Volcano Area Research Articles

Utilization of geospatial technology to monitor vegetation recovery after forest and land fires in 2023 in the Bromo Volcano Area, Indonesia

Abstract This study was conducted to identify the condition of savannah fields after forest and land fires in parts of the Bromo Volcano area, East Java, Indonesia, in September 2023. The research was conducted through remote sensing technology and integrated geographic information systems. The data used is remote sensing multitemporal data in the form of Sentinel 2 imagery. Sentinel 2 imagery is remote sensing data generated from Sentinel satellite recording. Sentinel 2 imagery was used in this study because it has excellent spatial and temporal resolution. The spatial resolution of Citra Sentinel is 10 meters, and its temporal resolution is ten daily. The data were analyzed using spatial and temporal approaches to determine the condition of the savanna before and after forest and land fires. The software used to analyze the data and visualize spatial information is Google Earth Engine (GEE) and Arc Map Version 10.6. The data analysis methods used include changes in the detection of burned areas using the normalized burn ratio (NBR) method, making fire class classifications based on the U.S. Geological Survey (USGS), post-fire monitoring using the normalized difference vegetation index (NDVI), and monitoring vegetation recovery from post-NDVI values—fires by comparing in different years in the same month using the fishnet method. The temporal months chosen to analyze the recovery process are September, October, November, and December 2023. Based on the study’s results, it is known that in September and October 2023, there has been no vegetation recovery. Vegetation began to look restored in November and December 2023.

IDENTIFIKASI JENIS TANAH DI KAWASAN GUNUNG TUJUH RESORT KERINCI UTARA, TAMAN NASIONAL KERINCI SEBLAT

Indonesia is known as the country that has the most active volcanoes, namely 30% in the world. The type of igneous rock determines the type and characteristics of the soil that will be formed. The soil in Indonesia's tropical forest volcano areas is dominated by volcanic soil or Andosol soil. The TNKS area is one of the areas that has Andosol soil. This research was conducted in March 2024 and was located in the lower mountain area of the Gunung Tujuh Region, Kerinci Seblat National Park using a field survey method. The stages of this research include taking soil samples in 6 layers with a height of each soil being 20 cm. The soil that has been taken is then analyzed using the Munsell Soil Color Chart book and the sense of touch directly. The research results show that the Hue value is the same in each layer, namely 7.5 YR and the color shows differences according to the depth of the soil, namely very dark, strong black, strong brown and dark brown. The soil structure is dominated by a crumb structure and texture of sandy loam, dusty clay loam and clay loam.

Insight into the 2021 Semeru volcano eruption from rapid monitoring of its pyroclastic deposits using Google Earth Engine and multi-sensor data

The objective of this study is to map the pyroclastic deposits resulting from the Semeru eruption in 2021 and to analyse the process of pyroclastic deposit formation, including the tephra and lithification phases, using multi-sensor data. The distribution of pyroclastic deposits was mapped using machine learning algorithms, Sentinel 2 and Sentinel 1 imagery on Google Earth Engine. Data acquisition in the Semeru volcano area was conducted both prior to and following the 2021 eruption. Additionally, field investigations were conducted to analyse the distribution of pyroclastic deposits, including the characteristics of individual layers, the lithification process of pyroclastic layers, and their relationship with the characteristics of the eruption. The results demonstrate that pyroclastic deposits in the proximal facies are composed of lithic, lapilli tuff, lava and tuff. The mapping results also indicate the presence of volcanic ash deposits in the central facies or summit area of Semeru, exhibiting distinctive characteristics associated with volcanic ash. The 2021 eruption has also resulted in rapid changes to river morphometry, as evidenced by notable shifts in a significant decrease in pixel values for NDVI (−0.0781-0.0625), a significant increase in pixel frequency of EVI (1800–6000), and MNDWI (1700–3000), respectively. The change of pyroclastic fall into consolidated tephra occurred from December 2021 to May 2023, where in May 2023 volcanic ash had changed into tuff and lapilli had changed into lapilli tuff. Furthermore, data from Sentinel-1 indicated that pyroclastic flows could be identified using both vertical and horizontal polarization. It can therefore be concluded that the 2021 eruption of Semeru exhibited distinctive characteristics of pyroclastic deposits, where some of the characteristics of the pyroclastic distribution can be monitored rapidly with Google Earth Engine. Therefore, the use of Google Earth Engine with integration of radar and optical data can be recommended to mapping pyroclastic deposits rapidly.

