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Showing papers by "Geophysical Survey published in 2021"


Journal ArticleDOI
TL;DR: In this article, the authors compared seismic tomography results with remote sensing and petrology data to identify deep and subaerial manifestations of pre-eruptive processes at Bezymianny volcano in Kamchatka shortly before its violent explosion on December 20, 2017.
Abstract: Strong explosive eruptions of volcanoes throw out mixtures of gases and ash from high-pressure underground reservoirs. Investigating these subsurface reservoirs may help to forecast and characterize an eruption. In this study, we compare seismic tomography results with remote sensing and petrology data to identify deep and subaerial manifestations of pre-eruptive processes at Bezymianny volcano in Kamchatka shortly before its violent explosion on December 20, 2017. Based on camera networks we identify precursory rockfalls, and based on satellite radar data we find pre-eruptive summit inflation. Our seismic network recorded the P and S wave data from over 500 local earthquakes used to invert for a 3D seismic velocity distribution beneath Bezymianny illuminating its eruptive state days before the eruption. The derived tomography model, in conjunction with the presence of the high-temperature-stable SiO2 polymorph Tridymite in juvenile rock samples , allowed us to infer the coexistence of magma and gas reservoirs revealed as anomalies of low (1.5) and high (2.0) Vp/Vs ratios, respectively, located at depths of 2–3 km and only 2 km apart. The reservoirs both control the current eruptive activity: while the magma reservoir is responsible for episodic dome growth and lava flow emplacements, the spatially separated gas reservoir may control short but powerful explosive eruptions of Bezymianny.

14 citations


Journal ArticleDOI
TL;DR: In this article, detrital zircon U-Pb ages (3575 grain ages from a total of 29 samples) from the Cenozoic sediments of offshore basins in East China were presented.

12 citations


Journal ArticleDOI
TL;DR: In this article, the authors study the Mw 5.6 Bystraya earthquake and its largest aftershock, which occurred on September 21, 2020 at the SW flank of the Baikal rift zone in the area, in which only few small seismic events have been detected during the whole period of instrumental observations.

8 citations


Journal ArticleDOI
30 Mar 2021
TL;DR: In this article, the Kola Division of the Geophysical Survey of the Russian Academy of Sciences has developed several original algorithms that appeared to be useful for seismic and infrasonic event location and discrimination.
Abstract: For many years, the Kola Division of the Geophysical Survey of the Russian Academy of Sciences carries out work on testing and implementation of modern techniques and algorithms for seismic and infrasonic data processing and event location. The KoD staff has developed several original algorithms that appeared to be useful for seismic and infrasonic event location and discrimination. In 2020, the LOS program was created. The most efficient tools for data processing and analysis, event location algorithms have been united in the program. The program also contains a modern mapping system and database. The following tools have been implemented: bandpass and adaptive filtration, polarization analysis and backazimuth computation for 3C stations, computation of backazimuths, and apparent velocities for seismic and infrasonic arrays (beamforming). To analyze records of infrasonic arrays the program has a cross-correlation tool, which enables to observe changes of signal’s backazimuths and apparent velocities in time. For seismic event location, the program uses two basic algorithms: minimization of origin time estimation residual and grid search based on generalized beamforming approach. These algorithms can be used in different combinations depending on the location scenario selected by a user. In addition, a new location algorithm based on a presentation of the seismic medium in a form of random graph where vertices correspond to points in the medium and edges are wave paths between the points, has been implemented. It can be useful for locating events in a substantially heterogeneous media, possibly with voids and cavities, as well as for taking into account the relief. This algorithm can be used, in particular, when locating events in mines using local mine seismic networks. The LOS program has been put into the practice of the Kola Division.

