ISSN 1819-7140, Russian Journal of Pacific Geology, 2017, Vol. 11, No. 4, pp. 237–250. © Pleiades Publishing, Ltd., 2017.
Original Russian Text © A.A. Stepashko, T.V. Merkulova, 2017, published in Tikhookeanskaya Geologiya, 2017, Vol. 36, No. 4, pp. 3–17.
Deep Structure, Genesis, and Seismic Activation of the Bureya
Orogen, Russian Far East
A. A. Stepashko* and T. V. Merkulova
Kosygin Institute of Tectonics and Geophysics, Far East Branch, Russian Academy of Sciences,
ul. Kim Yu Chena 56, Khabarovsk, 680000 Russia
Received March 15, 2016
Abstract⎯The Bureya orogen is a special object among the geodynamic factors determining the high seis-
micity of the Lower Amur region. Its location and deep structure are studied on the basis of comprehensive
geophysical and tectonic data. This orogen is a low-density lithospheric domain expressed by an intensive
negative gravity anomaly and Moho sunken down to 40 km depth. Within the limits of this lithospheric struc-
ture, contemporary uplifting takes place to form a meridional dome peaking at more than 2000 m altitude.
The position of the orogen in the regional structure gives us grounds to think that the Bureya orogen formed
in the Paleogene, at the finishing stage of tectonic block movement along the Pacific margin represented by
the NE-trending strike-slip faults of the Tang Lu Fault Zone. Compression was concentrated at the triple
junction between the Central Asian, Mongolian–Okhotian, and Sikhote Alin tectonic belts. The meridional
orientation of the Bureya orogen is associated with the parallel elongated Cenozoic depressions in the region.
The united morphotectonic system may have formed resulting from lithospheric folding under horizontal
shortening in the Paleocene–Eocene. The wavelength of the Lower Amurian fold system is 250 km, which is
consistent with the theoretical estimates and examples of lithospheric folds in other regions. The contempo-
rary activation of the Bureya orogen began in the Miocene, under the effect of the Amurian Plate front mov-
ing in the northeastern direction. As a result of shortening, the meridional cluster of weak (M ≥ 2.0) earth-
quakes formed along the western boundary of the orogenic dome. The most intensive deformations caused
another type of seismicity associated with the activation-related uplift of the mentioned orogen. As a result,
the so-called Bureya seismic zone formed above the apex of the dome, and it is here that the strongest
regional earthquakes (M ≥ 4.5) occur.
Keywords: deep structure, morphotectonics, seismicity, lithospheric folding, Amurian Plate, Tang Lu Fault
Zone, Bureya orogen, Russian Far East
The most serious problems in understanding the
nature of regional seismicity emerge when higher
activity is observed in intracontinental areas which are
located a priori far from lithospheric plate boundaries.
In these regions, deformations often accumulate in
multiple tectonic faults of different ranks and the lat-
eral distribution of earthquake epicenters therefore
becomes scattered, without any well-expressed spatio-
temporal tendencies. This diffuse style of seismicity is
observed in the Lower Amur region, Russian Far East
The character and genesis of the higher seismicity
in the Lower Amur region has been discussed many
times and from different, sometimes even opposite
viewpoints [2, 3, 8, 9, 15, 17, 19–21, 26, 28, 31, 34, 35].
The main attention has traditionally been paid to anal-
ysis of the relationships between seismicity and fault
structure and direct search for geological–geophysical
peculiarities that may determine the spatial distribu-
tion and intensity of earthquakes. This problem has
not been solved, suggesting a multifactor character of
regional deformations. The diffuse epicentral field in
the region likely reflects the aggregated pattern of
events occurring under the effects of relatively inde-
pendent tectonophysical mechanisms.
The only possible way to reveal the spatiotemporal
regularities of seismicity in such a situation is to under-
stand the geodynamic nature of the present-day defor-
mations. Two major tectonic factors controlling the
regional stress field in the Lower Amur region are well
known. In the southern part of the region, the main
structure is the Tang Lu Fault Zone (Fig. 1). The exact
position of the Tang Lu Fault Zone in the territory of
China is well mapped, whereas it is weakly traced and
remains questionable within the Russian borders [3, 5,
13, 27, 49]. In our opinion, the most reliable markers
of the position of the Tang Lu Fault Zone are the