Eruption Research Articles

Decadal prediction centers prepare for a major volcanic eruption

Abstract The World Meteorological Organization’s Lead Centre for Annual-to-Decadal Climate prediction issues operational forecasts annually as guidance for regional climate centers, climate outlook forums and national meteorological and hydrological services. The occurrence of a large volcanic eruption such as that of Mount Pinatubo in 1991, however, would invalidate these forecasts and prompt producers to modify their predictions. To assist and prepare decadal prediction centers for this eventuality, the Volcanic Response activities under the World Climate Research Programme’s Stratosphere-troposphere Processes And their Role in Climate (SPARC) and the Decadal Climate Prediction Project (DCPP) organized a community exercise to respond to a hypothetical large eruption occurring in April 2022. As part of this exercise, the Easy Volcanic Aerosol forcing generator was used to provide stratospheric sulfate aerosol optical properties customized to the configurations of individual decadal prediction models. Participating centers then reran forecasts for 2022-2026 from their original initialization dates, and in most cases also from just before the eruption at the beginning of April 2022, according to two candidate response protocols. This article describes various aspects of this SPARC/DCPP Volcanic Response Readiness Exercise (VolRes-RE), including the hypothesized volcanic event, the modified forecasts under the two protocols from the eight contributing centers, the lessons learned during the coordination and execution of this exercise, and the recommendations to the decadal prediction community for the response to an actual eruption.

Conduit armouring preceding explosive activity at an andesitic stratovolcano, an example from Taranaki Mounga, New Zealand

The strength and permeability of volcanic conduits can directly influence eruption dynamics via moderating the outgassing of ascending magma and the density of eruption plumes. Lithic clasts in pyroclastic ejecta can be used to understand the dynamic evolution of conduit walls because they are incorporated into the ascending melt-gas-particle mixture during volcanic eruptions. We examine the 1655 CE Burrell eruption of Taranaki Mounga, which transitioned from effusive activity to an explosive sub-Plinian phase and ended in unsteady columns. This episode was followed by a series of effusive eruptions of lower explosivity. Using textural analysis and physical properties, we distinguish five dominant lithic clast types within Burrell deposits that represent different regions of the shallow conduit and vent. Lithic types 1–3 represent juvenile (‘intrusive cognate’) and older (‘intrusive accessory’) conduit-filling plug materials. Lithic type 4 represents juvenile (‘extrusive cognate’) vent-filling lava dome extruded at the eruption onset, while Type 5 lithics (‘extrusive cognate’) represent sintered/compacted cognate material from the shallow vent accumulated during transitions in eruptive style. Crystalline andesite lithics (type 1) show a microlite-dominated groundmass. Hydrothermally altered andesite lithics (type 2) show breakdown of phenocrysts and increased seismic velocity relative to type 1 lithics. Brecciated andesite lithics (type 3) comprise fractured and sintered clasts of crystalline andesite. Glassy andesite lithics (type 4) show sub-rounded vesicles and glass-hosted microlites. Banded vitrophyre lithics (type 5) show bands of varying vesicularity, crystallinity and clast load. Physical property data reveals porosity, fracturing, sintering and alteration extent dictate dynamic changes in conduit permeability and potentially strength. Our results show how, during the explosive phase of the Burrell eruption, the conduit was lined with juvenile and remnant shallow plug material that was variably fractured, sintered and altered before being eroded and ejected. Comparison with previous work on Taranaki and dome-plug material from around the world shows how fracturing and sintering of conduit walls, combined with lining with dense juvenile material, cause overall permeability reduction and strengthening of the conduit. This inhibits outgassing and preserves conduit structure, facilitating the transition to explosive activity and the establishment of a stable eruption column.