Seismic vulnerability distribution of the earthquake prone area in Central Aceh

Abstract Central Aceh is known as an earthquake-prone area due to the presence of the Sumatra Fault and secondary fault crossing the area resulting the M 6.1 earthquake in 2013. The objective of the research is to investigate seismic vulnerability of Central Aceh. Microtremor observations were conducted at 25 locations in Central Aceh analysed using the Horizontal to Vertical Spectral Ratio (HVSR). Seismic amplification is represented by the maximum values of H/V. The dominant frequency f0 representing the sediment thickness was obtained when the H/V curve is maximum. The frequency values ranged from 14.9 to 25.9 Hz, and the seismic vulnerability values varied from 0.02 to 3.1. The top soil consists of thin layers of sedimentary material dominated by tertiary rocks. The rocks are classified as Type IV and Class I based on the dominant frequency values. This result is consistent with the geology, consisting of sedimentary and volcanic rocks. Areas with a seismic vulnerability value > 1.0 is considered to have a high risk of earthquake damage because they are likely to experience earthquake amplification. Areas with seismic vulnerability value > 1.0 are found in West Aceh and the Geureudong volcano area.

Imaging the Rivera and Cocos Plates Shape in Western Mexico from Local Seismicity Studies

Abstract The geometry of the Rivera and Cocos plates subduction below the North American plate has been studied using a total of 5337 hypocenters located in the region of Nayarit, Jalisco, Colima, and Michoacán states in western Mexico. Our results show that seismic features of the subduction at Jalisco block (JB), Colima rift zone (CRZ), and Michoacán block are well differentiated. Our study supports the hypothesis that the Jalisco subduction zone is composed of two fore-arc blocks, Banderas and Jalisco fore-arc blocks, separated by the Ipala canyon (Bandy fault). In this region, the crustal thickness of the JB is ∼30 km, whereas the Michoacán block is 35 km thick. We identified four crustal blocks along the coast in the JB from shallow seismicity data. Moreover, we found that the Rivera plate is segmented into three sections with different sizes and geometries evidenced by deep seismicity data. There is no evidence of a slab below the CRZ due to seismicity being scarce, except on the coast and the Colima volcano area where deep earthquakes (>70 km) are observed, which could be related to magmatic processes. The seismicity of the subduction process of the Cocos plate appears homogeneous, except for a seismic cluster at the mouth of Coalcomán River, where the epicentral area of the 1973 and 2021 earthquakes is located. Our results show that the Cocos plate is subducting with an inclination of 24°–30° and is slightly bent in a northwesterly direction. Therefore, our study suggests that current seismotectonic models of the region should be revised.

Analysis of fractures generated by faults at micro- and macro-scale and the influence on the secondary permeability: application to the Nevado del Ruiz area (Colombia)

This research contributes to the knowledge of the geothermal area of the Nevado del Ruiz Volcano (Colombia) by analyzing the secondary permeability and connectivity of fractures at microstructural and macrostructural level. Although the Nevado del Ruiz Volcano (NRV) area has had geothermal exploration studies for power generation since 1968, there is still no exploitation of its geothermal resources. The NRV geothermal reservoir is characterized by a low primary permeability and the presence of several geological faults crossing a tectonically active and complex region. The analysis was performed comparing a zone affected by intense faulting with another one characterized by the same lithology, but with less influence of faulting and located further from the volcano. Fractures were characterized at outcrops with the window sampling method, and petrographic analysis was performed to confirm the mineralogy of samples collected. At the microstructural scale it was found that faulting does not necessarily influence the interconnectivity of fractures, but it does influence their intensity, quantity, and strike. To analyze the influence of fractures on groundwater flow, it is suggested to consider three main aspects: secondary permeability, connectivity, and fracture intensity. The lithology of major geothermal interest in the NVR area (Pes) presented greater connectivity and fracture intensity, which, combined with the high foliation observed in field, increase its effective permeability. The secondary permeability of different lithologies in the NRV area ranged between 1.15 × 10–6 and 10.32 × 10–7 m2. Most of the hot springs were in areas of high macrostructural connectivity, supporting the idea that groundwater flow is dominated by the secondary permeability of rocks. Estimation of the secondary permeability and identification of areas of high fracturing and connectivity, contributes to the understanding of the NRV geothermal area, which is a key aspect when drilling for successful well production. The methodology presented is useful in the initial exploration phase in fractured geothermal reservoirs.

