Geophysical Institute Research Articles

МОНІТОРИНГ СЕЙСМОТЕКТОНІЧНИХ ПРОЦЕСІВ У ЗАКАРПАТСЬКОМУ ВНУТРІШНЬОМУ ПРОГИНІ ЗА РЕЗУЛЬТАТАМИ КОМПЛЕКСНИХ ГЕОФІЗИЧНИХ СПОСТЕРЕЖЕНЬ

The article is devoted to the study of relations between the parameter variations of geophysical fields and the geodynamic state of the Transcarpathian Inner Trough. The research aims at studying the relations between the geodynamic state, observed meteorological parameters, and seismic phenomena in the Transcarpathian Inner Trough. Exploration target: seismotectonic processes in the region based on the results of monitoring geophysical fields. The scope of research includes the spatiotemporal distribution of local seismicity, modern lateral movements of the Earth's crust in the Oaș deep-seated fault area, precipitation parameter variations, water level in the Tysa River in 2019–2020. Research methodology presupposes the use of dynamic characteristics of modern lateral movements of the Earth's crust, spatiotemporal distribution of local earthquakes, observation of precipitation, as well as the comparison of heavy precipitation intervals with periods of seismic intensification. The research uses data obtained in the course of monitoring geophysical observations in the Transcarpathian Inner Trough area, especially at monitoring geophysical stations of the Seismicity Department of the Carpathian region of S.I. Subbotin Institute of Geophysics of the National Academy of Sciences of Ukraine. The data on the movements of the Earth's crust have been obtained at "Korolevo" strainmeter station. The results are significant to study the possible occurrence of local seismicity in the region and to settle the issue of seismically hazardous territories, as well as prediction of seismically hazardous phenomena in the future. The research studies the relation between the dynamic characteristics of modern lateral movements of the Earth's crust in the central part of the Transcarpathian Inner Trough and local seismicity in periods of intensive precipitation. The authors studied the relations between precipitation parameter variations and spatiotemporal distribution of local seismicity in 2019–2020. The analysis of spatiotemporal distribution of local seismicity and precipitation parameter variations in 2020 testifies to a high correlation of geophysical data series: increased amounts of precipitation are accompanied by an increased number of registered local earthquakes in the region; the hydrological aspect of seismotectonic processes in the Transcarpathian Inner Trough has been substantiated. In 2020 rock compression could be observed in the Oaș deep-seated fault area.

Marine geophysical research in the first Ukrainian Antarctic expeditions: historical outline and some results

The article is devoted of the 25th anniversary of the First Ukrainian Marine Antarctic Expedition (1997). The short history of development the marine geophysical study of the deep structures of the World Ocean and Antarctica in the S. I. Subbotin Institute of Geophysics (National Academy of sciences of Ukraine) is presented. Main focus is on the results obtained during the implementation of the «State research programs in Antarctica». The main patterns of geophysical anomalies and their spatiotemporal distributions in West Antarctica were investigated. The lithosphere deep structured geophysical models well corresponds with the evolution processes of the continental margin of the West Antarctica. The built-depth sections record the large-scale processes of the formation of the Drake Passage and the western part of the Scotia Sea as a result of the primary crust fragments’ transformation and the geodynamic evolution of the region located between South America and West Antarctica. Some results for the assessment of mineral resources and hydrocarbon potential of the continental margin structures of the NW area of the Antarctic Peninsula are presented.

Can high-school students contribute to seismic risk mitigation? Lessons learned from the development of a crowd-sourced exposure database

On a global scale, one out of three people is exposed to earthquakes, and most injuries and deaths in case of seismic events are caused by the damage or collapse of residential buildings. Knowing the type and distribution of exposed assets, in particular buildings, is thus paramount for effective mitigation of disasters. Citizens' involvement in disaster risk reduction activities is constantly increasing by means of crowdsourced data collection, education/training and citizen science activities. In particular, schools have a central role in engaging young students and increasing risk awareness and preparedness. In this work, we explored whether students’ participation in this kind of activities can lead to the improvement of current exposure datasets, while increasing citizens' risk-related understanding. In 2021, due to the restrictions imposed by the COVID-19 pandemic, the National Institute of Oceanography and Applied Geophysics - OGS started a new project to be deployed in fully remote mode, named “CEDAS: building CEnsus for seismic Damage ASsessment”. The project consists in the collection and elaboration of crowdsourced data on main residential buildings typologies of northeastern Italy, a seismically active area which suffered consequences from strong past earthquakes. During the project, 170 high school students collected reports on more than 3200 buildings, performing a statistical analysis of theing results. The CEDAS project makes a first step beyond crowdsourcing activities and applies citizen science to exposure development. Results allow identifying the most common building typologies in the region and the challenges and opportunities associated with data collection and analysis. The experience collected during the CEDAS project shows that crowdsourcing and citizen science activities can contribute to both enhancing the exposure data available for the scientific community and increasing risk awareness among young students in the region.

