Òîì 31, 6, 2012 |
| Geological-geophysical investigations and recent volcanism O.V. Veselov, P.F. Volgin, L.M. Lyutaya. Sedimentary cover structure of the Pugachevo mud volcano area (Sakhalin) from geophysical modelling 4 A.V. Degterev, A.V. Rybin, I.V. Melekestsev, N.G. Razjigaeva. Explosive eruptions of the Sarychev Peak volcano in the Holocene (Matua Island, Central Kuril Islands): tephra geochemistry 16 D.N. Kozlov, R.V. Zharkov. Thermal imaging analysis of post-eruptive activity of Ekarma Volcano in 2010 (Kuril Islands) 27 T.M. Poberezhnaya. Endogenous sources of dioxin emission to the areas of tectonomagmatic activation (exemplified by the Sakhalin-Kuril region) 31 R.G. Kulinich, M.G. Valitov, Z.N. Proshkina. Geophysical fields, block structure and seismicity of the Central Kuril Islands 35 Earthquakes, tsunamis, and other dangers G.V. Shevchenko, V.N. Patrikeev. Statistical characteristics of northwestern Pacific abyssal irregularities and their potential impact on tsunami propagation 44 N.G. Razzhigaeva, L.A. Ganzey, T.A. Grebennikova, A.A. Kharlamov, V.M. Kaistrenko, Kh.A. Arslanov, A.O. Gorbunov. Paleotsunami manifestation in the Lesser Kuril arc in the Holocene 49 Y.V. Marapulets, B.M. Shevtsov, I.A. Larionov, M.A. Mishchenko, A.O. Shcherbina, A.A. Solodchuk. Geoacoustic emission response to deformation processes activation during earthquake preparation 59 V.N. Sychev, L.M. Bogomolov, N.A. Sycheva. On the daily quasi-periodicity and random component in the flow of seismic events 68 O.S. Sedaeva, V.P. Semakin, G.V. Shevchenko. Vertical displacements of the Earth’s surface from level data in the South Kuril Islands in relevance to the Shikotan earthquake of October 4(5), 1994 79 R.Z. Tarakanov, M.Yu. Andreeva. Role of the seismic focal zone in the formation and development of the Kuril-the Sea of Okhotsk Region structures 87 T.K. Zlobin, A.Yu. Polets. Geodynamic processes and natural disasters: classification, manifestation in the lithosphere of the Kuril-Sakhalin region 97 P. A. Kamenev, L.M. Bogomolov, S.A. Valetov. On estimatioin “in situ” of geomechanic parameters of sedimentary rocks from logging 109 Yu.V. Brusilovsky, A.N. Ivanenko, A.YU. Zhukovin, N.M. Tsovbun. Geomagnetic study of the central Kuril-Kamchatka island arc 115 Index of paperspublished in 2012 ã. 122 O.V. Veselov, P.F. Volgin, L.M. Lyutaya Sedimentary cover structure of the Pugachevo mud volcano area (Sakhalin) from geophysical modelling The geological-geophysical data on the group of the Pugachevo mud volcano area which lie in the zone of the submeridional Central Sakhalin fault (CSF) are analyzed. Results of geodensity and geothermal modeling from two orthogonal profiles passing through the central part of the Pugachevo area are examined. In the Late Cretaceous section of this area confined to the fault zone, a subvertical, narrow, abnormally deconsolidated cone-shaped zone extending from 1 km on the surface up to almost 4 km at its base (at the depths of more than 6 km), was distinguished. The density of deconsolidation blocks is 2.20–2.22 g/cm3, whereas in the adjacent blocks it reaches about 2.4–2.5 g/cm3. The largest deconsolidation block is located in the Aiskaya form-n (K1-2as), where a vast reservoir zone containing mainly hydrocarbon gas (HC) should be expected at depths deeper than 4400 m at temperatures more than 140°C. Modeling results showed that the main reservoir of gases periodically ejected by the Pugachevo mud volcano was in the tectonically fault zone of CSF at the depth of 4.5–5.6 km in the Aiskaya. Above are smaller intermediate reservoirs. The Pugachevo area is perspective for commercial hydrocarbon occurrences. Key words: Late Cretaceous deposits, density and temperature models, deconsolidation zone, reservoir, hydrocarbons, Pugachevo mud volcano, Sakhalin Island. A.V. Degterev, A.V. Rybin, I.V. Melekestsev, N.G. Razjigaeva Explosive eruptions of the Sarychev Peak volcano in the Holocene (Matua Island, Central Kuril Islands): tephra geochemistry The first results of tephrachronological researches of the Sarychev Peak volcano, the Matua Island, (Central Kuriles) are represented including the reconstruction of its eruptive history in the Holocene. Based on the study of the distribution of petrogenous oxides and microelements in the tephra sampled layer-by-layer from the reference section of soil-pyroclastic cover of Matua Island, a general trend of the geochemical evolution of the volcano products during the Holocene epoch is traced, their typification was made. The horizons of the transition ashes were identified. Key words: tephra, soil-pyroclastic sequence, Holocene, volcano, geochemistry, transition