Development of the Volcanic Disaster Risk Reduction Education Program Using the ICT Tool “YOU@RISK Volcanic Disaster Edition” —Practical Verification at a Junior High School in the Mt. Nasu Area—

This study developed a volcanic disaster risk reduction education program that aims to help junior high school students visually understand the risks of volcanic eruptions using map information and acquire independent assessments and actions to protect their own lives from eruption disasters. First, this program analyzed the present state, problems, and educational needs of volcanic disaster risk reduction education in Japan, and thereafter designed the learning content to fuse information and communication technology (ICT) education based on the Global and Innovation Gateway for All (GIGA) School Initiative promoted by Japan with disaster risk reduction education from a geographical viewpoint. We adopted the ADDIE model from instructional design theory to develop the program. An important feature of this program is the realization of geography learning using the “YOU@RISK Volcanic Disaster Edition,” a web-based GIS application developed by the National Research Institute for Earth Science and Disaster Resilience (NIED), as an ICT tool. Learners use YOU@RISK on their tablets and perform operations such as visualizing the risk range in the event of a volcanic eruption and searching for appropriate evacuation sites and routes, while acquiring the knowledge and skills necessary for geographical literacy and emergency response actions. The program is able to realize interactive learning, which is a step ahead of education that relies on conventional paper-based hazard maps. Among active volcanoes nationwide, Mt. Nasu was selected as target volcano for this study. In addition, a junior high school located in the area surrounding Mt. Nasu, Nasu Junior High School in Nasu Town, Tochigi Prefecture, was selected as the target school. The program was implemented by teachers using tablets provided for each student at the school. We evaluated the effectiveness of the program by measuring and analyzing the effects of learning through the practice. Consequently, the effectiveness of the volcanic disaster risk reduction education program using ICT was confirmed.

Organic matter enrichment model of fine-grained rocks in volcanic rift lacustrine basin: A case study of lower submember of second member of Lower Cretaceous Shahezi Formation in Lishu rift depression of Songliao Basin, NE China

Based on sedimentary characteristics of the fine-grained rocks of the lower submember of second member of the Lower Cretaceous Shahezi Formation (K1sh2L) in the Lishu rift depression, combined with methods of organic petrology, analysis of major and trace elements as well as biological marker compound, the enrichment conditions and enrichment model of organic matter in the fine-grained sedimentary rocks in volcanic rift lacustrine basin are investigated. The change of sedimentary paleoenvironment controls the vertical distribution of different lithofacies types in the K1sh2L and divides it into the upper and lower parts. The lower part contains massive siliceous mudstone with bioclast-bearing siliceous mudstone, whereas the upper part is mostly composed of laminated siliceous shale and laminated fine-grained mixed shale. The kerogen types of organic matter in the lower and upper parts are types II2–III and types I–II1, respectively. The organic carbon content in the upper part is higher than that in the lower part generally. The enrichment of organic matter in volcanic rift lacustrine basin is subjected to three favorable conditions. First, continuous enhancement of rifting is the direct factor increasing the paleo-water depth, and the rise of base level leads to the expansion of deep-water mudstone/shale deposition range. Second, relatively strong underwater volcanic eruption and rifting are simultaneous, and such event can provide a lot of nutrients for the lake basin, which is conducive to the bloom of algae, resulting in higher productivity of types I–II1 kerogen. Third, the relatively dry paleoclimate leads to a decrease in input of fresh water and terrestrial materials, including Type III kerogen from terrestrial higher plants, resulting in a water body with higher salinity and anoxic stratification, which is more favorable for preservation of organic matter. The organic matter enrichment model of fine-grained sedimentary rocks of volcanic rift lacustrine basin is established, which is of reference significance to the understanding of the organic matter enrichment mechanism of fine-grained sedimentary rocks of Shahezi Formation in Songliao Basin and even in the northeast China.

Sulfur dioxide sources in the stratosphere

Version 5.2 SO2 data from the Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS) in low Earth orbit are used to determine global altitude-latitude abundance distributions. This new data set has SO2 volume mixing ratios (VMRs) from 11.5 to 39.5 km in altitude from February 2004 to July 2023. The average background SO2 abundance is plotted along with the abundance for four different seasons. These distributions show that there is a stratospheric source of SO2 that comes from the decline in sulfate aerosol abundance with increasing altitude. The visible and near-infrared photolysis of sulfuric acid (H2SO4) is the primary source of SO2 in the middle stratosphere. There is also a source of SO2 in the upper stratosphere and mesosphere. The Brewer-Dobson circulation enhances SO2 at higher altitudes, particularly by descent near the winter pole. The elevated abundance of SO2 near the poles originates from meteoric sources as well as UV photolysis of H2SO4 in the mesosphere. Large volcanic eruptions release sulfur dioxide (SO2) into the lower stratosphere, where it persists for several months.

