Central Sakhalin Research Articles

О возможной связи между магнитными бурями и землетрясениями в определенных тектонических условиях (на примере о. Сахалин)

The paper considers topical issues of geophysics related to the possible influence of disturbances in the magnetosphere on seismicity. The study was conducted based on a detailed catalog of seismic events in southern Sakhalin for the period from 2003 to 2023. The paper aims to test the assumption that such an influence can manifest itself in individual seismogenic zones during their proximity to discharge. The testing was carried out in randomly selected segments of the West Sakhalin (WSF) and Central Sakhalin (CSF) faults. The coincidence of the moments of some seismic events (with M > 2.7) and magnetic storms with a high index (G1 and higher) was revealed in these segments. The LURR (load-unload response ratio) method was used to identify periods when fault segments were in a subcritical stress-strain state. It was shown that the main part of the coincidences occurred during the periods of increased abnormal activity of the LURR parameter.

Reconstruction of Tectonic Stresses in Central Sakhalin

Reconstruction of Tectonic Stresses in Central Sakhalin

РЕКОНСТРУКЦИЯ ТЕКТОНИЧЕСКИХ НАПРЯЖЕНИЙ ЦЕНТРАЛЬНОГО САХАЛИНА

The article presents the reconstruction of the tectonic stress field of the central part Sakhalin Island, obtained as a result of field tectonophysical studies in 2020–2022. The measurements made it possible to determine the predominant orientation of the main slickensides systems with different kinematics. The territory of Central Sakhalin is characterized by mainly subvertical orientation of the axis of maximum compression, as well as the subhorizontal and predominantly submeridionally directed axis of minimum compression (extension). The main revealed feature of Central Sakhalin is the predominance of horizontal extension as a type of stress state for the entire area. In its western part, horizontal shear and horizontal compression are significant. The number of horizontal extension conditions increases in the near-axial and eastern part of Central Sakhalin, closer to the Sea of Okhotsk. We found the cardinal difference between the obtained results of the stress field reconstruction and the results of similar studies in other geodynamically active regions of the country.

Автоматизированное картографирование разрывных нарушений в районе перешейка Поясок (Сахалин) по данным дистанционного зондирования

Automated mapping of disturbances in the earth’s crust allows you to quickly identify areas of development of dangerous geological processes, and to determine the measures that should be taken to organize the safe operation of extended linear structures (roads and railways, pipelines, power lines) that run through areas with difficult natural conditions. The main trigger mechanism causing the activation of dangerous geological processes is displacements in zones of active faults in the earth’s crust. Monitoring the state of fault zones and timely detection of manifestations of hazardous processes are urgent tasks for ensuring the sustainable development of regional infrastructure. The area of the Poyasok isthmus (Sakhalin Island) was chosen as the object of research, along the territory of which there are automobile and railway roads, power lines, and the main pipeline of the Sakhalin-2 project was laid along the isthmus coast. Lineament analysis of space images and SRTM data using the LEFA software package by binary morphological erosion method to highlight boundaries, as well as made selection long lines by performing mathematical operations using Canny algorithms, with subsequent Hough transformations, were carried out to identify faults of research territory. The obtained intermediate data were processed using the tools of the QGIS software package and made it possible to compile a map of disjunctive disturbances for the area under study. Lineament analysis made it possible to identify faults that bound the block megastructure of the Poyasok isthmus from the north and south. The saddle of Poyasok isthmus separates the large Central Sakhalin and South Sakhalin segments of the Hokkaido-Sakhalin system of island uplifts. Structures of the Central-Kamyshovy and South-Kamyshovy lifted megablocks (3 orders) in the West-Sakhalin Mountains adjoin directly to the saddle. The southern part of the Central-Kamyshovy mega-uplift is represented by a series of uplifts separated by narrow depressions bounded by faults. The number of uplifts increases with the distance to the north from the Poyasok isthmus. The northern part of the South-Kamyshovy mega-uplift is divided by faults of the northern-east strike into block structures. The obtained data are suitable for performing detailed seismic zoning.

