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Heterogeneities of short-period S wave attenuation field in the Altay lithosphere and its relation to seismicity

Authors: Копничев Юрий Федорович, Кунакова Ольга Константиновна, Соколова Инна Николаевна

Keywords: сейсмичность, землетрясение, литосфера

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Mapping of short-period S wave attenuation field in the lithosphere of Altay and adjacent territories of Mongolia and South Siberia have been conducted. The authors used a method based on an analysis of a ratio of maximum amplitudes for Sn and Pn waves. About 500 earthquake seismograms obtained by Makanchi and Ulan Bator stations at distances of ~300–1900 km have been processed. As a whole, shear wave attenuation is much stronger in the western part of the region relative to the eastern one. V-shaped strip of high attenuation in the uppermost mantle is picked out in the western part of the region. Rupture zones of Zaisan earthquake of 1990 (M=6.9) and Chu earthquake of 2003 (M=7.3) are connected with this strip. At the same time relatively low attenuation corresponds to rupture zones of large and great earthquakes with M≥7.0 that occurred before 1970. A conclusion has been made that zones of high fluid content in the Altay lithosphere, as in the other regions of Central Asia, are being formed prior to large shallow earthquakes. After large seismic events the fluids are ascending into the earth’s crust from the uppermost mantle during a few decades, which leads to diminishing attenuation of Sn waves.

New ring-shaped seismicity structures in the regions of Kurils and Kamchatka

Authors: Копничев Юрий Федорович, Соколова Инна Николаевна

Keywords: сейсмичность, землетрясение

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This paper presents spatial-temporal seismicity characteristics in three areas of the northern Kurils and southern Kamchatka. Earlier ring-shaped seismicity structures were picked up in these areas in two depth ranges: 0–33 and 34–70 km, which have been formed during a period of 01.01.1973-01.01.2009. It was shown, that after this period during the last 4.5 years parameters of some ring-shaped structures changed essentially, first of all within the range between 52° and 53° N. Similar changes were observed prior to some large and great earthquakes in the other subduction zones. This gives a reason to suggest a preparation for large earthquakes in these areas.

Characteristics of S wave attenuation field in rupture zones of two large earthquakes in South Asia and their relation to seismicity

Authors: Копничев Юрий Федорович, Соколова Инна Николаевна

Keywords: сейсмичность, землетрясение, литосфера, афтершок

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The characteristics of short-period shear wave attenuation and seismicity fields in rupture zones of two large earthquakes in South Asia (Kashmir, 08/10/2005, Mw 7.6 and Bhuj, 26/01/2001, Mw 7.7) are being studied. The authors used a method, based on an analysis of Sn and Pn waves amplitude ratio (by recordings of AAK-Kyrgyzstan and NIL-Pakistan seismic stations). It was shown, that strong and weak S wave attenuation is observed correspondingly in rupture zones of the interplate Kashmir and intraplate Bhuj earthquakes. Ring-shaped seismicity structure had been formed prior to the Kashmir earthquake (in contrast to the Bhuj event). Besides, several more aftershocks with M≥5.0 were recorded after the Kashmir earthquake in comparison to the Bhuj one. It is supposed, that big variations of attenuation and seismicity fields structure are connected with sharp difference of deep fluid content in the lithosphere of two rupture zones.

 

Some regularities of seismicity of Central and Western Uzbekistan

Authors: Усманова М.Т., Саттарова А.М.

Keywords: сейсмичность, сейсмограмма

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In article, distribution of space-temporal seismic activity of Western Tien-Shan region was considered. Two groups of strong earthquakes in Western and Central Uzbekistan were extracted. Regularity has been detected on redistribution of the accumulated tectonic energy in the form of seismicity alternatively on the regions. It was shown that earthquakes on hypocenters’ depths were distributed in certain seismogenic layers independent from their magnitude level. Deflections were discovered from the regularity of grouping of strong earthquakes in seismic regime of the region. Probably natural and technogenic triggers preceded the triple strong Gazly earthquakes in 1976 and 1984 with М=7,0–7.3. Natural triggers: active processes of fissures on the north Gazly with length ~ 100 km near Tamdibulak and absence for more than 40 years of appreciable earthquakes in epicentral region Gazly. Technogenic triggers: constant 40-years-long gas pump from “Gazly” fields and two nuclear explosions implemented near Gazly earthquakes in 1976 and 1984 of tectonic nature.

Ring-shaped seismicity structures in the region of Iran: possible preparation for large earthquakes

Authors: Копничев Юрий Федорович, Соколова Инна Николаевна

Keywords: сейсмичность, землетрясение, кольцевые структуры

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We have been studying some seismicity characteristics in the region of Iran including those connected with preparation for large earthquakes. It was established that ring-shaped seismicity structure have been formed within depth range of 0- 33 km prior to large Ezgeleh earthquake of 12.11.2017 (Mw=7,3). Shallow seismicity rings are characterized by threshold magnitude values (Mt1) and big axis lengths (L). Earlier we have obtained correlation dependences of Mt1 and lgL values on magnitudes of main events Mw for intracontinental earthquakes with mechanisms of reverse and oblique-reverse faulting, prevailing in the region of Iran. Using these dependences we estimated magnitude of large event which could be prepared in the area of ring structure: Mw=7,1±0,1 for the zone of the Ezgeleh earthquake. Big ring structures were identified at the south-west, north and east of Iran, where large earthquakes are not known according to instrumental and historical data. We estimated magnitudes of possible large earthquakes by characteristics of these structures: Mw=7,2±0,3, Mw=7,1±0,2 and Mw=6,6±0,1 in the regions mentioned respectively. Large seismic event, which probably is being prepared within the south-western part of Iran, can represent a special danger due to nearness of it’s source to the nuclear power plant “Busher”. We discuss the reasons of ring structures formation.