ash, Sarychev Peak, Kuril Islands. D.N. Kozlov, R.V. Zharkov Thermal imaging analysis of post-eruptive activity of Ekarma Volcano in 2010 (Kuril Islands) The results of thermal imaging survey of Ekarma volcano (Ekarma Island, the Kuril Islands) carried out during complex expedition works in 2010 just after its eruption are represented. The methods of thermal imaging survey and some ways of thermograph processing are described. Additionally, the problems and peculiar features of creation of electronic catalogue with the heat vision images are considered. The most significant results of thermograph analysis, optimal methods of correction of the thermal imaging observations, and the quality improvement of thermal imaging survey of active volcanoes are demonstrated. Key words: thermal imager, volcano, eruption, steam-gas column, Kuril Islands. T.M. Poberezhnaya Endogenous sources of dioxin emission to the areas of tectonomagmatic activation (exemplified by the Sakhalin-Kuril region) Data on dioxin content, mainly the highly chlorinated derivatives of PCDD, in the landscapes of contemporary active volcanoes and in the buried volcanic ash, in the fresh emissions of a dirt volcano have been obtained. It is shown that there exist endogenous sources of dioxin emission to the biosphere in the areas of tectonic and volcanic activity. It has been supposed that the flow of very toxic chemical compounds-dioxins to the biosphere in geologicaltime scale was continuous, and this undoubtedly was of environmental importance for biota, which is difficult to assess at the present-day level of knowledge. Key words: dioxins, solfataric field, dirt volcano, volcano-tectonic activity, Kuril Islands, Sakhalin Island. R.G. Kulinich, M.G. Valitov, Z.N. Proshkina Geophysical fields, block structure and seismicity of the Central Kuril Islands On the basis of the combined analysis of seismologic information with gravity and magnetic fields and relief of the acoustic basement it was revealed that the largest earthquakes that occurred near the Central Kuril Islands in 2006-2009 were related to the block structure of the Earth’s crust. Aftershocks of the largest earthquakes recorded in 2006 and 2007 have become foreshocks for the earthquakes followed in 2007 and 2009, respectively. In total, the earthquakes that have occurred in this area in the period of 2006-2012, are closely related to the existing here tectonic destructive zone, clarifies its position and objectively supports the earlier concept on its superimposed and intersecting character with respect to the Kuril Island Arc. Key words: earthquakes, geophysical fields, block structure, Vityaz Ridge, Kuril trench, Central Kuril Islands. G.V. Shevchenko, V.N. Patrikeev Statistical characteristics of northwestern Pacific abyssal irregularities and their potential impact on tsunami propagation Set echograms obtained during realization of the project «Pacific transects» in the second half of the 1980s, was digitized with the same step within a strip one mile wide. As a result of the processing of these materials, spectral and statistical characteristics of the bottom relief irregularities of the northwestern Pacific abyssal plateau have been obtained. It is shown that the law of spectral density decrease in the wavelength range of irregularities from 2 to 100 miles is in good agreement with the law k-2. In parallel with this two ranges can be distinguished in this spectrum: small-scale (2-8 miles long and 50 m averaged high) and medium-scale (10-40 miles long and 120 m high). We obtain estimates of the damping ratio of the tsunami wave by the interaction with the irregularities of the bottom topography - for forward scattering of about = 0.2 h-1 and reverse = 0.1 h-1. Transformation of the initial single pulse in the wave train, the delay of the maximum wave relative to the time of arrival of the tsunami, and the increase in the duration of the oscillations are related with the forward scattering. Key words: seismic profile, abyssal plateau, irregularities of bottom topography, spectrum, scattering, tsunami, delay, Pacific. N.G. Razzhigaeva, L.A. Ganzey, T.A. Grebennikova, A.A. Kharlamov, V.M. Kaistrenko, Kh.A. Arslanov, A.O. Gorbunov Paleotsunami manifestation in the Lesser Kuril arc in the Holocene Data on paleotsunami records for some islands of the Lesser Kuril group are discussed. Sedimentation features during the tsunami of different intensity are analyzed. In addition, the age of the most significant tsunami events was determined, and their recurrence interval in the Middle-Late Holocene was defined. Key words: paleotsunami, tsunamigeneous sediments, age and