Наблюдения обратного сейсмоэлектрического эффекта II рода при электрозондированиях в районе Центрально-Сахалинского разлома

The results of experiments on electrical sounding of the near-surface layer of the Earth's crust in the fault zone, which have involved a recording of seismoacoustic and seismic noise in the close zone near the source (the primary dipole source), are represented. The experiments were carried out in 2021-2022 in the southern part of the Central Sakhalin fault with the use of the generator of electric pulses developed at IMGG FEB RAS, output electric power being up to 3 kW. The aim was to reveal seismoacoustic signatures of the medium reaction to the soundings with current pulses of 5–13 A. The generator provided significantly higher current in the dipole than its typical characteristics in the case of soundings for electrical exploration by resistance methods, as well as in the case of conventional seismic and electrical exploration. At the same time, the range of current amplitudes was much smaller in comparison with the case of a deep sounding based on application of geophysical MHD generators or other extra high-power electric pulses units. Up to now, the inverse seismoelectric effect has remained practically unexplored at currents in the “intermediate” range of ~10 A and scale lengths of the order of few hundreds of meters. The presence or absence of the medium reaction to electrical soundings was distinguished by the records of molecular-electronic sensors developed by R-sensors LLC: the CME-6111 broadband seismometer and the hydrophone, installed at a distance of about 50 m from one of the poles of the electric dipole source. An increase in the average level of seismoacoustic noise during electrical soundings was revealed, which is essentially a variety of the inverse seismoelectric effect of the second kind (excitation of elastic waves during an electric current run in a two-phase medium). Previously, no similar signature of medium reaction to the current pulses was noted in the close zone adjacent to one of the dipole electrodes. The noise level increase occurs almost without delay after the start of electrical soundings, and this is in accordance with the previously obtained results on the responses of seismic acoustic emission to powerful current pulses, which were used for a deep sounding in the Northern Tien Shan.

ONOR EARTHQUAKE on August 14, 2016, Mw=5.8 (Sakhalin Island)

On August 14, 2016 at 11h15m UTS there was a strong earthquake with Mw=5.8 in the central part of the Sakhalin Island, which felt in nearby settlements with an intensity of up to Ii=5–6 by the MSK-64 scale. The greatest intensity of shaking was recorded in the village of Onor, closest to the epicenter. Within 2 weeks after the earthquake, more than 130 aftershocks were registered by regional seismic stations. The aftershock zone is extended in the NW-SE direction. Subhorizontal compressional stresses of the NE-SW orientation were realized in the earthquake foci. The type of movement in the source is a reverse-fault with a slight strike-slip component. The fault plane with the south-western dip direction was adopted as an operational. The earthquake source belongs to one of the secondary structures of the Central Sakhalin oblique-reverse fault, which cuts through a section of the Western Sakhalin Mountains in the direction of the western coast. The active block of the fault is the eastern wing, underthrusting under the western one. Based on the results of the macroseismic inspection, theoretical isoseists are calculated and constructed. Such a rare strong earthquake aroused wide interest among specialists and allowed them to test several new methods and technical solutions, as well as obtain new information about the seismicity and tectonics of the Sakhalin region. This article presents a comprehensive overview of seismological information on this earthquake, mainly based on the results of earlier publications.

On the Relationship of an Active Fault Seismicity with the Gas Production Dynamics by Example of the Aniva Gas Fields on Sakhalin Island

On the example of the Aniva gas fields, Sakhalin island located in the immediate vicinity of the active Central Sakhalin Fault, the dependences of the seismicity level on the gas production rate are shown. The distribution of earthquake epicenters is usually confined to the boundaries of the developed fields. While the areas of the fields themselves remain almost aseismic. The main contribution to the level of local seismicity is made by the regional Central Sakhalin Fault and its impact zone structures. It is noted that during the entire production time, there was no significant earthquake in their vicinity that would have caused damage to the social infrastructure. However, the obvious correlation between the production dynamics and seismic activity makes it necessary to further study and monitor the seismicity in the fields area.

Моделирование напряженно-деформированного состояния земной коры о. Сахалин: влияние гидроизостазии

The paper attempts to answer the question about the role of contribution of the hydroisostasy to the stress-strain state of the Earth’s crust on the Island of Sakhalin. The hydroisostasy contribution was estimated by simulation by means of finite element method. The mesh grid for the calculation was constructed using the real values of the depth of the Moho discontinuity surface and the topography of Sakhalin Island with adjacent shelf areas. The calculation took into account the Central Sakhalin fault zone. Lateral displacements as a result of strain and lateral displacements combined with vertical ones were simulated separately. Comparison of the results of the stress-strain state simulation, taking lateral displacements and their combination with vertical ones into account, clearly demonstrates the significance of the hydroisostasy contribution to the stress-strain state of the Earth’s crust in the Sakhalin region.

