the volcanic gas, most trace elements are predicted to reach gas-solid equilibrium, resulting in the formation of secondary minerals. At high temperatures (∼700–1000 °C), the mineral assemblage forming is dominated by quartz, Ca-Na-K feldspars, and Mg-pyroxene, containing minor concentrations of other alkali and alkaline earth metals. Further cooling and decompression leads to the formation of minerals including magnetite, pyrite, chalcocite, and chalcopyrite together with other less abundant oxides (V, Cr, Ga, W, and Sn) and sulfides (Zn, Pb, Ni, Co, Cd, Mo, Ag, As, and Bi), and eventually a range of sulfates and sulfosalts (Li, K, Na, Rb, Cs, Be, Mg, Ca, Sr, Bi, Mn, Fe, Zn, Pb, and Sn) at the lowest temperatures (∼100–300 °C). For most trace elements, fumarole emission concentrations reflect higher gas-solid equilibrium temperatures than those observed during sampling, suggesting gas-solid equilibria at high temperatures followed by incomplete re-equilibration upon further cooling near the surface.</div><div>Trace element fluxes span over eight orders of magnitude, ranging from &gt;100 kg/day to ∼1·10⁻⁶ kg/day. Silica, Al, and B consistently exhibit the highest fluxes, followed by alkali and alkaline earth metals, various transition metals and metalloids, with rare earth elements and actinides displaying the lowest fluxes. Generally, the trace element fluxes are lower compared to neighboring Stromboli and Etna, except for Pb, Bi, B, As, Sb, and Te.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"458 ","pages":"Article 108235"},"PeriodicalIF":2.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143180866","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Eruptive dynamics of open-vent andesitic volcanoes retrieved from petrological and componentry analysis of recent explosive phases (2020−2022) of Sangay (Ecuador)","authors":"Nicole Vizuete ,&nbsp;Pablo Samaniego ,&nbsp;Benjamin Bernard ,&nbsp;Jean-Luc Devidal ,&nbsp;Diego F. Narváez ,&nbsp;Céline Liorzou ,&nbsp;Silvana Hidalgo","doi":"10.1016/j.jvolgeores.2024.108238","DOIUrl":"10.1016/j.jvolgeores.2024.108238","url":null,"abstract":"<div><div>Since its reawakening in 2019, Sangay volcano (Ecuador) experienced a continuous, low magnitude eruptive activity that was disrupted by some mild-explosive pulses. Andean communities in central Ecuador and the Guayaquil International Airport have been affected by the ash fallouts. Through componentry, geochemical and petrological analysis, we studied ash and lapilli samples, emitted during the mild-explosive eruptions of 2020–2021 and during the minor eruptions of 2022, to document the changes in eruptive dynamics, constrain the pre-eruptive physical conditions, and identify the potential triggering mechanisms. Major elements whole-rock compositions show a progressive decrease in silica content, from andesitic to basaltic andesitic compositions, and a concomitant increase in magnesium content over time. Componentry, textures and chemical variations in groundmass glass support the idea that Sangay's shallow plumbing system hosts magmas that have evolved in composition, having variable physical properties that control the eruptive dynamics. The change in eruptive style towards more explosive dynamics in 2020–2021 was probably associated with the feeding of a more mafic and gas-rich magma from deep. The consequence, reflected in the groundmass glass chemistry and componentry data, is the “excavation” of the partially crystallized magma stalling in the conduits, which led to the observation of the more diverse compositions in the juvenile material. This work contributes to a better understanding of the eruptive behavior of long-lived, open-vent andesitic volcanoes, and to explore the link between eruptive dynamics and the petrological evolution of magmas.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"458 ","pages":"Article 108238"},"PeriodicalIF":2.