Valorization and investigation of volcanic ash as an aggregate building brick component

Abstract The devastating series of Taal volcanic eruptions from 2020 to 2022 covered several locations in the Philippines under a thick layer of ashes, destroying properties and halting business operations. In response, the Biñan City Government in Laguna, Philippines, proposed the development of eco-friendly bricks by leveraging the pervasive amounts of spewed volcanic ash as part of its solid waste management program. The materials recovery facility of the city produced several brick blends of combined Taal volcanic ash, cement mortar, and plastic waste materials. This study investigates the potential of Taal volcanic ash as an aggregate building brick component by measuring the compressive strength of the formulated bricks. With different blends of aggregate components, the bricks were tested for their durability based on the ASTM C67/C67M-20 standard after curing between 15 to 30 days. Per the ASTM C62-17 standard, all brick blends that were cured for 30 days including those with volcanic ash and plastic waste as aggregate components fall under the negligible weathering grade. This indicates that these bricks will be durable in building and structural applications where the average compressive strength requirement for bricks is at least 10.3 MPa. A regression model was also fitted with an adjusted r 2 value of 0.9413 and a p-value of < 2.2 × 10−16 using the experimental data.

Phasing and climate forcing potential of the Millennium Eruption of Mt. Baekdu

The Millennium Eruption of Mt. Baekdu, one of the largest volcanic eruptions in the Common Era, initiated in late 946. It remains uncertain whether its two main compositional phases, rhyolite and trachyte, were expelled in a single eruption or in two. Investigations based on proximal and medial ash have not resolved this question, prompting us to turn to high-resolution ice-core evidence. Here, we report a suite of glaciochemical and tephra analyses of a Greenlandic ice core, identifying the transition from rhyolitic to trachytic tephra with corresponding spikes in insoluble particle fallout. By modeling annual snow accumulation, we estimate an interval of one to two months between these spikes, which approximates the hiatus between two eruptive phases. Additionally, negligible sulfur mass-independent fractionation, near-synchroneity between particle and sulfate deposition, and peak sulfur fallout in winter all indicate an ephemeral aerosol veil. These factors limited the climate forcing potential of the Millennium Eruption.

Melt viscosity tracks the volcanic and magmatic evolution of the 2021 Tajogaite eruption, La Palma (Canary Islands)

After more than 50 years of repose, on September 19, 2021, a volcanic eruption began at the Cumbre Vieja ridge on La Palma, Canary Islands. The combined effusive and explosive activity generated a > 12 km2 lava flow field with a new cone nearly 200 m higher than pre-eruptive topography and a vast tephra blanket. The immediate impact was locally devastating, destroying nearly 2000 buildings, blocking two main and numerous secondary roads, and inundating high-value agricultural land.The hybrid nature of the eruption and the observed variations in eruption intensity motivated a thorough investigation of bulk liquid viscosity at high temporal resolution. Collection of 82 lava samples was achieved at a near daily resolution over the course of the 85-day-long event (through the end of the eruption on December 13, 2021). All the samples were remelted, and liquid viscosity was measured in a concentric cylinder viscometer from 1500 °C down to incipient crystallization temperatures. These data constitute the highest temporal resolution viscosity dataset obtained for an eruptive sequence to date.A tripartite viscosity pattern is identified at isothermal conditions: 1) during the fissure opening and establishing stage (days 1–20) a linear decrease in melt viscosity occurred; 2) during most of the eruption duration (days 21–70) viscosity was constant and 3) from day 70 until the end of the eruption viscosity increased again. We interpret this pattern as magma being extracted from different parts of the plumbing system over the course of the eruption. Accordingly, we show that viscosity time series can help shed light on some of the complexities of volcanic plumbing system. Additionally, the presented results highlight the monitoring potential of the viscosity assessment approach, specifically in regard to forecasting eruption behavior using direct information about magma mobility and detecting changes in magmatic plumbing system dynamics.

