Devonian dikes of the Urik-Belaya and Shagayte-Gol-Urik zones and Miocene lavas of the Urik volcanic field are spatially associated with each other at the structural junction between the Neoproterozoic Tuva-Mongolian massif and Siberian craton. The former dike belt is represented by basalts and basaltic andesites of tholeiitic series and the latter one by trachybasalts, trachyandesitic basalts of moderately alkaline series and trachybasalts, phonotephrites of highly alkaline one. The Urik volcanic field is composed of trachybasalts and trachyandesitic basalts of moderately alkaline series. A partial similarity between magmatic series of different age is found in terms of major oxides, trace elements, and Sr, Pb isotopes. The common component corrected for age was defined through its converging mixing trends with those of the lithospheric mantle and crust. The component identification was a basis for deciphering the nature of isotopic and geochemical heterogeneity of evolved magmatic sources. It was inferred that the common component characterizes either a modified (depleted) reservoir of the lower mantle or, more likely, a local region of the convecting asthenospheric mantle that underlies the Tuva-Mongolian massif. The latter interpretation assumes the formation of a locally convecting asthenosphere in the middle Neoproterozoic, along with the development of the Oka zone at the massif, and puts constrains on later sufficient processing of the asthenosphere due to rising plumes or subducting slabs.

Results of hydroacoustic observations of signals from weak earthquakes in natural conditions in the region of the Southern Kuril Islands are presented. Some earthquakes were registered by the the Yuzhno-Kurilsk Seismic Station, other were only recorded by hydrophone stations. The observations were specific as seismic signals were recorded in shallow waters, i.e. in high noise level conditions. Hydrophones were installed in Lake Lagunnoe (Kunashir) and Khromovaya Bay (Shikotan). Our analysis of hydroacoustic records received from the hydrophone stations revealed no evident precursory response of the geological medium to weak distant events. This means that neither before the period of earthquake preparation nor during the earthquake preparation period, any geoacoustic emission was not detected. It is shown that despite the unfavourable noise level conditions, even distant weak earthquakes can be confidently registered by hydrophone stations, and pending application of proper signal processing techniques, it can be possible to determine arrival times of seismic waves and to measure parameters of seismic waves. It is also established that the frequency spectrum of acoustic signals from the weak earthquakes recordable by the hydrophone stations is continuous and of noise type in the frequency range up to 90–100 Hz. It is revealed that in some cases, weak earthquakes and microearthquakes may be forerun by low frequency signals.

The catastrophic Simushir earthquake occurred on 15 November 2006 in the Kuril-Okhotsk region in the Middle Kuril Islands which is a transition zone between the Eurasian continent and the Pacific Ocean. It was followed by numerous strong earthquakes. It is established that the catastrophic earthquake was prepared on a site characterized by increased relative effective pressures which is located at the border of the low-pressure area (Figure 1).

Based on data from GlobalCMT (Harvard), earthquake focal mechanisms were reconstructed, and tectonic stresses, the seismotectonic setting and the earthquakes distribution pattern were studied for analysis of the field of stresses in the region before to the Simushir earthquake (Figures 2 and 3; Table 1).

Five areas of various types of movement were determined. Three of them are stretched along the Kuril Islands. It is established that seismodislocations in earthquake focal areas are regularly distributed. In each of the determined areas, displacements of a specific type (shear or reverse shear) are concentrated and give evidence of the alteration and change of zones characterized by horizontal stretching and compression.

The presence of the horizontal stretching and compression zones can be explained by a model of subduction (Figure 4). Detailed studies of the state of stresses of the Kuril region confirm such zones (Figure 5). Recent Geodynamics

The established specific features of tectonic stresses before the catastrophic Simushir earthquake of 15 November 2006 contribute to studies of earthquake forecasting problems. The state of stresses and the geodynamic conditions suggesting occurrence of new earthquakes can be assessed from the data on the distribution of horizontal compression, stretching and shear areas of the Earth’s crust and the upper mantle in the Kuril region.

Large intraplate subduction earthquakes are generally accompanied by prolonged and intense postseismic anomalies. In the present work, viscoelastic relaxation in the upper mantle and the asthenosphere is considered as a main mechanism responsible for the occurrence of such postseismic effects. The study of transient processes is performed on the basis of data on postseismic processes accompanying the first Simushir earthquake on 15 November 2006 and Maule earthquake on 27 February 2010.

