Journal articles on the topic 'Volcano seismology'

Volcanoes are the most rapidly changing and difficult to study geological features. Identifying physical signatures of processes occurring during seismic and volcanic activity is one of the most important problem in seismology. Here we reveal temporal changes of seismic velocity in the upper crust for two years of eruption activity of the Redoubt volcano. Based on correlation of continuous records of seismic noise at pairs of stations, we obtained correlograms for selected time periods. Using the stretching method, we obtained relative velocity changes between stations. These variations appear to be consistent with the results of repeated tomography that was previously derived based on body waves from local earthquakes.

The Instituto Nicaragüense de Estudios Territoriales (INETER) is the institution responsible for volcano monitoring in Nicaragua. The Volcanology Division of the General Directorate of Geology and Geophysics currently monitors six active volcanoes by means of seismology, gas measurements, optical webcams, and visual and satellite observations. The volcano monitoring network that INETER maintains is in continuous expansion and modernization. Similarly, the number of technical and scientific personnel has been growing in the last few years. 2015 was the busiest year of the last two decades: Momotombo volcano erupted for the first time in 110 years, a lava lake was emplaced at the bottom of Masaya volcano’s Santiago crater, and Telica volcano experienced a phreatic phase from May to November. Although we have increased our monitoring capabilities, we still have many challenges for the near future that we expect to resolve with support from the national and international geoscientific community. El Instituto Nicaragüense de Estudios Territoriales (INETER) es la institución responsable de la vigilancia volcánica en Nicaragua. Su División de Vulcanología actualmente vigila seis volcanes activos por medio de sismicidad, emisiones de gases, cámaras ópticas, observaciones visuales y teledetección satelital. La red de monitoreo de volcanes que mantiene INETER está en continua expansión y modernización. Del mismo modo, el número de personal técnico y científico ha estado creciendo en los últimos años. El año 2015 fue el año más ocupado que tuvimos en las últimas dos décadas, debido a que el volcán Momotombo entró en erupción por primera vez en los últimos 110 años, se emplazó un lago de lava en el fondo del cráter Santiago (volcán Masaya), y el volcán Telica experimentó una fase freática de mayo a noviembre. A pesar del progreso realizado, todavía tenemos muchos desafíos para el futuro cercano que esperamos lograr con los recursos nacionales y de la comunidad geocientífica internacional.

Independent Component Analysis (ICA) is an emerging new technique in the blind identification of signals recorded in a variety of different fields. ICA tries to find the most statistically independent sources from an observable random vector, with the only restriction that all sources but at most one are non-Gaussian; no other a priori information on sources and mixing dynamic system are needed. The applications of these techniques to the analysis of volcanic time series are relatively few to date. In this paper we show that ICA is a suitable technique to separate a volcanic source component from ocean microseisms background noise in a seismic dataset recorded at the Mt. Merapi volcano, Indonesia. The encouraging results obtained with this methodology in the presented case study support their wider applicability in volcano seismology.

This report provides a brief description of the field work on the Kuril Islands. It was performed within the framework of the R&D theme, projects of the RSF and the RFFR, which are realized in the laboratory of postmagmatic processes of the Institute of Volcanology and Seismology FEB RAS. Hydrological and hydrochemical works were performed on the rivers draining the slopes and thermal fields of the Sinarka, Kuntomintar volcanic massifs (Shiashkotan Island), and the Vernadsky and Karpinsky Ridges (Paramushir Island). The study of the chemical erosion of volcanic islands and the assessment of the hydrothermal export of magmatic volatiles are the goals of this work. Infrared photography was taken and the total flux of volcanic SO2 and diffusion flux of CO2 were measured on thermal fields in the caldera of Golovnin volcano. A detailed hydrogeochemical survey was made on the thermal fields of the Ebeko volcano to study the relationship of volcanic and hydrothermal activity of the volcano. For further analytical work, a large number of water and gas samples were taken and a representative collection of rocks and sediments was collected during the expedition.

This report gives a brief description of field work on the Kuril Islands in summer 2021 carried out by staff of the Institute of Volcanology and Seismology of FEB RAS within the framework of the Institute research theme and projects of the Russian Science Foundation (RSF) and Russian Fund for Basic Research (RFBR). To study chemical erosion of volcanic islands and to estimate hydrothermal export of magmatic volatiles, hydrological and hydrochemical works were carried out on the rivers draining the slopes and thermal fields of the Baransky volcano and the Bogdan Khmelnitsky volcanic massif (Iturup Island). Detailed hydrochemical studies with water sampling at different depths and a bathymetric survey of Lake Kipyashchey located in the caldera of Golovnin volcano (Kunashir Island) were performed. We also proceeded with studying the CO2 diffusion flux through thermal fields and volcanic lakes. In the course of ongoing regime observations on Ebeko volcano (Paramushir Island), aerial and infrared imaging of its near-crater part was carried out. For the first time since the eruption began in 2016, a quadcopter survey of the lake located in the Srednii (middle) crater of the volcano was conducted. For further analytical studies a large number of water and gas samples were taken, and the collection of sediments was replenished.

Abstract Mount St. Helens in Washington State erupted violently (Volcano Explosivity Index = 5) on 18 May 1980. During the previous two months, intense seismic activity at the volcano was recorded by a combination of continuous analog-tape recordings, paper drum recordings, and a recently installed triggered digital event computer system. Because of the technological constraints of the time, the digital data available cover only a little more than 1% of the two-month period. The paper drum records only exist for a few of the seismic stations and are also quite incomplete. However, the analog-tape data from some stations is near complete for almost the whole two months. During the period 2005–2014, these old analog tapes were recovered from storage and digitized to generate standard digital data for archiving at the Incorporated Research Institutions for Seismology Data Management Center. This recovery process was long and complicated but, for the most part, was fairly successful. Although the quality of these recovered data is nowhere near as good as modern digital seismograms, this dataset does provide a near-continuous record of the significant seismic sequence that led up to the major volcanic eruption. It includes the large variety of seismic signals from different types of volcanic earthquakes and harmonic tremor and should be a valuable resource for those studying volcanic seismicity.