Spread or Splash: The Ubiquitous Role of Droplets in Mafic Explosive Eruptions

AbstractMagma fragmentation is an essential process driving explosive volcanic eruptions, generating a distribution of pyroclasts with characteristic shape and grain size. These characteristics are often used to inform on the energetics of magma fragmentation and the associated eruption style and intensity. However, a portion of these pyroclasts, droplets when still in the molten state, are likely to be generated through impact mechanisms (i.e., collisions), and subsequent secondary fragmentation (i.e., splashing). Here, we successfully apply and dynamically scale concepts and findings of liquid droplet impacts in engineering to magma fragmentation processes in volcanology. We compile and model physical data for two mafic melt compositions (kimberlite and basalt) and use specific eruption examples from Igwisi Hills, Kīlauea and Stromboli volcanoes to define composition‐specific impact dynamics. Pyroclast impact dynamics have a direct control on in‐conduit processes, eruption dynamics, and ash dispersal. For low viscosity mafic melts such as kimberlite and basalt, pyroclast impacts can lead to both splash and deposition on the conduit wall, resulting either in conduit clearing or conduit narrowing, respectively. In both cases, shifting the impact regime toward surface deposition will lead to an inexorable decay in explosiveness, potentially switching the eruption style to effusive behavior. This has direct consequences for the transport of volcanic ash at the surface and inferring magma fragmentation processes (e.g., energies) from the depositional record.

Detecting covolcanic ionospheric disturbances using GNSS data and a machine learning algorithm

Many natural and man-made phenomena cause ionospheric responses that can be captured in total electron content data obtained from Global Navigation Satellite System observations. However, the increasing volume of the data poses challenges for its analysis. This study provides an algorithm for detecting covolcanic ionospheric disturbances in total electron content time series based on machine learning. Using the Sarychev Peak eruption (June 11–16, 2009) as an example, we identified and labeled the observational data, proposed data features, and generated datasets. The design and number of features were chosen considering the computational efficiency of the algorithm and its potential applicability in monitoring systems. A machine learning model based on a gradient boosting technique was trained and achieved a Matthews correlation coefficient of 0.86 on the test dataset, indicating the high quality. The proposed algorithm detects 96% of the disturbances in the datasets with a minimal number of false positives (48 out of 200 test files), exhibiting a significant improvement compared with the conventional STA\\LTA algorithm, which detected only 11% of the disturbances. The validation of the algorithm on data corresponding to the Calbuco (2015) and Hunga Tonga-Hunga Ha’apai (2022) volcanoes eruptions showed 94% and 81% of the disturbances detected, respectively.

Eruptive Products from the Bezymianny Volcano Eruption of April 7, 2023

Eruptive Products from the Bezymianny Volcano Eruption of April 7, 2023

Effects of a recent volcanic eruption on the isolated population of the iconic red-billed chough in La Palma, Canary Islands.

The effects of volcanic eruptions on ecosystems, particularly on oceanic islands, have been widely studied because of their important role in land formation, climate patterns and biological processes. Although these phenomena can lead to habitat loss, population decline and even species extinction, their effects on isolated populations, especially vertebrates, are not fully understood due to the paucity of pre-eruption data and in situ observations. Here, we assess the impact of the recent eruption of the Tajogaite volcano in La Palma, Canary Islands, on a unique population of red-billed choughs (Pyrrhocorax pyrrhocorax), an emblematic bird species that symbolises the natural heritage of the island. Pre- and post-eruption surveys showed that the eruption did not significantly affect the overall size or distribution of the population, although the number of choughs decreased after the eruption in the northern and central roosts, and increased in the southern ones. Although the eruption resulted in the release of toxic gases and ash, the observed changes in chough distribution and numbers could be attributed to environmental variability and the use of different foraging areas by individuals rather than direct effects of the volcano. The high mobility of choughs may have allowed them to avoid the negative effects of the volcano in the immediate aftermath of the eruption. Future studies are recommended to assess the long-term effects of volcanic ash on feeding habitats and the possible accumulation of contaminants, such as heavy metals, in the food chain. This will allow not only to monitor the presence of these compounds in ecosystems, but also to understand the response of this species to environmental changes and ensure its conservation.

