Journal of Volcanology and Seismology最新文献

Rawa Danau Volcanic Complex (RDVC) in the western part of Banten—Western part of Java Island, Indonesia, holds records and histories of past violent volcanic eruption. These past volcanic activities manifested as huge Rawa Danau caldera and massive Banten Tuff pyroclastic deposits that are distributed for more than ten kilometres away from the source and have played an important role in shaping the morphology of Banten. Previous studies suggest that Banten Tuff is composed of various pumiceous pyroclastic deposits presumably formed in Early Pleistocene. The deposits cover vast area of Banten, and their thickness exceeds 200 m. Despite their significance, there are no detailed studies that discuss the stratigraphic and eruption dynamics of the deposits. This paper provides new insight on the eruption dynamics based on fieldwork observation, volcanic stratigraphy, and petrologic interpretation. The study focuses on the eastern flank of RDVC, where the well-preserved stratified outcrops are located. Aligned with previous studies, the deposit can be divided into two major eruption sequences: 1) Lower Banten Tuff (LBT) and 2) Upper Banten Tuff (UBT). LBT is interpreted as lithic-bearing ignimbrite with accompanying surge deposit and considered as a single-phase eruption. Lithic-rich characteristics in this unit suggest that LBT might be related to the caldera-forming mechanism. On the other hand, UBT shows a more dynamic sequence. It is composed of two fallout units followed by an ignimbrite formed by the eruption column collapse. The appearance of banded pumice in UBT with contrasting andesitic and rhyolitic compositions suggests a mafic injection as the eruption trigger. Pumice and ash compositions are mostly in dacitic to rhyolitic range, with several samples in andesitic range. Componentry analysis suggests that all eruptions were magmatic in origin.

Sixteen morphometric relief parameters have been identified whose positive anomalies correspond with seismic areas in the Greater Caucasus. An analysis of four parameters which were considered to provide the most information using the γ-operator in fuzzy logic has enabled us to develop a scheme for an index of neotectonic activity that was used along with the results of computerized geodynamic simulation to identify zones of possible earthquake sources. The new approach does not require detailed information on present-day and paleo seismicity, hence can be used to deal with an analogous problem for territories whose seismotectonics is poorly known. We have demonstrated an interrelationship between recent deformations and regional seismicity, and the possibilities offered by the method of lineament analysis due to Yu.V. Nechaev (2010) for identification of active faults.

This study is assessing the tsunami hazard for a segment of the Kamchatka western coast around the Oktyabrsky Spit. The motivation is to ensure transportation access to the village of Oktyabrsky and to the fish processing facilities situated on the Spit. The hazard estimates were derived by the worst case method. An analysis of seismicity and historical data on tsunami occurrences in the Sea of Okhotsk resulted in identification of two tsunami-generating zones that constitute threat to the Oktyabrsky coast segment, with a set of model tsunami-generating earthquakes being determined for each zone. For this set of models we conducted numerical modeling for tsunami generation and propagation, resulting in a selection of model sources that would pose the greatest threat to the coastal strip of interest. The next step involved refining calculations for these sources using a sequence of nested grids to find the parameters of tsunami impact on the coast. The main results of the present study consist in identification of tsunami-generating zones that pose the highest threat to the Oktyabrsky coast, the selection of tsunami-generating model sources in these zones, and estimates of parameters that characterize extreme tsunami waves posing threat to this coast strip.

We have obtained the first data on the chemical composition of the eruptive materials from the explosive eruption of Bezymianny volcano on April 7, 2023. Our unique collection includes freshly sampled pumice lapilli from the eruption and juvenile blocks from pyroclastic flows. We have identified interesting patterns in both macro components and specific chalcophile elements, such as copper. The rocks we studied belong to medium-K two-pyroxene basaltic andesite (55.5‒57 wt % SiO₂), with mafic enclaves characterized by a slightly more primitive composition (53.7 wt % SiO₂). According to mineral geothermometry data, the phenocrysts of basaltic andesite crystallized at temperatures in the range from 940 to 960°C, while the formation of phenocryst rims and microlites occurred at 980°C, which corresponds to conditions immediately before the eruption. The composition of volcanic glass allows us to estimate the pressure at which the magma reached the last equilibrium with crystallizing phases before eruption (0.5‒0.6 kbar). Based on these findings, we have formulated hypotheses about the potential evolution of the shallow magma chamber of Bezymianny volcano during the period from 2017 to 2023.

The northwestern part of the Sevan–Shirak structural formation zone of the Lesser Caucasus contains ultra-high-K siliceous ignimbrites dating back to the Late Eocene–start of Early Oligocene (?), which associate with high-K volcanics of the calc-alkaline and shoshonite series. During Eocene–Oligocene time the Sevan–Shirak zone was an ensialic island arc with a Hercynian metamorphic basement. The formation of high-K and especially ultra-high-K rocks was due to the effects of mantle fluids on the continental crust.

This paper presents an analysis of recorded variations (anomalies) in the potential gradient of electrical field in the atmosphere caused by the propagation of eruption plumes discharged by eruptions of Shiveluch and Bezymianny volcanoes in Kamchatka. The anomalies were recorded at various distances from eruption centers and under different conditions of atmospheric stratification. These conditions have enabled us to show that the eruption plumes of Shiveluch and Bezymianny possessed a 3D electrostatic structure that is consistent with a known phenomenological model derived on the basis of surveys conducted on various volcanoes worldwide. According to this model, the top of an eruption plume contains a positive volumetric electrostatic charge, while the respective charges are negative in the middle, and positive in the lower part of the plume.