Edward R. D. Scott (1947–2021): A tribute to an exceptional scientist and wonderful man

Edward R. D. Scott (1947–2021): A tribute to an exceptional scientist and wonderful man

SEISMICITY of the CARPATHIANS in 2015

The article describes seismic observations in the Carpathian region in 2015, which were carried out, as before, by two organizations from two states: in Ukraine – the Seismicity department of the Carpathian region of the Institute of Geophysics of the NAS of Ukraine, in Moldova – the Seismology laboratory of the Institute of Geology and Seismology of the Academy of Sciences of Moldova. 20 stationary digital stations with a processing center in L'viv and six stations with a center in Chisinau operated in Ukraine and Moldova respectively. Different programs, local hodographs and magnitudes were used. The consolidated catalogue of earthquakes was created in L'viv. The total number of earthquakes in 2015 was NΣ=164 in the ranges: KR=4.7–12.2, h=1–160 km. The total seismic energy ΣE=5.381012 J. 23 earthquakes with depths h=50–160 km were located in the Vrancea zone. The maximum earthquake with KR=12.2 was registered on January 24 in the Vrancha mountains with hрР=89 km. In the Precarpathian region, nine events with energy classes KR=4.7–8.9 were registered, the total seismic energy of which is ΣЕ=1.25109 J. Increased seismic activity was observed in Transcarpathia. A series of tangible earthquakes with aftershocks was recorded in the Tyachiv area. Their total number was NΣ=77. The strongest tangible earthquake occurred in the area of Okrugla village on July 19 with KR=11.1. The earthquake source is located in the Earth's crust at a depth of h=7.7 km. The earthquake was felt by the population in the epicentral area with an intensity of I=6. In addition, this earthquake, like 5 others, was felt in the territory of northern Romania. In general, a decrease in the seismicity level in the Carpathians in 2015 was observed compared to that in 2013 and 2014.

Preface

IV National Scientific Conference with Foreign Participants “Geodynamical Processes and Natural Hazards” 4th GeoProNH 2021 This issue presents the proceedings of the National scientific conference with foreign participants “Geodynamical Processes and Natural Hazards” (4th GeoProNH). The 4th GeoProNH was held from September 6 to 10, 2021, at the Institute of Marine Geology and Geophysics. This Institute is located in Yuzhno-Sakhalinsk (Russia) and is rightfully considered a regional center for the study of earth sciences.This conference provides a forum for international researchers, academics and practitioners to discuss, share and exchange their latest research and experience progress associated with the geosciences. The Sakhalin and Kuril Islands are parts of the Pacific Ring of Fire, so this region undergoes almost all possible geohazards: earthquakes, tsunamis, volcano eruptions, etc. We have called for the research papers on natural hazards and geodynamics, hydrophysics (dangerous marine phenomena), geophysics, geochemistry, volcanology, geoecology, geomorphology and other earth sciences. At the same time, we did not limit ourselves exclusively to research papers, many recent papers and reviews can be found in the conference collection. More than a hundred scientists, experts and postgraduates from France, Japan, Kyrgyzstan, and Russia took part in the 4th GeoProNH Conference and discussed the current state of the art and advances in geosciences related to the analysis of natural hazards and/or their preventions.Due to the COVID-19 pandemic situation during the 2021 year, it was not easy to hold a regular conference. There were travel restrictions and regulations from the World Health Organization and the local Government to be complied with to stop the spread of the COVID-19 in terms of physical distancing. In this uncertain condition we didn’t postponed Conference since the most part of participants have confirmed their intention to arrive to Sakhalin and address their research findings at this conference. Thus, the committee of 4th GeoProNH has decided to organize the real meeting with high safety degree. Also, we provided the virtual meeting for our participants from France and Japan, who couldn’t be with us, using ZOOM.The list of notable speakers in 2021 includes such outstanding scientists like, The list of members of scientific and organizing committees of the conference include next scientists, Conference Photos are available in this pdf.

