scholarly journals General regularities of seismic activity of Northern Armenia in connection with block structure and tectonic activity

2020 ◽  
Vol 11 (3) ◽  
pp. 595-605
Author(s):  
K. S. Ghazaryan ◽  
R. S. Sargsyan
Keyword(s):  
Spatial Distribution ◽  
Seismic Activity ◽  
Block Structure ◽  
Focal Mechanisms ◽  
Tectonic Activity ◽  
Seismic Events ◽  
Long Period ◽  
Fault Structures ◽  
Block Structures ◽  
Regular Patterns

The study is focused on searching for spatial regularities in the occurrence of earthquake hypocenters in different geological settings in Northern Armenia. Tectonic-geomorphological indices are applied to define the tectonic activity of blocks composing the study area, which was manifested within a long period of time, starting from the neotectonic development period. The blocks are classified accordingly. The regional seismic activity is analysed considering the block structure of the study area. Earthquake focal mechanisms are determined, and dominant displacement trends are identified. Based on the comparative analysis of the blocks’ tectonic activity indicators and the locations of seismic events differing in strength, regular patterns of spatial distribution of seismic events are identified. It is established that the earthquake hypocenters of different strength occur in certain block structures; and the predominant types of movements in the earthquake hypocenters are largely determined by types of fault structures. It is emphasized that investigating the blocks’ neotectonic activity is important for discovering the general patterns of spatial distribution of seismic events.

scholarly journals Recent geodynamics, active faults and earthquake focal mechanisms of the zone of pseudosubduction interaction between the Northern and Southern Caucasus microplates in the southern slope of the Greater Caucasus (Azerbaijan)

2018 ◽  
Vol 9 (4) ◽  
pp. 1099-1126 ◽  
Author(s):  
T. N. Kangarli ◽  
F. A. Kadirov ◽  
G. J. Yetirmishli ◽  
F. A. Aliyev ◽  
S. E. Kazimova ◽  
...  
Keyword(s):  
Seismic Activity ◽  
Active Faults ◽  
Accretionary Prism ◽  
Focal Mechanisms ◽  
Northern Caucasus ◽  
Seismic Events ◽  
Southern Slope ◽  
Compression Process ◽  
Greater Caucasus ◽  
Southern Caucasus

Our study was focused on the active tectonics of the southern slope of the Greater Caucasus within Azerbaijan. The study area is the zone of under-thrusting (pseudosubduction) interaction between Southern and Northern Caucasus continental microplates, which caused the tectonic stratification of the Alpine formations into various allochthonous and parauthochthonous thrust slices of southern vergency between the Middle Bajocian and Quaternary periods. These slices are grouped into the nappe complexes that form the modern structure of the trough in the study area. The large linearly stretched tectonic units (megazones) correspond to the axis of the Alpine marginal sea basin, the consolidated crust of which is subjected to destruction and thinning. The trough’s Alpine cover was compressed in the underthrust zone and pushed southwards. As a result, an accretionary prism formed allochthonously overlapping the northern side of the Southern Caucasus microplate by the system of gently dipping overthrusts. During the continental stage of Alpine tectogenesis (starting from the end of Miocene), intensive lateral compression process was caused by intrusion of the frontal wedge of the Arabian indenter into the buffer structures of the southern frame of Eurasia. This is evidenced by the GPS monitoring data on modern geodynamic activity, which demonstrates the Southern Caucasus block’s intensive (up to 29 mm/year) intrusion in the northern rhumbs as compared to the relative stability of the Northern Caucasus microplate (0–6 mm/year). This, in turn, is a reflection of the ongoing pseudosubduction regime (continental subduction or S-subduction) at the band of collision junction of these microplates. It is suggested that this process caused historically observed seismic activity in the study area, wherein the earthquakes occurred mainly in the southern slope’s accretionary prism area and the adjacent strip of the Southern Caucasus microplate. In this article, we analyze and correlate the whole range of seismic events that occurred in the study area until 2017 and the focal mechanisms of the recently recorded earthquakes (2012–2016). It is established that earthquake foci are confined either to the intersection nodes of variously trending ruptures with the faults of different directions or to the planes of deep tectonic ruptures and lateral displacements along the unstable contacts between the material complexes with different competence. The focal mechanisms of seismic events reveal various, mostly near-vertical, planes of normal and strike-slip faults. However, the earthquake foci are generally confined to the intersection nodes between the Caucasus and anti-Caucasus-striking rupture dislocations. The results of our studies are interesting in terms of their real-time application for drawing a regional summary of causes for both geodynamic and seismic activity of the Greater Caucasus system and the adjacent areas of Alpine-Himalayan fold belt.

