Ventura, Guido

The plumbing systems of subduction-zone volcanoes consist of magma reservoirs with different degrees of evolution at multiple depths. The geometries of plumbing system of intraplate monogenetic volcanic fields are generally characterized by basaltic magma ascending from the mantle and/or a shallower reservoir along dikes. However, the shape and vertical extent of these plumbing systems are largely unknown due to the rareness of robust geophysical data. The possible role of faults and mountain chains in controlling the geometry of magma reservoirs is also poorly understood. To address these limitations, we present a three-dimensional resistivity structure beneath the Holocene Jingpohu Monogenetic Volcanic Field (JMVF) in the Zhangguangcai Range (ZGC), northeastern China. The resistivity model was derived from the magnetotelluric data in a dense net-like array. We identified an inverted cone-shaped high-resistivity (~10,000 Ω m) anomaly below the ZGC. This anomaly traverses almost the entire crust. We interpret this high-resistivity anomaly to be the stiff basement of the ZGC. At the base of the resistive volume, we resolved a sill-like, low-resistivity anomaly that occurs at the top of the lithospheric mantle. Sheet-like low-resistivity anomalies surrounding the high-resistivity body depart from the lithospheric mantle. We interpret these sill- and sheet-like anomalies as a trans-crustal saucer-shaped magma plumbing system beneath the JMVF. This system involves multi-level magma reservoirs, including basaltic magma at its base, basaltic dikes/sills swarms in the middle and sill intrusions in the upper crust. We propose that the stiff crustal root and the topographic loading of the ZGC work together to deflect the upward magma propagation towards the edges of the ZGC. The magma ascent to the surface is probably controlled by preexisting, lithospheric faults. Our data show how mountain chains, together with the crustal structure, play a key role in controlling the geometry of multi-level plumbing systems of intraplate monogenetic volcanic fields.

The Changbaishan Tianchi intraplate volcano is one of the most active and hazardous volcanoes of NE Asia, characterized by a summit caldera formed after the 946 CE ‘Millennium’ Plinian eruption. From December 2020 to June 2021, the frequency and magnitude of earthquakes at Tianchi were significantly higher than during background periods, with hundreds of earthquakes (46 events per month in average) and reaching a local magnitude of ML 3.1. This study reports a comprehensive deformation analysis and geophysical inversion scheme aimed to unveil the dynamics of this period. Multi-temporal InSAR analysis results of 32 ALOS-2 images from 2018 to 2022 show that the surface deformation is a combination of seasonal fluctuations (± 25 mm in average, with a maximum ± 45 mm) and a long-term positive component. The least squares linear regression of the deformation time series and temperature data, isolates the seasonal fluctuations, revealing a clear upliftsubsidence process from June 2020 to July 2021 in the caldera area. To constrain the Tianchi plumbing system dynamics, a combined inversion scheme consisting of three deformation sources is designed. The inversion results and the seismic records indicate that Tianchi volcano has experienced a low-level unrest episode from December 2020 to June 2021. The shallower plumbing system, located at about 5–9 km depth and modelled by pressurized spheroids, underwent a cumulative volume increase of 26 × 106 m3 from November 2018 to April 2021, followed by a volume decrease of 9 × 106 m3 from April to July 2021. This suggests magma uprising from the 14 km deep storage zone to the shallower plumbing system, followed by depressurization of the plumbing system due to the escape of fluids. This research provides a comprehensive understanding of the magma and fluid migration dynamics within the Tianchi multi-level plumbing system for the first time.

In this paper, the Multi-Temporal Interferometric Synthetic Aperture Radar (MT-InSAR) technology is adopted to monitor the Line of Sight (LOS) displacement of Fushun West Opencast Coal Mine (FWOCM) and its surrounding areas in northeast China using Sentinel-1 Synthetic Aperture Radar (SAR) images acquired from 2018 to 2022. The spatial-temporal evolution of urban subsidence and the south-slope landslide are both analyzed in detail. Comparison with ground measurements and cross-correlation analysis via cross wavelet transform with monthly precipitation data are also conducted, to analyze the influence factors of displacements in FWOCM. The monitoring results show that a subsidence basin appeared in the urban area near the eastern part of the north slope in 2018, with settlement center located at the intersection of E3000 and fault F1. The Qian Tai Shan (QTS) landslide on the south slope, which experienced rapid sliding during 2014 to 2016, presents seasonal deceleration and acceleration with precipitation, with the maximum displacement in vicinity of the Liushan paleochannel. The results of this paper have fully taken in account for the complications of large topographic relief, geological conditions, spatial distribution and temporal evolution characteristics of surface displacements in opencast mining area. The wide range and long time series dynamic monitoring of opencast mine are of great significance to ensure mine safety production and geological disaster prevention in the investigated mining area.

