scholarly journals TECTONIC POSITION, SISMOLOGICAL AND GEOLOGICAL MANIFESTATION OF 7 SEPTEMBER 2009 ONI?II EARTHQUAKE FOCUS ON THE SOUTHERN SLOPES OF THE GREAT CAUCASUS

2017 ◽  
Author(s):  
Е.А. Рогожин
Keyword(s):  
Main Shock ◽  
Focal Depth ◽  
Seismic Source ◽  
Epicentral Area ◽  
Strong Earthquakes ◽  
North East ◽  
The North ◽  
Tectonic Position ◽  
South Slope ◽  
Racha Earthquake

В статье приведены сейсмологические и сейсмотектонические материалы о главном толчке и афтершоках Онийского-II землетрясения 7 сентября 2009 г. с Мs = 5,8 на южном склоне Большого Кавказа. Положение облака эпицентров основного толчка и афтершоков совпадает с северной ветвью очаговой зоны Рачинского землетрясения 29.04.1991 г. с МS = 7,0, I0 = 7-8. Глубина гипоцентра основного толчка составляет 8?15 км. В качестве действующей в очаге принята пологая плоскость, погружающаяся в север – северо-восточном направлении. Тип подвижки по такой плоскости – надвиг с компонентами правостороннего сдвига. Сейсмодислокации носили вторичный, гравитационный характер. Результаты палеосейсмологические исследований, проведенных в восточной части эпицентральной области, Рачинского землетрясения, показали, что в этом сейсмической очаге и раньше происходили сильне сейсмические толчки. Согласно полученным данням возраст предыдущего сильного землетрясения в Рача-Джавской зоне (т. е. до 1991 г.) – около 2000 лет назад. Еще одно, болем древнее событие произошло около 6000 лет назад. Период повторяемости сильних землетрясений, подобных катастрофе 1991 г., таким образом, составляет в среднем 2000-3000 лет. The article provides seismological and seismotectonic materials about the main shock and aftershocks of the Oni-II earthquake of 7 September 2009, with MS = 5,8 on the South slope of the Greater Caucasus. The position of the cloud of epicenters of the main shock and aftershocks coincides with the northern branch of the focal zone of 29.04.1991 Racha earthquake, MS = 7,0, I0 = 7?8. The focal depth of the main shock is 8 to 15 km. As the active in the focus adopted the sloping plane, plunging to the North – North-East direction. Type progress on such a plane – thrust with component of right-lateral strike-slip. Seismodislocationswere of secondary gravitational nature. The results of paleoseismological studies conducted in the Eastern part of the epicentral area of the Racha earthquake, showed that this seismic source the strong seismic shocks happened before. According to the obtained data, the age of the previous strong earthquake in the Racha – Dzhava zone (i.e., before 1991) – about 2000 years ago. Another, more ancient event occurred about 6,000 years ago. The recurrence period of strong earthquakes, similar to the disaster of 1991, thus, is an average of 2000?3000 years.

Advances in earthquake-swarms monitoring networks WEBNET and REYKJANET

2020 ◽  
Author(s):  
Jakub Klicpera ◽  
Jana Doubravová ◽  
Josef Horálek
Keyword(s):  
Main Shock ◽  
Plate Boundary ◽  
Earthquake Swarms ◽  
Monitoring Networks ◽  
Epicentral Zone ◽  
Epicentral Area ◽  
The North ◽  
Short Period ◽  
West Bohemia ◽  
Reykjanes Peninsula

<p>The IG CAS in cooperation with IRSM CAS operates two local seismic networks deployed to monitor the seismic swarms in West Bohemia/Vogtland, Czechia and Reykjanes Peninsula, Iceland. </p><p>WEBNET monitors the region of West Bohemia since 1991 developing from 4 short period stations to 24 broadband stations today. The seismoactive region West Bohemia/Vogtland lies in the border area between Czechia and Germany in the western part of Bohemian Massif. It is an intra-continental area with persistent swarm-like seismicity but rarely also main-shock after-shock sequences may occur. </p><p>REYKJANET local seismic network is situated in Reykjanes Peninsula on Southwest Iceland. The area is an onshore part of the mid-Atlantic plate boundary between the North America and Eurasia Plates. The seismic activity of Reykjanes peninsula is represented by typical main-shock after-shock sequences as well as earthquake swarms. The REYKJANET network was built in 2013 and it consists of 15 stations placed around the epicentral area.</p><p>Both networks have been substantially upgraded during the last years. In case of REYKJANET the replacement of old sensors and digitizers with new ones made the operation easier and ready for near future plan to stream the waveform files in real time. WEBNET network which was long years divided into two subnets – on-line permanent stations and off-line autonomous stations, was recently homogenized by eco-powering and 4G LTE data connecting of the off-line stations. Additonally, the micro network HORNET was deployed within the WEBNET epicentral zone to monitor Horka water dam.</p><p>Data from both above mentioned networks are automatically searched for seismic events by the neural-network-based detector designed by Doubravová et al. (2016, 2019) providing event list with completeness magnitude Mc=0 for REYKJANET and Mc=-0.5 for WEBNET. The main difference of sensitivity is given by different noise levels of the two networks.</p>

