DETAILED STRUCTURE OF ATTENUATION FIELD IN THE WESTERN TIEN SHAN BASED ON SHORT PERIOD CODA WAVES

O.I. Aptikaeva

Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia

Abstract. The seismic coda waves attenuation characteristic in Western Tien Shan region were studied in this paper. The short-period coda waves of the local earthquakes recorded by the CHISS in 1960-1984 and digital seismogram data of 150 earthquakes that occurred in Western Tien Shan region during 2005 to 2017 and recorded at AAK station of the KNET network have been analyzed. The attenuation field is represented by a high Q factor zones, close to isometric in plan (blocks) and linear zones of strong attenuation (weakened zones), which coincide with the fault zones. The structure of the attenuation field agrees with the structure of the S-wave velocity field and the velocity anomalies of P-waves: low-velocity anomalies correspond to low-Q zones.

The most pronounced conductors revealed using magnetotelluric data coincide with the low-Q zones, which indicates their substantial fluid-saturation. The sources of the strongest earthquakes with K>16.0 are confined to the zones of maximum attenuation contrast, to the boundaries of the blocks and the weakened zones, where the mobility of the blocks is determined by the reduced viscosity of the low-Q and small thickness of the high-Q layers. The relationship between the features of seismic processes and spatial inhomogeneities of the attenuation field against the background of variations in the Earth's rotation velocity is also considered.

Keywords: сoda waves, Q factor, attenuation field

About the author

APTIKAEVA Olga Ivanovna – Candidate of Physical and Mathematical Sciences, Leading Researcher. Schmidt Institute of Physics of the Earth of the Russian Academy of Sciences. 123242, Moscow, ul. Bolshaya Gruzinskaya, 10, building 1. Phone: (499) 254-24-05. E-mail: aptikaevaoi@mail.ru

Cite this article as: Aptikaeva O.I. Detailed structure of attenuation field in the Western Tien Shan based on short period coda waves, Voprosy Inzhenernoi Seismologii (Problems of Engineering Seismology), 2018, Vol. 45, No. 2, pp. 21–32. [in Russian]. DOI: 10.21455/VIS2018.2-2

English translation of the article will be published in Seismic Instruments, ISSN: 0747-9239 (Print) 1934-7871 (Online), https://link.springer.com/journal/11990), 2019, Volume 55, Issue 2.