Preface

The opening of the eleventh International Youth Scientific School-Conference "Theory and Numerical Methods for solving Inverse and ill-posed Problems" was held on August 26, 2019 at Novosibirsk State University.The first ten school-conferences, held from 2009 to 2018, showed the relevance and scientific significance of the chosen subject [1,2,3]. Over the past years, researchers, graduate students and undergraduates from Russia, Belarus, Ukraine, Kazakhstan, Uzbekistan, Kyrgyzstan, as well as from China, the USA, Germany, France, Italy, Japan, the UK, Brazil, Malaysia took part in the school-conferences. For 10 years, representatives of 78 universities, 134 research institutes and more than 20 companies (Total, Baker-Hughes, Schlumberger, Rosneft and others) participated actively at school-conferences.The Conference continued until September 4. The participants were very interested in the reports of academicians S. K. Godunov (Sobolev Institute of Mathematics, Novosibirsk), M. A. Guzev (Institute of Applied Mathematics, Vladivostok), I. A. Taimanov (Sobolev Institute of Mathematics, Novosibirsk), E. E. Tyrtyshnikov (Marchuk Institute of Numerical Mathematics, Moscow), corresponding members of the RAS V.V. Vasin (Krasovsky Institute of Mathematics and Mechanics, Ekaterinburg), S. I. Kabanikhin, G. A. Mikhailov (Institute of Computational Mathematics and Mathematical Geophysics, Novosibirsk ), V. G. Romanov (Sobolev Institute of Mathematics, Novosibirsk).

Peer Review Declaration

All papers published in this volume (IOP Conference Series: Earth and Environmental Science) have been peer reviewed through processes administered by the Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.• Type of peer review: Single-anonymous: authors’ identities are known to the reviewers, reviewers’ identities are hidden from authors.Main criteria used by Reviewers when accepting/declining papers:1. Relevance to the scope of the Conference2. Suitability & length of the title3. Scientific originality4. Adequacy of the abstract5. Scientific quality6. Text quality7. English level• Conference submission management system:Full paper submission was fully managed by editorial board of Conference• Number of submissions received: 53 full papers• Number of submissions sent for review: 51 full papers• Number of submissions accepted: 48 full papers• Acceptance Rate (Number of Submissions Accepted/Number of Submissions Received X 100): 90.56 %• Average number of reviews per paper: 2 (117 reviews)• Total number of reviewers involved: 51 reviewers (15 institutes) from 3 countries• Any additional info on review process:The review process and revision were conducted 3 rounds on average for each paper since the first submission after presentation at the conference. The first step was to check the format of paper and base quality of English level. The second-round of review was organized for papers with minor remarks from reviewers, for example the graphics or style. The third round required only for papers that need major modifications (scientific discussion on topic). All reviewers were asked to complete the review within enough time ranged no more than three weeks. We have asked authors to revise according to suggestions by reviewers within time ranged between 7-10 days. After being accepted, the final English proofread and format checking our specialists were carried out to ensure the quality prior to submission to IOP EES.• Contact person for queries:Name: Aleksandr Zakupin, Ph.D.Affiliation: Institute for Marine Geology and Geophysics, Department of SeismologyEmail: a.zakupin@imgg.ru

Technique for the imaging crystalline basement according to the DSS data

The method of deep seismic sounding (DSS), the observation systems in which are characterized by an irregular arrangement of both sources and receivers along the profile, a significant step between receivers, as well as maximum source-receiver distances exceeding several hundred kilometers, makes it possible to obtain an image of the crystalline basement using seismic migration fields of reflected/refracted waves. The main part of the existing migration methods, the use of which makes it possible to form an image of the deep structure of the study area in the dynamic characteristics of the recorded wave field, is focused on processing seismic data obtained by the method of reflected waves with multiple overlap observation systems (MOV—CDP). And, as a rule, these migration methods are designed for a smooth change in speed with depth. At the same time, at the boundary of the crystalline basement, the speed changes very sharply, which must be taken into account when processing data using migration. The proposed method for constructing an image of the crystalline basement is based on the use of finite-difference migration of the field of reflected/refracted waves, which was developed at the Institute of Geophysics named after S. I. Subbotin National Academy of Sciences of Ukraine. This migration method is designed to isolate supercritically reflected and refracted waves recorded from the basement in the far zone of the source and takes into account the full trajectory of waves passing through a two-layer medium, at the boundary of which there is a significant jump in velocity. Thus, the migration of the field of reflected/refracted waves makes it possible to obtain a correct image of the structure of the refractive layer of the crystalline basement. The article describes in detail the algorithm of the technique for constructing an image of the crystalline basement using finite-difference migration of the field of reflected/refracted waves and its difference from similar methods of migration. The advantages and disadvantages of the proposed method are shown when solving problems of regional seismic research. Explained and illustrated the features of constructing the image of violations on the border of the foundation. The effectiveness of the technique is demonstrated on a model example and real seismic data observed by the DSS method on the territory of Ukraine.