scholarly journals MUYAKAN-II EARTHQUAKE on MAY 23, 2014 with КР=14.3, Mw=5.5, I0=7–8 (Northern Baikal region)

2020 ◽  
pp. 323-333
Author(s):  
N. Gileva ◽  
V. Melnikova ◽  
A. Seredkina ◽  
Ya. Radziminovich
Keyword(s):  
Seismic Moment ◽  
Main Shock ◽  
Moment Tensor ◽  
Seismic Hazard Assessment ◽  
Baikal Rift Zone ◽  
Temporal Analysis ◽  
Seismic Moment Tensor ◽  
Depth Range ◽  
North East ◽  
The North

We consider the May 23, 2014 Muyakan earthquake (Mw=5.5) occurred in the Muyakan Range at the north-east of the Baikal rift zone near the eastern tunnel portal of the Baikal-Amur Mainline. This event was followed by numerous aftershocks (КР=5.6–9.9) which number exceeded 2000 by the end of the year. Spatio-temporal analysis of the Muyakan seismic sequence shows that its epicentral field consists of two isolated clusters: eastern and western ones. All the main events including the foreshocks, main shock and the strongest aftershocks (Mw=4.4; 4.5) occurred in the eastern cluster while only small seismic events (КР<10.0) were recorded in the western one. Seismic moment tensor was calculated for the Muyakan earthquake from surface wave amplitude spectra. As a result, we obtained information about the rift type focal mechanism, scalar seismic moment (M0=1.9•1017 Nm), moment magnitude (Mw=5.5) and hypocentral depth (h=24 km). From regional data, hypocentral depths of the main shock and the major number of the following earthquakes (80 %) were distributed in the depth range h=3–11 km. Maximum intensity of the main shock (4–5 according to MSK-64) was felt in Severomuysk urban village (=29 km). The obtained results could be used for seismic hazard assessment of the crucial part of the Baikal-Amur Mainline.

scholarly journals Modeling of the stress-strain state in the earthquake epicenter area (Kumamoto Earthquake, Japan), 16.04.2016 M 7.3

2017 ◽  
pp. 48-54
Author(s):  
V. N. Morozov ◽  
A. I. Manevich
Keyword(s):  
Elastic Modulus ◽  
Strain State ◽  
Main Shock ◽  
Depth Interval ◽  
Stress Strain ◽  
Epicentral Area ◽  
Kumamoto Earthquake ◽  
Stress Strain State ◽  
Crustal Earthquake ◽  
North East

On the 16th of April, 2016, a strong earthquake with M 7,3 occurred in the Kumamoto prefecture (Kyushu, Japan). This earthquake is the strongest in the last 30 years in this area. For a day before the main shock, two foreshocks with M 6,4 were registered. For seven days after the main shock, aftershocks activity spread to the north-east and south-west, most of the hypocentres of the aftershocks with M 6,4 were localized within the seismogenic layer in the depth interval from 5 to 10 km. The authors have modeled a stress-strain state (SSS) of the epicentral area be fore the earthquake and after it (after the formation of the main fault). For this purpose, a software package is used, that allows 2-D formulation (plane strain condition), for modeling SSS block heterogeneous geological environment, disrupted by a system of tectonic faults. The faults are modeled in the form of extended zones of the dispersed geomaterial, which elastic modulus are significantly lower than the elastic modulus of the environmental media. A structural-tectonic scheme of the Kumamoto earthquake area is used. An analysis of the results of SSS modeling has been done for the area 30x40 km before and after the earthquake. It is shown that the area and magnitude of the stress intensity in anomalous zones are the predictive signs of the location and intensity of a possible strong crustal earthquake, and the vector of the rapid decrease in the potential energy of deformation could be a guide for the most probable direction of tectonic rupture during a crustal earthquake. The results received can be useful in a deterministic approach to seismic hazard assessment and carrying out the geophysical observations focused on the forecast of the strong crustal earthquakes in the continental areas.