SUMMARY In addition to enabling the physical processes of volcanic systems to be better understood, seismology has been also used to infer the complexity of magma pathways and plumbing systems in steep-sided andesitic and stratovolcanoes. However, in these volcanic environments, the application of seismic location methods is particularly challenging and systematic comparisons of common methods are lacking. Furthermore, little is known about the characteristic seismicity and deep structure of Lascar volcano, one of the most historically active volcanoes in northern Chile known to produce VEI-4 eruptions. To better understand the inner processes and deep structure of Lascar, the local broad-band seismic monitoring network was densified during a temporal installation in 2014–2015. Herein, we focus on the local seismicity during the 2014–2015 unrest episode, during which we recorded numerous seismic events mainly classified as long-period (LP) type, but also denote volcano-tectonic (VT) activity. Specifically, a long-lasting phase of LP activity is observed over a period of ∼14 months that starts in tandem with a pulse of VT activity. The LP rate and amplitude are modulated over time; they are lower in the initial phase, rise during the intermediate period from October 2014 to July 2015, and finally slowly decay while approaching the eruption time. The location of LPs is challenging due to the typical lack of clear seismic onsets. We thus encompass this problem by comparing a broad range of different standard and novel location techniques to map the source region of LPs by fitting the amplitude decay, polarization patterns, coherence of characteristic functions and cross-correlation differential times. As a result, we principally constrain LP locations within the first 5 km depth below the summit extending downward along a narrow, conduit-like path. We identify different regions of complexity: VTs dominate at depth, both VTs and LPs cluster in an intermediate depth region (down to 1.5 km), suggesting a change in the plumbing system geometry, and LPs dominate the shallowest region. Based on these results, we infer the presence of a subvertical conduit extending down to a depth of ∼5 km, and a region of path divergence, possibly accommodating a magma plumbing system, at a depth of ∼3 km beneath the volcano summit. Identifying the locations of complexities in the magma pathways at Lascar may help identify future unrest. The results are compared with independent observations, demonstrating the strength of the location method used herein that will be tested at volcanoes elsewhere.

ABSTRACT The additional observation of three components of rotational ground motions has benefits for tilt-seismometer coupling (e.g., ocean-bottom seismometry and volcano seismology), local site characterization, wavefield separation, source inversion, glacial and planetary seismology, as well as the monitoring of structural health. Field applications have been mostly hampered by the lack of portable sensors with appropriate broadband operation range and weak-motion sensitivity. Here, we present field observations of the first commercial portable broadband rotation sensor specifically designed for seismology. The sensor is a three-component fiber-optic gyro strictly sensitive to ground rotation only. The sensor field performance and records are validated by comparing it with both array-derived rotation measurements and a navigation-type gyro. We present observations of the 2018 Mw 5.4 Hualien earthquake and the 2016 central Italy earthquake sequence. Processing collocated rotation and classical translation records shows the potential in retrieving wave propagation direction and local structural velocity from point measurements comparable to small-scale arrays of seismic stations. We consider the availability of a portable, broadband, high sensitivity, and low self-noise rotation sensor to be a milestone in seismic instrumentation. Complete and accurate ground-motion observations (assuming a rigid base plate) are possible in the near, local, or regional field, opening up a wide range of seismological applications.

The Servicio Geológico Colombiano (SGC) was created in 1916 and has been dedicated to the research and monitoring of active volcanoes in the country since the disaster resulting from the eruption of Nevado del Ruíz Volcano in 1985, where more than 25000 people died due to lahars. Today the SGC has three Volcanological and Seismological Observatories in the cities of Manizales (SGC-OVSM), Popayán (SGC-OVSPop), and Pasto (SGC-OVSP), from where 23 active volcanoes are monitored. The three observatories manage an instrumental network of about 740 stations (permanent and portable) as well as signal repeaters, and cover the disciplines of seismology, geodesy, geochemistry, and potential field, amongst others. Volcanic hazard assessment is also carried out by the SGC, producing hazard maps and reports. These tasks are complemented by programs for promoting geoscience knowledge transfer to the public, developed through different strategies. Although at this time, data derived from volcanic monitoring are not available online, the SGC is analysing this need, for implementation in the near future. El Servicio Geológico Colombiano (SGC) fue creado en 1916, y se ha dedicado a la investigación y monitoreo de los volcanes activos en el país desde el desastre resultante de la erupción del volcán Nevado del Ruíz en 1985, donde más de 25000 personas murieron debido a la ocurrencia de lahares. Hoy en día, el SGC tiene tres Observatorios Vulcanológicos y Sismológicos en las ciudades de Manizales (SGC-OVSM), Popayán (SGC-OVSPop) y Pasto (SGC-OVSP), desde donde se monitorean 23 volcanes activos. Los tres observatorios manejan una red instrumental de aproximadamente 740 estaciones (permanentes y portátiles), como también repetidoras de señal, y cubren las disciplinas de sismología, geodesia, geoquímica y campos de potencial, entre otras. La evaluación de la amenaza volcánica también es realizada por el SGC, produciendo mapas e informes. Estas tareas se complementan con programas para promover transferencia de conocimientos geocientíficos al público, desarrollados a través de diferentes estrategias. Aunque en este momento los datos derivados del monitoreo volcánico no están disponibles en línea, el SGC está analizando esta necesidad para su implementación en un futuro cercano.

Abstract A series of four Mw>6 earthquakes struck the northern region of Lombok, eastern Indonesia, in a span of three weeks from late July to mid-August 2018. The series was thought to be associated with the Flores thrust, but the exact mechanism causing the unusual earthquake series has remained elusive. Our Interferometric Synthetic Aperture Radar analysis, combined with insights from seismology, indicates that the events originated at different hypocenter depths with differing fault geometries, which may explain the cascading behavior of the events, and indicates that better imaging of active fault geometry might provide some insight into future rupture behavior on other similar thrust systems. Our static stress change calculations suggest that the earlier events in the sequence played a role in promoting the later events. In addition, the second event brought the most significant impact on a nearby volcano, by causing volumetric expansion at its shallow magma plumbing system and unclamping its magma ascent zone, which may potentially have an impact on its future eruptive activity. However, no volcanic activity has so far occurred after the earthquakes. Finally, our damage proxy maps suggest that the second event caused the greatest damage to buildings.

On 3 June 2018, Fuego volcano experienced a VEI = 3 eruption, which produced a pyroclastic density current (PDC) that devastated the La Réunion resort and the community of Los Lotes, resulting in over 100 deaths. To evaluate the potential hazard to the population centers surrounding Fuego associated with future PDC emplacement, we used an integrated remote sensing and flow modeling-based approach. The predominate PDC travel direction over the past 15 years was investigated using thermal infrared (TIR) data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument validated with ground reports from the National Institute of Seismology, Volcanology, Meteorology, and Hydrology (INSIVUMEH), the government agency responsible for monitoring. Two different ASTER-derived digital elevation model (DEM) products with varying levels of noise were also used to assess the uncertainty in the VolcFlow model results. Our findings indicate that the recent historical PDC travel direction is dominantly toward the south and southwest. Population centers in this region of Fuego that are within ~2 km of one of the volcano’s radial barrancas are at the highest risk during future large eruptions that produce PDCs. The ASTER global DEM (GDEM) product has the least random noise and where used with the VolcFlow model, had a significant improvement on its accuracy. Results produced longer flow runout distances and therefore better conveys a more accurate perception of risk. Different PDC volumes were then modeled using the GDEM and VolcFlow to determine potential inundation areas in relation to local communities.