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143180895","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Automated seismo-volcanic event detection applied to popocatépetl using machine learning","authors":"Karina Bernal-Manzanilla ,&nbsp;Marco Calò ,&nbsp;Daniel Martínez-Jaramillo ,&nbsp;Sébastien Valade","doi":"10.1016/j.jvolgeores.2024.108261","DOIUrl":"10.1016/j.jvolgeores.2024.108261","url":null,"abstract":"<div><div>Popocatépetl, one of Mexico's most active volcanoes, exhibits high seismicity since its reactivation in 1994. Identifying and classifying its different seismo-volcanic events is crucial for understanding the volcano's dynamics. Machine Learning (ML) methods have proven effective in this task; however, their accuracy often relies on large-scale labeled datasets and they are typically tested on single stations. This may limit a broader applicability across seismic networks monitoring volcanoes. Here, we present an updated ML-based workflow for the automated detection and classification of long-period (LP) events, tremors (TR), and volcano-tectonic (VT) earthquakes at Popocatépetl, using continuous seismic recordings from 2019 to 2023. The workflow leverages data from a network of up to 19 seismic stations, enhancing event classification with a limited labeled dataset and improving reliability across multiple stations. The workflow is divided into two stages: the first stage generates LP and TR catalogs by training a classification model using Popocatépetl's data. The second stage creates the VT catalog using a pre-trained phase-picking and phase association models, alongside standard seismological methods for event location. The automatic catalogs generated by our workflow accurately captured the temporal and spatial trends of seismicity at Popocatépetl over more than four years, including periods of increased volcanic activity. Our approach also identified additional events not reported in manual analyses, improving the detection of trends related to volcanic processes, such as activity related to dome emplacement, periods of explosive activity, and potential system pressurization.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"458 ","pages":"Article 108261"},"PeriodicalIF":2.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143180867","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fault intersection-related stress rotation controls magma emplacement at the Nevados de Chillán Volcanic Complex","authors":"Javier Espinosa-Leal ,&nbsp;John Browning ,&nbsp;José Cembrano ,&nbsp;Thomas Mitchell ,&nbsp;Flavia Rojas ,&nbsp;Max Moorkamp ,&nbsp;W. Ashley Griffith ,&nbsp;Philip Meredith","doi":"10.1016/j.jvolgeores.2024.108255","DOIUrl":"10.1016/j.jvolgeores.2024.108255","url":null,"abstract":"<div><div>It has been suggested that fracture and fault intersections promote enhanced transport of fluids in the brittle crust by forming zones of increased permeability. However, the underlying mechanisms that control the emplacement of magma at fault intersections remain poorly understood. To better understand the relation between magma emplacement, volcano development and fault zone intersections, we examine the Nevados de Chillán Volcanic Complex (NChVC, 36.8°S) in the Southern Andean Volcanic Zone. The complex is thought to be located atop the intersection between two sets of NE-right lateral strike-slip faults and a seismically active regional scale NW-oriented inherited structure, also interpreted as a regional fault zone. We collected data on the orientation and frequency of tens of dykes and thousands of fractures, at the volcano scale, from representative outcrops using three-dimensional digital image correlation techniques, with images taken from Unmanned Aerial Vehicles (UAVs). We use these data to generate a conceptual model of the response of the different fracture sets to regional loads and the potential consequence in terms of magma emplacement. In our conceptual model, N-S to NW-SE striking fractures become reactivated by fault intersection-related local stress field rotations. This, in turn, favors NW-SE aligned magma emplacement, and the evolution of NW-SE aligned volcanoes. Our findings provide a mechanical explanation for rotated magma emplacement pathways, which do not necessarily require a transient stress state imposed by unlocking the megathrust.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"458 ","pages":"Article 108255"},"PeriodicalIF":2.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143180349","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Linking monitoring data and timescales of mafic recharge during the 2013–17 eruption at Volcán de Colima, Mexico","authors":"Gerallt E. Hughes ,&nbsp;Chiara Maria Petrone ,&nbsp;Hilary Downes ,&nbsp;Nick R. Varley ,&nbsp;Dulce Vargas-Bracamontes ,&nbsp;Raul Arámbula-Mendoza ,&nbsp;Edgar A. Cortes-Calderon ,&nbsp;Yannick Buret","doi":"10.1016/j.jvolgeores.2025.108285","DOIUrl":"10.1016/j.jvolgeores.2025.108285","url":null,"abstract":"<div><div>Timescales of mafic magma recharge beneath Volcán de Colima have been calculated from diffusion modelling of reversely zoned pyroxene crystals erupted in the 2013–17 interplinian eruptive period. The results suggest that injections of low volume mafic magma are periodic and ephemeral, residing in the plumbing system for only weeks to months before eruption. At least three separate periods of magma recharge and mixing occurred within <em>c</em>. 