scholarly journals Earthquake july 17, 2017, Mw = 7.8 near the Komandorsky islands and strong seismic manifestations in the western segment of Aleut island arc

2019 ◽  
pp. 52-66
Author(s):  
A. I. Lutikov ◽  
E. A. Rogozhin ◽  
G. Yu. Donzova ◽  
V. N. Zhukovez
Keyword(s):  
Seismic Moment ◽  
Main Shock ◽  
Seismic Source ◽  
Focal Mechanisms ◽  
Commander Islands ◽  
The West ◽  
Slow Increase ◽  
Commander Island ◽  
Western Segment ◽  
Tectonic Position

The tectonic position, seismological characteristics and features of the aftershock process of the source of the strongest Near-Aleutian earthquake on July 17, 2017 on the Commander Islands with Мw = 7.8 are considered. The analysis showed that the seismic source according to the distribution of aftershock epicenters in the form of a linearly elongated narrow zone with a length of about 400 km almost completely occupied the northern slope of the Commander island elevation and was located in the Bering fault zone. It covered the whole of this seismic-generating zone up to the transverse structure to the west of the Near Islands (Attu is.). In accordance with the focal mechanisms solution and the nature of the displacements in the foci of the main shock, the strongest foreshocks and aftershocks, the shift in the source was an almost pure right-sided shift. The aftershock process of the July 17 earthquake developed quite enough inertly for an earthquake of such strength. In addition, it has two features in comparison with the aftershock processes of most of the Kuril-Kamchatka earthquakes: 1) low release of the cumulative scalar seismic moment (M0cum aft), which according to various estimates was from 0.75% to 1.0% of the seismic moment of the main shock (M0me); 2) a very slow increase in the deficit in the release of the seismic moment (M0). At the same time, the duration of the quasi-stationary phase of M0cum release in aftershocks, estimated at about ½ year and covering a significant part of the duration of the entire aftershock process of this earthquake, seems unusually long. These features of the aftershock process of the Middle Aleutian earthquake on July 17, 2017 distinguish it from the aftershock processes characteristic of most strong Kuril-Kamchatka earthquakes. In general, its source can be considered as a transform between the two Benioff zones – Aleutian and Kuril-Kamchatka, and not subduction, that is characterise the last two.

scholarly journals Macroseismic intensity investigation of the November 2014, M=5.7, Vrancea (Romania) crustal earthquake

2016 ◽  
Vol 59 (5) ◽  
Author(s):  
Angela Petruta Constantin ◽  
Iren Adelina Moldovan ◽  
Andreea Craiu ◽  
Mircea Radulian ◽  
Constantin Ionescu
Keyword(s):  
Seismic Event ◽  
Main Shock ◽  
Focal Depth ◽  
Earthquake Occurrence ◽  
Epicentral Area ◽  
Ground Shaking ◽  
Crustal Earthquake ◽  
Historical Times ◽  
Vrancea Seismogenic Region ◽  
North Latitude

On November 22, 2014 at 21:14:17 local hour (19:14:17 GMT) a  M<sub>L</sub>=5.7 crustal earthquake occurred in the area of Marasesti city of Vrancea county (Romania) - the epicenter was located at north latitude 45.87° and east longitude 27.16°, with a focal depth of 39 km. This earthquake is the main shock of a sequence that started with this and lasted until the end of January. During the sequence, characterized by the absence of foreshocks, a number of 75 earthquakes were recorded in 72 hours, the largest of which occurred in the same day with the main shock, at 22:30 (M<sub>L</sub>= 3.1). The crustal seismicity of Vrancea seismogenic region is characterized by moderate earthquakes with magnitudes that have not exceeded M<sub>W</sub> 5.9, this value being assigned to an earthquake that occurred in historical times on March 1, 1894 (Romplus catalogue). Immediately after the 2014 earthquake occurrence, the National Institute for Earth Physics (NIEP) sent macroseismic questionnaires in all affected areas, in order to define the macroseismic field of ground shaking. According to macroseismic questionnaires survey, the intensity of epicentral area reached VI MSK, and the seismic event was felt in all the extra-Carpathian area. This earthquake caused general panic and minor to moderate damage to the buildings in the epicentral area and the northeast part of country. The main purpose of this paper is to present the macroseismic map of the earthquake based on the MSK-64 intensity scale.

scholarly journals Global earthquakes in the 2021 first half according to the GS RAS