This special issue of JDR features 18 papers and reports on an international 2010 to 2015 cooperative project entitled gEnhancement of Earthquake and Volcano Monitoring and Effective Utilization of Disaster Mitigation Information in the Philippines.h This project is being conducted under the SATREPS program (Science and Technology Research Partnership for Sustainable Development), cosponsored by the JST (Japan Science and Technology Agency) and JICA (Japan International Cooperation Agency). The Philippines is one of the worldfs most earthquake and volcano disaster-prone countries because it is located along the active boundary between the Philippine Sea Plate and Eurasian Plate. Collisions by the two plates generate plate subductions and crustal stress that generates earthquakes and volcanic activities on the archipelago. The Philippines has experienced numerous disastrous earthquakes, the most recent being the 1990 M7.8 Luzon earthquake, which killed over 1,000 local residents. A damaging earthquake also occurred during this 5-year project, in October 2013, on Bohol Island, causing about 200 deaths when houses and other buildings collapsed. Volcanoes are another major killer in the Philippines. The largest in the last century was when the Taal volcano erupted in 1911, killing 1,300 by a base surge. The 1991 Mt. Pinatubo eruption is known as the largest volcanic event in the 20th century. The Mayon volcano is also known to be a beautiful but dangerous volcano that frequently erupts, causing lahars ? steaming moving fluid masses of volcanic debris and water ? that damaged villages at the foot of the mountain. The PHIVOLCS (Philippine Institute of Volcanology and Seismology), a governmental agency mandated to monitor earthquakes and volcanoes, provides earthquake and volcano information and alerts to the public. It also conducts research on the mechanisms behind such natural phenomena and on evaluating such hazards and risks. The PHIVOLCSfs other mission is educating people and society on being prepared for disasters. Earthquake and volcano bulletins and alerts, research output, and educational materials and training provided by PHIVOLCS have enriched knowledge and enhanced measures against disaster. The primary target of this SATREPS project is to enhance existing monitoring networks, whose equipment has been provided by Japanese ODA (Official Development Aid). Through the SATREPS project, we have introduced the latest technology to provide the public with more accurate information more quickly. This project also promotes research for deepening the understanding of earthquakes and volcano activities in better assessing hazard and risk. Project components, tasks, and main Japanese organizations are as follows: 1) Earthquake and tsunami monitoring, NIED 1-1) Advanced real-time earthquake source information, Nagoya University 1-2) Real-time seismic intensity network, NIED 1-3) Tsunami monitoring and forecasting, NIED, JMA 2) Evaluation of earthquake generation potential, Kyoto University 2-1) Campaign and continuous GPS observation, Kyoto University, GSI 2-2) Geological and geomorphological studies of earthquake faults, Kyoto University 3) Integrated real-time monitoring of the Taal and Mayon volcanoes, Nagoya University 3-1) Seismic and infrasonic observation, Nagoya University 3-2) Continuous GPS monitoring, Kyoto University 3-3) Electromagnetic monitoring, Tokai University 4) Provision of disaster mitigation information and promotion of utilization, NIED 4-1) Simple seismic diagnosis, NIED 4-2) Tsunami victims interview manga (comic book form) and DVD, NIED 4-3) Disaster information portal site, NIED <span style="font-size: xx-small;">*NIED: National Institute for Earth Science and Disaster Prevention; JMA: Japan Meteorological Agency; GSI: Geospatial Information Authority of Japan</span> This issuefs first article by Melosantos et al., reports on results of installing a broadband seismometer network to provide seismic data used in the next two articles. Papers by Bonita and Punongbayan detail the results of SWIFT, a new earthquake source analysis system that automatically determines the location, size, and source mechanisms of moderate to large earthquakes. The report by Inoue et al. describes the development of the first instrumental intensity network system in the Philippines, followed by a report on its deployment and observation by Lasala et al. The article by Igarashi et al. describes the development of a tsunami simulation database for a local tsunami warning system in the Philippines. The next five papers represent the 2) Earthquake Generation Potential project component. Ohkura et al. detail the results of campaign GPS observations on Mindanao Island, which first delineated the detailed plate movement and internal deformation of Mindanao. Tobita et al. report the results of the first continuous GPS observations across the Philippine Fault. The next three papers describe the results of geological and geomorphological studies of the Philippine Fault on Mindanao Island by Perez et al., the 1973 Ragay Gulf Earthquake by Tsutsumi, and submarine mapping of the Philippine Fault by Yasuda et al.. These results provide insights on the recurrence and sizes of large damaging earthquakes in different areas. An electromagnetic study of the Taal volcano reported by Alanis et al. and the GPS monitoring of the Mayon volcano detailed by Takagi et al. are a part of intensive studies of these two volcanoes. Scientific research results were published in advance in other international journals by the research group concerning 3) Integrated Real-Time Volcano Monitoring of the Taal and Mayon Volcanoes. Real-time information on these volcanoes are telemetered to Manila and checked regularly as a part of standard operational procedures. Real-time earthquake and tsunami information by 1) Earthquake and Tsunami Monitoring has already been implemented in the monitoring system. The last five papers and reports cover results for 4) Provision of Disaster Mitigation Information and Promotion of Utilization. Imai et al. report on a full-scale shaking table test of typical residential Philippines houses made of hollow concrete blocks. They demonstrate the importance of following building codes. A paper by Imai et al. introduces simple seismic diagnosis for masonry houses as a practical tool for raising peoplefs awareness of housing vulnerability to earthquakes. Salcedo et al. report a dissemination strategy for the practical tools. The last two papers, by Villegas, report on video interviews made with Philippino tsunami survivors in the Tohoku area following the 2011 Great East Japan Earthquake. The results are compiled and selected stories published in comic-book form as easy-to-understand educational materials on tsunami disaster awareness. Information on earthquakes and volcanoes provided by the enhanced monitoring system, research output, and educational materials obtained through the SATREPS project are provided to stakeholders to enhance measures against disasters at various levels and in different timeframes. Readers of this special issue can reference information through a newly established SATREPS project portal site, the PHIVOLCS Disaster Information Portal, at <a href="http://satreps.phivolcs.dost.gov.ph/">http://satreps.phivolcs.dost.gov.ph/</a>. It can also be accessed from the PHIVOLCS web page at <a href="http://www.phivolcs.dost.gov.ph/">http://www.phivolcs.dost.gov.ph/</a>. Finally, I extend my sincere thanks to all authors and reviewers involved in this special issue.

Abstract. Seismology and geodesy are generally seen as the most reliable diagnostic tools for monitoring highly active or erupting volcanoes, like Mt. Etna. From the early 1980's, seismic activity was monitored at Mt. Etna by a permanent seismic network, progressively improved in the following years. This network has been considerably enhanced since 2005 by 24-bit digital stations equipped with broad-band (40 s) sensors. Today, thanks to a configuration of 33 broad-band and 12 short-period stations, we have a good coverage of the volcanic area as well as a high quality of the collected data. In the framework of the VULCAMED project a workgroup of Istituto Nazionale di Geofisica e Vulcanologia has taken on the task of developing the seismic monitoring system, through the installation of other seismic stations. The choice of optimal sites must be clearly made through a careful analysis of the geometry of the existing seismic network. In this paper, we applied the Seismic Network Evaluation through Simulation in order to evaluate the performance of the Etna Seismic Network before and after the addition of the stations in the candidate sites. The main advantage of the adopted method is that we can evaluate the improvement of the network before the actual installation of the stations. Our analysis has permitted to identify some critical issues of the current permanent seismic network related to the lack of stations in the southern sector of the volcano, which is nevertheless affected by a number of seismogenic structures. We have showed that the addition of stations at the candidate sites would greatly extend the coverage of the network to the south by significantly reducing the errors in the hypocenter parameters estimation.