Phylogeography and genetic structure of a subarctic-alpine shrub species, Alnus alnobetula (Ehrh.) K. Koch s. l., inferred from chloroplast DNA markers

The green alder Alnus alnobetula s. l., a widely distributed subarctic-alpine shrub species, has been studied using three chloroplast DNA regions: trnH-psbA, trnS-trnG, and psaA-trnS. In addition, new chloroplast primers coding the trnT-GGT cpDNA regions and five cpDNA microsatellite loci (cpSSR) have been developed for this species. The population subdivision is very high (Nst = 0.869, Gst = 0.807, Fst = 0.883), suggesting a distinct phylogeographic structure (Nst > Gst, p < 0.0001) and a sharp contrast between the haplotype-rich eastern part of the species range and the almost completely uniform western part (Siberia, Ural). According to a phylogenetic analysis, the common haplotype of A. alnobetula subsp. fruticosa in the western part of the range originated from northeastern refugia (West Beringia) as a result of interglacial recolonization, including bottleneck events. Three highly divergent cpDNA lineages of green alder that have been resolved in the Russian Far East are largely concordant with A. alnobetula subsp. kamtschaticа, A. alnobetula subsp. mandschurica, and A. alnobetula subsp. maximowiczii. The populations of Sakhalin Island are divided into three phylogeographic groups (southern, central, and northern) corresponding to the different floristic zones and different subspecies. The green alder populations from central Sakhalin have a haplotype-rich composition including different genetic lineages that confirm the existence of a hotspot of genetic diversity in this part of the island.

Endogenic and Exogenic Hazardous Relief-Forming Processes on Sakhalin Island

Endogenous and exogenous relief-forming processes on Sakhalin Island are very dynamic. This can be due to both geological and tectonic (the position of the island on the border of tectonic plates, the predominance of easily destroyed rocks), and geographic factors (including the active interaction between oceanic and continental air masses and altitude). An active Central Sakhalin fault separating microplates provides primary control over seismicity and can have a noticeable effect on mud volcanism. The activity of a mud volcano, taking into account the impact on adjacent valleys, can affect up to 10 km2. The most common exogenous processes of the island are landslides, avalanches and mudflows. Up to 70% of Sakhalin’s territory is subject to these dangerous processes. They are also often triggered by seismic events. It is extremely difficult to predict the exact location and type of activated processes, as well as the time and frequency of their activation. The proposed map of tension in geomorphic systems makes it possible to conduct a reconnaissance assessment of the region, as well as a comparison between individual zones and determine the most dangerous ones.

Картографирование разломов на территории Cеверо-Cахалинской равнины по данным дистанционного зондирования земли

The article presents the results of the research of the fault zones of earth’s crust within the North Sakhalin plain using the lineament analysis of the SRTM model. The faults be identified in order to increase the information content of the maps of geological content. SRTM data was used as input. The analysis performed using the functionality of the LEFA software package. The use of SRTM data made it possible to assess disjunctive disorders in territory of the north of Sakhalin Island. The images of surface were analyzed using the binary-morphological erosion operation or using Canny mathematical algorithms with further digital processing by means of Hough Transform. The paper reveals the position of linear elements in different parts of the North Sakhalin plain. Excellent test of the quality of performed definitions was the results of earlier studies of the eastern part of the North Sakhalin Plain, which were carried out in connection with the development of hydrocarbon deposits and after the strong Neftegorsk earthquake. The data obtained served as the basis for drawing up a map of disjunctive disturbances of Sakhalin Island at scale of 1:500,000. Depending from scale, spatial resolution, and level of generalization of image, disjunctive disturbances of different lengths (transregional, regional, sub-regional, local) and ranks (1 rank from a few to hundred meters, 2 rank from a hundred meters to a kilometer, 3 rank from 1 km to 35 km, 4 rank from 35 to 100 km, 5 rank more than 100 km). The analysis of the SRTM model with the help of the LEFA toolkit allowed us to identify the zones where the earth’s crust fractures are located. The analysis of the SRTM model with the help of the LEFA toolkit allowed us to identify the zones where the earth’s crust fractures are located. As aresult of the analysis, the West Sakhalin, Central Sakhalin, Hokkaido-Sakhalin (Upper Piltun segment), Piltun, Garomai, Val-Langri, Gyrgylany-Daginsky, South Baikal, Udyl and many other faults of less than rank 2 were identified. The main results of the work will be useful in choosing places for the construction of economic and industrial facilities, as well as in the search and exploration of mineral deposits.