Organization of the stationary seismological observations point

The Institute of Geophysics of the NASU organizes and carries out continuous regional and local seismic observations on the territory of Ukraine. The article presents a universal modern model of seismic activity monitoring process, which is used in most international seismological agencies (USGS, EMSC, NEIC) and describes a typical stationary point of seismological observations of the National Seismological Network of the Institute of Geophysics of NAS of Ukraine. Seismological network of observations is a complex of systems consisting of stationary seismological points of registration of seismic waves, the distributed system of transfer and collecting of the seismological information, and also the center of operative processing of the data arriving from data registration points. The process of conducting regime seismological observations of local and remote seismic events on the territory of Ukraine and adjacent regions is described. Some important aspects of the need for comprehensive processing of registered events to identify local earthquakes and assess the current activity of tectonic structures in Ukraine are presented. The seismological network of the National Seismological Center of the Institute of Geophysics of the National Academy of Sciences of Ukraine is represented by a small number of stationary observation points: «Kiev-IRIS», «MI02-Poltava», «MI03-Skvyra», «MI04-Dnipro», «MI05-Stepanivka», «MI07-Mykolaiv», «ODS-Odesa», «MIU-Kryvyi Rih», and «MI06-Kremenchug». This number of seismological observation points does not actually provide seismic observation data to the central, eastern and southern parts of the territory of Ukraine and does not allow to reliably determine the level and quantitative characteristics of its seismic hazard. The seismic recorder Guralp CMG-40T manufactured by the British company GURALP SYSTEMS LIMITED is offered as optimal for the conditions and financial realities of Ukraine when organizing a stationary seismic observation point. It is proposed to use the seismological processing package SeisComP, which works on the SeedLink protocol, which is the basis of the data collection system by the Internet. This software product is the de facto world standard in the field of seismological data processing.

TECTONOMAGMATIC EVOLUTION OF THE EOCENE VOLCANISM OF THE TALYSH ZONE (AZERBAIJAN)

Link for citation: Karimov V.M. Tectonomagmatic evolution of the Eocene volcanism of the Talysh zone (Azerbaijan). Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2021, vol. 332, no. 11, рр. 200-211. In Rus. The relevance. At present, the question arises of the need to clarify the typomorphic features of magmatic complexes, as factors that determine the geodynamic regimes of their formation and to clarify the potential ore content. In this regard, the article examines the features of the Talysh magmatic complexes, which makes it possible to elucidate the tectonomagmatic evolution of this complexly constructed region in the Caucasus. Purpose of research is to clarify the tectonomagmatic evolution of the Eocene volcanism of the Talysh zone within Azerbaijan. Objects: Eocene volcanism, volcanogenic trachybasalt-trachyandesite-basalt-phonolite formation, petrochemical composition of rocks, evolution of the primary melt. Methods: petrographic studies of rocks, chemical composition of rocks by X-ray spectral analysis, isolation of magmatic complexes. In addition, the results of analyzes of the studied samples for petrogenic elements were used, both published in the literature and obtained by X-ray fluorescence analysis on a multichannel X-ray spectrometer SRM-25 at the Institute of Geology and Geophysics, Baku. Minerals were analyzed on a JXA-8200 JEOL (Japan) electron microprobe at the Karpinsky All-Russian Geo-logical Research Institute (St. Petersburg). Results. The analysis of the conducted studies shows that during the period from the Paleozoic to the Quaternary, inclusive, in the development of the structures of the Talysh fold zone, there is a certain sequence in its inception. In the structure of the zone, there are structural stages corresponding to the pre-collisional (Cretaceous–Eocene) and collisional (Oligocene–Miocene) periods of the region's development. Paleogene volcanic formations of Talysh make up the southeastern segment of the northern volcanoplutonic belt, in the structure of which the volcanic trachybasalt-basaltic trachyandesite-phonolite (Early-Middle and Late Eocene) and intrusive subalkaline ultrabasic (Late Eocene–Oligocene) formations are distinguished. The volcanic formation includes two complexes: (Early-Middle Eocene) absarokite-shoshonite-alkaline basaltic and (Late Eocene) basaltic trachyandesite-phonolite. The petrographic and petrochemical characteristics of the volcanic rocks that make up the first formation are given. It was found that if the process of differentiation in the Early-Middle Eocene had more distinct character with the initial formation of more magnesian rock varieties (picrite-trachybasalts), and subsequently more ferruginous (trachyandesites and basaltic trachyandesites), then such accumulation of iron is not observed in porphyry trachyandesites. This petrochemical feature is obviously associated with the duration of the break in volcanism caused by the formation of a thick sedimentary-tuffaceous sequence, accompanied by the formation and manifestation of an intermediate chamber of average composition. Volcanism in the Late Eocene was undifferentiated and had a contrasting character, i. e. was not accompanied by the formation of average differences. The appearance in the Late Eocene of leucite phonolites, which are an alkaline branch, and the absence of transitional differences indicate the autonomous development of vitrobasalts and leucite phonolites, possibly associated with the process of early decomposition of the initial melt under subcrustal conditions. It is concluded that from the early phases of the manifestation of Eocene volcanism to the later, the change in the material composition laterally is expressed in the manifestation of more alkaline facies with a significant predominance of K over Na and with a greater correspondence to the differentiates of the Shoshonite series.