Abstract We adapt from volcano seismology an automated method of locating icequakes with poorly defined onsets and indistinguishable seismic phases, which can be tuned to either body or surface waves. The method involves (1) the calculation of the root-mean-squared amplitudes of the filtered envelope signals, (2) a coarse-grid search to locate the hypocentres of the seismic events using their amplitudes and (3) refinement of hypocentre locations using an iteratively damped least-squares approach. First, we calibrate the adapted method by application to real data, recorded using a network of six passive seismometers, in response to surface explosions in known locations on the western margin of the Greenland ice sheet. Second, we present a seismic modelling experiment simulating rapid supraglacial lake drainage driven hydrofracture through 1 km thick ice. The test reveals horizontal and vertical location uncertainties of ∼121 m and 275 m, respectively. Since seismic emissions from glaciers and ice sheets often have complex waveforms akin to those considered here, our adapted method is likely to have widespread applicability to glaciological problems.

Ninety-eight Quaternary volcanoes have been identified in the Ecuadorian Andes and the Galápagos Islands, from them, nine experienced at least one eruption in the last twenty years. Additionally, about 35 % of the Ecuadorian population live in areas that could be affected by future volcanic eruptions. The Instituto Geofísico of the Escuela Politécnica Nacional (IG-EPN) monitors and evaluates Ecuador’s volcanic hazards: nineteen volcanic hazard maps and hundreds of related articles have been published as a result of its research. The monitoring networks include eighteen volcanoes, with more than 266 stations, which also form the basis for early warning systems at several volcanoes. Volcanic activity is widely communicated by the IG-EPN through periodic information published in different media (website and social networks). Ecuadorian volcanoes will erupt in the future and, therefore, the IGEPN continuously updates its monitoring and hazard assessment practices and improves communication channels and protocols to successfully fulfil its responsibilities. Noventa y ocho volcanes cuaternarios han sido identificados en los Andes ecuatorianos y Galápagos de los cuales nueve han experimentado erupciones al menos una vez en los últimos veinte años. Adicionalmente, alrededor del 35 % de la población ecuatoriana vive en zonas que podrían ser afectadas durante futuras erupciones. El Instituto Geofísico de la Escuela Politécnica Nacional (IG-EPN) monitorea y evalúa la amenaza volcánica del país y, como resultado de sus investigaciones, diecinueve mapas de amenaza volcánica y centenares de artículos científicos han sido publicados. Las redes de vigilancia comprenden dieciocho volcanes e incluyen más de 266 estaciones, que son parte también de los sistemas de alerta temprana. La actividad volcánica es comunicada amplia y periódicamente por el IG-EPN a través diferentes medios (página web y redes sociales). Comprendiendo que futuras erupciones ocurrirán en Ecuador, el IG-EPN continúa actualizando sus prácticas de vigilancia y evaluación de la amenaza, y mejorando sus protocolos de comunicación para cumplir exitosamente sus responsabilidades.

The end goal of the projects under the Philippine Institute of Volcanology and Seismology – Japan International Cooperation Agency – Japan Science and Technology Agency – Science and Technology Research Partnership for Sustainable Development (PHIVOLCS-JICA-JST-SATREPS) Program on Enhancement of Earthquake and Volcano Monitoring and Effective Utilization of Disaster Mitigation Information in the Philippines is to provide rapid, reliable and usable information on earthquakes, tsunamis, and volcanoes to the public. Component 4 of this program involves the provision of disaster mitigation information and promotion of utilization. Practical tools for the evaluation of vulnerability and safety of houses in the Philippines were developed in this component. Two tools were developed during the project; a 12-point questionnaire for self-check for earthquake safety of concrete hollow block houses in the Philippines (Tool 1) and a software program to evaluate the safety and earthquake vulnerability of houses (Tool 2). These tools aim to raise the awareness of stakeholders such as house owners, local engineers, building officials, and local government units, as well as function as an educational tool for the quick and simple evaluation of the vulnerability and safety of houses. The tools were disseminated to the specific users for enabling the effective utilization of disaster mitigation information. Various strategies were implemented for disseminating these tools: a launch activity was conducted during PHIVOLCS InfoSentro, an activity implemented by PHIVOLCS to update the public on its recent programs, projects, and activities; a copy of Tool 1 was uploaded on the PHIVOLCS website; training modules were developed; and training programs and workshops were conducted for users.

PENENTUAN LOKASI PERGERAKAN MAGMA GUNUNG API SOPUTAN BERDASARKAN STUDI SEBARAN HIPOSENTER GEMPA VULKANIK PERIODE MEI 2013 – MEI 2014 ABSTRAK Gunung api Soputan merupakan gunungapi type strato yang aktif hingga saat ini. Aktifitasnya diduga dimulai pada masa plistosen bawah (kurang lebih 1,8 juta tahun yang lalu). Gempa vulkanik merupakan gempa yang terjadi akibat aktivitas gunungapi. Hal ini disebabkan oleh pergerakan magma ke atas di dalam gunungapi. Penelitian ini bertujuan untuk mengetahui letak hiposenter gempa vulkanik serta mengetahui letak pergerakan magma Gunung Soputan. Prinsip dari penelitian ini dilakukan dengan menganalisis data gempa vulkanik periode Mei 2013 – Mei 2014 yang berupa data sekunder dari hasil rekaman (seismogram) Gunung Soputan pada 3 stasiun seismometer yaitu stasiun Aesoput, Winorangian, dan Silian. Data gempa diolah dengan menggunakan software seismologi yang ada. Hasil penelitian menunjukkan bahwa distribusi hiposenter gempa vulkanik Gunungapi Soputan menyebar pada daerah kubah lava dan cenderung kearah barat laut, dengan kedalaman 100 m –– 8000 m di bawah kubah lava. Dari hasil analisa hiposenter diketahui terjadi pergerakan magma oleh gempa vulkanik dalam (VA), hal ini disebabkan posisi hiposenter yang naik menuju kubah lava. Kata Kunci: Gunung Soputan, Hiposenter, dan Pergerakan Magma ABSTRACT Soputan volcano is strato volcano that active till today. Its activity supposed began at down Pleistocene (1,8 million years ago). Volcanic earthquake is one of matter that caused by volcano. This happened because magmatic movement inside volcano. This research aimed to know location of hypocenter also to know location of magmatic movement Soputan volcano. Principles from this researchis conducted by analyzing volcanic earthquake data at May 2013 to May 2014 that consist secondary data from recording data (seismogram) volcano Soputan on 3 stations seismometer are Aesoput station, Winorangian, and Silian. The earthquake data processed using seismologic software. Result researchis shows that distribution of hypocenter volcanic earthquake soputan volcano scattered at lava dome area and inclined to northwest, that located on depth 100 m to 8000 m from lava dome. Result from hipocenter analyse to find a magmatic movement by deep volcanic earthquake (VA), this happened because position of hypocenter up movement to lava dome. Keywords: Mount Soputan, Hipocenter, and Magmatic Movement