A Geophysical Investigation of the Pâclele Mici Mud Volcano in Romania Using Deep Geoelectrical Surveys

This work presents a case study of a geoelectrical exploration of understudied mud volcanoes in Romania, specifically the Pâclele Mici mud volcano from Buzău County. Using a geoelectrical technique facilitated by the distributed network of V-FullWaver equipment, we present, to our knowledge, the first deep 3D case study of a mud volcano in the country. The findings indicate that while geoelectrical surveys in such environments are met with important challenges in terms of soil conductivity, they nonetheless provide a viable approach to uncovering the complex structures and processes of mud volcanoes. We map a part of the mud volcano, showing that the active subsurface part corresponds only partly with what is visible on the surface, and suggest a framework for an in-depth analysis of the extensive mud volcano area.

Analysis of Subsurface Resistivity Distribution of the Kelud Volcano Using Magnetotelluric Method

Indonesia has the world’s most active volcanoes, with more than 30% of them lying within its borders. The Kelud volcano erupted in 2007, resulting in the development of a Lava Dome in the crater lake. This phenomena is known as effusive. The magnetotelluric approach is used in this study to predict the subsurface resistivity distribution in the Kelud volcano area. Data was obtained at 10 different locations around the Kelud volcano area. The subsurface structure of the Kelud Volcano can be identified based on resistivity values that show significant differences, according to the modelling results. According to the findings, the surface resistivity surrounding the Kelud volcano ranges from 1 to 100 ohm. The main structure of the hydrothermal system’s clay cap was discovered at a depth of 1000 m from the surface in the western part of the summit, with resistivity values ranging from 1-10.m. With a resistivity of more than 100 ohm.m., a high resistivity forming a conduit appears in the centre of the summit area. The subsurface structure values obtained indicate that these structures are volcanic.

Comparative Study of Literacy Enhancement on Volcanic Disaster Reduction for the Residents and Visitors in Mt. Ontakesan and Other Volcanic Areas

After the eruption of Mt. Ontakesan Volcano in 2014, Ontakesan Volcano Laboratory, Nagoya University was established in 2017 to keep and develop the face-to-face relationship between the local community and volcano experts. In 2018, the Ontakesan Volcano Meister System also started to undertake activities for volcanic disaster management and promotion of the regional economy. Additionally, two visitor centers opened in Kiso Town (at the foot of Mt. Ontakesan) and Otaki Village (at the entrance of the trail to the summit) in 2022. We compared these activities in the Ontakesan area with other volcanic areas (Usuzan, Bandaisan, Hakoneyama, Fujisan, Asosan, Unzendake, and Sakurajima) from the perspective of literacy enhancement on volcanic disaster management. We made an interview survey of the organizations/facilities responsible for volcanic disaster prevention education in these volcano areas to evaluate the activity of the Ontakesan Voclano Meisters. We considered common and specific issues among them to clarify the characteristics of literacy enhancement for volcanic disaster reduction in the Ontakesan area. In all the organizations that we surveyed, there is a common emphasis on the education for children to transfer disaster memories to the next generation and to raise their awareness of disaster prevention. Though the Ontakesan Volcano Meisters have less interaction with the local residents than other areas, they exceed in the enlightenment for climbers and have made efforts to raise the safety awareness of climbers on site since their establishment.