Сейсмоакустические наблюдения с применением молекулярно-электронных гидрофонов на Сахалине и южных Курильских островах (о. Кунашир)

The article presents the main characteristics and studies spectral and recording capabilities of experimental samples of three types of molecular-electronic hydrophones with different sizes of electrochemical converting cells, which were installed in the central part of the south of Sakhalin Island and on Kunashir Island (southern part of the Kuril ridge) at the end of 2018. A hydrophone on a new technological basis (with an increased sensor sensitivity relative to previously conducted studies) was approved on Kunashir Island. Equipment of this type was used for observations on the territory of the Sakhalin region for the first time. As a result of continuous seismoacoustic observations on Kunashir Island, in seven cases out of 35 studied (from May 1, 2019 to February 29, 2020) earthquakes, a low-frequency anticipatory signal (LFAS) was detected, and all seven events had a depth of hypocenter of more than 80 km. In the area of the Central Sakhalin fault, in addition to the possibility of registering the LFAS, spectral features in the recording of waveforms were studied for different conditions of instrument installation. It is shown that the influence of such atmospheric factor as wind load significantly affects hydrophones located in a shallow water body and a shallow open borehole. It is shown that the influence of such atmospheric factor as wind load significantly affects hydrophones located in a shallow water body and a shallow open borehole. However, molecular-electronic hydrophones have demonstrated the ability to fully record seismic events regardless of the installation conditions of the equipment.

Новые данные о новейшем напряженном состоянии земной коры острова Сахалин (по структурно-геоморфологическим индикаторам тектонических напряжений)

To verify the ideas about neotectonic and modern stresses of Sakhalin, we analyze structural and geomorphological signs of the stress state of this region, discovered during field work in 2019–2020. Along with updated field measurements using the structural-geomorphological method, data on crustal deformation based on GPS/GLONASS measurements are presented. Data from geophysical studies (seismological and borehole methods) are given. The identification of three types of areas with different geodynamic regime: transtension, transpression and strike – slip (simple shift) is confirmed. Variations of the current stress field at the boundaries of regions with different geodynamic regime for the formation of new faults are noted. Northern Sakhalin has specific directions of compression axes of neotectonic stresses, expressed in North-Eastern orientations, in contrast to the prevailing sublatitudinal orientations on the entire island. Studies have shown that in the south of Sakhalin, the border between the Amur and Okhotsk microplates runs along the West Sakhalin fault rather than the Central Sakhalin fault.

КРИЛЬОНСКОЕ ЗЕМЛЕТРЯСЕНИЕ 25 ноября 2013 г. с Mw=5.2, I0р=6–7 (о. Сахалин)

On November 25, 2013, at 03:23 UTC, an earthquake with a magnitude of МwGCMT=5.2 was recorded in the Laperuz Strait water area. This earthquake was the strongest in the south of Sakhalin Island in 2013. Parameters of the earthquake have been determined by data of seismic stations of the regional network of GS RAS Sa-khalin branch, seismic stations of global network IRIS (GSN) and Hokkaido University. Earthquake parameters on data of regional network are in accordance with data of the international seismological centers. The intensity of concussions in some areas of Sakhalin was 4–5 points on a scale of MSK-64 and 3 points on the JMA scale on the island of Hokkaido. The focus shift has happened under conditions of close horizontal compression, seismodislocation type – uplift. The earthquake of 2013 has arisen in the place of regional tec-tonic structures contact – breaks of West Sakhalin and Central Sakhalin. The seismic model was described by data of local network of field stations. Results of observations of an earthquake on November 25, 2013 are written in this article.

Use of Waveform Cross Correlation to Reconstruct the Aftershock Sequence of the August 14, 2016, Sakhalin Earthquake

The waveform cross correlation technique is used to detect signals from aftershocks of the ML = 6.1, August 14, 2016, Sakhalin earthquake using regional seismic network data. Regular P- and S-wave phase arrivals are associated with seismic sources; the resulting cross correlation bulletin is compared with a standard seismic bulletin for the same aftershock sequence. An advantage of the cross correlation bulletin is that it has more detected seismic events tied to three or more stations and a lower catalog completeness threshold; even the epicenters of the weakest aftershocks are located with greater accuracy. The exact aftershock locations tend to cluster along a narrow zone related to the Central Sakhalin Fault.