The formation and growth mechanisms of Mid-Ocean Ridges (MOR) are relatively well known, whereas those of back-arc spreading ridges are comparatively less known because geophysical, geochemical, and morphological data are scarce and of low density. Here we present a high-resolution bathymetry of the Marsili Seamount (MS; 1Ma 3 ka), which represents the inflated spreading ridge of the 2Ma old Marsili back-arc basin associated to the subduction of the Ionian Sea below the Calabrian Arc and Tyrrhenian Sea. MS is 70 km long, 30 km wide, and its height reaches about 3000 m from surrounding seafloor. Our new digital bathymetric model has a 5 m grid cell size resolution and covers the MS bathymetry from 1670 mbsl to the top at 491 mbsl. We conduct morphometric and morphological analyses of the bathymetry and recognize landforms due to volcanic, tectonic, hydrothermal and gravity processes. MS consists of volcanoes related to fissural and central-type activity, this latter located at the northern and southern tips of the main dike swarms. Dike swarms represent the surface expression of different ridge segments whose strikes are controlled by the larger scale back-arc spreading processes and by the local occurrence of an active hydrothermal field. This latter develops in a flat area between two partly overlapping ridge segments where historical volcanism and extensional processes concentrate. Such ridges represent the embryonic stage of the formation of transform-like faults. Central volcanoes, the northern of which is characterized by a caldera, form at the tips of MS because the decrease in width of the major volcanic fissures promotes vent localization associated with the formation of sill-like reservoirs from which central-type vents may develop. Gravity processes affecting the MS flanks are due to shallow seafloor sliding. Caldera collapses affecting the northernmost central-type polygenic volcano must be included in the evaluation of the hazard related to potential tsunami. Inward dipping faults characterize the MS eastern flank suggesting a moderately asymmetric growth of the spreading ridge possibly associated with the eastward opening of the Marsili back-arc. The Marsili back-arc spreading rate is similar to those of MOR slow spreading ridges. However, the MS morphology resembles that of fast spreading ridges. These two features also characterize more extended back-arc spreading ridges (e.g. the Mariana in Western Pacific). We conclude that, independently from the spatial scale, the increase in the ridge accretion rate is related to the progressive addition of a subduction-related component to a pure spreading mantle source.

Back-arc basins (BABs) are associated with plate margins where crustal shortening, seafloor spreading, and volcanism coexist. The Vavilov basin (Tyrrhenian Sea) is a Pliocene BAB associated with the Apennine-Tyrrhenian Sea subduction system and characterized by mantle exhumation. The NNE-SSW elongated Vavilov seamount represents the easternmost and younger spreading ridge of the Vavilov basin. Here we present results of a morphological and magnetic study of the Vavilov seamount. Our results show that the seamount represents the last stage of the eastward asymmetric opening of the BAB. Its plumbing system consists of a dike swarm emplaced during the reversed Matuyama epoch and a younger shallow reservoir feeding the central and eastern sectors during the normal Brunhes epoch. This evolution is associated with the progressive loading of the edifice due to lava flow emplacement. The asymmetry of the seamount mirrors the asymmetric opening of the Vavilov back-arc basin.

The plumbing system of volcanoes in crustal convergent settings consists of vertically superimposed, sill-like reservoirs. The shallower reservoirs are generally filled by less dense and SiO2-richer magmas. The plumbing systems of spreading ridges are supposed to be simpler and characterized by prevailing sub-parallel vertical dykes. Here, we present the results of thermo-barometric determinations from minerals and modelling of potential field data at the Marsili spreading ridge in the Southern Tyrrhenian Sea back-arc oceanic basin. The Marsili plumbing system consists of sill-like, large SiO2-rich magma reservoirs located at the Moho depth and sub-vertical basaltic dykes crossing the whole oceanic crust. The formation of deep-seated silicic reservoirs is associated with a decrease in the back-arc spreading rate. The geometry of the plumbing system of spreading ridges may be not dissimilar from that of volcanoes at convergent margins.

The pore structure and storage volume of rocks are crucial parameters to evaluate the favorability of hydrocarbon reservoirs. The unconventional volcanic reservoirs in the Songliao Basin (NE China) include lava and pyroclastics of different composition. Here we apply the X-ray computed microtomography (micro-CT) to reconstruct the 3D pore space of selected samples (basaltic lava, rhyolitic lava and rhyolitic pyroclastics) at depths between 2283 and 3757 m. We reconstruct the morphology and size distribution of the pores. The pore structure records the effects of superimposed volcanic, alteration, and compaction-burial processes. This latter process produces fractures in the rhyolitic pyroclastic rocks. The basaltic lavas have larger, connected pores filled by alteration minerals with a prolate shape, and unconnected, smaller, blade-like, empty pores. The hydrothermal alteration reduces the porosity and the rock is impermeable being the smaller voids unconnected. The basaltic lavas are good cap rocks but very poor reservoir rocks. The rhyolitic lava flows and pyroclastics, some of which placed in the gas zone of the Songliao reservoirs, show prevailing interconnected fractures due to burial processes and minor pores around crystals formed by syn-eruptive heterogeneous gas nucleation. The pore connectivity is ensured by the fractures and the permeability may be high, also depending on the volume, more than on the number, of the pores. Rhyolites may be good reservoir 2 rocks. We search for possible relationships between porosity and permeability and do not find a clear relation between these two parameters as well as between depth and permeability. Although our analysis is valid within a length scale between about 20 μm and 1 cm, the methodological approach used here can be extended to other reservoirs to study the evolution of the pore systems as a function of the different processes affecting the volcanic rocks.