The purpose of the ForM@Ter LArge-scale multi-Temporal Sentinel-1 InterferoMetry service (FLATSIM) is the massive processing of Sentinel-1 data using multi-temporal interferometric synthetic aperture radar (InSAR) over large areas, i.e., greater than 250,000 km2. It provides the French ForM@ter scientific community with automatically processed products using a state of the art processing chain based on a small baseline subset approach, namely the New Small Baseline (NSBAS). The service results from a collaboration between the scientific team that develops and maintains the NSBAS processing chain and the French Spatial Agency (CNES) that mirrors the Sentinel-1 data. The proximity to Sentinel-1 data, the NSBAS workflow, and the specific optimizations to make NSBAS processing massively parallel for the CNES high performance computing infrastructure ensures the efficiency of the chain, especially in terms of input and output, which is the key for the success of such a service. The FLATSIM service is made of a production module, a delivery module and a user access module. Products include interferograms, surface line of sight velocity, phase delay time series and auxiliary data. Numerous quality indicators are provided for an in-depth analysis of the quality and limits of the results. The first national call in 2020 for region of interest ended up with 8 regions spread over the world with scientific interests, including seismology, tectonics, volcano-tectonics, and hydrological cycle. To illustrate the FLATSIM capabilities, an analysis is shown here on two processed regions, the Afar region in Ethiopa, and the eastern border of the Tibetan Plateau.

We use both seismology and geobarometry to investigate the movement of melt through the volcanic crust of Iceland. We have captured melt in the act of moving within or through a series of sills ranging from the upper mantle to the shallow crust by the clusters of small earthquakes it produces as it forces its way upward. The melt is injected not just beneath the central volcanoes, but also at discrete locations along the rift zones and above the centre of the underlying mantle plume. We suggest that the high strain rates required to produce seismicity at depths of 10–25 km in a normally ductile part of the Icelandic crust are linked to the exsolution of carbon dioxide from the basaltic melts. The seismicity and geobarometry provide complementary information on the way that the melt moves through the crust, stalling and fractionating, and often freezing in one or more melt lenses on its way upwards: the seismicity shows what is happening instantaneously today, while the geobarometry gives constraints averaged over longer time scales on the depths of residence in the crust of melts prior to their eruption. This article is part of the Theo Murphy meeting issue ‘Magma reservoir architecture and dynamics'.

As one of the most sensitive instruments for deformation monitoring in geophysics, borehole strainmeter has the capability to record a large spectrum of tectonic and environmental signals. Sensors are usually deployed near active faults and volcanoes and provide high-resolution continuous recordings of seismic and aseismic signals, hydrological variations (rainfall, groundwater level) and natural hazards (tropical cyclones, landslides, tsunamis). On the occasion of the 50th anniversary of the installation of the first Sacks–Evertson borehole strainmeter, in central Japan, we present an overview of the major scientific contributions and advances enabled by borehole strainmeter measurements in Taiwan since their installation in the mid 2000s. We also propose a set of future research directions that address recent challenges in seismology, hydrology and crustal strain modeling.

AbstractFlood basalts in associated volcanic rifted margins, such as the North Atlantic Igneous Province, have a significant component of lavas which are preserved in the present day in an offshore setting. A close inspection of the internal facies architecture of flood basalts onshore provides a framework to interpret the offshore sequences imaged by remote techniques such as reflection seismology. A geological interpretation of the offshore lava sequences in the Faroe–Shetland Basin, using constraints from onshore analogues such as the Faroe Islands, allows for the identification of a series of lava sequences which have characteristic properties so that they can be grouped. These are tabular simple flows, compound-braided flows, and sub-aqueously deposited hyaloclastite facies. The succession of volcanic rocks calculated in this study has a maximum thickness in excess of 6800 m. Down to the top of the sub-volcanic sediments, the offshore volcanic succession has a thickness of about 2700 m where it can be clearly identified across much of the area, with a further 2700 m or more of volcanic rock estimated from the combined gravity and seismic modelling to the north and west of the region. A large palaeo-waterbody is identified on the basis of a hyaloclastite front/apron consisting of a series of clinoforms prograding towards the eastern part of the basin. This body was > 500 m deep, must have been present at the onset of volcanism into this region, and parts of the water body would have been present during the continued stages of volcanism as indicated by the distribution of the hyaloclastite apron.

The Great East Japan Earthquake and Tsunami has reawakened people to the reality of large-scale earthquakes that recur in cycles of several hundred to a thousand years. The historical resources and archeology research group, which was established in 2014 within the Coordinating Committee of Earthquake and Volcanic Eruption Prediction Researches, is collaborating with researchers of seismology, history, archeology, and information science to investigate infrequent earthquakes using historical documents that record earthquakes and traces of disasters at archeological sites. To this end, we are creating a database of published historical sources of earthquakes to make the data readily accessible, and reexamining these sources and uncovering new historical material to investigate earthquakes that occurred in pre-modern times. We are also engaged in research on relief efforts for victims of past earthquakes and the post-disaster reconstruction process.

Abstract Seismologists are eagerly seeking new and preferably low-cost ways to map and track changes in the complex structure of the top few kilometers of the crust. By understanding it better, they can build on what is known regarding important, practical issues. These include telling us whether imminent earthquakes and volcanic eruptions are generating telltale underground signs of hazard, about mitigation of induced seismicity such as from deep injection of wastewater, how the Earth and its atmosphere couple, and where accessible natural resources are. Passive seismic imaging usually relies on blind correlations within extended recordings of Earth’s ceaseless “hum” or coda of well-mixed, small vibrations. In this article, we propose a complementary approach. It is seismic interferometry using opportune sources—specifically ones not stationary in time and moving in a well-understood configuration. Its interpretation relies on an accurate understanding of how these sources radiate seismic waves, precise timing, careful placement of pairs of listening stations, and seismic phase differentiation (surface and body waves). Massive freight trains were only recently recognized as such a persistent, powerful cultural (human activity-caused) seismic source. One train passage may generate a tremor with an energy output of a magnitude 1 earthquake and be detectable for up to 100 km from the track. We discuss the source mechanisms of train tremors and review the basic theory on sources. Finally, we present case studies of body- and surface-wave retrieval as an aid to mineral exploration in Canada and to monitoring of a southern California fault zone. We believe noise recovery from this new signal source, together with dense data acquisition technologies such as nodes or distributed acoustic sensing, will deeply transform our ability to monitor activity in the shallow crust at sharpened resolution in time and space.

