Volume 28, 5, 2009 |
|
Preface 3 C.U. Kim, V.I. Mikhailov, R.S. Sen , Ye.P. Semenova. The August 2, 2007 Nevelsk earthquake: instrumental data analysis 4 N.F. Vasilenko, A.S. Prytkov, Ch.U. Kim, H. Takahashi. Coseismic Earth’s surface deformations resulting from the Aug 2, 2007 (MW = 6.2) Nevelsk earthquake (Sakhalin Island) 16 I.N. Tikhonov. Strong earthquake prediction within the south-western shelf of Sakhalin Island, and its realization during the August 2, 2007 Nevelsk earthquake 22 A.I. Zaitsev, D.P. Kovalev, A.A. Kurkin, B.V. Levin, Ye.N. Pelinovskiy, A.G. Chernov, A. Yalchiner. Tsunami on Sakhalin on August 2, 2007: mareograph evidence and numerical simulation 30 P.D. Kovalev, G.V. Shevchenko, D.P. Kovalev, A.G. Chernov, D.Ye. Zolotukhin. Simushir and Nevelsk tsunamis registration in the port of Kholmsk 36 V.L. Lomtev, M.G. Gurinov. Tectonic conditions of Nevelsk earthquake (August 2, 1007, M ~ 6.1) 44 T.K. Zlobin, A.Yu. Polets. Catastrophic Simushir earthquakes of November 15, 2006 (MW = 8.3) and of January 13, 2007 (MW = 8.1), and deep structure of the Middle Kurils Earth’s crust 54 N.G. Tomilin. Pair earthquakes on the Kurils 64 Yu.L. Rebetsky. Stress state of the Earth’s crust of the Kurils and Kamchatka before the Simushir earthquakes 70 M.Yu. Andreeva, Ye.V. Sasorova, B.V. Levin. The features of within-year earthquake distributions in the Kuril region 86 M.N. Luneva, D.A. Safonov. Seismic anisotropy beneath Southern Sakhalin by S-wave parameters of deep focus earthquakes 96 Reviews B.A. Voronov, P.V. Ivashov. Ecological principles of water-management work 107 Memorial dates Scientific heritage of Solomon M. Tilman (90th birth anniversary) 110 Obituaries Valiliy F. Bely (1929–2009) 112 C.U. Kim, V.I. Mikhailov, R.S. Sen , Ye.P. Semenova The August 2, 2007 Nevelsk earthquake: instrumental data analysis The catalogue of the 2007 Nevelsk earthquake (MW=6.2) aftershocks is prepared according to the data of the local network of digital seismic stations, installed in the south of Sakhalin Island. Hypocentral parameters are determined by the method of inversion of seismic wave travel times. The analysis of miscalculations of epicenter determination is carried out. The particulars of spatial-temporal distribution of aftershocks in the source zone of the August earthquake are obtained. The analysis of results of investigations made it possible to come to the conclusion that a strong aftershock is an earthquake-subsource, which has its own source zone. Basically, this allows us to resolve doubts on the estimation of magnitude parameters and the aftershock zone size of the Nevelsk earthquake. N.F. Vasilenko, A.S. Prytkov, Ch.U. Kim, H. Takahashi Coseismic Earth’s surface deformations resulting from the Aug 2, 2007 (MW = 6.2) Nevelsk earthquake (Sakhalin Island) The Nevelsk earthquake, MW = 6.2, occurred in the Tatar Strait, southwest of Sakhalin Island. The crustal deformations of the Sakhalin shore associated with this event were revealed by satellite radiointerferometry. The dislocation models of the main shock and its strong aftershocks with W-dipping fault planes were constructed based on satellite interferometry and seismological data. The performed investigations allowed us to estimate dislocations and geometrical parameters of seismic ruptures. The calculation of the coseismic vertical and horizontal surface displacements was made. In contrast to one-dimensional land displacements determined from satellite interferometry data, three-dimensional surface deformations for the epicental zone were estimated. I.N. Tikhonov Strong earthquake prediction within the south-western shelf of Sakhalin Island, and its realization during the August 2, 2007 Nevelsk earthquake Materials of the long- and short-term predictions of the destructive earthquake with the magnitude MLH = 6.6 ± 0.6 within the south-western shelf of Sakhalin Island are described. The long-term prediction was issued in December 2005, and was affirmed by the Russian Council of Experts on earthquake forecast and seismic hazard assessment in August 2006. The