Calibration of vulnerability and fragility curves from moderate intensity Italian earthquake damage data

The objective of this work consists in the calibration of vulnerability and fragility curves for the main masonry building classes detected in Lunigiana and Garfagnana (north-west of Tuscany, Italy). The large-scale procedure aims at providing damage and unusability scenarios starting from a seismic hazard map and a typological/structural characterisation of the building stocks lying in the different sub-municipal homogeneous areas.The damage and vulnerability data collected in more than 3000 AeDES survey forms of rapid damage assessment, filled out in Lunigiana and Garfagnana after the June 21, 2013 Earthquake, along with the information derived from a fast visual screening of the facilities, have been processed to develop a specific database in a Geographical Information System (GIS) environment. The latter and the shakemaps downloaded from the National Institute of Geophysics and Volcanology have allowed to compare the actual fragility of the building sample with the expected one, which has been evaluated according to the Macroseismic Method.The study concludes with a conservative proposal of modification for the vulnerability and fragility curves, for low values of EMS-98 macroseismic intensity (IV-VI) or PGA (0.04 g–0.30 g), and the identification of empirical correlations between the percentage of unusable buildings and the EMS-98 damage levels or the shaking parameters.

Occurrence of anomalies in soil radon volume activity before tectonic earthquakes

Research subject. Earthquakes are a global problem for the entire world population. Therefore, a search for ways to predict and prevent tectonic events is a highly relevant task. Despite the existence of controversial opinions on the possibility of predicting tectonic earthquakes, research in this direction continues. Among numerous possible precursors of earthquakes, anomalies in the volume radon activity (VRA) are the most physically justifed ones. The aim of this research was to compare the observed anomalies of soil radon with the recorded seismic events in order to fnd common patterns. The research area was the Kuril Islands. VRA monitoring was conducted at the South Kuril Geophysical Station of the Institute of Marine Geology and Geophysics of the Far Eastern Branch of the Russian Academy of Sciences.Methods and materials. Measurements were carried out in the advective mode: soil air from a depth of 70 cm was forcibly delivered to the detector using a pump. For a retrospective analysis, we took registered seismic events with a magnitude greater than 4 that occurred within a radius of 500 km from the monitoring station in Yuzhno-Kurilsk during 2011–2018. Statistical data were processed using Microsoft Excel, Statistica software. Results. A method for comparing radon anomalies and earthquakes was developed. Using the developed methodology, it was found that the geodynamic criterion of ≥2 (the ratio of earthquake magnitude to logarithm of distance from event epicenter to the monitoring station in km) can be used when comparing VRA anomalies with tectonic earthquakes. Out of the 166 considered tectonic earthquakes meeting the geodynamic criterion of ≥2.148, the events were preceded by VRA anomalies. The position of the earthquakes was determined relative to the extremum of previous anomalous radon values in the time interval. Eac of the considered earthquakes meeting the geodynamic criterion ≥2, which had been preceded by a radon anomaly, occurred either after its extremum or coincided with it in time. Conclusions. The manifestation of tectonic earthquakes in VRA anomalies after passing the extremum can be considered as a short-term prognostic criterion and be used for distinguishing between “near” and “far” events.