3 years in October 2013–April 2014, September 2014–June 2015 and November 2015–September 2016. These timescales have been compared with the continuous seismic monitoring of the volcano and quasi-continuous gas monitoring data. Each eruptive phase shows different patterns between petrological and monitoring data, suggesting a complex mixing-eruption relationship, which may be related to the frequency and volume of recharge events, as well as the thermal state of the magma reservoir. Low frequency or low volumes of magma injection may result in a lack of correlation with any change in the monitoring data. High frequency of magma injections priming the magma reservoir results in a strong correlation between recharge events and monitoring record, which may be useful for interpreting future monitoring data.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"460 ","pages":"Article 108285"},"PeriodicalIF":2.4,"publicationDate":"2025-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143372146","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Limited surface deformation, seismicity, and seismic velocity changes observed in Valles Caldera over decadal timescales","authors":"Nathan Maier ,&nbsp;Emily E. Rodriguez ,&nbsp;Ronni Grapenthin ,&nbsp;Andy Newman ,&nbsp;Carly Donahue ,&nbsp;Eric Lindsey ,&nbsp;Peter Roberts ,&nbsp;Savannah Devine","doi":"10.1016/j.jvolgeores.2025.108283","DOIUrl":"10.1016/j.jvolgeores.2025.108283","url":null,"abstract":"<div><div>The Valles Caldera, located in Northern New Mexico, is one of the three young caldera systems within the United States to host past super-volcanic eruptions. Extensive geophysical work has indicated the presence of a shallow crustal magma body and a near-surface geothermal system; yet, no accompanying observations exist to constrain the transient nature of the system, which is a critical first step in assessing contemporary hazards both volcanic in nature and on nearby fault systems. Here, we present three independent data products to assess the current state of the Valles Caldera; a geodetic survey of thirteen benchmarks to measure time-averaged surface deformation across two decades, a decade-long record of intra-caldera microseismicity detected by template matching, and decadal-scale seismic velocity changes derived from ambient noise. The combined results suggest a quiescent system that does not have the characteristics commonly associated with active magmatic systems. We found limited surface deformation within the Valles Caldera over the 20-year survey period. The vertical and horizontal velocity fields suggest that a contracting intra-caldera deformation source could be present, however additional data is needed to confirm at a two-sigma confidence level. We detected 46 small magnitude earthquakes (&lt; 1.15 M_d) within the caldera with no evidence of seismic swarms since 2012. Seismic velocities were found to be stable over a 12-year period at depths consistent with the location of a previously inferred magma body. Each dataset in isolation has its limitations, most notably the geodetic survey, where we cannot rule out aliasing of the data due to transient changes occurring between survey periods, or unaccounted for biases due to equipment changes. However, compared to observations at other caldera and volcanic systems, the combined datasets suggest that the Valles Caldera is not currently in an active phase, where surface deformation consistent with a magmatic source, seismic swarms, and velocity changes often coincide with inferred magma, fluid or gas movement. Our results suggest that monitoring for a change-of-state should be continued and highlight the challenges of monitoring slowly deforming systems using campaign methods where different survey equipment was used.