6 citations


Journal ArticleDOI
TL;DR: The tectonic nature of Early Palaeozoic Kwangsian orogeny in the South China Block (SCB) is still debated, due to controversy whether there was a Cambrian ocean between the Yangtze Block and the Ca
Abstract: The tectonic nature of Early Palaeozoic Kwangsian orogeny in the South China Block (SCB) is still debated, due to controversy whether there was a Cambrian ocean between the Yangtze Block and the Ca

4 citations


Journal ArticleDOI
TL;DR: A new class of models of hysteretic converters which generalizes the classical play-operator with stochastic properties (defining curves of this operator are treated as non-deterministic and have a random distribution) is proposed.
Abstract: A new class of models of hysteretic converters which generalizes the classical play-operator with stochastic properties (defining curves of this operator are treated as non-deterministic and have a random distribution) is proposed. In this case an output of stochastic converter is defined as a random process. The correctness of the definition of the corresponding converter in terms of a special limit construction is proved. Within this definition an output of the corresponding converter is determined at arbitrary continuous inputs. Properties of introduced converters are investigated and illustrative examples are presented.

4 citations


Journal ArticleDOI
30 Mar 2021
TL;DR: The concept of creation and operation of autonomous points of instrumental seismic observations, as the main element of the development of a system for collecting seismological data, is proposed and shown in detail.
Abstract: The main stages of creation and development of a seismic monitoring network of the Sakhalin Division GS RAS are considered. The main types of seismic data recording equipment used in the Sakhalin Division GS RAS are listed. The structure of the seismological data collection system of the Sakhalin Division GS RAS and its components are presented. The concept of creation and operation of autonomous points of instrumental seismic observations, as the main element of the development of a system for collecting seismological data, is proposed. The implementation of autonomous points of instrumental seismic observations is shown in detail on the example of the creation of emergency rescue centers for monitoring and forecasting emergency situations on the Kuril Islands of the EMERCOM of Russia in the Sakhalin Region. An assessment of the current state of the system for collecting seismological data in the Sakhalin Division GS RAS and its registration capabilities is given. The significance of the system for collecting seismological data of the Sakhalin Division GS RAS as a part of the large-scale research facilities of the GS RAS - a complex of continuous seismic monitoring of the Russian Federation, adjacent territories, and the world

3 citations



Journal ArticleDOI
21 May 2021
TL;DR: In this article, an analysis of microseisms registered on gas-condensate field area is devoted to an analysis, where a microseismic anomaly is outlined in NW part of the area and proves correct by 3 seismic CDP profiles and interpreted as a reservoir.
Abstract: This study is devoted to an analysis of microseisms registered on gas-condensate field area. Presence of seismic emission effect on a part of the area is demonstrated. A microseismic anomaly is outlined in NW part of the area and proves correct by 3 seismic CDP profiles and interpreted as a reservoir. The results of the special processing was compared to the results of a set of other geophysical methods. Correlation between the found anomaly and an anomaly found with aerogamma-specrtometry is shown. The results can be used in an integrated interpretation of geophysical data for oil and gas reservoirs of both structural as nonstructural types.

2 citations


Journal ArticleDOI
TL;DR: In this paper, the authors proposed a fault identification method based on topographic maps, such as elevation, rivers, and lakes, to predict coal and gas outbursts in coal mines.
Abstract: The formation and development of faults are a manifestation of stress concentrations and energy release in crustal rocks, and faults have a great influence on the occurrence of dynamic mine disasters. This study proposed mapping technology as a fault identification method. The mapping procedure included four steps: (1) Drawing points on topographic maps. The information of topographic maps, such as elevation, rivers, and lakes was copied onto sulfuric acid paper. (2) Classifying the landform. Based on the highest and lowest points in the studied area, the minimum elevation difference was calculated and the elevation points were graded according to the minimum elevation difference. (3) Determining the block boundaries. The elevation points in the same grade were categorized into the same blocks. (4) Mapping the fault distribution. The boundaries between different blocks were considered as faults. In this regard, numbers were assigned to the faults, and a graphic scale, coordinate grid, and legends were added to the map. Fault identification for classes I–V was conducted at different scales. Fault identification for the next class always retained the previous results. Using this method, the faults in the Pingdingshan coal mining zone were divided into classes I–V. By comparing the classes with historical coal and gas outbursts, it was indicated that more than 90% of the coal and gas outbursts occurred in the vicinity of faults, especially at the intersections of multiple faults and in areas with concentrated faults. This study provided a scientific basis for predicting coal and gas outbursts.