Impact of the “Mengabu (Facing Ash Storms) Disaster Preparedness” Program on Adolescents’ Knowledge About Disaster Preparedness in Kresik Tuo Village, Kayu Aro District, Kerinci Regency, Jambi

Natural disasters have become an integral part of people's lives in Indonesia, disrupting daily activities and causing significant impacts. Indonesia, located in the Ring of Fire, faces a high risk of volcanic eruptions, including the active Mount Kerinci which has the potential to cause disasters such as volcanic ashfall. Kresik Tuo Village, located near Mount Kerinci, faces a direct threat from this eruption. The community, especially the youth, need to improve their preparedness and knowledge to deal with potential disasters. The "MENGABU Siaga dalam Bencana" program is designed to improve the preparedness of the Kresik Tuo Village community in dealing with potential volcanic ashfall, with the hope of contributing to the development of community preparedness strategies in disaster-prone areas. To improve the knowledge of youth in Kresik Tuo Village related to disasters and disaster preparedness. The study used the Pre-Experimental research method with a Prepost Test Design. Sampling used a non-probability sampling technique with convenience sampling according to the inclusion and exclusion criteria of 40 respondents. Wilcoxon test shows that there is a significant increase in the knowledge of youth preparedness for the eruption of Mount Merapi after being given the "Mengabu Siaga dalam Bencana" program. All respondents experienced an increase in knowledge, as indicated by a positive ranks value of 40 and a p value = 0.000. Conclusion: The results of the study indicate that there is a significant effect of the "Mengabu (Mengabu Storm Ash) Siaga Dalam Bencana" Program on Youth Preparedness Knowledge for Disasters in Kresik Tuo Village, Kayu Aro District, Kerinci Regency, Jambi in increasing youth knowledge.

Manajemen Risiko Usahatani Cabai Rawit: Studi Kasus Di Kawasan Gunung Merapi

Cayenne pepper (Capsicum frutescens L) is a common horticultural commodity cultivated by farmers in the Mount Merapi area. Farmers in this region face the risk of fluctuating productivity due to unpredictable volcanic eruption activities. This study aims to describe the types, sources, and levels of risk, analyze and examine risk management in bird's eye chili farming based on risk levels, risk mapping, and the total household income analysis of bird's eye chili farmers in Mount Merapi. The sample consists of 100 farmers selected through simple random sampling, with the criteria being residents who have been farming cayenne pepper for 10 years in the Mount Merapi area, growing cayenne pepper as the main commodity on their farmland, and farmers with and without additional income sources outside of farming. Data analysis includes risk analysis, total household income analysis, and descriptive quantitative analysis. In Pakem Subdistrict, the coefficient of variation values for production, price, and profit risks are 0.67, 0.08, and 1.20, respectively. In Dukun Subdistrict, these values are 0.55, 0.14, and 2.40, respectively. Lastly, in Selo Subdistrict, the values are 0.45, 0.07, and 0.84, respectively. Household income analysis is divided into two categories: farmers with additional income sources outside of farming and those without additional income sources in each district. The highest average total household income of cayenne pepper farmers is found in Selo Subdistrict. Important considerations in agricultural risk management include providing insurance for cayenne pepperi, market development, and land diversification.

The relative contributions of internal variability and external forcing to Pacific Walker Circulation over the last millennium

Abstract Pacific Walker Circulation (PWC) is an important component of tropical atmospheric circulation. Current studies have mainly focused on PWC changes over recent decades and the near future, while less effort has been devoted to long-term PWC variations. In this study, we investigate PWC changes over the last millennium (LM) based on the Community Earth System Model Last Millennium Ensemble (CESM-LME). The simulated PWC variations show no significant trend but do reveal decadal fluctuations during the LM, which underestimate the strengthened LIA-MCA PWC differences indicated by proxy-based reconstructions. A quantitative estimation of the contributions made to PWC variability from internal variability and external forcing is conducted by using multiple linear regression (MLR) analysis. The internal variabilities contribute approximately 80% to the changes of PWC during the LM, among which the Interdecadal Pacific Oscillation (IPO) has the largest contribution. In the positive phase of the IPO, the Indo-Pacific sea-level pressure (SLP) gradient decreases, and anomalous westerlies occur in the tropical western Pacific, corresponding to a weakened PWC. The relationships between the IPO and PWC show multidecadal to centennial fluctuations, suggesting that other internal modes or external forcings may have modulated the IPO-PWC relationship. Volcanic forcing is also an important contributor to PWC variability during the LM. The simulated PWC significantly weakens and lasts for 1-2 years after large volcanic eruptions. The El Niño-like SST pattern and the corresponding zonal SLP gradient lead to the PWC weakening following large volcanic eruptions.