Diversity and Functional Role of The Coleoptera Order in The Nglanggeran Ancient Volcano Area, Yogyakarta

The aim of this research that was conducted in the Nglanggeran Ancient Volcano Area Yogyakarta was to determine the diversity and functional role of Coleoptera in the area. The research was conducted by survey, with observation method, in March-April 2021. Data were collected through purposive random sampling with Sorting, Yellow Pan Trap, and Hunting methods. The results of research at six stations indicated the presence of 30 individuals belonging to four families of Arthropoda order Coleoptera, namely Lilioceris lilii (Chrysomelida), Charidotella sexpunctata (Chrysomelidae), Lytta stygica (Meloidae), Anisodactylus nigerrimus (Carabaeidae), and Harmonia axyridis (Coccinellidae). Based on their functional roles, the Carabaeidae and Coccinellidae families that dominate this finding act as predators, while the Chrysomelidae and Meloidae families act as herbivores. The results of the analysis using PAST 4.07b software show that Coleoptera diversity in the area is included in the low diversity index category with a value of 0.773, a low species richness index with a value of 0.6213, and an evenly distributed abundance index with a value close to 1.ABSTRAK: Penelitian yang dilakukan di Kawasan Gunung Api Purba Nglanggeran Yogyakarta ini bertujuan untuk mengetahui keanekaragaman dan peran fungsional Coleoptera di kawasan tersebut. Penelitian dilakukan secara survei, dengan metode observasi pada bulan Maret-April 2021. Data dikumpulkan melalui purposive random sampling dengan kombinasi metode Sorting, Yellow Pan Trap, dan Hunting. Hasil penelitian di enam stasiun menunjukkan adanya 30 individu yang termasuk ke dalam empat famili Arthropoda ordo Coleoptera yaitu Lilioceris lilii (Chrysomelida), Charidotella sexpunctata (Chrysomelidae), Lytta stygica (Meloidae), Anisodactylus nigerrimus (Carabaeidae), dan Harmonia axyridis (Coccinellidae). Berdasar peran fungsionalnya, famili Carabaeidae dan Coccinellidae yang mendominasi temuan ini berperan sebagai predator, sedangkan famili Chrysomelidae dan Meloidae berperan sebagai herbivor. Hasil analisis menggunakan software PAST 4.07b menunjukkan bahwa keanekaragaman Coleoptera di kawasan tersebut termasuk ke dalam kategori indeks keanekaragaman rendah dengan nilai 0,773, indeks kekayaan jenis rendah dengan nilai 0,6213, dan indeks kelimpahan yang merata dengan nilai mendekati 1.

Crustal Thickness and Vp/Vs Ratio Determination beneath Tangkuban Parahu Volcano, West Java, Indonesia using Receiver Function Analysis

Tangkuban Parahu, an active stratovolcano located approximately 15 km north of Bandung City in Indonesia, is the focal point of this study. The research aims to examine seismic structures within the crust beneath the Tangkuban Parahu Complex. To accomplish this, a teleseismic receiver function method was employed, utilizing broadband seismic stations along a seismological profile within the Tangkuban Parahu Volcano area. Waveform data were collected during the period from October 24, 2021, to March 31, 2022, for analysis. Various seismic wave phases, including P, Ps, PpPs, and PsPs, were identified in the recorded waveforms, within a time window extending from -2 seconds before the onset of the P-wave to 20 seconds after its onset. The analysis and modelling were conducted using the H-κ stacking receiver function technique. The findings of the H-κ stacking receiver function revealed notable variations in crustal structures, encompassing crustal thickness and the average crustal composition, as indicated by the Vp/Vs ratio, within the Tangkuban Parahu Volcano area. Preliminary results suggest that the crust beneath Tangkuban Parahu, estimated based on data from single seismic station, possesses a thickness of approximately 32.3 km, with a corresponding Vp/Vs ratio of around 1.746.

Integration of Residual Terrain Modelling and the Equivalent Source Layer Method in Gravity Field Synthesis for Airborne Gravity Gradiometer Test Site Determination