The methodology of modelling a viscoelastic relaxation process after a large intraplate subduction earthquake is presented. A priori parameters of the selected model describing observed postseismic effects are adjusted by minimizing deviations between modeled surface displacements and actual surface displacements recorded by geodetic methods through solving corresponding inverse problems.

The presented methodology yielded estimations of Maxwell’s viscosity of the asthenosphere of the central Kuril Arc and also of the central Chile. Besides, postseismic slip distribution patterns were obtained for the focus of the Simushir earthquake of 15 November 2006 (Mw=8.3) (Figure 3), and distribution patterns of seismic and postseismic slip were determined for the focus of the Maule earthquake of 27 February 2010 (Mw=8.8) (Figure 6). These estimations and patterns can provide for prediction of the intensity of viscoelastic stress attenuation in the asthenosphere; anomalous values should be taken into account as adjustment factors when analyzing inter-seismic deformation in order to ensure correct estimation of the accumulated elastic seismogenic potential.

Using the modified formalism of [Dorogokupets, Oganov, 2005, 2007], equations of state are developed for diamond, Ag, Al, Au, Cu, Mo, Nb, Pt, Ta, and W by simultaneous optimization of shock-wave data, ultrasonic, X-ray, dilatometric and thermochemical measurements in the temperature range from ~100 K to the melting temperature and pressures up to several Mbar, depending on the substance. The room-temperature isotherm is given in two forms: (1) the equation from [Holzapfel, 2001, 2010] which is the interpolation between the low pressure (x≥1) and the pressure at infinite compression (x=0); it corresponds to the Thomas-Fermi model, and (2) the equation from [Vinet et al., 1987]. The volume dependence of the Grüneisen parameter is calculated according to equations from [Zharkov, Kalinin, 1971; Burakovsky, Preston, 2004] with adjustable parameters, t and δ. The room-temperature isotherm and the pressure on the Hugoniot adiabat are determined by three parameters, K', t and δ, and K0 is calculated from ultrasonic measurements. In our study, reasonably accurate descriptions of all of the basic thermodynamic functions of metals are derived from a simple equation of state with a minimal set of adjustable parameters.

The pressure calculated from room-temperature isotherms can be correlated with a shift of the ruby R1 line. Simultaneous measurements of the shift and unit cell parameters of metals are conducted in mediums containing helium [Dewaele et al., 2004b; 2008; Takemura, Dewaele, 2008; Takemura, Singh, 2006], hydrogen [Chijioke et al., 2005] and argon [Tang et al., 2010]. According to [Takemura, 2001], the helium medium in diamond anvil cells provides for quasi-hydrostatic conditions; therefore, the ruby pressure scale, that is calibrated for the ten substances, can be considered close to equilibrium or almost absolute. The ruby pressure scale is given as P(GPa)=1870⋅Δλ/λ0⋅(1+6⋅Δλ/λ0). The room-temperature isotherms corrected with regard to the ruby scale can also be considered close to equilibrium or almost absolute. Therefore, the equations of state of the nine metals and diamond, which are developed in our study, can be viewed as almost absolute equations of state for the quasi-hydrostatic conditions. In other words, these equations agree with each other, with the ruby pressure scale, and they are close to equilibrium in terms of thermodynamics. The PVT relations derived from these equations can be used as mutually agreed pressure scales for diamond anvil cells in studies of PVT properties of minerals in a wide range of temperatures and pressures. The error of the recommended equations of the state of substances and the ruby pressure scale is about 2 or 3 per cent. Calculated PVT relations and thermodynamics data are available at http://labpet.crust.irk.ru.

Издательством «Научный мир» (г. Москва) переведена на русский язык и опубликована книга «Paleoseismology», подготовленная под редакцией известного американского ученого Дж. МакКалпина – одного из крупнейших научных авторитетов в области палеосейсмологии. Это уже второе, дополненное и переработанное, американское издание фундаментального труда, впервые увидевшего свет в 1996 г. в издательстве Academic Press [McCalpin, 1996] и до настоящего времени являющегося наиболее часто цитируемой работой по проблемам палеосейсмологии.