СЕМЕЙСТВА ДЛИННОПЕРИОДНЫХ ЗЕМЛЕТРЯСЕНИЙ НА ВУЛКАНЕ МОЛОДОЙ ШИВЕЛУЧ (РОССИЯ) В 2022–2023 ГОДАХ

On April 10, 2023, the strongest eruption of the Young Shiveluch volcano ( Russia, Kamchatka Peninsula) in the last 60 years occurred. The eruption was preceded by a long seismic activity since the end of July 2022. Earthquakes during this period were mainly long-period, occurring in the area of the extruding extrusive dome. The paper describes the grouping of earthquakes into families according to the similarity of waveforms, and their comparison with the activity of the Young Shiveluch volcano. For the period of monotonic, with a constant rate, dome extrusion, when the pressure in the channel was constant, earthquakes were grouped into long-term families. The period before the culmination phase is characterized by a greater number of families, which is interpreted as an indicator of instability of the environment. Such an increase in the number of earthquake families allows us to predict more accurately the beginning of the culmintion phase of eruptions of andesitic Young Shiveluch volcano.

The Khonkho tephra: A large-magnitude volcanic eruption coincided with the rise of Tiwanaku in the Andes

We report a tephra deposit in the southern Lake Titicaca Basin, Bolivia, which was deposited by a major, previously unrecognized eruption sometime between AD 400 and 720. Archaeological data suggest these centuries were characterized by a substantial community migration to Tiwanaku, where social interaction networks gave birth to one of the Andes’ first large complex societies. Here we provide an initial characterization of this tephra, based on samples from the archaeological site Khonkho Wankane. The same tephra is present at two other archaeological sites in the region. Given the great distance to the nearest active volcano, this tephra layer likely derives from a large-magnitude, Late-Holocene explosive eruption of a Central Andean volcano. We suggest that this major event be included in the human history of the region, given its inferred magnitude and wide dispersal area. Future research could confirm the Khonkho tephra at other sites, identify the source volcano, estimate its volume, and more precisely date the eruption.

Genesis of the Ulaan silver-lead–zinc deposit in Northeast Mongolia: Constraints from S and Pb isotopes, together with U-Pb and Rb-Sr geochronology

The Ulaan silver-lead–zinc deposit (hereinafter referred to as the Ulaan deposit) is identified as the largest silver-lead–zinc polymetallic deposit in Mongolia, with proved reserves including 2,240 tons of silver (Ag; average grade: 49 g/t), 440,000 tons of lead (Pb; average grade: 1.13 %), and 810,000 tons of zinc (Zn; average grade: 2.07 %). However, the genesis of this deposit remains unclear. The Ag-Pb-Zn ore bodies in the deposit, occurring as cylinders in shape within the Middle-Late Jurassic rhyolites, are governed by a concealed breccia pipe. The ore minerals include galena, sphalerite, and pyrite, followed by chalcopyrite, hematite, stibnite, and siderite. The primary alterations of the surrounding rocks include silicification, chloritization, kaolinization, argillization, carbonatization, and skarnization. The Rb-Sr dating of sulfide minerals and associated vein minerals in the ores yielded isochron ages varying in a range of 146 ± 3 Ma (n = 6, MSWD=1.3), suggesting mineralization during the Late Jurassic. The δ34S values of sulfide minerals in the ores range from 1.6 ‰ to 4.3 ‰, suggesting that the sulfur originated primarily from magmas or deep sources. The isotopic compositions of coexisting sphalerite-galena minerals in the deposit revealed mineralization temperature estimates ranging between 331 °C and 449 °C, indicating a medium- to high-temperature ore-forming conditions. The sulfide minerals exhibit 208Pb/204Pb ratios ranging from 38.138 to 38.301, 207Pb/204Pb ratios from 15.543 to 15.594, and 206Pb/204Pb ratios from 18.318 to 18.354, suggesting that ore-forming metals, represented by Pb, also originated primarily from mantle source. The zircon U-Pb dating of rhyolites in the ore-hosting strata and ore-controlling breccia pipes yielded ages of 160.6 ± 1.7 Ma (n = 24, MSWD=0.68) and 161.6 ± 1.6 Ma (n = 30, MSWD=0.89), respectively, indicating volcanic eruptions during the early Late Jurassic. These ore-hosting rhyolites exhibit characteristics of A-type rhyolites, suggesting that they were formed in an intracontinental extensional environment. These rhyolites share similar rare earth element (REE) distribution patterns with fluorite formed in the main mineralization stage, suggesting a genetic link between the mineralization and magmatic processes. This study proposes that the Ulaan deposit was a hydrothermal deposit formed in an extensional environment following the closure of the Mongol-Okhotsk Ocean, with ore-forming metals and hydrothermal fluids associated with volcanic rocks or magmatic-hydrothermal processes.