To calibrate airborne gravity gradiometers currently in development in China, it is urgent to build an airborne gravity gradiometer test site. The site’s selection depends on the preknowledge of high-resolution gravity and gradient structures. The residual terrain modelling (RTM) technique is generally applied to recover the short-scale gravity field signals. However, due to limitations in the quality and resolution of density models, RTM terrain generally assumes a constant density. This assumption can introduce significant errors in areas with substantial density anomalies and of reggued terrain, such as volcano areas. In this study, we promote a method to determine a high-resolution gravity field by integrating long-wavelength signals generated by EGM2008 with short-wavelength signals from terrain relief and shallow density anomalies. These short wavelength signals are recovered using the RTM technique with both constant density and density anomalies obtained through the equivalent source layer (ESL) method, utilizing sparse terrestrial gravity measurements. Compared to the recovery rate of 54.62% using the classical RTM method, the recovery rate increases to 86.22% after involving density anomalies. With this method, we investigate the gravity field signals over the Wudalianchi Volcano Field (WVF) both on the Earth’s surface and at a flight height of 100 m above the terrain. The contribution of each part and their attenuation characters are studied. In particular, the 5 km × 5 km area surrounding Bijiashan (BJS) and Wohushan (WHS) volcanos shows a strong gravity signature, making it a good candidate for the test site location. This study gives the location of the airborne gravity gradiometer test site which is an essential step in the instruments’ development. Furthermore, the method presented in this study offers a foundational framework for future data processing within the test site.

Pemanfaatan Potensi Wisata Berbasis Sumber Daya Alam Dan Budaya (Studi Kasus Desa Ekowisata Pancoh Yogyakarta)

Pancoh Ecotourism Village is located in the Yogyakarta Merapi Volcano area. The location of the village whichis quite high and cool makes many people develop natural and cultural products to attract tourists. The researchobjective is to examine the utilization of natural and cultural resources as a tourist attraction. Tourism activitiespresented to tourists and management of destinations with the concept of Ecotourism. The research method usedis descriptive qualitative research with an exploratory approach. Methods of data collection by observation,interviews, and documentation. Investigation of informants using purposive sampling with a total of 10informants. The data analysis method used is an interactive model consisting of data collection, data reduction,data presentation, and drawing conclusions. The results of this study are natural resources in the form ofprocessing the potential of the natural environment and not making many changes to the actual conditions. Thetourist attractions are river crossings, rice field plows, fish ponds, embung, salak gardens, and biogas. Local artsand culture are used as tourism activities such as the Wiwitan Tradition and playing gamelan. Tourists can learnabout preserving traditional ceremonies and traditional musical instruments. Local people are involved in alltourism activities. So that people can benefit economically, on the other hand, nature, and culture can still beproperly preserved. Pancoh Ecotourism Village Management can be an example of a destination that maximizesthe natural and cultural potential of the village.

Composition of Phenocrysts in Lamproites of Gaussberg Volcano, East Antarctica

—This paper presents numerous new data on the geochemical composition of olivine, clinopyroxene, and leucite phenocrysts, as well as spinel inclusions in olivine and quench glass from lamproites of Gaussberg volcano (East Antarctica). Most of the olivine phenocrysts in the Gaussberg lamproites are high Mg varieties (Fo89–91) with elevated Ni contents (up to 4900 ppm) and high Ni/Co ratios. According to data of about 320 clinopyroxene analyses, two groups of diopsidic phenocrysts have been established. Group I consists mainly of high-Mg varieties (Mg#>80), while group II clinopyroxenes are less magnesian (Mg# 52–80). The main difference between the clinopyroxenes of the two groups is the elevated contents of Al2O3, FeO and reduced TiO2, Cr2O3, and NiO in the compositions of group II compared to group I, as well as different contents of trace elements, which may reflect their crystallization from different types of primary melts. According to the study of ~550 grains of leucite phenocrysts in the Gaussberg lamproites, it was shown that they correspond to the ideal stoichiometry of leucite K[AlSi2O6] and are enriched in Na2O (0.05–0.35 wt %), but depleted in K2O (19.9–20.9 wt %) compared to leucites from lamproites of other provinces. The BaO content reaches 0.3 wt %, SrO –0.04 wt %. The iron content in most leucite phenocrysts varies within 0.7–1.2 wt % Fe2O3, but some grains have the low Fe2O3 contents (<0.5 wt %). In leucite microlites of the groundmass and rims of phenocrysts, the Fe2O3 content can reach 2.4 wt %, which may indicate more oxidized conditions at lava eruption. Based on the study of natural samples, existing experimental data and numerical models, the order and conditions of crystallization of the Gaussberg lamproites were obtained. Crystallization proceeded in the following order: chromian spinel → chromian spinel + olivine → olivine + leucite (± chromian spinel) → olivine + leucite + clinopyroxene (± chromian spinel). The near-liquidus assemblage represented by high-Mg olivine phenocrysts with inclusions of Cr-spinel was formed in the temperature range from 1180 to 1250°C. Further crystallization of the melt with the formation of an association of olivine+leucite+clinopyroxene phenocrysts could occur at pressures below 2 GPa and temperatures of 1070–1180°C, corresponding to the presence of water in the magmatic system. Estimates of the redox conditions of crystallization of lamproites obtained using different oxybarometers vary in a wide range from QFM-0.5 to QFM+2.3. The elevated Ni contents in liquidus olivines of Gaussberg indicate the high nickel contents in the source. It is shown that the formation of ultra-alkaline magmas in the Gaussberg volcano area is likely related to melting of the continental lithosphere, which was heterogeneous and included both the peridotite mantle and hydrous pyroxenite fragments.