We report composition, grain size, and rheological data related to the mud emitted as a consequence of the maximum moment magnitude (Mw max = 6.5) on 30 October 2016, commonly referred to as the Norcia earthquake (central Italy), and on the activity of pre-existent mud volcanoes affected by the central Italy seismic sequence started on 24 August 2016. The emission sites were located at Monteleone di Fermo and Santa Vittoria in Matenano, two municipalities near the town of Fermo (Marche Region, Italy). We sampled, measured, and analyzed the products of mud emissions 3 days after the mainshock to characterize the mud by geochemical, mineralogical, and rheological analyses. The muds’ geochemical composition and low electrical conductivity suggest a continental origin, likely belonging to the Colombacci Formation. The collected muds are silt–sand–water-rich suspensions characterized by a Bigham rheology with viscosity values between 6.3∙107 and 6.9∙105 Pa∙s. The calculated minimum fluidization velocity of the mud suspensions is between 0.05 m/s (grain size of 2 μm) and 0.74 m/s (grain size of 8 μm). Water-rich mud suspensions flowing on a slope move faster as the water content increases up to 30 wt.%. At higher values, the velocity remains almost constant due to the disaggregation of bonds among the solid particles in the mixtures.

Archaeological sites may be exposed to different types of risks related to wars, natural phenomena, and illicit human activities. Quantitative data on the type and extent of the damages and destructions suffered by these sites are of primary importance for their reparation and the planning of conservation and defence actions. The Apurlec Monumental Archaeological Complex (about seventh–fourteenth century AD, Peru, “Intangible and Essential Heritage” of the Peruvian Ministry of Culture) includes platforms, canals, and rectangular ceremonial/administrative enclosures. Between June and August 2021, Apurlec has been affected by a partial destruction of its southern sector. Here we present the results of two UAV photogrammetric surveys conducted before (23 January 2021) and after (30 August 2021) the destructive event. The comparison of the orthoimages and the Digital Surface Models obtained form the two surveys allow us to detect illicit activities as earth removal to collect construction material, creation of cultivable areas, and steal manufacts from archeological excavations. We calculate that the area covered by the destruction is 121,665 m2 (perimeter of about 2 km2) the removed material amount to 401,513.5 m3, a value corresponding to a mass of about 702,648.63 ton. The post-destruction topography is lower of about 3.3 m with respect to the original one. Our anytical and metholodological approach could be extended to other archeological sites potentially exposed to anthropic and natural hazards.

The investigation of submarine volcanoes and the tsunamigenic potential of possible movements on their flanks is arduous. In most cases, the lack of specific information about the eruptions' history and their consequences does not allow a comprehensive analysis in terms of hazard. Nevertheless, useful clues on the possible occurrence of mass movements on seamounts can be obtained from a series of research fields. These account for morphological studies, observations of hydrothermal activity, collection of geophysical data (for example, detailed DEM, seismic profiles, magnetic data), etc. In this context, this study presents new bathymetric data of the Vavilov submarine volcano (Tyrrhenian Sea, Italy) and a detailed morphological analysis of the structure. The latter allows the identification of zones potentially prone to mass movements and the development of numerical scenarios to investigate the tsunami potential associated to these movements on the Vavilov flanks. Results prove that the waves generated by the mass displacements in the proposed scenarios (involving sliding volumes between 0.32 km3 and 1.7 km3) reach maximum values in the order of centimetres, not considering dispersive effects. Eventually, a scenario involving the partial collapse of the west flank of the Vavilov Seamount is simulated, although the occurrence of such an event in the past is still debated due to the uncertainties related to the origin and development of the volcano dome. In this scenario, water elevation as high as 10 m are found in large portions of the Tyrrhenian coasts: waves are large enough to emplace sizeable tsunami deposits onshore, that could have been preserved until today in some specific stretches of the coast and could be detected by a finalised geological search. This study belongs to a series of works devoted to the submarine structures of the Tyrrhenian Sea aiming to disclose the tsunamigenic potential of submarine mass movements on their flanks.