Abstract The Mexican National Seismological Service (SSN) was founded on 5 September 1910, in response to commitments made by Mexico to the International Association of Seismology in 1903. The first seismic instruments installed in 1904 were a Bosch–Omori seismograph and a Palmieri seismoscope. The SSN was formally inaugurated on 5 September 1910, a few days before the revolution broke out; a political struggle that lasted over two decades. The SSN was inaugurated with a central station in Tacubaya, Mexico City, and two secondary stations. Wiechert seismographs were selected by the SSN for its budding network. Despite the adverse economic and political situation, the SSN managed to grow and install more stations during the turmoil. Besides the installation of new seismic stations and reporting the location and macroseismic data of earthquakes in Mexico, the SSN staff produced remarkable reports of important earthquakes that occurred in those early years. Notable among these are the detailed reports on the 19 November 1912 and 4 January 1920 earthquakes on the Trans-Mexican volcanic belt. These reports have shaped the estimations of seismic hazard in this highly populated region of Mexico. In the first aftershock studies reported, the SSN took Wiechert instruments to the epicentral areas of a large subduction earthquake in 1907 and to the city of Xalapa, in the vicinity of the 1920 crustal earthquake. With foresight in those early years of seismology, the SSN scientists correctly attributed the 1912 earthquake to a local active fault. The seismograms collected in 1920 confirmed that it was a crustal earthquake and not an in-slab event. Lack of funding and official interest did not permit the modernization of the SSN for many decades. National interest in the Service was boosted by the 19 September 1985 destructive earthquake.

Abstract We present two new seismic velocity models for Alaska from joint inversions of body-wave and ambient-noise-derived surface-wave data, using two different methods. Our work takes advantage of data from many recent temporary seismic networks, including the Incorporated Research Institutions for Seismology Alaska Transportable Array, Southern Alaska Lithosphere and Mantle Observation Network, and onshore stations of the Alaska Amphibious Community Seismic Experiment. The first model primarily covers south-central Alaska and uses body-wave arrival times with Rayleigh-wave group-velocity maps accounting for their period-dependent lateral sensitivity. The second model results from direct inversion of body-wave arrival times and surface-wave phase travel times, and covers the entire state of Alaska. The two models provide 3D compressional- (VP) and shear-wave velocity (VS) information at depths ∼0–100 km. There are many similarities as well as differences between the two models. The first model provides a clear image of the high-velocity subducting plate and the low-velocity mantle wedge, in terms of the seismic velocities and the VP/VS ratio. The statewide model provides clearer images of many features such as sedimentary basins, a high-velocity anomaly in the mantle wedge under the Denali volcanic gap, low VP in the lower crust under Brooks Range, and low velocities at the eastern edge of Yakutat terrane under the Wrangell volcanic field. From simultaneously relocated earthquakes, we also find that the depth to the subducting Pacific plate beneath southern Alaska appears to be deeper than previous models.

Abstract. In the eastern sector of Mexico City the sub soil consists of high contrasting sequences (lacustrine and volcanic inter bedded deposits) that favor the development of erratic fracturing in the surface causing damage to the urban infrastructure. The high-resolution geophysical prospecting are useful tools for the assessment of ground deformation and fracturing associated with land subsidence phenomena. The GPR method allowed to evaluate the fracture propagation and deformation of vulcano-sedimentary sequences at different depths, the main electrical parameters are directly related with the gravimetric and volumetric water content and therefore with the plasticity of the near surface prospected sequences. The active seismology prospection consisted in a combination of Seismic Refraction (SR) and Multichannel Analysis of Surface Waves (MASW) for the estimation of the velocity of the mechanical compressive (P) and the shear (S) waves. The integration of both methods allowed to estimate the geomechanical parameters characterizing the studied sequence, the Poisson Ratio and the volumetric compressibility. The obtained mechanical parameters were correlated with laboratory measured parameters such as plasticity index, density, shear strength and compressibility and, GPR and seismic profiles were correlated with the mapped fracture systems in the study area. Once calibrated, the profiles allowed to identify the lithological contact between lacustrine and volcanic sequences, their variations of thicknesses in depth and to assess the deformation area in the surface. An accurate determination of the geometry of fracturing was of the most importance for the assessment of the geological risk in the study area.

Abstract Waveforms from the NORESS array were analyzed for 147 industrial explosions during the 1985 to 1988 period, along a profile running east from Oslo (NORESS) to Helsinki to Leningrad (OHL profile). The events were 250 to 1300 km from NORESS and had local magnitude in the range 2.0 to 3.5. Event locations and origin times constrained by the University of Helsinki's regional seismic network provide a reliable basis for travel-time estimation at NORESS. We also used data recorded by NORSAR in 1979 for three shots on the FENNOLORA north-south, long-range seismic profile, which were near the OHL profile. Analysis of mantle P-wave signals from the explosions showed that first arrivals could be traced continuously to a distance of 750 to 800 km, where there is a cutoff and shift of approximately 2.0 to 2.5 sec in the travel-time curve and an increase in average apparent velocity. Interpretation of the observed travel times and waveforms for this profile suggests a low-velocity zone from approximately 105 to 135 km depth. Combined analysis of the seismic data with a Bouguer gravity map indicates the presence in the upper mantle of a high-velocity, high-density body of linear extent approximately from 200 to 300 to 500 to 600 km east of the NORESS array. It is postulated that this body may represent the root of an ancient volcanic system, in which lighter, silicic constituents were depleted from the upper mantle during the eruptive phase.

The article presents (on 21 August, 2017) the prediction of the established global prediction thermohydrogravidynamic principle (of the developed thermohydrogravidynamic theory containing the cosmic geophysics and the cosmic seismology based on the author’s generalization of the first law of thermodynamics for non-stationary cosmic gravitation) concerning the strongest intensifications (since 18 July, 2017 and before 26 February, 2018) of the global seismotectonic, volcanic, climatic and magnetic processes of the Earth determined by the maximal (near 7 November, 2017) combined integral energy gravitational influence on the internal rigid core of the Earth (and on the Earth as a whole) of the planets (Mercury, Venus, Mars and Jupiter) and the Sun due to the gravitational interactions of the Sun with Jupiter Saturn, Uranus and Neptune. The prediction is based on the established global prediction thermoshydrogravidynamic principle (used for the considered real planetary configurations of the Earth and the planets of the Solar System during the range 2004 2017) and on the statistical analysis of the previous strongest earthquakes occurred near the calculated dates of the local maximal combined planetary and solar integral energy gravitational influences (during the range 2004 2016) on the internal rigid core of the Earth.

