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Count articles: 3
Heterogeneities of short-period S wave attenuation field in the Altay lithosphere and its relation to seismicityRead annotation Download PDF
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 KamchatkaRead annotation Download PDF
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 seismicityRead annotation Download PDF