August 17(18), 2006 Gornozavodsk earthquake with the magnitude MW = 5.6 was the beginning of realization of this forecast. After 6 days from its occurrence, short-term prediction of a much more serious seismic event in the alarm region was prepared. One year later the prediction proved to be correct with respect to the 2 August, 2007 Nevelsk earthquake with the magnitude MW = 6.2 (MLH = 6.2). A.I. Zaytsev, D.P. Kovalev, A.A. Kurkin, B.V. Levin, E.N. Pelinovsky, A.G. Chernov, A. Yalciner Tsunami on Sakhalin on August 2, 2007: mareograph evidence and numerical simulation Instrumental data on tsunami registration on Sakhalin Island and Hokkaido Island are presented. Numerical simulation of tsunami propagation in the Tatar Strait was performed. Results of numerical computations are in satisfactory agreement with the observed data. P.D. Kovalev, G.V. Shevchenko, D.P. Kovalev, A.G. Chernov, D.Ye. Zolotukhin Simushir and Nevelsk tsunamis registration in the port of Kholmsk The analysis of the Simushir (November 16, 2006) and Nevelsk (August 2, 2007) tsunami records obtained by bottom pressure gauge in Kholmsk Bay was carried out. The dominant role of the zero mode of eigen oscillations in the bay in the process of wave field formation was shown: in the initial record interval in the case of the remote tsunami source, and an hour and a half after the first wave in the case of the close tsunami. Numerical modeling showed that in the case of the Nevelsk earthquake with the meridional elongation of the source, the longer waves propagated in the direction of Kholmsk, and they did not generate eigen oscillations of the bay. These oscillations were generated an hour and a half later, when the shorter waves reflected from the Primorye coast arrived. V.L. Lomtev, M.G. Gurinov Tectonic conditions of Nevelsk earthquake (August 2, 1007, M~6.1) The paper offers data of field investigation and study of coastal tectonic deformations of the August 2, 2007, M~6.1 Nevelsk tsunamigenic earthquake in August-September, 2007. As a result, the southern, central and northern benches were uplifted for 0.5-1.5 m and partly drained. Also, structural ridges, seaward of Lovetskaya Bay, formed. On the basis of the new model of Kamyshîvy (West-Sakhalin) anticlinorium as a structure of Quaternary or Middle Quaternary crust shear, possible relation of the earthquake to slow gravitational creep or creep of the upper crust at its western slope accompanied with squeezing of Middle Miocene Nevelsk siltstones is discussed. T.K. Zlobin, A.Yu. Polets Catastrophic Simushir earthquakes of November 15, 2006 (Mw=8.3) and of January 13, 2007 (Mw=8.1), and deep structure of the Middle Kurils Earth’s crust The catastrophic earthquakes with magnitudes of 8.3 and 8.1 which occurred on November 15, 2006 and January 13, 2007 in the region of Simushir Island were compared with the results of land-and-marine deep seismic research by DSS, correlation refraction method, method of converted waves of earthquakes and seismic reflection method in the region of the Middle Kuril arc. The structure of the Earth’s crust and focal zones of these earthquakes was considered based on the research. The focus of the main shock of the November 15, 2006 earthquake was established to be located on the bend of the seismofocal zone beneath the near-insular trench slope on the outer side of the subsiding lithospheric plate in the sharply uplifted granulite-basite (“basaltic”) crustal layer that replaced the granulite-gneiss layer at a depth of 7-15 km. Incidentally, the seismic velocity increased from 6.4 km/sec to 7.1 km/sec. The source of the January 13, 2007 earthquake was located under the deep-sea trench axis. Aftershocks were concentrated in two bands of 60-120 km wide stretching along the trench strike, and also in the third zone – an orthogonal island arc. The relation between the earthquake epicenters and regional faults is established. The main shock of the November 15, 2006 earthquake was defined as a low-angle thrust fault; and the main shock of the January 13, 2007 earthquake, as a normal