scholarly journals SAKHALIN

2020 ◽  
pp. 152-161
Author(s):  
T. Fokina ◽  
D. Safonov ◽  
D. Kostylev ◽  
V. Mikhaylov
Keyword(s):  
Seismic Activity ◽  
Focal Mechanisms ◽  
Local Network ◽  
Seismic Events ◽  
Regional Network ◽  
Strong Earthquakes ◽  
Seismic Regime ◽  
Seismic Stations ◽  
Macroseismic Effect

A review of the Sakhalin seismicity in 2014 based on the data of regional network is given. The network included four stationary and ten temporary digital seismic stations. This network was supported by ten stations of local network operating in the south of Sakhalin. Parameters of 450 seismic events, including 25 explosions, and focal mechanisms for 4 events are determined. 22 earthquakes had a macroseismic effect. The map of earthquake completeness and the map of epicenters are given. The distribution of crust and deep earthquakes on magnitude and their summarized energy for seven seismoactive areas in comparison with average parameters for 2001–2013 are presented. For each area and the region as a whole, an analysis of the seismic regime parameters in 2014 in comparison with long-term parameters is given, tangible and strong earthquakes are described. The seismicity of the Sakhalin region in 2014 can be characterized as a moderate one. Somewhat increased seismic activity was recorded in the East Sakhalin and Southeastern areas.

scholarly journals The recent instrumental seismicity of Syria and its implications

2018 ◽  
Vol 57 (2) ◽  
Author(s):  
Mohamad Khir Abdul-Wahed ◽  
Jamal Asfahani
Keyword(s):  
Seismic Activity ◽  
Current Knowledge ◽  
Active Faults ◽  
Historical Seismicity ◽  
Focal Mechanisms ◽  
Seismic Events ◽  
Earthquake Activity ◽  
Return Periods ◽  
Cluster Type ◽  
Large Earthquakes

This contribution is an attempt to enlarge the current knowledge about the recent instrumental seismicity, recorded during the period 1995- 2012 by the Syrian national seismological network, as well as the seismotectonic settings in Syria. The recent instrumental seismicity has shown that the earthquake activity has produced a little number of low magnitude events. Consequently, it indicates that this activity is actually passing through a relative quiescence in comparison with the historical seismicity. The correlation between the instrumental seismicity and the seismotectonic features was performed by analyzing spatial distributions of seismic events and focal mechanisms of some strongest events. The current results, allow observing many types of the seismic activity as follows: Swarm-type, Cluster- type, and Occasional-type, which could improve the understanding of the behavior of the seismically active faults. The long return periods of large earthquakes (M?5) and the shortness of instrumental seismicity, prevent us to completely characterize the seismic activity and to discover all the active faults in the country.

scholarly journals BAYKAL and TRANSBAIKALIA

2019 ◽  
Author(s):  
Valentina Melnikova ◽  
N. Gileva ◽  
O. Masalskii
Keyword(s):  
Seismic Activity ◽  
Rift Zone ◽  
Baikal Rift Zone ◽  
Strike Slip ◽  
Focal Mechanisms ◽  
Normal Faults ◽  
Seismic Events ◽  
High Degree ◽  
South Baikal

The seismicity of Pribaikalye and Transbaikalia in 2013 is reviewed. 6706 earthquakes with КР≥5.6 were recorded there during that year. Most of them (92 %) are located in the Baikal rift zone. The high degree of clustering of seismic events is observed in South Baikal and Baikal-Muja areas. The largest earthquake with Mw=4.3 was in the Baikal-Muja area. Focal mechanisms of 47 earthquakes (КР9.6) were determined in 2013. Most of them correspond to normal faults, with strike-slip component contribution in some cases. Overall, the rate of seismic activity observed in Pribaikalye and Transbaikalia in 2013 was low.