2021 ◽  
Vol 3 (3) ◽  
pp. 7-27
Author(s):  
Yuri Vinogradov ◽  
Marina Ryzhikova ◽  
Natalia Petrova ◽  
Svetlana Poygina ◽  
Marina Kolomiets
Keyword(s):  
Main Shock ◽  
Seismic Energy ◽  
Focal Mechanisms ◽  
Eastern Coast ◽  
Strong Earthquakes ◽  
The North ◽  
The Earth ◽  
Northern Mongolia ◽  
The Russian Federation ◽  
North Western

Data on the 2021 first half Earth seismicity at the level of strong earthquakes with magni-tudes mb6.0 according to the Alert Service of the Geophysical Survey RAS are given. The review also includes information on 81 earthquakes in Russia and adjacent territories, felt in the settlements of the Russian Federation. For 14 strong earthquakes, within one or two days after their occurrence, Informational messages were published, and information about the focal mechanisms was giving. The strongest earthquake of the Earth with MS=7.8 (Mw=8.1) occurred on March 4 at the Kermadec Islands, New Zealand. The largest human casualties and material damage during the study period were caused by catastrophic earth-quakes with MS=5.1 (Mw=5.8) and MS=5.9 (Mw=6.3), which occurred on January 14 at the Sulawesi Island, Indonesia. As a result of the earthquakes, 81 people died, 826 were injured. The strongest earthquake in Russia was the March 16 earthquake with MS=6.7 (Mw=6.6) off the eastern coast of Kamchatka. The maximum shaking intensity in Russia (I=6) was manifested by the strong Khuvsgul earthquake with MS=7.2 (Mw=6.8), which took place on January 11 in the Northern Mongolia, near the border with Russia. The position of the main shock and its aftershocks indicate the intensification of the seismic process in the north-western part of the Khuvsgul rift zone. According to the focal mechanisms of the main shock and two strong aftershocks, the stress of the northwest/southeast extension prevails in this zone, and the predominant slip type along the faults of the northeast strike is a nor-mal fault. The global seismic energy released in the 2021 first half remains, as in the previ-ous two years, at a reduced level, relative to the average for the last 11.5 years, which indi-cates a continuing seismic calm.

scholarly journals DZHIRGA EARTHQUAKE on April 27, 2014, Mw=4.9, КР=13.3, I0=7 (Northern Baikal Region)

2020 ◽  
pp. 307-316
Author(s):  
Ya. Radziminovich ◽  
N. Gileva ◽  
A. Seredkina ◽  
V. Melnikova
Keyword(s):  
Epicentral Distance ◽  
Focal Depth ◽  
Seismic Hazard Assessment ◽  
Normal Fault ◽  
Aftershock Sequence ◽  
North East ◽  
The North ◽  
North Eastern ◽  
Fault Kinematics ◽  
Weak Shocks

We consider the April 27, 2014, Mw=4.9 Dzhirga earthquake, occurred within the north-eastern end of the Barguzin Depression. The event is the second one by energy level in the study area for the period of instrumental observations. The earthquake was followed by an aftershock sequence of 75 weak shocks recorded till the end of the year. The focal mechanism was determined from surface wave records from 13 digital broadband seismic stations of the IRIS networks. The obtained solution demonstrates the normal fault kinematics with both nodal planes striking north-east that corresponds to the regional fault pattern. The focal depth is estimated equal to 19 km. The maximum observed intensity was 5 points on the MSK-64 scale at the epicentral distance of 13 km. The Dzhirga earthquake analysis made it possible to fill in the lack of seismological information about the study area. The data obtained can be used for refinement of seismic hazard assessment of the north of the Barguzin Basin.

Aftershocks of the 13 December 1982 North Yemen earthquake: Conjugate normal faulting in an extensional setting

1987 ◽  
Vol 77 (6) ◽  
pp. 2038-2055
Author(s):  
C. J. Langer ◽  
G. A. Bollinger ◽  
H. M. Merghelani
Keyword(s):  
Main Shock ◽  
Aftershock Sequence ◽  
Focal Mechanisms ◽  
Data Set ◽  
Epicentral Area ◽  
Focal Mechanism Solutions ◽  
The North ◽  
Composite Focal Mechanism ◽  
Good Agreement ◽  
Extensional Setting

