Preview

Geodynamics & Tectonophysics

Advanced search
Vol 1, No 4 (2010)

PALEOGEODYNAMICS

331-418 1951
Abstract
The Olkhon region of the Western Pribaikalie is highly attractive for geologists due to the presence of diverse metamorphic complexes and highly complicated combinations of folded structures in this region. The Olkhon region is located within the area of the Pribaikalsky National Park of Russia. At abundant outcrops in the subject area, various geological aspects resulting from the Early Palaeozoic collision system can be studied in detail. By its parameters, the subject area can be considered a «geodynamic proving ground». In recent years, abundant aerospace materials on the area have been accumulated, and long-term field studies resulted in many discoveries and findings which encourage critical revision of the initial conceptions. The material available allows compilation of a new package of geological maps in hard and electronic versions.

TECTONOPHYSICS

419-440 1673
Abstract

Association of earthquake hypocenters with fault zones appears more pronounced in cases with more accurately determined positions of the earthquakes. For complex, branched structures of major fault zones, it is assumed that some of the earthquakes occur at feathering fractures of smaller scale.It is thus possible to develop a «seismological» criterion for definition of a zone of dynamic influence of faults, i.e. the zone containing the majority of earthquakes associated with the fault zone under consideration.

In this publication, seismogenic structures of several fault zones located in the San-Andreas fault system are reviewed. Based on the data from a very dense network of digital seismic stations installed in this region and with application of modern data processing methods, differential coordinates of microearthquakes can be determined with errors of about first dozens of meters.It is thus possible to precisely detect boundaries of the areas wherein active deformation processes occur and to reveal spatial patterns of seismic event localization.

In our analyses, data from the most comprehensive seismic catalog were used. The catalogue includes information on events which occurred and were registered in North California in the period between January 1984 and May 2003. In this publication, the seismic data processing results and regularities revealed during the analyses are compared with the data obtained from studies of fault structures, modeling and numerical simulation results. Results of quantitative research of regularities of localization of seismic sources inside fault zones are presented.

It is demonstrated by 3D models that seismic events are localized in the vicinity of an almost plain surface with a nearly constant angle of dip, the majority of events being concentrated at that conventional surface.

Detection of typical scopes of seismicity localization may prove critical for solution of problems of technogenic impact on fault zones for the purpose of partial stress release. The obtained results suggest that the region, wherein active deformation takes place during preparation of medium earthquakes (M≤6.5÷7.0), includes a number of local «strips», each about 100 m in width. The latter size is comparable to a scope of technogenic capabilities of producing an impact on geo-environment. It is hoped that studies of both fine spatial and temporal patterns of seismicity in the vicinity of fault zones will allow to find reliable pinpoints for definition of both place and time for implementation of technogenic impacts.

In our opinion, the implemented study demonstrates the burning need to establish test sites with dense and wellequipped local seismic networks in Russia.

RECENT GEODYNAMICS

441-447 1415
Abstract
On 27 August 2008, a strong earthquake occurred in the Southern Baikal area. Its focus was located within the Baikal rift zone which characterized with high seismicity. The general location and approximate strength of the earthquake were thus expectable, whereas the shock occurred at an unexpected time, as usual. The article provides a brief review of the geological environment and macro-seismic effects of the earthquake. It also reviews a set of seismic and hydrogeochemical indicators which are interpreted as precursors of the given earthquake. Considering such precursors, the fact that the Baikal deepwater helium content had changed before the main shock was recorded for the first time in the region under study.

OBITUARY

448-449 691
Abstract

Leading Researcher, Institute of the Earth’s Crust, Siberian Branch of RAS, Irkutsk, Russia.

11 August 1935 – 12 October 2010



Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.


ISSN 2078-502X (Online)