Analysis of ring-shaped seismicity structures in the region of the Northern Caucasus: possible preparation for large earthquakes

Authors: Копничев Юрий Федорович, Соколова Инна Николаевна

Keywords: сейсмичность, землетрясение

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We have been studying some seismicity characteristics in the region of Northern Caucasus since 1964. It was established that ring-shaped seismicity structure have been formed within depth range of 0–33 km prior to large Racha earthquake of 29.05.1991 (Mw=7,0). Seismicity rings are characterized by threshold magnitude value (Mt) and big axis length (L). Earlier we have obtained correlation dependences of Mt and lgL values on magnitudes of main events Mw for intracontinental earthquakes with mechanisms of reverse and oblique-reverse faulting, prevailing in the region of Northern Caucasus. Using these dependences we estimated magnitudes of large event which could be prepared in the area of ring structure: Mw=7,1±0,2 for the zone of the Racha earthquake. This value is close enough to real magnitude of the event mentioned. New big ring structures were identified at the western outskirt of the Great Caucasus and in the region of the Eastern Caucasus, where large earthquakes are not known according to instrumental and historical data. We estimated magnitudes of possible large earthquakes by characteristics of these structures: Mw=7,0±0,2 and Mw=6,9±0,2 in the regions mentioned respectively. Large seismic event, which probably is prepared at the westernmost part of the Great Caucasus, can represent a special danger due to great density of population and nearness of a few big cities: Krasnodar, Novorossiysk, Sochi etc. It is supposed that ring structures formation is a consequence of geologic systems self-organization, connected with deep-seated fluids migration.

CTBTO data and data products in seismic monitoring in RUSSIA

Authors: Маловичко А.А., Старовойт О.Е., Коломиец М.В., Габсатарова И.П., Рыжикова М.И.

Keywords: сейсмичность, ОДВЗЯИ, мониторинг, KNDC, СТВТО

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The paper describes experience of Geophysical Service (GS) RAS gained from use of CTBTO data and its data products as well as of KNDC data and data products in seismic monitoring in Russia and in bordering areas in near-real time mode data processing in 2016–2017. It is demonstrated the usage of waveforms, arrivals and Bulletin SEL1 data when in location by EEAS events on Russian territory.

Registration of underground nuclear tests and initiated seismicity in North Korea in 2016–2017 by Russian seismic stations

Authors: Маловичко А.А., Коломиец М.В., Габсатарова И.П.

Keywords: сейсмичность, Ядерные испытания, Северная Корея

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The magnitude and spectral discriminants of the PNS 09.09.2016 and 03.09.2017 are described in comparison with the records of the events following the most strong test on September 3, 2017, the collapse phenomenon, 8 minutes after the test, and two earthquakes, probably of induced character, on 23.09. 2017 and 12.10.2017, which occurred near the Pungery test site. The strongest test in North Korea made it possible to study the features of the wave pattern at teleseismic distances (Δ>30°).

Seismo-tectonics of eastern Tien-Shan and Dzhungariya

Authors: Мукамбаев Айдын Серикович, Абдрахматов К.Е., С. Grützner, G. Campbell, R.T. Walker, D. Mackenzie, J. Jackson, Аширов Б.М., Айтмырзаев Ж.С., Джанабилова С.О., Елдеева М.С.

Keywords: сейсмичность, землетрясение, сейсмотектоника

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It was demonstrated that within the eastern part of Northern Tien-Shan and Dzhungarya active faults with wings shifted in the late Pleistocene – Holocene have the striking different from the direction of the newest structures, mainly sublateral ones. These faults represent right-shift disjunctive structures of north-western strike. They are the responsible ones for modern seismic situation at the investigated territory

Assessment of the seismic risk of the Kapshagai hydroelectric station

Authors: Гессель М.О., Неверова Н.П., Хайдаров М.С.

Keywords: сейсмичность, Капшагайская ГЭС, плотина

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The seismicity of the region of Kapshagai hydro-electrical station dam’s location has been analyzed. Objects of maninduced impact of continuous nature located under the zone of direct impact from the vibrations of turbine motors of hydro-electrical station and pit explosions. Based on a number of earthquakes before and after the filling up of the water reservoir in 1970 as well as on the increase of the share of medium earthquakes in 2011–2018, a conclusion is made on the increasing man-induced seismicity. The attention is drawn to the location of the water reservoir directly on the Altyn-Emelskiy fault and the possibility of this fault’s activation during further hard man-induced impact.