Response of peat-rich permafrost to a warming climate on the northeast Tibetan Plateau

Permafrost degradation leads to the release of organic carbon to the atmosphere, and in turn, affects climate change. The amount of organic carbon released to the atmosphere depends on the thawing rate of peat-rich permafrost. However, the exact mechanism of peat-rich permafrost thawing is still unclear. Here we choose two locations on the northeast Tibetan Plateau: the peat-rich EBoTA (“peatland”) site, and the mineral-rich PT5 (“mineral”) site. We use the Geophysical Institute Permafrost Laboratory model to reveal the response of permafrost to warming climate from 1850 to 2100 applying different shared socioeconomic pathways (SSPs). Monthly soil temperature increased during the historical and future periods at both sites, but a slower trend is evident at the peatland site relative to the mineral site. Seasonally, the warming trend is faster in winter than that in summer at both sites. Active layer deepening at the mineral site is 3–12 times that of the peatland site. In addition, permafrost will persist until 2100 in all but one of the SSPs at the peatland site. At the mineral site, all permafrost will degrade to seasonally frozen ground, with only taliks remaining for all future scenarios. These changes indicated a slower response of peat-rich permafrost to climate change, due to peat's low thermal conductivity and high soil moisture. These results could be useful in permafrost carbon studies.

Prompt seismic data sharing for the 2021 Maduo earthquake in Qinghai province, China

An MS7.4 earthquake struck west China in Maduo county, Guoluo prefecture, Qinghai province on May 22, 2021, at 2:04 Beijing time (18:04 UTC on May 21, 2021), which broke the quiet period of Chinese mainland for 1382 days without earthquakes of magnitude 7 or higher. The analysis of the seismic data sequence would play an important role in the in-depth study of the Maduo earthquake and the Bayan Har block. The Institute of Geophysics, China Earthquake Administration (CEA), compiled observation data recorded through 57 broadband seismometers within 500 km of the earthquake epicenter and intended to share for further researches in earthquake science community. The shared dataset included waveforms of the event and its sequence with magnitudes of 3.0 or higher that occurred between May 22–31, 2021 with a sampling rate of 100 sps along with the continuous waveforms of 20 Hz and 100 Hz. Additionally, the seismic instrument response files also were shared. The event and continuous waveform records could be downloaded by submitting a request through the web platform of the Earthquake Science Data Center of the Institute of Geophysics, CEA (www.esdc.ac.cn).

An accessible seismological dataset of 2021 Yangbi MS6.4 earthquake

A MS6.4 earthquake occurred on 21 May 2021 in Yangbi county, Dali prefecture, Yunnan, China, at 21: 48 Beijing Time (13: 48 UTC). Earthquakes with an M3.0 or higher occurred before and after the main shock. Seismic data analysis is essential for the in-depth investigation of the 2021 Yangbi MS6.4 earthquake sequence and the seismotectonics of northwestern Yunnan. Institute of Geophysics, China Earthquake Administration (CEA), has compiled a dataset of seismological observations from 157 broadband stations located within 500 km of the epicenter, and has made this dataset available to the earthquake science research community. The dataset (total file size: 329 GB) consists of event waveforms with a sampling frequency of 100 sps collected from 18 to 28 May 2021, 20-Hz and 100-Hz continuous waveforms collected from 12 to 31 May 2021, and seismic instrument response files. To promote data sharing, the dataset also includes the seismic event waveforms from 20 to 22 May 2021 recorded at 50 stations of the ongoing Binchuan Active Source Geophysical Observation Project, for which the data protection period has not expired. Sample waveforms of the main shock are included in the appendix of this article and can be downloaded from the Earthquake Science website. The event and continuous waveforms are available from the Earthquake Science Data Center website (www.esdc.ac.cn) on application.