3D inversion modelling of gravity data for identification of subsurface structures in the mud volcano area of Sedati, Sidoarjo

Many mud volcanoes are found in Central Java and East Java in the north, but research on mud volcanoes is still limited. This research focuses on the Sedati mud volcano area, Sidoarjo with a research area of 500x400 meters. Measurement of gravity method data with 88 points spaced 50 meters to determine the value of rock density and subsurface structure of Sedati mud volcano area. From the data that has been obtained, data processing is carried out to obtain a map of the distribution of regional and residual gravity anomaly values. From the anomaly data, 3D inversion was carried out to obtain a map of the subsurface structure. The 3D gravity inversion modelling results show that there is high density rock block which is interpreted as a basin that holds the reservoir from the mud volcano. Near the surface and around the mudflow in the study area, the distribution of low density is caused by the presence of mud content. There is a possibility that there is a fault zone with a west-east direction from the study area. The results of the 3D gravity model incision show that the weak zone in the study area is a zone of accumulation of mud which has a density value of 1.8 g/cm3 at a depth of 20 meters to 500 meters.

Identification of Permeable Structures and Heat Source in the Geothermal Working Area of Galunggung Volcano and the Heat Source Connectivity to the Karaha-Cakrabuana Area Using Gravity Data

Galunggung volcano area is a geothermal concession area that adjacent with Karaha-Cakrabuana concession area with a distance around 1 km. Indonesian Government planning to build power plant in 2025 so additional research needed to support the plan. Gravity survey could help in identifying permeable structure (fault) as well as heat source to a certain depth. The results of data processing showed the presence of faults seen on the FHD, SVD, and ABL residual maps, while for heat sources it was shown from the closed contour patterns on the ABL, residual, and regional maps. Derivative analysis in strengthens the position and type of fault from the match between the maximum FHD value and zero SVD value. From these results, identified the existence of three faults in the study area and were all identified as normal faults. 3D modelling gave a picture of density contrast in research area. From the section profile that pass through Galunggung and Telaga Bodas crater, heat source was interpreted as density with value 2.8 – 3.0 gr/cm3 and marked by orange to red color that coincide below Galunggung crater and continoued to Talaga Bodas crater at depths below -3000 masl. This indicate that both concession area was connected.

Size Segregated Carbonaceous Aerosol Down to Ultrafine Particle in Medan City, Indonesia

In this study, the distribution of PMs and their carbonaceous components, including organic (OC) and elemental carbon (EC) was evaluated to determine how much carbon profiles within ambient aerosol differ between four different sites in Medan city or (roadside (RS), school environment (SE), industrial area (IA), and volcano area (VA). Samples were taken by using ambient nano sampler (ANS) from February 19th to March 12th, 2019. Carbon analyser followed by IMPROVE_TOR methods was used to evaluate the carbonous component in all sites. Overall, OC is the primary carbon component, comprising more than 60% of all sites. Regarding particle size, the largest OC content was recorded in PM0.5-1 across all locations, suggesting that this particle size should be the primary focus of future evaluations of the consequences of biomass burning. The concentration of soot-EC dropped with the increase in particle size, since it was commonly influenced by vehicle emissions, which typically generated ultrafine and fine particles. PM0.1 has the greatest concentration of soot-EC. Due to their proximity to the city’s busiest thoroughfare, RS and SE sites had a larger soot-EC proportion than the two remaining sites (IA and VA) (Sisingamangaraja Street).