Abstract. Ionospheric perturbations by natural geophysical activity, such as volcanic eruptions and earthquakes, have been studied since the great Alaskan earthquake in 1964. Measurements made from the ground show a variation of the critical frequency of the ionosphere layers before and after the shock. In this paper, we present an experimental investigation of the electron density variations around the time of the Bhuj earthquake in Gujarat, India. Several experiments have been used to survey the ionosphere. Measurements of fluctuations in the integrated electron density or TEC (Total Electron Content) between three satellites (TOPEX-POSEIDON, SPOT2, SPOT4) and the ground have been done using the DORIS beacons. TEC has been also evaluated from a ground-based station using GPS satellites, and finally, ionospheric data from a classical ionospheric sounder located close to the earthquake epicenter are utilized. Anomalous electron density variations are detected both in day and night times before the quake. The generation mechanism of these perturbations is explained by a modification of the electric field in the global electric circuit induced during the earthquake preparation. Key words. Ionosphere (ionospheric disturbances) – Radio Science (ionospheric physics) – History of geophysics (seismology)

ABSTRACT We explore the detectability of M2 tidal tilt in the western part of the United States, using seismic velocity data from 40 stations in the EarthScope Transportable Array (TA) network. We augment these data with data from two additional stations both collocated at the Piñon Flats Observatory (PFO) in southern California (networks TA and Incorporated Research Institutions for Seismology [IRIS] International Deployment of Accelerometers [IDA]). We find a good agreement between the acceleration-tilt derived from the TA seismic data with the theoretical model (body Earth and ocean loading for M2). These results are also consistent with prior studies using borehole tiltmeters operated at PFO (Wyatt and Berger, 1980; Wyatt et al., 1982). We find statistically significant M2 tilt anomaly responses that correlate with large lateral variations in rock properties in Yellowstone National Park, which stem from volcanic sources in the region. We also examined deviations in the M2 tidal tilt mode in regions with other geological features including the Cascades volcanic range and a large plutonic body located in Idaho and eastern Oregon. Of these, only the Cascadia data show evidence of lateral variances of elastic properties, similar to that of the Yellowstone Caldera (YC). We conclude that tilt measurements from seismic noise data can successfully identify relatively large structural changes in elastic properties of the crustal Earth (e.g., the YC) and significant change in the elastic properties (e.g., Cascadia subduction zone). But, when the features are smaller and/or have a more muted variation in the elastic properties (e.g., the plutonic body in Idaho and eastern Oregon), the induced changes in the tilt values are too small to be detected using TA data.

This paper traces some of the main developments in the study of earthquakes and their scientific investigation from 1755 (the year of the Great Lisbon Earthquake: GLE) to 1855. The GLE was widely reported and discussed, though at that time there was no systematic and accurate collection of seismic data so that the event did not in itself lead to significant scientific advances. But an idea is given of the attempts as regards Portugal and Spain to explain the GLE in the terms of the day. In 1760, John Michell described methods for ascertaining (in principle) the position of what would today be called the GLE's epicentre and its focal depth. His attempted explanation of the quake is described. The Calabrian Earthquake (1783) was followed by more systematic studies of its effects, showing how the centre of damage could be identified and estimates made of zones of equal damage (isoseismal zones). The undulatory nature of seismic displacements was recognized by Michell and others, but some observers in Italy thought they detected "vorticose" motion - an idea supported by the clockwise and anticlockwise rotation of the stones of two obelisks disturbed by the Calabrian Earthquake. The association of earthquakes with volcanoes received ongoing discussion through the century following the GLE and electrical explanations were also popular, particularly in Italy. The connection of volcanoes with land elevation or subsidence attracted the attention of Lyell and Darwin. The idea of isoseismal maps was adumbrated by von Buch in relation to the Silesian Earthquake of 1799 and a simple isoseismal map was drawn for the Rhineland Earthquake by Egen (1828) and a simple intensity scale proposed. Von Humboldt described earthquakes and volcanoes he had studied in South and Central America, but failed to establish any systematic system for their recording, and unhelpfully he gave rise to the notion of "craters of elevation" to account for the formation of volcanoes. Through the first half of the nineteenth century, extensive efforts were made to catalogue historical data on earthquakes' timing, location, and intensity, and their concomitant astronomical and meteorological circumstances, but initially few useful patterns could be discerned. There was no network of seismic stations, and the pendulum instruments for earthquake detection and recording were largely ineffective. The early development of seismoscopes/seismographs is described, but none worked satisfactorily in the period under discussion (except for Mallet's method for detecting artificial seismic disturbances). In the 1840s, William Hopkins published mathematical analyses of crustal deformations and earthquake phenomena and the transmission of seismic waves. He recognized two kinds of wave, which travelled at different velocities, and on that basis he proposed methods for determining the focal position of an earthquake. But the wave velocities were not known accurately and, though valid in principle, his method, utilizing the different travel-times for the two kinds of waves, could not be applied immediately. Studying the Visp Earthquake (1855), Georg Volger (with August Petermann) drew two isoseismal maps and proposed a numerical intensity scale, but it was not generally applicable since Volger allocated a value of ‘0’ to the region of maximum intensity and ‘6’ to the areas where motion was just discernible. Robert Mallet's work in the early 1850s was fundamental and marked the beginning of modern seismology (his term). Using artificial explosions and accurate clocks, he measured (longitudinal) wave velocities in soft sediments and hard granite, finding that velocities were higher for the latter. His catalogue of earthquakes and his plot of their distribution worldwide yielded a map that matches modern maps of plate boundaries. Mallet was stimulated by Lyell's drawings of the rotated Calabrian obelisks, and he showed that such movements could be produced by seismic waves, and "vorticose" motions need not be invoked. Soon after 1855, improved seismic detectors and recorders were devised and the systematic seismic investigations began. The period discussed in the present paper could be said to belong to the "pre-paradigm" stage of seismology.

The article presents (on 28 February, 2017) the prediction (made on 25 February, 2018) of the established global prediction thermohydrogravidynamic principle (of the developed thermohydrogravidynamic theory containing the cosmic geophysics and the cosmic seismology based on the author’s generalization of the first law of thermodynamics for non-stationary cosmic gravitation of the Solar System and our Galaxy) concerning the first subrange (in 2018) of the strongest intensifications (since 26 February and before 24 August, 2018) of the global seismotectonic, volcanic, climatic and magnetic processes of the Earth determined by the minimal (in 2018 near 26 May, 2018) combined integral energy gravitational influence on the internal rigid core of the Earth (and on the Earth as a whole) of the planets (Mercury, Venus, Mars and Jupiter) and the Sun due to the gravitational interactions of the Sun with Jupiter Saturn, Uranus and Neptune. The prediction is based on the established global prediction thermohydrogravidynamic principle (used for the considered real planetary configurations of the Earth and the planets of the Solar System during the range 2004 ÷ 2018) and on the statistical analysis of the previous strongest earthquakes occurred near the calculated dates of the local minimal combined planetary and solar integral energy gravitational influences (during the range 2004 ÷ 2017) on the internal rigid core of the Earth.