About seismic observations on Sakhalin with the use of molecular-electronic seismic sensors of new type

To conduct complex geophysical observations in the area of the Central Sakhalin Fault, an experimental geophysical test site was created, including a broadband molecular electronic type station and a new development of the Molecular Electronics Center - molecular electronic hydrophone. A module for placing a molecular-electronic seismometer at the test site has been developed and arranged. The noise level of the seismometer was analyzed and compared with the reference data. The results of hydroacoustic observations of weak earthquakes in the area of the Central-Sakhalin fault using a molecular-electron hydrophone are presented. The characteristics of the recorded acoustic emission signals from earthquakes perceived by the hydrophone station (frequency spectrum, arrival times of seismic waves) are investigated. The issues of operation and maintenance of molecular-electronic sensors with seismic signal data logger at various stages of seismological observations (setting up equipment, acquisition and storing data) were considered. The analysis of recording capabilities of seismic equipment was performed. Conclusions about the advantages and disadvantages of molecular-electronic sensors and their use on Sakhalin are made.

Bear and Dog Remains From an Agnevo River Sacred Site (Central Sakhalin)

The article compares data using archeo-zoological methods with ethnographic data for the first time. Brown bear and domestic dog bone mounds reveal rituals of the indigenous population of the Far East. Bear and dog bones uncovered on the central west coast of Sakhalin in front of a small grotto at the mouth of the Agnevo River establish the existence of a Nivkh sacred site. The disposal of the bones has permitted identification of the sacred site as belonging to the Ksyusvongun kin group. Traces on the bones have underscored distinctive kin group rites, distinguishing them from other Sakhalin Nivkh groups, and have indicated the possible influence of Amur Nivkh and island Ainu.

Геофизические исследования в южной части Центрально-Сахалинского разлома с использованием нового комплекса оборудования

Геофизические исследования в южной части Центрально-Сахалинского разлома с использованием нового комплекса оборудования

Современная сейсмичность в районе Центрально-Сахалинского разлома (юг о. Сахалин): ложная тревога или отодвинутый прогноз?

Современная сейсмичность в районе Центрально-Сахалинского разлома (юг о. Сахалин): ложная тревога или отодвинутый прогноз?

Late Eocene granites in the Central Sakhalin Island (Russian Far East) and its implication for evolution of the Sakhalin-Hokkaido orogenic belt

The Sakhalin-Hokkaido orogenic belt along the western margin of the Okhotsk Sea is an important early Cenozoic accretionary orogen related to subduction of the Paleo-Pacific oceanic plate. In order to study the Eocene evolution of this accretionary orogen and related magmatism, we carried out zircon UPb dating, whole-rock elemental and SrNd isotopic analyses on the Langeri and Val'za granitic plutons that intruded the East Sakhalin accretionary complex in the central Sakhalin Island. Zircon UPb dating results revealed that the Langeri and Val'za plutons were emplaced in the late Eocene at 38–36 Ma. Whole-rock elemental data indicate that granitoids are mainly peraluminous S-type with subordinate I-type granites, and all granitic samples show arc-like geochemical affinity. Whole-rock SrNd isotopic results show consistent low initial 87Sr/86Sr ratios (0.7042 to 0.7049), positive εNd(t) values (+1.7 to +3.1) and young Nd two-stage model ages (611 to 717 Ma). Elemental and isotopic data reveal that granitic rocks of the Langeri and Val'za plutons were generated from remelting of metasediments and amphibolites in the accretionary complex. From comprehensive analyses of regional tectonics, we concluded that the late Eocene granitic rocks were generated in a syn-collisional tectonic setting, marking the timing for formation of the Sakhalin-Hokkaido orogenic belt. The middle-late Eocene welding of the Okhotsk Sea Plate and the Eurasia Plate is the most plausible mechanism that caused crustal thickening beneath the Sakhalin Island, and anatexis of metasediments and oceanic crustal materials in the lower crust might be responsible for the formation of late Eocene granitic rocks. Considering the Eocene tectonic events in NE Asia, late Paleocene to early Eocene subduction of the Kula-Pacific ridge beneath the Hokkaido Island and Eocene initial rift of pull-apart basins along strike-slip fault system in the Hokkaido and Sakhalin Islands may also contribute to the emplacement of Eocene magmatism in the Sakhalin-Hokkaido orogenic belt.