2 citations


Journal ArticleDOI
TL;DR: In this article, the authors assessed the NBL of total dissolved solids in various groundwater units in the Pearl River Delta (PRD) where urbanization is a large scale and discussed factors controlling groundwater salinity contamination in the PRD.
Abstract: Assessing natural background levels (NBLs) of chemical components in groundwater is useful for the evaluation of groundwater contamination in urbanized areas. The present study assessed the NBL of total dissolved solids (TDS) in various groundwater units in the Pearl River Delta (PRD) where urbanization is a large scale and discussed factors controlling groundwater salinity contamination in the PRD. Results showed that the NBL of TDS in groundwater in the coastal-alluvial plain was more than 1.5 times that in other groundwater units because of the seawater intrusion in this groundwater unit. By contrast, interactions of water and soils/rocks were the main factors controlling the NBLs of TDS in other groundwater units. Groundwater salinity contamination in the PRD was positively correlated with the urbanization level. Wastewater from township-village enterprises and industrial wastewater were likely to be the main sources for groundwater salinity contamination in the PRD. Moreover, the wastewater leakage from sewer systems was one of the main pathways for groundwater salinity contamination in urbanized areas, because the proportion of groundwater salinity contamination in urbanized areas formed in 1988–1998 was more than 1.5 times that in urbanized areas formed in 1998–2006 regardless of groundwater units. Besides, sewage irrigation and leakage of landfill leachate were also important sources for groundwater salinity contamination in the PRD.

Journal ArticleDOI
01 Sep 2021
TL;DR: In this article, the authors proposed a method to improve the quality of the information provided by the users by using the information gathered from the users' own data, such as the data collected by the service provider.
Abstract: Работа посвящена обобщению одной из самых «популярных» конструктивных моделей гистерезиса - преобразователя Прейзаха (континуальная система неидеальных реле, соединенных параллельно). Во многих прикладных задачах, связанных с моделированием гистерезисных эффектов, где априори предполагается доменная структура носителей гистерезисных свойств (многократное перемагничивание ферромагнитных составляющих электромагнитных систем, поляризация сегнетоэлектрика в зависимости от напряженности электрического поля, зависимость занятости от цены на монотоварных рынках и др.), приходится сталкиваться с необходимостью учитывать неопределенности в реакциях отдельных доменов на внешнее воздействие. В настоящей работе предложен инструментальный метод, позволяющий учитывать такие неопределенности посредством стохастических моделей элементарных носителей гистерезисных свойств. Рассмотрены основные свойства дискретной и континуальной систем реле, параметры которых трактуются как случайные величины, при этом выход системы реле представляется как случайный процесс. Исследована корректность определения, в частности, установлена независимость выхода (случайного процесса) от способа дискретизации в рамках предельного перехода от конечной к континуальной системе неидеальных реле, а также установлена управляемость и монотонность (в рамках соответствующего определения) стохастического аналога преобразователя Прейзаха.

Journal ArticleDOI
TL;DR: L-band PALSAR-1/2 SAR data can effectively monitor the velocity changes of glaciers before and after the glacier leaping, which can provide important data support for the monitoring and early warning of glacier disasters.

Patent
Roberts Roger1
02 Mar 2021
TL;DR: In this paper, a device implementing antennas transmitting and receiving electromagnetic waves for measuring the surface dielectric of a pre-defined surface area is described, which can be a small portion of a large surface, or a surface of a sample extracted from a larger volume.
Abstract: A device implementing antennas transmitting and receiving electromagnetic waves for measuring the surface dielectric of a pre-defined surface area is disclosed herein. This area can be a small portion of a large surface, or a surface of a sample extracted from a larger volume. The sample might be cylindrical in shape. The device includes a dielectric spacer of known dielectric properties and geometries, placed between the material under test and the transmitting and receiving antennas. The dielectric value and thickness of the dielectric spacer are selected so as to control the effective area over which the dielectric is measured.