recurrence of the tsunami, Holocene, the Lesser Kuril Range. Y.V. Marapulets, B.M. Shevtsov, I.A. Larionov, M.A. Mishchenko, A.O. Shcherbina, A.A. Solodchuk Geoacoustic emission response to deformation processes activation during earthquake preparation The results of geoacoustic emission investigations which are carried out on Kamchatka peninsular since 1999 are presented. The peculiarity of the experiments is the application of broad-band piezo-ceramic hydrophones for registration of the emission; the hydrophones are installed in water at the bottom of natural and artificial water reservoirs. Application of such type receivers allows us to broaden the registration frequency range up to 0.1 Hz – 11 kHz compared with the standard hydrophones. Three-component vector receivers with the same frequency range have been used simultaneously to study the spatial structure of geoacoustic emission and the mode of medium particle movement in a wave. In the course of investigations it was determined that 1–3 days before strong earthquakes anomalies of geoacoustic emission in kilohertz frequency range are registered at the distances of the first hundreds of kilometers from an epicenter. As an alternative to anomalies a sharp increase in geoacoustic impulse amplitude and frequency closely resembling micro-earthquakes in form which last from tens of minutes to several hours has been taken. Signals at such frequencies cannot propagate from the epicenters of preparing earthquakes and are response of a medium at the registration point to the change of its stress-strain state. The forming field of stresses determines a primary orientation of the emission sources, which can be assessed by vector-phase methods. The results of the integrated investigations of the emission and the Earth’s surface deformations evidences that anomalies before earthquakes are observed with considerable increasing deformation rate both during near surface rock compression and tension. Key words: geoacoustic emission, deformations, hydrophone, combined receiver, laser strainmeter – interferometer, Kamchatka. V.N. Sychev, L.M. Bogomolov, N.A. Sycheva On the daily quasi-periodicity and random component in the flow of seismic events Distributions of seismic events have been analyzed for two seismically active regions with different geodynamic conditions (Central Asia and the Far East) aiming at distinguishing quasi-periodicity (daily variations, at first) and sequences which correspond to realization of a random process. It has been demonstrated that the phase of daily variations of averaged seismic activity is synchronized with the local time rather than that of lunar-solar tides. This is testimony to an ionosphere origin (triggering) since the regular daily variations coupled with daytime/night time alteration are typical for the effects related to ionosphere. It has also been shown that the series of seismic events in short-term time intervals is correspondent with realization of random process described by Poya distribution. Key words: seismic event, catalogue, energy class, quasi-periodicity, random distribution, Central Asia, Far East. O.S. Sedaeva, V.P. Semakin, G.V. Shevchenko Vertical displacements of the Earth’s surface from level data in the South Kuril Islands in relevance to the Shikotan earthquake of October 4(5), 1994 The materials of the sea level observations at the coastal tide gauges of the South Kuril Islands and the north-eastern part of the Hokkaido Island before and after the Shikotan earthquake of October 4(5), 1994 were analyzed. At the Hanasaki and Malokurilsky stations, taking into account changes in the direction of average annual sea level values from the beginning of observations till 1986, three periods were identified for which a total displacement of the Earth’s surface (cm) and their mean velocity (cm/year) were specified. Within these periods short-term intervals with anomalous displacements and velocities were revealed, which are associated with the earthquakes occurred at relatively small distances from the stations. During the period from 1986 to 1990, in the area under consideration a gradual elevation of the Earth’s surface took place, while in 1991 all stations registered its rapid subsidence. By the average annual sea level values, the greatest subsidence of the Earth’s surface during and after the earthquake (October-December, 1994) occurred in the Shikotan Island (-55 cm) and Nemuro Peninsula (-11 cm). The negative bias is also recorded at the Kurilsk and Abashiri stations, in the regions of other gauges the Earth’s surface uplift was observed. Taking into account the correction for atmospheric