Performance of a rotational sensor at Etna, Italy focusing on back-azimuth estimations of volcano-seismic events

2021 ◽  
Author(s):  
Martina Rosskopf ◽  
Eva P. S. Eibl ◽  
Gilda Currenti ◽  
Philippe Jousset ◽  
Joachim Wassermann ◽  
...  
Keyword(s):  
Rotation Rate ◽  
Mount Etna ◽  
Seismic Events ◽  
Volcano Seismology ◽  
Rotational Seismology ◽  
Long Period ◽  
Tectonic Events ◽  
Back Azimuth ◽  
Seismic Wavefield

<p>The field of rotational seismology has only recently emerged. Portable 3 component rotational sensors are commercially available since a few years which opens the pathway for a first use in volcano-seismology. The combination of rotational and translational components of the wavefield allows identifying and filtering for specific seismic wave types, estimating the back azimuth of an earthquake, and calculating local seismic phase velocities.</p><p>Our work focuses on back-azimuth calculations of volcano-tectonic and long-period events detected at Etna volcano in Italy. Therefore, a continuous full seismic wavefield of 30 days was recorded by a BlueSeis-3A, the first portable rotational sensor, and a broadband Trillium Compact seismometer located next to each other at Mount Etna in August and September of 2019. In this study, we applied two methods for back-azimuth calculations. The first one is based on the similarity of the vertical rotation rate to the horizontal acceleration and the second one uses a polarization analysis from the two horizontal components of the rotation rate. The estimated back-azimuths for volcano-tectonic events were compared to theoretical back-azimuths based on the INGV event catalog and the long-period event back-azimuths were analyzed for their dominant directions. We discuss the quality of our back azimuths with respect to event locations and evaluate the sensitivity and benefits of the rotational sensor focusing on volcano-seismic events on Etna regarding the signal to noise ratios, locations, distances, and magnitudes.</p>

Basic principles for building seismic monitoring systems in rockburst-hazardous coal seam mining

2021 ◽  
pp. 8-12
Author(s):  
E. E. Razumov ◽  
◽  
S. M. Prostov ◽  
G. D. Rukavishnikov ◽  
S. N. Mulev ◽  
...  
Keyword(s):  
Seismic Activity ◽  
Average Energy ◽  
Seismic Monitoring ◽  
Acoustic Properties ◽  
Signal Frequency ◽  
Monitoring Systems ◽  
Seismic Events ◽  
Seismic Monitoring Systems ◽  
Seismic Sensors ◽  
Seam Mining

The main directions of development of seismic monitoring systems in underground mineral mining are analyzed. The expediency of passive registration of natural seismic activity is proved, which provides prediction of geodynamic phenomena by locating the centers of seismic events and determining their energy level. The methods of active seismic monitoring (seismic tomography, cross-borehole survey, recording of seismic signal from a rock-breaking tool) are technically more difficult to implement. The promising methods for processing seismic information are geolocation, neural network technology, cluster analysis, and integration with numerical stress–strain analysis of and changes in acoustic properties of rock mass. The configuration of the platform developed at VNIMI and the GITS seismic monitoring system, which includes from 6 to 12 three-component seismic sensors installed permanently in wells or on pedestals, is described. The detailed layouts of seismic sensors at recording points and in gateways in extraction panels are presented. The main technical characteristics of GITS are given: the signal frequency range is 0.1–1000 Hz, the minimum recorded signal level is 0.01 mV. The main test data of GITS in Komsomolskaya mine of Vorkutaugol are described: the average annual levels of seismic activity and energy of seismic events are found to be relatively stable; the relationship between seismic event with the maximum total energy and the alternating increment in the relative criterion is defined, and the local increase in the average energy of a single event in time from the moment the main roof caving is identified. Aimed to substantiate the regional and local prediction criteria of probability of geodynamic events caused by confining pressure, VNIMI implements integrated research in mines in different regions.

scholarly journals Stratigraphy of amethyst geode-bearing lavas and fault-block structures of the Entre Rios mining district, Paraná volcanic province, southern Brazil

2013 ◽  
Vol 86 (1) ◽  
pp. 187-198 ◽  
Author(s):  
LÉO A. HARTMANN ◽  
LUCAS M. ANTUNES ◽  
LEONARDO M. ROSENSTENGEL
Keyword(s):  
Block Structure ◽  
Underground Mines ◽  
Mining District ◽  
Volcanic Province ◽  
Fault Block ◽  
River Bed ◽  
World Class ◽  
Entre Rios ◽  
Block Structures