fault. N.G. Tomilin Pair earthquakes on the Kurils Areas of pair strong earthquakes including the Simushir earthquakes along the Kuril trench have been defined based on the kinetic concepts of the strength of solid state, multilevel rock structure and the hierarchical model of rock destruction based on them. The analysis of space-time kinetics of these areas has shown the absence of any physical features compared to those for single event preparation. Yu.L. Rebetsky Stress state of the Earth’s crust of the Kurils and Kamchatka before the Simushir earthquakes Stress reconstruction of the Earth’s crust of the northwestern Pacific subduction zone was performed on the basis of the cataclastic analysis method and data on stress relief for the 2006 Simushir earthquake. This made it possible to calculate not only orientation of the principal stress axes but also stress magnitudes. Our calculations have shown that the magnitude of rock cohesion for this part of the crust is about 12 bar, and maximum shear stresses are not more than 300 bar. The propagation area of the Simushir earthquake is characterized by medium values of effective pressure and has no zones with high stresses. It means that this area is a seismic hazard region for large-scale brittle destruction. M.Yu. Andreeva, Ye.V. Sasorova, B.V. Levin The features of within-year earthquake distributions in the Kuril region It was shown in the last years that the earthquake occurrence probability in some regions depended on the latitude of the study region and on the Moon and Sun tidal forces, which are determined by the mutual arrangement of the bodies in the Sun-Earth-Moon system. The observed irregularity in the Far Eastern regions (South, Central, and North Kuril Islands, and Hokkaido Island) was noticed before. The objective of our work is to prove statistical significance of irregularity in seismic events distribution in the course of year, and also to indicate that this irregularity manifests itself in different ways for earthquakes with various source depths and with various energy levels. The hypothesis about uniform earthquakes distributions in the course of year for shallow events is rejected; however, it is shown that deep earthquakes are distributed uniformly. It is first attempted to determine the stability degree of within-year irregularity of seismic events with respect to the duration of the observation time interval (from 28 to 5 years). Two peaks are noted in the earthquake annual distribution. The relation of peaks of within-year seismic activity to the position of the Earth on the ecliptic plane is considered. The principal maximum of seismic activity falls on November-March (corresponding to the minimum Earth-Sun distance). M.N. Luneva, D.A. Safonov Seismic anisotropy beneath Southern Sakhalin by S-wave parameters of deep focus earthquakes Shear wave splitting parameter measurements of deep focus earthquakes registered by 12 Southern Sakhalin local net seismic stations for the period of 2005-2007 are presented. The study reveals heterogeneous distribution of anisotropic properties beneath the Southern Sakhalin area. Azimuths of fast S-wave polarization beneath stations located in the central part of the island are aligned along NNW and NNE-NE directions, normal to and along the Kuril trench. Beneath stations located along the western and eastern coasts, fast S-wave polarization azimuths change their directions from NNW to E-SE following southward station locations. The highest anisotropy degree up to 0.9-1.5% is recognized beneath the central part of Southern Sakhalin. In general, the maximum values of split shear wave time delays are observed in the case of fast shear wave azimuth orientation along N-NE beneath active fault zones. The analysis of time delay variations with depth shows their weak depth dependence. It is assumed that the highest anisotropy originated in the upper layers of the medium up to 250 km depth. The results obtained for dominating S-wave frequency of 1-5 Hz represent mainly mid-scale anisotropy of the top of the medium under study. |