pressure, the vertical displacement of the Earth’s surface directly during the Shikotan earthquake were verified (46 cm in Malokurilsk and 21 cm in Hanasaki). On the basis of the analyzed data and published materials, the most probable mechanism for the Shikotan earthquake, in our opinion, is the right shift-upthrust, followed by lowering of the near-shore block and its subduction beneath the ocean block. Key words: vertical displacement of the Earth’s surface, sea level, tide gauge, earthquake, mechanism, thrust, shift, compression axis, nodal plane, Kuril Islands, Hokkaido Island. R.Z. Tarakanov, M.Yu. Andreeva Role of the seismic focal zone in the formation and development of the Kuril-the Sea of Okhotsk region structures A model of the seismic focal zone is presented to explain formation and functioning of the seismic focal zone based on the near-surface compressive stresses acting at the continent-to-ocean boundary and dislocation theory. The magmatic chambers are shown to be confined to the areas where seismic focal zone crosses the lower viscosity asthenospheric layers located at the depths of 60-80, 120-150 and 220-300 km. Morphological and tectonic features of the different elements of the Kuril – the Sea of Okhotsk Region are examined. The Greater and Lesser Kuril Ridges were found differing markedly in functioning time inferred from geophysical fields and geological-petrographic composition. Key words: seismic-focal zone, magmatic chambers, deep-water trench, the Sea of Okhotsk, Greater and Smaller Kuril Ridges. T.K. Zlobin, A.Yu. Polets Geodynamic processes and natural disasters: classification, manifestation in the lithosphere of the Kuril-Sakhalin Region The paper considers geodynamic processes and natural disasters which were classified on their manifestation on the Earth as a whole, in its solid mantle and in the lithosphere of the Kuril-Sakhalin region. A possible link between two major types of disasters - earthquakes and volcanic eruptions – is discussed. In addition, an accident or regularity (periodicity) of natural disasters, duration of the processes and their bifurcation were considered. Energy sources of geodynamic processes and the main natural disasters were presented. Key words: geodynamic processes, natural disasters, the Earth’s crust and upper mantle, earthquakes, volcanoes, Kuril Islands, Sakhalin. P. A. Kamenev, L.M. Bogomolov, S.A. Valetov On estimatioin “in situ” of geomechanic parameters of sedimentary rocks from logging Basic geomechanic parameters of sedimentary rocks have been calculated from geophysical observations of the boreholes on Polyarninskoy oilfield, Sakhalin Island. The Young’s modulus and shear modulus have been evaluated by acoustic logging data. Poisson’s ratio has been estimated by two methods: based on the values of elastic moduli, and from natural gamma ray activity of the rocks. All the data obtained can be followed to construct geomechanical model of the oilfield and estimate local stress distribution pattern «in situ». Besides, these results may be applicable for estimating «in situ» stress-deformed state of the sedimentary rocks of the oilfield area. Key words: geomechanics (geomechanic parameters), Poisson’s ratio, shear modulus, Young’s modulus, Sakhalin Island. U.V. Brusilovskiy, A.N. Ivanenko, A.U. Zhukovin, N.M. Tsovbun Geomagnetic studies of the central Kuril-Kamchatka Island arc The results of the magnetic studies performed during the complex geological-geophysical expeditions by the scientific research vessel Academician M.A. Lavrent’ev, in September-October, 2010, are considered. The aim of the expedition was to conduct geological-and-geophysical works to specify the boundaries of the destruction zone in the central part of the Kuril island arc, its structural plan and reconstruction of tectono-magmatic processes which are responsible for the described zone formation. It is shown that the study area .represents a zone of high tectonic fragmentation with active manifestation of young magmatism, mainly of volcanogenic type. Since the study area and the region of survey during 2005–2006 and 2010 are located in the same morphostructural zone and occupy the adjacent areas, one can assume the identity of the tectonic processes forming the entire part of the zone as a whole. We also make the conclusion of a possible similar origin and mechanism of formation of the source of magnetic anomalies within the investigated area and in the so-called “magnetic belt” in the Hokkaido Island area. Key words: sea gradient magnetic survey, magnetic field, the Kuril Islands, Pacific Ocean, non-volcanic arc, young volcanism, magnetic field transformation. |