An interpretation of Cueva de la Huachizca, Santa Clara del Cobre, Michoacan, Mexico

Cueva de la Huachizca is located in the humid forests of the Municipio of Santa Clara del Cobre, Michoacán. During the Postclassic period (1300−1520 ad), Santa Clara del Cobre was a part of the Tarascan Señorio. Ethnographic accounts describe the use of Cueva de la Huachizca as a place of refuge during the Cristero Rebellion (1921−1926). Recent investigations suggest a long history of use including graffiti and inscriptions from the 1800s–1900s and a rock art panel. The panel consists of pecked petroglyphs depicting a man facing an eagle, above a spiral motif. Stylistic analysis of the panel suggests that the rock art was created during pre-Hispanic times, likely by the Postclassic Tarascans. As observed in several regions of Mesoamerica, for the Tarascans, caves were also liminal spaces and had an important role in Postclassic Tarascan cosmology. A ceramic resinera, a pine resin pot, an eagle’s feather, and charcoal were also recovered. The resinera age was estimated by researchers at Archaeomagnetic Services, Geophysics Institute at the National Autonomous University of México-Campus Morelia, Michoacán to between 1921 and 1980. Ethnographic and ethnohistoric accounts describe caves as houses of fertility and rain deities, an idea that while slightly transformed, has survived over 500 years of colonization, and remains in the communities’ social memories. These findings demonstrate the cave’s significance among the descendent communities and Cueva de la Huachizca as an important sacred site.

Geological features for the formation of gas-geochemical fields, including helium and hydrogen, in the water and sediments at the Vietnamese part of the South-China Sea

The paper presents the results of a complex joint Russian-Vietnamese geological, geophysical and oceanographic expedition in the South-China Sea (R/V “Akademik M.A. Lavrentyev”, cruise 88, 2019), as well as related joint Russian-Vietnamese marine and land researches in the area of north and south Vietnam under a series of local FEB RAS – VAST grants. The organizers of the marine expedition are the V. I. Ilyichev Pacific Oceanological Institute of the Far Eastern Branch of the Russian Academy of Sciences (POI FEB RAS) and the Institute of Marine Geology and Geophysics of the Vietnam Academy of Science and Technology (IMGG VAST). In comparison with the Sea of Japan and the Sea of Okhotsk, it can be noted that the active bottom degassing on the on the Vietnamese shelf and slope have is a local, although the intensity of gas-geochemical anomalies is comparable to similar zones in the Far Eastern Seas. For the first time, anomalous methane fields (up to 5000 nl/l) were found in the water column of the South-China Sea, which are comparable to anomalies on the oil and gas shelf and the gas-hydrate-bearing slope of Sakhalin Island. Metamorphosed sedimentary and volcanic rocks were discovered for the first time in the southern part of Catba Island (Gulf of Tonkin), which indicates the introduction of an endogenous body into the sedimentary strata and its further transformation. In connection with the discovery in 2020 of the large Ken Bau gas field at the southern end of the sedimentary basin of the Red River, the forecast of POI scientists about the presence of significant hydrocarbon reserves in this area was confirmed. The work was carried out within the framework of the joint Vietnam-Russia Laboratory for Marine Sciences and Technology (V. I. Ilyichev Pacific Oceanological Institute of the Far Eastern Branch of the Russian Academy of Sciences and the Institute of Marine Geology and Geophysics Vietnam Academy of Science and Technology). The expedition of the R/V “Akademik M.A. Lavrentyev” (cruise 88) is part of a series of expeditions in accordance with the UN Decade dedicated to the Ocean Science for Sustainable Development.

Seven Decades of Publishing with the Institute of Geophysics, Polish Academy of Sciences

Seven Decades of Publishing with the Institute of Geophysics, Polish Academy of Sciences

Robust estimation of model parameters of the probability integral method based on CA-rPSO

This paper introduces a framework for robustly estimating the parameters of the probability integral method (PIM). According to the framework, the initial robust estimates of the PIM parameters are firstly obtained by combining the cultural algorithm and rand particle swarm optimisation (CA-rPSO) with the LTS method. As a byproduct, an initial standard deviation can be calculated and used to determine the initial weights of the measurements according to the Institute of Geodesy and Geophysics (IGGIII) down-weighting scheme. Meanwhile, a modified CA-rPSO (referred to as CA-rPSO-IGGIII) is constructed, where the IGGIII scheme is introduced to alleviate the adverse influence of outliers. Then, the initial robust estimates and the standard deviation can act as a priori information for the CA-rPSO-IGGGIII to search for the optimal estimates. Experiments with simulated and real data demonstrate that the proposed method can robustly estimate the PIM parameters.