The Entre Rios mining district produces a large volume of amethyst geodes in underground mines and is part of the world class deposits in the Paraná volcanic province of South America. Two producing basalt flows are numbered 4 and 5 in the lava stratigraphy. A total of seven basalt flows and one rhyodacite flow are present in the district. At the base of the stratigraphy, beginning at the Chapecó river bed, two basalt flows are Esmeralda, low-Ti type. The third flow in the sequence is a rhyodacite, Chapecó type, Guarapuava subtype. Above the rhyodacite flow, four basalt flows are Pitanga, high-Ti type including the two mineralized flows; only the topmost basalt in the stratigraphy is a Paranapanema, intermediate-Ti type. Each individual flow is uniquely identified from its geochemical and gamma-spectrometric properties. The study of several sections in the district allowed for the identification of a fault-block structure. Blocks are elongated NW and the block on the west side of the fault was downthrown. This important structural characterization of the mining district will have significant consequences in the search for new amethyst geode deposits and in the understanding of the evolution of the Paraná volcanic province.

scholarly journals Seismic activity in the focus of the Uglegorsk earthquakes, Sakhalin Island in relevance to intensive development of coal deposits

2021 ◽  
Author(s):  
Dmitry Kostylev ◽  
Natalya Boginskaya ◽  
Alexander Zakupin
Keyword(s):  
Brown Coal ◽  
Coal Mine ◽  
Seismic Activity ◽  
Large Scale ◽  
Slope Angle ◽  
Sakhalin Island ◽  
Corner Frequency ◽  
Seismic Events ◽  
Velocity Spectrum ◽  
Human Engineering

Abstract Induced seismicity is an increase in seismic activity caused by the human engineering. An example of such activity is the mineral exploration, large water reservoirs construction, exploitation of underground oil and gas storages, etc. The authors studied the seismicity in the Uglegorsky district of Sakhalin region, where the Solntsevskoye brown coal field is located, which is the most promising in the island. Its area is over 100 sq. km, and productive strata of the Verkhneduiskaya formation with a thickness of up to 600 m contains 12 coal seams, 8 of which are working. Active mining of brown coal is carried out at the Solntsevsky coal mine, and blasting operations are performed on a large scale, that, as a result, does not exclude the relation of the seismic process to technogenic seismicity. The earthquake recurrence curves for two decades beginning from 2000 to the present were constructed in the work to compare the characteristics of the seismic regime in the studied area. The difference in the slope angle of recurrence graph during the period of 2011-2020 (the period of the most active development of the Solntsevsky coal mine) from the previous decade is quite significant. The maps of spatiotemporal distribution of seismic events epicenters in the vicinity of Solntsevsky coal mine are constructed. The contraction of zones of seismic events concentration to the mining areas, first of all to the Solntsevsky coal mine, have been found. Such a combination allows us to talk about an increase in seismicity of the region during the last years and change in its character from the natural to a mixed natural and technogenic. The focal mechanisms of the largest earthquakes occurred in the Uglegorsky district have been constructed in order to prove the change in seismicity character and reasons for the earthquake occurrence in the studied area. The mechanisms of seismic events of 2020 are classified as strike-slip faults, that is not character for the most earthquakes on the territory of Sakhalin Island. The authors made an attempt to determine the regularities of the parameters of the produced blasts and earthquakes through dynamic parameters of the seismic events foci by means of studying the frequency content of earthquakes and blasts in order to determine a corner frequency from the focal velocity spectrum.

scholarly journals VÝJIMEČNÉ ZEMĚTŘESENÍ JV. OD POZNANĚ (POLSKO) ZAZNAMENANÉ 6. 1. 2012

2012 ◽  
Vol 19 (1-2) ◽  
Author(s):  
Josef Havíř ◽  
Jana Pazdírková ◽  
Zdeňka Sýkorová
Keyword(s):  
Seismic Activity ◽  
Historical Earthquakes ◽  
Seismic Events ◽  
Local Magnitude ◽  
Sequence Of Events ◽  
The Earth ◽  
Moderate Earthquake ◽  
South Moravia

On January 6, 2012, a moderate earthquake was observed in a region SE of Poznań (local magnitude ML = 3.6 according to Institute of Physics of the Earth, IPE). In this region, there haven‘t been known any historical earthquakes so far, and no natural seismic activity has been observed up to present. Similar rare occurrences of weak and moderate earthquakes were observed in a region near Kaliningrad in 2004 (sequence of events, local magnitude of strongest event being 5.0) and in south Moravia region near Znojmo in 2000 (local magnitude ML = 2.5). These facts show that even in seismically quiet regions occurence of weak to moderate seismic events (with value of magnitude ranging from 3 to 5) could be expected.

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