Abstract The eastern margin of North America has undergone multiple episodes of orogenesis and rifting, yielding the surface geology and topography visible today. It is poorly known how the crust and mantle lithosphere have responded to these tectonic forces, and how geologic units preserved at the surface related to deeper structures. The eastern North American margin has undergone significant postrift evolution since the breakup of Pangea, as evidenced by the presence of young (Eocene) volcanic rocks in western Virginia and eastern West Virginia and by the apparently recent rejuvenation of Appalachian topography. The drivers of this postrift evolution, and the precise mechanisms through which relatively recent processes have modified the structure of the margin, remain poorly understood. The Mid-Atlantic Geophysical Integrative Collaboration (MAGIC) experiment, part of the EarthScope USArray Flexible Array, consisted of collocated, dense, linear arrays of broadband seismic and magnetotelluric (MT) stations (25–28 instruments of each type) across the central Appalachian Mountains, through the U.S. states of Virginia, West Virginia, and Ohio. The goals of the MAGIC deployment were to characterize the seismic and electrical conductivity structure of the crust and upper mantle beneath the central Appalachians using natural-source seismic and MT imaging methods. The MAGIC stations operated between 2013 and 2016, and the data are publicly available via the Incorporated Research Institutions for Seismology Data Management Center.

Abstract Low-frequency sound ≤20 Hz, known as infrasound, is generated by a variety of natural and anthropogenic sources. Following an event, infrasonic waves travel through a dynamic atmosphere that can change on the order of minutes. This makes infrasound event classification a difficult problem, as waveforms from the same source type can look drastically different. Event classification usually requires ground-truth information from seismic or other methods. This is time consuming, inefficient, and does not allow for classification if the event locates somewhere other than a known source, the location accuracy is poor, or ground truth from seismic data is lacking. Here, we compare the performance of the state of the art for infrasound event classification, support vector machine (SVM) to the performance of a convolutional neural network (CNN), a method that has been proven in tangential fields such as seismology. For a 2-class catalog of only volcanic activity and earthquake events, the fourfold average SVM classification accuracy is 75%, whereas it is 74% when using a CNN. Classification accuracies from the 4-class catalog consisting of the most common infrasound events detected at the global scale are 55% and 56% for the SVM and CNN architectures, respectively. These results demonstrate that using a CNN does not increase performance for infrasound event classification. This suggests that SVM should be the preferred classification method, as it is a simpler and more trustworthy architecture and can be tied to the physical properties of the waveforms. The SVM and CNN algorithms described in this article are not yet generalizable to other infrasound event catalogs. We anticipate this study to be a starting point for development of large and comprehensive, systematically labeled, infrasound event catalogs, as such catalogs will be necessary to provide an increase in the value of deep learning on event classification.

The medium of visual representation played a crucial role in the Enlightenment project of taking intellectual possession of nature, and of dominating it. Pictures helped to categorize the various natural phenomena, to disseminate knowledge about their appearance and, so to speak, to capture them on paper or canvas. From the middle of the eighteenth century onwards, natural historians treating extreme and threatening natural phenomena, such as volcanoes, earthquakes, waterspouts or geysers, increasingly supplemented their written accounts with engraved illustrations. In this paper, I concentrate on the visual treatment of earthquakes in learned publications. I discuss two different types of graphic representation of this natural phenomenon, which had always been considered as virtually ‘undepictable’.After the great earthquake of Lisbon in 1755, research into the subject was greatly stimulated. Two scholars, the British natural philosopher John Michell and the Dutchman Johan Drijfhout, published earthquake treatises in learned journals, and each complemented his text with a diagrammatic illustration. By translating their theoretical considerations into the abstract form of geological sections, these natural philosophers moulded a new visual language for seismology and earth history. An entirely different example of visual representation as a tool in research into earthquakes can be seen in the approach to the earthquake in Calabria in 1783. The Neapolitan Academy of Science and Letters sent some of its members to investigate the devastating effects of this earthquake on the landscape and the nature of the country. The topographical changes were recorded on the spot by trained draughtsmen, with the aim of providing accurate and comprehensive visual documentation. The pictures are remarkable in the way they reveal a conflict between the new demands of modern empirical science and the established ‘picturesque’ conventions of landscape painting.

Differences have been discovered in the deep structures of North and South Kamchatka, which raises a question about a boundary between these regions. This problem has been studied on the basis of the seismologic, inverse seismic tomographic (P-waves) and geoelectrical data obtained in recent years, as well as the information on magnetometry, gravimetry, tectonics and magmatism of the study area. Comprehensive analysis of the geological and geophysical data shows differences in the structure of the crust and upper mantle in North and South Kamchatka and common features of the deep structures of South Kamchatka and the Kuril Islands. A presumed boundary between North and South Kamchatka is related to the zone of transverse deep faults crossing the peninsula. It is evidenced by P-wave velocity anomalies at different levels of the lithosphere. This fault zone is associated with a change in the geometry and strike of the high-velocity focal layer, and reflected in the modern tectonic plan as the Petropavlovsk-Malkinsky zone of transverse dislocations. In this zone, the Avacha-Koryak group of modern volcanoes is also NW-oriented. We propose a geoelectric model showing the depths along the profile constructed across the zone. In its deep part, the model includes sub-vertical anomalies of increased electrical conductivity. The anomalies are related to deep faults. Increased electrical conductivity may be due to the presence of magmatic melts feeding volcanoes. The results obtained in our study give evidence of the common features of the deep structures of South Kamchatka and the Kuril island arc and demonstrate the differences between the deep structures of North and South Kamchatka, being separated by the zone of faults, which may penetrate into the upper mantle. It is suggested that the identified features in the South Kamchatka structure are due to deep processes taking place not only at the side of the Pacific Ocean, but also at the southern margins of the Sea of Okhotsk. These findings are of interest for geodynamics, volcanology, tectonics and other Earth sciences.

Study of petrological and geochemical characteristics of mantle peridotite xenoliths in Pliocene alkaline basalt in Nghia Dan (West Nghe An) was carried out. Rock-forming clinopyroxenes, the major trace element containers, were separated from the xenoliths to analyze for major, trace element and Sr-Nd isotopic compositions. The data were interpreted for source geochemical characteristics and geodynamic processes of the lithospheric mantle beneath the region. The peridotite xenoliths being mostly spinel-lherzolites in composition, are residual entities having been produced following partial melting events of ultramafic rocks in the asthenosphere. They are depleted in trace element abundance and Sr-Nd isotopic composition. Some are even more depleted as compared to mid-ocean ridge mantle xenoliths. Modelled calculation based on trace element abundances and their corresponding solid/liquid distribution coefficients showed that the Nghia Dan mantle xenoliths may be produced of melting degrees from 8 to 12%. Applying various methods for two-pyroxene temperature- pressure estimates, the Nghia Dan mantle xenoliths show ranges of crystallization temperature and pressure, respectively, of 1010-1044°C and 13-14.2 kbar, roughly about 43km. A geotherm constructed for the mantle xenoliths showed a higher geothermal gradient as compared to that of in the western Highlands (Vietnam) and a conductive model, implying a thermal perturbation under the region. The calculated Sm-Nd model ages for the clinopyroxenes yielded 127 and 122 Ma. 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