Journal ArticleDOI
TL;DR: The interpretation of 2D seismic data, as well as results of onshore structural field studies and dating of post-kinematic granite plutons, suggest post-collisional extensional/transtensional regimes potentially driving development of the South Chukchi-Hope Basin this article.
Abstract: The South Chukchi–Hope Composite Tectono-Sedimentary Element (CTSE) rests on the Neocomian folded basement formed as a result of the South Anyui palaeo-ocean closure. The interpretation of 2D seismic data, as well as results of onshore structural field studies and dating of post-kinematic granite plutons, suggest post-collisional extensional/transtensional regimes potentially driving development of the South Chukchi–Hope Basin. The orogenic collapse occurred during the Aptian–Albian, and was followed by continued polyphase extensional/transtensional regime during the Late Cretaceous and Cenozoic. Depositional environments in the basin were most likely to have been non-marine in the Cretaceous and Early Tertiary, and marine from the Late Oligocene (?)–Miocene onwards. Three onshore wells in the adjacent depocentres penetrated Tertiary sediments and have had gas shows from two sites. Geochemical surveys registered anomalies of thermogenic and biogenic methane, and in some instances higher molecular ethane–penthane gases in sea-bottom sediments above gas chimneys observed on seismic lines. The CTSE is characterized by a very high present-day thermal gradient of up to 48°C km−1 recorded in the Alaskan wells and was previously considered to be gas prone.

Journal ArticleDOI
21 May 2021
TL;DR: In this paper, it is proved that refraction horizons on depth interval of 0-1.5 km are geologic boundaries in sedimentary cover on Ayan-Yuryakh tectonic block.
Abstract: Digital processing of refracted waves data, which are registered on North-East part of profile3-DV, is done. Time sections and velocity model are formed. It is proved, that refraction horizons on depth interval of 0-1.5 km are geologic boundaries in sedimentary cover on Ayan-Yuryakh tectonic block. Refraction boundary on depth of ~1.0 km is not lithologic border on Inyaly-Debin block. Layers, which are potentially productive for ore mineral resources, are substracted by low values of V/V (1.66-1.70) on depth below 1.0 km, on Inyaly-Debin block and Orotukan-Balygychan elevation.

Journal ArticleDOI
21 May 2021
TL;DR: In this article, the first results of the study of the Gorlovskaya depression in the area of coal deposits of the Novosibirsk region by methods of ground electrical prospecting using transient electromagnetic sounding and electrical tomography were presented.
Abstract: The article presents the first results of the study of the Gorlovskaya depression in the area of coal deposits of the Novosibirsk region by methods of ground electrical prospecting using transient electromagnetic sounding and electrical tomography. Near-surface models were obtained to depths of 100 m, as well as deep geoelectric characteristics of the sedimentary filling of the depression and the eastern fault boundary.

Journal ArticleDOI
TL;DR: In this article, the authors conducted experiments on the joint registration of avalanches in the Khibiny mountain range using seismic and infrasonic sensors during work on the forced descent of the snow mass.
Abstract: In the winter months of 2018-2020 the Kola Branch of the Unified Geophysical Service RAS conducted experiments on the joint registration of avalanches in the Khibiny mountain range using seismic and infrasonic sensors during work on the forced descent of the snow mass. The aim of the experiments is to assess the possibility of avalanche detection using the geophysical methods. The lack of representative statistics on the frequency and regularity of avalanches is the reason for the relevance of developing methods of their remote registration. The difficulty of registering avalanches is due to their occurrence often in hard-to-reach areas and in poor visibility conditions. To record signals generated by avalanches, different configurations of infrasound panels consisting of three spatially separated sensors (MPA 201 or Hyperion IFS-4000 microbarographs) and a portable seismic station Guralp CMG-6TD were used. As a result of the experiments, infrasound recordings were obtained at different distances from the avalanche source. The infrasound group recordings collected from the experiments were processed using an automatic detector implementing amplitude and cross-correlation signal detection methods. The spectral composition of the recordings and their characteristic appearance were analyzed. Avalanche-induced signals are characterized by long duration and changes in azimuth to the source. The dominant frequencies of the signal lie in the region of 1-10 Hz. Conclusions are made about the insufficient sensitivity of the seismic method when the seismometer is located at a distance of the first kilometers from the avalanche source, as well as the high applicability of the infrasound method for recording the facts of avalanches. The results obtained will make it possible to develop a methodology for automatic detection of signals generated by avalanches using the data of infrasound registration. This is the necessary basis for building a system for continuous monitoring of avalanche activity.

Journal ArticleDOI
TL;DR: The Tugeman Li-Be deposit has been found to have a postcollision extensional event and a previously unknown mineralising event in China as discussed by the authors, which is the only known event in the world with a precollision event.