The coulomb stress changes for correlation analysis of tectonic earthquake activity and volcanic of the 2001–2010 Merapi eruption based on focal mechanism data

The incident of increased seismic activity of the Merapi volcano was initiated by several tectonic earthquake phenomena. Analysis of the mechanism of tectonic earthquakes can be studied based on the combination of static stress on the rock. This paper describes the distribution of the Coulomb stress changes due to the interaction that occurs in tectonic earthquakes with volcanic activity. The data in the calculation of the Coulomb stress distribution are secondary in the form of tectonic seismicity data downloaded from the ISC (International Seismological Center), USGS (United States Geological Survey), and Global CMT (Global Centroid Moment Tensor) catalogs between 2001 and 2010. Calculation results and data analysis is the occurrence of an increase in Coulomb stress response in the Merapi Volcano area with a value range of 0.2–10 ​kPa at a depth of 2–4 ​km below the peak of Merapi Volcano. The Coulomb stress changes distribution is thought to indicate the accumulation of stress due to tectonic earthquakes that downward at the top of the volcano, thereby affecting the stability of the magma chamber and causing volcanic activity at the Merapi volcano.

Moment magnitude for earthquakes in the Etna volcano area

SUMMARYAccurate quantification of seismic activity in volcanic regions is an important asset for improving hazard and risk assessment. This is especially true for densely populated areas, as in the case of Etna volcano (Southern Italy). There, the volcanic hazard is amplified by the seismic risk of active faults, especially on the eastern flank of the volcano. In such a context, it is common to rely on moment magnitude (MW) to characterize seismicity and monitor the energy released during an eruption. In this study, we calculate the moment-based magnitude (MW) for selected seismic data sets, using different approaches in distinct magnitude ranges to cover the widest possible range of magnitude that characterizes Etna's seismicity. Specifically, we computed the MW from a data set of moment tensor solutions of earthquakes that occurred in the magnitude range 3.4 ≤ ML ≤ 4.8 during 2005–2020; we created a data set of seismic moment and associated MW for earthquakes 1.0 ≤ ML &amp;lt; 3.4 obtained by analysing source spectra; we fine-tuned two relationships, for shallow and deep earthquakes, to obtain MW from response spectra. Finally, we calibrated a specific relationship between MW and ML for the Etna area earthquakes in the range 1.0 ≤ ML ≤ 4.8. All the empirical relationships obtained in this study can be applied in real-time analysis of the seismicity to provide fast and robust information on the released seismic energy.

Microbial biomineralization under extreme conditions: Case study of basaltic rocks, Tolbachik Volcano, Kamchatka, Russia

Microorganisms (bacteria, fungi and others) are considered to be the pioneers of the settlement under extreme conditions and take an active part in biomineralization and soil formation. We studied biofilms and for the first time identified the presence of microbial biomineralization in extreme conditions of Tolbachik Volcano area, Russia. Rock samples with lichen / cyanobacteria biofilms were studied by a complex of methods (optical and scanning electron microscopy, powder X-ray diffraction and energy-dispersive X-ray spectroscopy). We found that the acidic environment of biofilms favor oxalate biomineralization under the action of lichens and suppresses the carbonate biomineralization under the action of cyanobacteria. Calcium (whewellite, Ca(C2O4)·H2O, and weddellite, Ca(C2O4)·(2.5-x)H2O (0 ≤ x ≤ 0.25)) and copper oxalates (moolooite, Cu(C2O4)·nH2O) were found in lichen biofilms. Direct relationship between the age of lichen and intense of biomineralization was discovered. It was shown that the lichens not only extract calcium and heavy metals (Cu, Pb) from the basaltic rock (both in situ and from weathered particles of the same rock brought by the wind) but increase their content in biofilm. The lichen species Psilolechia leprosa, Sarcogyne hypophaea, Rinodina cf. gennarii, and Ochrolechia subplicans subsp. subplicans can form oxalates. It was also found that (1) calcium and copper oxalates can be localized in the same lichen, (2) the species producing oxalic acid do not always produce oxalates and (3) the ratio of whewellite and weddellite formed by the same species lichen can vary significantly. Obtained results show high abundancy of biomineralization in terrestrial environment, including extreme and provide some insights into mechanisms of microbial biomineralization.