Plate boundaries in the Far East region of Russia (from GPS measurement, seismic-prospecting, and seismological data)

Abstract:The interaction between the Amur, Pacific and Eurasian tectonic plates initiates seismic activity at the plate margins as well as in the plate periphery, as evidenced by intracontinental earthquakes. In the Amur plate, the dynamics of intercontinental seismicity is controlled by deformation wave fronts comprising a regular pattern of equidistant zones [Sherman, 2013]. According to [Trofimenko et al., 2015a[Trofimenko et al., , 2015b, maximum values of seismic activity in the range of magnitudes 2≤M≤4 also form a sequence of spatial cells in the form of seismic clusters from the east (Sakhalin -Sakh) to the west (the western boundary of the Baikal rift zone -BRZ ) (Fig. 1). One of the main characteristics of the seismic process is seismic activity migration given as sequential activation of seismogenic structures within the seismically active zones and on the global scale [Vikulin et al., 2012;Khain, Khalilov, 2008]. Direct observations show that crust deformation migrates from the Japan-Kuril-Kamchatka subduction zone towards the continent, and the estimated migration rates range from 10 to 140 km per year (e.g. [Ishii et al., 1978;Kasahara, 1979;Harada et al., 2003;Yoshioka et al., 2015]). In the Baikal and Amur regions (107-140°E), the fronts of deformation waves migrate at a rate of 5-20 km per year [Sherman, 2007[Sherman, , 2013. Considering the order of magnitude, this rate is comparable to the rates of crust deformation migration from the Japan-Kuril-Kamchatka zone (10-100 km per year). Our studies show that the sequential activation of the seismic clusters in the northeastern segment of the Amur plate (Sakh -TanLu -Al-St) occurs at a rate of 1000 km per year [Trofimenko et al., 2015a] (Fig. 1). In the meridional tectonic structures, the shifting chains of maximum seismicity values are sequentially replaced by minimum values (i.e. inversion zones). Based on the spatial cycles with the phase shift of the maximum seismic activity values at the rate of 1000 km per year, it is possible to represent the dynamics of seismicity in the form of a process initiated by long-period stress waves/deformations. According to [Mogi, 1968;Kasahara, 1979;Malamud, Nikolaevskii, 1989;Saprygin et al., 1997;Harada et al., 2003;Bykov, 2005Bykov, , 2014Sherman, 2007Sherman, , 2013Sherman, , 2014Milyukov et al., 2013], slow deformation waves of the global and regional scale are generated at the margins of lithospheric plates. Under this concept, the migration rate of seismic activity and the spatial extent of seismic cycles can be identified as the velocity and length of deformation waves. Using the data on seismicity of the most active region of the Baikal rift zone -the northwestern segment of the Amur plate, we have studied the periodic components of seismicity along the entire northern boundary of the Amur plate. An indirect evidence of the existence of deformation waves is the migration of anomalies of geophysical fields and its correlation with the migration of seismic activity. The space-time anomalies of the magnet...

Section: волновая динамика сейсмической активностиunclassified

Slow Deformation Waves in the Seismic Regime and Geophysical Fields at the Northern Margin of the Amur Plate

Trofimenko¹,

Быков

Grib³

2018

“…Чукотское море расположено в зоне современного растяжения земной коры (аналог лаптевоморской и байкальской зон, выделяемых на северовостоке Азии) [Levi et al, 2009;Timofeev et al, 2012]. Активность грабен-рифтовой системы здесь проявлена в виде субмеридиональных и субширотных мезораннекайнозойских рифтогенных структур [Shipilov, 1989;Polyak et al, 2010;Timofeev et al, 2012], напоминающих систему пулл-апарт бассейнов. Среди неотектонических структур рассматриваемой системы наиболее известен Чукотский грабен [Shipilov, 1989;Alekseev, 2002], состав-ной частью которого является желоб Геральда (рис.…”

Section: краткая геолого-геофизическая характеристика и особенности оunclassified

Late Holocene Sedimentation in Active Geological Structures of the Chukchi Sea

Вологина¹,

Калугин²,

Дарин³

et al. 2018

The article presents the detailed analysis results considering bottom sediments from the Chukchi Sea. Two core samples, b16 and НС-8 were taken from the northern Herald Canyon 150 km northeast from NE Wrangel Island. Core b16 has been studied in more detail. According to the 210 Pb measurements, the recent sedimentation rate amounts to 0.9 mm/y-1 at the sampling point. In the bottom layer of the core sample, the minimum concentrations of biogenic components (SiO2bio, Corg, Ntot, and Br) and the increased concentrations of cold-water diatom species Thalassiosira antarctica may result from low biological productivity during the Maunder Minimum. A correlation with recent global warming (11-22 years) is shown by the increased concentrations of SiO2bio, Corg, Ntot, and Br and the decreased values of magnetic susceptibility and X-ray density in the top layer (1-2 cm) of the same core sample. The results of our geochemical and diatom analysis support the available literature data and confirm that the Late Holocene sedimentation in the Chukchi Sea takes place in the zone wherein the water transits from the Pacific to the Arctic Ocean.

“…На зону их взаимодействия оказывает влияние северозападное направление движения Тихоокеанской плиты и юговосточное -Охотоморской [Bird, 2003], расположение желобов в зоне контактов (белыми стрелками показано направление смещения Тихоокеанской плиты) [Beavan et al, 2002;Apel et al, 2006]. (Евразийской) [Seno et al, 1996;Timofeev et al, 2012;Apel et al, 2006]. КурилоКамчатская дуга простирается более чем на 2000 км от полуострова Камчатка и его сочленения с Алеутской дугой в районе Командорских островов, вдоль Курильских островов до о. Хоккайдо.…”

Section: Introductionunclassified

Focal Mechanisms of Earthquakes in the Subduction Zone of the Western Pacific Plate

Bushenkova

Kuchay

2022

Deformation features of the subducting Pacific lithospheric plate are considered according to the data on earthquake focal mechanisms. The territory includes the convergent boundaries between the Pacific Plate and the North American (in the Aleutian arc region), the Okhotsk, the Eurasian and the Philippine plates.It has been shown that the angle of subducting Pacific Plate in the Aleutian subduction zone affects the focal mechanisms of earthquakes that occurred in the upper, 35 km part of the oceanic plate in the zone of its bending. There occur normal-fault earthquakes at a steep-angle subduction and rare thrust earthquakes at a shallow-angle subduction. The azimuthal orientation of P-axes of the focal mechanism solutions in the upper (1–70 km) contact zone corresponds to the Pacific Plate displacement vector when the plate fragments are subducting west-northwestwards. There occurs a change in azimuthal orientation of the compression axes in the subducting plate at a depth of more than 70 km: the axes occupy different azimuthal sectors showing difference in the orientation of their slope, with the orientations of the T-axes become multidirectional.The calculation of seismotectonic deformations was carried out based on the data on focal mechanisms of 7768 earthquakes. It was revealed that the Exx and Ezz deformation fields are the most homogeneous at depths of 1–70 km. The pattern of seismotectonic deformations changes abruptly for deep parts of the subducting plate (105–200, 200–400, and 400–700 km), there are observed heterogeneous deformation fields Exx, Eyy and Еzz with alternating episodes of extension and shortening.There has been proposed the author’s scheme of the influence of the upper mantle convection structure on the geometry of the subducting plate (slab) as a potential catalyst for the processes responsible for the separation of seismic activity zones and the change of earthquake types with depth and in different parts of the extended subduction zone.