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 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 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.

Seismic activity along a Cretaceous magmatic intrusion in Monchique, SW Iberia

2020 ◽  
Author(s):  
Analdyne Soares ◽  
Susana Custódio ◽  
Marta Neres ◽  
Dina Vales ◽  
Luís Matias
Keyword(s):  
Seismic Activity ◽  
Active Faults ◽  
Plate Boundary ◽  
Velocity Model ◽  
Historical Record ◽  
Focal Mechanisms ◽  
Magmatic Intrusion ◽  
Mainland Portugal ◽  
3D Velocity Model ◽  
Paleozoic Rocks

<p>Iberia, located at the southwestern end of Europe, displays a complex pattern of seismic activity, with most known active faults slipping at low rates (< 1 mm/yr). However, the seismic activity is remarkable, with numerous earthquakes in the historical record proving destructive. The earthquake cluster in mainland Portugal that has a highest rate of seismic activity is very localized (small spatial extent), extends vertically from 5 to 20 km depth and lays on the Monchique late Cretaceous magmatic intrusion, in SW Portugal. This magmatic intrusion forms strong rheological contrast between the intruded magmatic rocks and surrounding Paleozoic rocks. Furthermore, it is the locus of abundant natural water springs. Several pertinent questions remain to be answered concerning earthquakes in Monchique: Are earthquakes in Monchique simply a response to tectonic stresses (given the proximity of Monchique to the EU-AF plate boundary), with the localization of brittle failure in the region facilitated by the rheological contrast between the Cretaceous intrusion and surrounding Paleozoic rocks? Do fluids play a role in facilitating slip in existing fractures? Or, conversely, is the circulation of fluids facilitated by the faulting that results from the rheological contrasts? Are there hazardous faults in Monchique? In this presentation, we re-analyze in detail the seismic data recorded by the regional permanent seismic network, in order to better understand the relationship between seismic activity and igneous intrusion. In particular, we re-locate earthquakes using NonLinLoc and PRISM3D, a 3D velocity model for the region. At a subsequent step, we re-locate earthquakes using HypoDD. We also perform a clustering analysis based on waveform similarity and compute focal mechanisms for the region. The results show that earthquakes align along two main directions, E-W and NNE-SSW, coinciding with surface features of the magmatic intrusion. Focal mechanisms indicate dominantly strike-slip faulting, with the possible fault planes coinciding with the favored directions of earthquake lineations. We investigate the spatio-temporal evolution of seismicity and address possible forcing mechanisms, including tidal forcing.</p><p> </p><p> </p><p><span>The author would like to acknowledge the financial support  FCT through project</span><span> UIDB/50019/2020 </span>– IDL and PTDC/GEO-FIQ/2590/2014 - SPIDER.</p>

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 Revelation of Potentially Seismic Dangerous Tectonic Structures in a View of Modern Geodynamics of the Eastern Caucasus (Azerbaijan)

2021 ◽  
Author(s):  
Talat Kangarli ◽  
Tahir Mammadli ◽  
Fuad Aliyev ◽  
Rafig Safarov ◽  
Sabina Kazimova
Keyword(s):  
Stress State ◽  
Active Faults ◽  
Focal Mechanisms ◽  
Seismic Events ◽  
Tectonic Structures ◽  
The North ◽  
Potential Source ◽  
Deep Faults ◽  
Source Zones ◽  
Lateral Displacements

The stress state of the earth’s crust in the Eastern Caucasus, located in the zone of collision junction of the North Caucasian, South Caucasian, and Central Iranian continental massifs, is a consequence of the inclusion of the Arabian indenter into the buffer structures of the southern framing of Eurasia at the continental stage of alpine tectogenesis. This evidenced from the results of geophysical observations of the structure and seismic-geodynamic activity of the region’s crust. The latter, at the neotectonic stage, was presented as underthrust of the South Caucasian microplate under the southern structures of Eurasia. The analysis and correlation of historical and recent seismic events indicate the confinement of most earthquake foci to the nodes of intersection of active faults with various orientations or to the planes of deep tectonic ruptures and lateral displacements along unstable contacts of material complexes of various competencies. The focal mechanisms of seismic events reveal various rupture types, but in general, the earthquake foci are confined to the nodes of intersection of faults of the general Caucasian and anti-Caucasian directions. Based on the observed weak seismicity, active areas of deep faults were identified, which are accepted as potential source zones.

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.

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.

Looking for the hidden morphological signature of active faults in a Low Strain Rate region: clues from the eastern Kachchh region (NW India) 

2021 ◽  
Author(s):  
Eshaan Srivastava ◽  
Nicolò Parrino ◽  
Javed Malik ◽  
Fabrizio Pepe ◽  
Pierfrancesco Burrato
Keyword(s):  
Strain Rate ◽  
Multidisciplinary Approach ◽  
Surface Deformation ◽  
Active Faults ◽  
Tectonic Geomorphology ◽  
Seismic Events ◽  
Rate Region ◽  
Ongoing Work ◽  
Morphotectonic Evolution ◽  
Low Strain Rate

<p>The Kachchh region (NW India), a pericratonic rift basin delimited by E-W trending major thrust faults, is a Low Strain Rate region[PB1] . In this area, the tectonic forcing magnitude is stronger enough to trigger infrequent significant earthquakes but not enough to overprint the climatic forcing signature. As a consequence, the active faults sources of the largest seismic events are largely poorly known and their geomorphic signature is subdued. </p><p>Instrumental and paleoseismological evidence highlights that the eastern part of Kachchh experienced a significant number of seismic events such as the 1819-06-16 Allah Bund earthquake (Mw 7.8, also known as the Rann of Kutch earthquake), the 1956-07-21 Anjar earthquake (Mw 6.1), the 2001-01-26 Bhuj earthquake (Mw 7.6) and the 2006 events (Mw 5.0 and 5.6 earthquake occurred along Island Belt Fault and Gedi fault). </p><p>In this region, the unavailability of useful outcrop information due to a significant climatic overprinting of the fault’s morphological signatures hampers the detection and parametrization of actively deforming faults.</p><p>For this reason, in this ongoing work, we propose a multidisciplinary approach, aimed at detecting active geological structures and their related [PB2] surface deformation, which mainly consists of quantitative tectonic geomorphology and paleoseismological analyses and structural interpretation and modelling. Preliminary results are a morphotectonic evolution model and 3D fault model of the study area. Finally, we stress the concept that only a multidisciplinary approach could provide useful information to understand better the highly debated active tectonic framework of the study area.</p>

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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