The period of more than twenty years in which recent movements in the Mountainous Altai were measured by methods of satellite geodesy includes various phases of the seismic process. A network consisting of 20 observing stations extends over a large area from Novosibirsk City in the north to the Mongolian border in the south, from the border with Kazakhstan in the west to the Sayan Mountains in the east. The Chuya earthquake of September 2003 divides, in a natural manner, the period of observation from 2000 to 2022 into several phases: the preseismic (2000‒2003), the coseismic (2003‒2004), the postseismic phase for the epicentral area of the Chuya earthquake (2004‒2013), and the interseismic phase for the other regions of the Mountainous Altai that have not been seriously affected by the earthquake (2000‒2022). The data supplied by multiyear measurements were analyzed using special programs of the most recent modifications. We have identified conspicuous features in the displacement fields during each phase: anomalous displacement rates before the Chuya earthquake, the coseismic displacements during the earthquake, postseismic effects in the epicentral zone, and slow tectonic movements. Our interpretation relied on 2D and 3D elastic and viscoelastic models of the crust. The depth of focus has been determined (14 km), as well as the two-meter relative right lateral displacement jump on the seismic fault. With a two-layered model, we obtained the value of viscosity in the lower crust for a variety of elastic modulus values η = 5 × 10¹⁹‒1.1 × 10²⁰ Pa s. The recent movements in that part of the Mountainous Altai which has not been affected by the Chuya earthquake were 0.8 mm/yr toward NNW. The rate of surface deformation in the southern mountainous part reached 2 × 10^–8/yr in the epoch 2000‒2022, which is an order of magnitude higher than that in the northern flat part of the area of study.

Volcanic eruptions can bring about lava flows, posing significant hazards and rare direct threats to human life, but they can also cause extensive damage to property and economic activities. Managing volcanic disasters demands swift and accurate information on the behaviour and evolution of lava flows, particularly regarding their extension, displacement, and trajectory. This study addresses numerical and laboratory modelling to understand the dynamics of a lava flow and its frontal advancement. Laboratory experiments of a lava flow analogue, exhibiting a non-Newtonian Herschel–Bulkley fluid behaviour, have been conducted. The fluid parameters at varying temperatures have been determined on the basis of the rheometer and thermal camera measurements. A flow of the Herschel–Bulkley fluid (the lava flow analogue with the fluid parameters determined from the laboratory experiments) is then simulated numerically using the Abaqus software, where a smoothed particle hydrodynamics method has been implemented. A run-out distance, frontal flow displacement, and flow velocity have been determined during laboratory and numerical modelling. When the fluid parameters measured at a constant temperature of 80°C are used, the numerical results diverge from the experimental results over time. To mimic closely the dynamics of the lava flow analogue inferred from the laboratory experiment with its dynamics in the numerical modelling, time-dependent adjustments to the Herschel–Bulkley fluid parameters determined at lower temperatures have been introduced by changing their values during a numerical simulation. This study underscores the importance of constraining parameters of numerical models by the values obtained from laboratory measurements.

This study reports comprehensive research (archeological, archaeo- and paleo-seismological, as well as georadar profiling), which enabled us to find out the cause of destruction for the South Churubash settlement (a big manor in the chora around the town of Nymphaion) in eastern Crimea. A strong seismic event whose possible rupture went along the southwestern boundary of the Churubash Liman, which is a segment of the Parpach–Taman active fault, led to the formation of landslide bodies southwest of the rupture. The nearly north–south plane of scar for one of these has traversed the ancient settlement through its middle, having produced a visible flexure in the juvenile soil of this archeological monument—an earthquake-induced gravitational deformation. Large seismic slip at the fault plane had destroyed all structures and led to large deformations in the lower rows of the masonry: tilts, shifts, and rotations of parts of the walls—earthquake-induced inertial deformations. Considering that the earthquake rupture was nearby, and that all houses have been destroyed in the settlement, we hypothesize that the manor was caught in the epicentral zone of an ancient earthquake where the intensity of seismic motion was at least Io ≥ IX. Judging by the findings of amphorae brands, black glazed pottery, as well as of a Bosporus coin, this large manor in the chora of Nymphaion came to the end of its existence owing to a strong earthquake and a fire in the beginning of the fourth quarter of the 4th century BC. We may have previously observed traces of this earthquake in Nymphaion: as an example, the structures of Nymphaion dating back to the 5th—4th centuries BC had been completely or partly destroyed. Further surveys of active geological structures and archeological monuments would enable a more accurate parameterization of the seismic event identified in this study, which would serve the purpose of a more accurate assessment of earthquake hazard for the Crimean Peninsula.

This paper presents the first results from the monitoring of local seismicity in Severnaya Zemlya from the end of 2016 to 2023 inclusive as recorded by a single permanent seismic station installed on Bolshevik Island. A total of 73 local seismic events have been identified with P and S phases. We considered the question whether these events could be classified (earthquakes or icequakes) by comparing waveforms and spectral-temporal analysis diagrams with regional earthquakes that have occurred in the archipelago area. The spatio-temporal distribution and the rate of migration for the events show that glacial events can arise by stress release in glaciers as shallow crustal earthquakes occur within ~30 km. It is shown that, when a seismograph network is difficult to deploy, even a single permanent seismic station can furnish useful information on glacial events and crustal earthquakes.