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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.

 

100 years after Kemin catastrophe: new data about focus

Authors: Мукамбаев Айдын Серикович, Михайлова Наталья Николаевна

Keywords: землетрясение

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New data related to focal parameters of catastrophic Kemin earthquake of 1911 were collected and generalized. The magnitude exceedance of the event was revealed in Kazakhstan earthquake catalogues. Discrepancies in Kemin earthquake epicenter location between global and regional catalogues were found. New data should be considered in works on seismic zoning and prediction of seismic impact on critical facilities.

Civil and scientific application of IMS network data in earthquake hazard assessment

Authors: Шанкер Д., Али С.М., Сингх М.

Keywords: землетрясение, ДВЗЯИ, система мониторинга

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International Monitoring System (IMS), using four technologies – seismic, hydroacoustic, infrasound and radionuclide. While awaiting entry-into-force, the IMS is operating in test mode yet, even now, monitoring data have potential use among the scientist for the social welfare means. Contribution to the earthquake hazard and related earthquake engineering determinations is a big development and knowledge expansion of the one of the cited technology i.e. seismic. In this direction Indonesian region bounded by 14°S–10°N and 93–141°E, which is one of the most seismically Trans-Asian and Circum-Pacific belts type active plate regions of the world where large to great earthquakes have occurred during the past hundred years have been considered. Nineteen years recent earthquake data from June 13, 1999 to July 10, 2017 have been taken from International Monitoring System (IMS) Network setup by Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO), Vienna Austria. These data analyses shows that earthquake occurrences agrees with the Gumbel’s Type I extreme distribution function and has been applied to analyses those maximum magnitude data with a satisfactory degree of correlation (0.96). The earthquake hazard that existed in Indonesian region been quantified in terms of recurrence periods and probabilities of occurrence of earthquake of any given magnitude. This investigation indicates that the most probable largest annual earthquakes are close to 6.0. Also, most probable earthquake that may occur in an interval of 50 years is estimated as 6.8. Other medium to large size earthquakes which are expected to occur in this region has been predicted that may help in engineering investigations at particular site and decision making problems if planning to develop certain region for infrastructural activities. 

New details of seismic history and contemporary seismicity of the Jungariya territory

Authors: Мукамбаев Айдын Серикович, Михайлова Наталья Николаевна, Аристова И.Л., Полешко Н.Н.

Keywords: землетрясение, Джунгария

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New data on seismic history of Jungariya were presented. Additional catalogs of strong earthquakes created the basis for geo-dynamic constructions and tectonic interpretations in Jungariya. The detected epicenters of the strongest earthquakes must be taken into consideration when calculating the maps of seismic zoning of new generation.

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.

Variations of the geomagnetic parameters during earthquake of magnitude M=6.4, occurred 25 november 2016

Authors: Мукашева С.Н., Соколова О.И., Малимбаев А.М.

Keywords: землетрясение, геомагнитные параметры

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This report presents the results of a detailed analysis of the variations in geomagnetic parameters on the eve and during the strong earthquake of November 25, 2016 (M=6.4) that occurred in the border area of Tajikistan, China and Kyrgyzstan. To assess the state of the geomagnetic field, the data of the geomagnetic observatory “Alma-Ata”, the international code – AAA; geographical coordinates [43.25ºN; 76.95ºE]; geomagnetic coordinates [34.3ºN, 152.7ºE]. A detailed analysis of the variations of the seconds values of the X-, Y-, Z-components of the geomagnetic field showed that sinusoidal oscillations with periods of the order of 52–55 minutes appear before the earthquake in variations of the geomagnetic field.

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