Cross-fade sampling: extremely efficient Bayesian inversion for a variety of geophysical problems

SUMMARY This paper introduces cross-fade sampling, a computationally efficient Markov Chain Monte Carlo simulation method that uses a semi-analytical approach to quickly solve Bayesian inverse problems that do not themselves have an analytical solution. Cross-fading is efficient in two ways. First, it requires fewer samples to obtain the same quality simulation of the target probability density function (PDF). Secondly, it is much faster to evaluate the posterior probability of each sample than conventional sampling methods for simulating Bayesian posterior PDFs. Conventional methods require evaluating the prior probability (which describes your a priori constraints) and data likelihood (which describes the fit between the observations and the predictions of the model) for each sample model. However, cross-fading does not require evaluating the data likelihood, meaning that ‘big data’ can be fit with zero additional computational cost. Further, the cross-fading approach can be used to calculate the marginal likelihood associated with a model design, facilitating model comparison and Bayesian model averaging. Topics covered in this paper include derivation of the cross-fade approach and how it can be used to simulate Bayesian posterior PDFs and compute the marginal likelihood, discussion of the class of problems to which cross-fading can be applied (with examples from earthquake statistics, earthquake ground motion modelling, volcanic eruption forecasting, and finite fault slip modelling), demonstration of efficiency relative to existing sampling methods and discussion of how cross-fading can be used to account for prediction errors (i.e. epistemic errors) as part of the geophysical inverse problem.

Observations of Tsunami Waves on the Pacific Coast of Russia Originating from the Hunga Tonga-Hunga Ha'apai Volcanic Eruption on January 15, 2022

The Hunga Tonga-Hunga Ha´apai volcanic eruption on January 15, 2022 generated a tsunami that affected the entire Pacific Ocean. Tsunami from the event have been generated both by incoming waves from the source area, with a long-wave speed in the ocean of ~ 200–220 m/s, and by an atmospheric wave propagating at a sound speed ~315 m/s. Such a dual source mechanism created a serious problem and was a real challenge for the Pacific tsunami warning services. The work of the Russian Tsunami Warning Service (Yuzhno-Sakhalinsk) during this event is considered in detail. The tsunami was clearly recorded on the coasts of the Northwest Pacific and in the adjacent marginal seas, including the Sea of Japan, the Sea of Okhotsk and the Bering Sea. We examined high-resolution records (1-min sampling) of 20 tide gauges and 8 air pressure stations in this region for the period of January 14–17, 2022. On the Russian coast, the highest waves, with a trough-to-crest wave height of 1.3 m, were recorded at Malokurilskoe (Shikotan Island) and Vodopadnaya (the southeastern coast of Kamchatka). Using numerical simulation and data analysis methods, we were able to separate the oceanic “gravity” tsunami waves from propagating atmospheric pressure waves. In general, we found that on the outer (oceanic) coasts and the southern coast of the Sea of Okhotsk, oceanic tsunami waves prevailed, while on the coast of the Sea of Japan, oceanic and atmospheric tsunami waves had similar heights.