TITLE:
Regularities of Seismicity of Western and Central Uzbekistan (Southwestern Part of Western Tien-Shan Region)
AUTHORS:
Makhira T. Usmanova, Abdusattor M. Sattarov
KEYWORDS:
Strong Earthquakes, Shuttle Migration of Seismicity, Cyclic Recurrence of Large Earthquakes, Natural and Technogenic Triggers
JOURNAL NAME:
Open Journal of Earthquake Research,
Vol.10 No.4,
November
30,
2021
ABSTRACT: The paper discusses the spatial and temporal
distribution of seismic activity in the southwestern part of the Western Tien
Shan. The study identifies four groups of strong earthquakes that occurred in
Western and Central Uzbekistan. The regularity of redistribution of the
accumulated tectonic energy in the form of shuttle migration of seismicity with
the recurrence rate of a group of strong earthquakes has been revealed. The
synchronicity of periods of seismic activation of the Western Tien Shan
(regional structure) and the Asian part of the Mediterranean-Asian seismic belt
(structure of a large-regional scale) was found. At the same time, deviations
from synchronicity are noted in the form of delays in the periods of seismic
activation between the considered structures. The seismicity study revealed a
deviation from the regularity of grouping of strong earthquakes in the seismic
regime of the region. This was observed in the Gazli earthquakes. The strongest
triple Gazli earthquakes of 1976 and 1984 with М = 7.0 - 7.3 were
preceded by natural and technogenic triggers. Natural triggers included active
fracturing (large fractures up to 100 km in length) in the north of Tamdybulak
area, the absence any of tangible earthquakes
in the epicentral area of Gazli for more than 40 years, and the appearance of
small mud volcanoes—griffins before a
strong earthquake. The technogenic triggers included a 40-year gas pumping at
the Gazli fields and two underground nuclear explosions in 1966 (#273) and 1968
(#142) produced near the epicenter of the tectonic Gazli earthquakes of 1976
and 1984.