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"460 ","pages":"Article 108283"},"PeriodicalIF":2.4,"publicationDate":"2025-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143226115","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Insights into caldera cycles obtained from the eruption ages and chemistry of the youngest products of Nisyros volcano, South Aegean Arc","authors":"Valerie Locher ,&nbsp;Răzvan-Gabriel Popa ,&nbsp;Marcel Guillong ,&nbsp;Olivier Bachmann","doi":"10.1016/j.jvolgeores.2025.108281","DOIUrl":"10.1016/j.jvolgeores.2025.108281","url":null,"abstract":"<div><div>Hazards posed by volcanism are strongly associated with the volcanoes' shifts in eruptive styles, as they often alternate between effusive and explosive activity with little to no forewarning. These shifts are thought to be governed by processes happening in conduits and reservoirs feeding magmas to the surface. In hope to forecast eruptive activity (including styles), it is critical to better understand these governing processes. Here, we consider the case study of Kos-Nisyros-Yali volcanic field (Aegean Arc), which has experienced several caldera-collapse events in the last few hundreds of thousands of years and undergone multiple shifts in eruptive style. We conduct bulk-rock geochemical analyses and U<img>Th disequilibrium dating of zircon on eight of the post-caldera domes, which form the youngest volcanic deposits on Nisyros, to better understand the most recent stage of activity at this volcano and its implications on future eruptions. Zircon U/Th ages indicate that the domes formed between ca. 26 ka and 13 ka, 30 ky after the volcano's most recent caldera-collapse eruption. We observe a spatial migration of vents as well as a slight shift to more mafic bulk-rock compositions with time, which could reflect a growing influence of persistent mafic recharge pulses into the upper-crustal magma chamber throughout the eruptive period. Based on the eruption timings, compositions of fumaroles, and recent observations during unrest on Nisyros, we suggest that the upper-crustal magma reservoir is currently in a water-saturated state, which favors its growth and infrequent effusive eruptions.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"460 ","pages":"Article 108281"},"PeriodicalIF":2.4,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143225771","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Seabed stability inferred from the 2019–2020 earthquake swarm under a volcanic cone field and slopes of Condor Seamount, Azores","authors":"Neil C. Mitchell ,&nbsp;Fernando Tempera ,&nbsp;Thomas A. Morrow ,&nbsp;Joaquim Luis ,&nbsp;Christian Hübscher ,&nbsp;Telmo Morato","doi":"10.1016/j.jvolgeores.2025.108279","DOIUrl":"10.1016/j.jvolgeores.2025.108279","url":null,"abstract":"<div><div>Knowledge of the strength of submarine volcaniclastic deposits is important for assessing the stability of slopes of such materials and their geohazards but is difficult to measure. An opportunity for an alternative evaluation has been presented by an earthquake swarm under a volcanic seamount in the Azores. Attenuation relationships applied to earthquake data suggest that a cone field and flanks of the seamount experienced horizontal accelerations of &gt;0.3 g during the swarm. However, multibeam sonar data collected before and after the swarm suggest that no slope failures occurred. Furthermore, in backscatter data collected after the swarm, low intensities below slopes suggest that muddy aprons were undisturbed by landslide debris. The swarm overlies cones with slopes near typical repose angles of non-cohesive particles. During earthquake shaking, the direction of maximum acceleration deviates from that due to gravity alone. We show that cone slopes effectively experienced much steeper gradients than their repose angles during the swarm. As they survived the shaking without failing, they were effectively stronger than non-cohesive sediment. We use a pseudo-static analysis to investigate the implied sediment strength, finding a ratio of undrained shear strength to vertical stress of &gt;0.4–0.5. This implies shear strength of &gt;24–30 kPa at 10 m depth below seabed. We speculate that carbonate cements and/or compaction may be responsible. If shallow areas are more widely strengthened, slope failure may then be less likely during moderate (M_L ∼ 4.0 or less) seismic shaking and hence be less hazardous than if the slopes comprised wholly non-cohesive materials.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"460 ","pages":"Article 108279"},"PeriodicalIF":2.4,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143350203","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}