S-WAVE ATTENUATION FIELD AND SEISMOTECTONICS OF EASTERN ANATOLIA

O.I. Aptikaeva

Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, 123242 Russia

e-mail: aptikaevaoi@mail.ru

Abstract. The seismic coda waves attenuation characteristic in theEastern Anatolia region were studied. The short-period coda waves about 400 earthquakes that had been occurring in theEastern Anatolia region since 1989 until 2018 were analyzed. In this work we used three-component digital records seismic events of more than 3.5 in magnitude, and epicentral distances are 10–600 km. S-wave attenuation was estimated from short-period coda envelopes (including those of Lg wave coda) at a frequency of ~1 Hz. The features of the structure of the S-wave attenuation field in the upper mantle near Lake Van are similar to those for other seismically active zones. The attenuation field is represented blocks with weak attenuation, being close to isometric in plan where the attenuation decreases in the direction from the boundaries to the central of the blocks (Q-factor reaches 300–700) and strong attenuation zones. Among the zones of strong attenuation, usually linearly elongated, the most noticeable are the echeloned zone (north of 39 ° N), associated with the North Anatolian Fault, here QS ~ 80-110 (in the north - to QS ~ 60) and the thrust fold belt Bitlis-Zagros (QS ~ 60-70). Sources of the strongest earthquakes with M > 6.0, including the Van 1976 and 2011 earthquakes, are confined to the boundaries of blocks. The attenuation field structure coincide with the velocity field structure – low-velocity anomalies correspond to low-Q zones. The volumes with which intense localized seismicity is associated (earthquake swarms) and along which can migrate deep fluid are revealed. Seismic activation in such volumes precedes large seismic events (for example, the 2011 Van earthquake). It is assumed that such volumes can be interpreted as local seismogenic sources.

Keywords: coda waves, Q-factor, S-wave 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. 123241, Moscow, ul. Bolshaya Gruzinskaya, 10, bld. 1. E-mail: aptikaevaoi@mail.ru

Cite this article as: Aptikaeva O.I. S-wave attenuation field and seismotectonics of Eastern Anatolia, Voprosy Inzhenernoi Seismologii (Problems of Engineering Seismology), 2019, Vol. 46, No. 3, pp. 32–49 [in Russian]. https://doi.org/10.21455/VIS2019.3-3

English translation of the article will be published in Seismic Instruments, ISSN: 0747-9239 (Print)

1934-7871 (Online), https://link.springer.com/journal/11990