Abstract The North Yemen epicentral locale in the southwestern part of the Arabian Peninsula is 200 to 300 km landward from the active rifting of the Red Sea and Sea of Aden. The magnitude 6.0 (MS and mb) main shock of 13 December 1982 locally caused considerable death, injury, and damage and was followed by an extensive aftershock sequence. A 12-day study employing a 10-station portable seismograph network was conducted between 29 December 1982 and 9 January 1983. Hypocentral locations were determined for 230 shocks selected from the thousands of recorded events (duration magnitudes between 1.8 and 4.6). These aftershocks define a source volume that is roughly 20 × 20 × 10 km. From that volume, about half (∼110) of only the best-constrained hypocenters with depths greater than 3 km were selected for detailed analysis. The 110 aftershock data set was divided into subsets according to geographic position (northern and southern) and temporal sequencing (a distinct aftershock sequence late in the monitoring period). A series of composite focal mechanisms show the aftershocks are dip-slip faulting (normal) on planes with north-northwest to northwest strikes and with dips that are variable in amount (∼30° to ∼80°) and direction (southwest and northeast). The strike and extensional nature of these composite focal mechanism solutions are in good agreement with the main shock focal mechanisms, the surficial and bedrock geology of the epicentral area, and the linear surface cracks observed in the field there following the December main shock. We interpret the spatial distribution of our results to describe conjugate faulting episodes associated with north-northwest striking faults.

scholarly journals Earthquake july 17, 2017, Mw = 7.8 near the Komandorsky islands and strong seismic manifestations in the western segment of Aleut island arc

2019 ◽  
pp. 52-66
Author(s):  
A. I. Lutikov ◽  
E. A. Rogozhin ◽  
G. Yu. Donzova ◽  
V. N. Zhukovez
Keyword(s):  
Seismic Moment ◽  
Main Shock ◽  
Seismic Source ◽  
Focal Mechanisms ◽  
Commander Islands ◽  
The West ◽  
Slow Increase ◽  
Commander Island ◽  
Western Segment ◽  
Tectonic Position

The tectonic position, seismological characteristics and features of the aftershock process of the source of the strongest Near-Aleutian earthquake on July 17, 2017 on the Commander Islands with Мw = 7.8 are considered. The analysis showed that the seismic source according to the distribution of aftershock epicenters in the form of a linearly elongated narrow zone with a length of about 400 km almost completely occupied the northern slope of the Commander island elevation and was located in the Bering fault zone. It covered the whole of this seismic-generating zone up to the transverse structure to the west of the Near Islands (Attu is.). In accordance with the focal mechanisms solution and the nature of the displacements in the foci of the main shock, the strongest foreshocks and aftershocks, the shift in the source was an almost pure right-sided shift. The aftershock process of the July 17 earthquake developed quite enough inertly for an earthquake of such strength. In addition, it has two features in comparison with the aftershock processes of most of the Kuril-Kamchatka earthquakes: 1) low release of the cumulative scalar seismic moment (M0cum aft), which according to various estimates was from 0.75% to 1.0% of the seismic moment of the main shock (M0me); 2) a very slow increase in the deficit in the release of the seismic moment (M0). At the same time, the duration of the quasi-stationary phase of M0cum release in aftershocks, estimated at about ½ year and covering a significant part of the duration of the entire aftershock process of this earthquake, seems unusually long. These features of the aftershock process of the Middle Aleutian earthquake on July 17, 2017 distinguish it from the aftershock processes characteristic of most strong Kuril-Kamchatka earthquakes. In general, its source can be considered as a transform between the two Benioff zones – Aleutian and Kuril-Kamchatka, and not subduction, that is characterise the last two.

Ras al Khaimah: further archaeological discoveries

Antiquity ◽  
1976 ◽  
Vol 50 (200) ◽  
pp. 216-222
Author(s):  
Beatrice De Cardi
Keyword(s):  
United Arab Emirates ◽  
The State ◽  
Focused Attention ◽  
North East ◽  
The North ◽  
History Of ◽  
The City

Ras a1 Khaimah is the most northerly of the seven states comprising the United Arab Emirates and its Ruler, H. H. Sheikh Saqr bin Mohammad al-Qasimi, is keenly interested in the history of the state and its people. Survey carried out there jointly with Dr D. B. Doe in 1968 had focused attention on the site of JuIfar which lies just north of the present town of Ras a1 Khaimah (de Cardi, 1971, 230-2). Julfar was in existence in Abbasid times and its importance as an entrep6t during the sixteenth and seventeenth centuries-the Portuguese Period-is reflected by the quantity and variety of imported wares to be found among the ruins of the city. Most of the sites discovered during the survey dated from that period but a group of cairns near Ghalilah and some long gabled graves in the Shimal area to the north-east of the date-groves behind Ras a1 Khaimah (map, FIG. I) clearly represented a more distant past.

Sign in / Sign up

Export Citation Format

Share Document