Dynamics of Induced Seismicity during the Filling of the Nurek Reservoir     

V. B. Smirnov  A. V. Ponomarev  T. I. Kartseva  V. O. Mikhailov  R. K. Chadha  F. Aidarov 《Izvestiya Physics of the Solid Earth》2018,54(4):641-651

The seismological data in the area of induced seismicity in the region of the Nurek reservoir are analyzed. The analysis is based on the developed database for the earthquakes that occurred from 1955 to 1989 and is aimed at finding the regularities in the variations of the parameters of the transitional seismic regime caused by filling a reservoir. These parameters include the b-value—the slope of the graph of the Gutenberg–Richter frequency–magnitude relationship, the fractal dimension d of the set of the epicenters, and fracture cycle parameter q = αb ? d, where coefficient α determines the ratio between the magnitude and source size M = α log l + β. It is shown that during the filling of a reservoir, these parameters undergo statistically reliable variations: at the initial stages, the b-value increases, the fractal dimension of the set of epicenters decreases, and the fracture cycle parameter q grows and becomes positive in the middle of the time interval of reservoir filling. After a reservoir is filled, these parameters recover their background values. The aftershock sequences of the three strongest earthquakes—before, in the beginning, and in the middle of the reservoir filling period—are studied. It is confirmed that the Omori parameter p for the aftershock sequences during filling is smaller than for the earthquake before filling. Based on the dynamics of the studied parameters, it is conjectured that the relaxation time of the transitional seismic regime after the emergence of induced seismicity is about 10 years.  相似文献   

The effective stiffness of modern unreinforced masonry walls          下载免费PDF全文

Bastian Valentin Wilding  Katrin Beyer 《地震工程与结构动力学》2018,47(8):1683-1705

Code design of unreinforced masonry (URM) buildings is based on elastic analysis, which requires as input parameter the effective stiffness of URM walls. Eurocode estimates the effective stiffness as 50% of the gross sectional elastic stiffness, but comparisons with experimental results have shown that this may not yield accurate predictions. In this paper, 79 shear‐compression tests of modern URM walls of different masonry typologies from the literature are investigated. It shows that both the initial and the effective stiffness increase with increasing axial load ratio and that the effective‐to‐initial stiffness ratios are approximately 75% rather than the stipulated 50%. An empirical relationship that estimates the E‐modulus as a function of the axial load and the masonry compressive strength is proposed, yielding better estimates of the elastic modulus than the provision in Eurocode 6, which calculates the E‐modulus as a multiple of the compressive strength. For computing the ratio of the effective to initial stiffness, a mechanics‐based formulation is built on a recently developed analytical model for the force‐displacement response of URM walls. The model attributes the loss in stiffness to diagonal cracking and brick crushing, both of which are taken into account using mechanical considerations. The obtained results of the effective‐to‐initial stiffness ratio agree well with the test data. A sensitivity analysis using the validated model shows that the ratio of effective‐to‐initial stiffness is for most axial load ratios and wall geometries around 75%. Therefore, a modification of the fixed ratio of effective‐to‐initial stiffness from 50% to 75% is suggested.  相似文献   

The behavior of seasonal variations in induced seismicity in the Koyna–Warna region,western India     

V. B. Smirnov  D. Srinagesh  A. V. Ponomarev  R. Chadha  V. O. Mikhailov  M. G. Potanina  I. M. Kartashov  S. M. Stroganova 《Izvestiya Physics of the Solid Earth》2017,53(4):530-539

Based on the earthquake catalog data for the Koyna–Warna region of induced seismicity in western India, the seasonal variations in seismic activity associated with annual fluctuations in the reservoir water level are analyzed over the time span of the entire history of seismological observations in this region. The regularities in the time changes in the structure of seasonal variations are revealed. The seasonal seismic activity is minimal in May–June when the reservoir level is lowest. During the remaining part of the year, the activity has three peaks: the fall peak in September, winter peak in November–December, and spring peak in February–March. The first mentioned peak, which falls in the phase of the water level reaching its maximal seasonal value is considered as the immediate response of the fluid saturated medium to the additional loading under the weight of reservoir water. The two subsequent maxima concur with the decline phase in the reservoir level and are interpreted as the delayed response associated with the changes in the properties of the medium due to water diffusion. It is shown that the intensities of the immediate and delayed responses to the seasonal water level variations both vary with time as does their ratio. The probable factors affecting the variations in the intensity of the seasonal components of the reservoir-induced seismicity are discussed.  相似文献   

Geodynamic Modeling of the Process of the Formation and Evolution of Lithospheric Structures: the Experience of Schmidt Institute of Physics of the Earth,RAS     

Mikhailov  V. O.  Timoshkina  E. P. 《Izvestiya Physics of the Solid Earth》2019,55(1):102-110

Izvestiya, Physics of the Solid Earth - The main results obtained at the Institute of Physics of the Earth of the Russian Academy of Sciences (IPE RAS) in the numerical geodynamic modeling of the...  相似文献   

Proposal for selection of control,preventive and rehabilitation measures based on degradation land level and geoindicators in the fortaleza metropolitan region,State of Ceará, Brazil     

Lázaro Valentin Zuquette  Jaime Quintas dos Santos Collares  Osni José Pejon 《Environmental Geology》2007,52(5):899-922

Preventive, controlling, rehabilitative and corrective measures to improve the environmental quality of the hydrographic basins of the Fortaleza metropolitan region in the state of Ceará (Brazil) are presented based on geological and geotechnical data, land degradation rates and sources, and other geoindicators. The region is affected by coastal and stream erosion, gravitational mass movement, dunes, silting, and water pollution, sanitary landfills in inappropriate sites, decommissioned and abandoned aggregate mining, and swamp areas. Geoindicators were used to classify each of the 12 hydrographic basins as possessing low (4), intermediate (3), or high (5) degradation levels. A group of 59 environmental management measures related to ecological, bioengineering, mechanical, policy and administrative, agricultural and clean-up methods was selected. From this general group a set of 31 measures was chosen considering goals, efficacy for specific environmental problems, suitability for large or small areas, behavior under different annual climatic conditions, environmental problems of the region, geological and geotechnical limitations and degradation level of the basins. A set of the more suitable geoindicators was selected for monitoring efficiency of the measures for each basin.  相似文献   

On the properties of earthquake precursors in the electrostatic field of the surface atmosphere     

Yu. M. Mikhailov 《Izvestiya Physics of the Solid Earth》2007,43(4):336-339

The paper presents results of the analysis of occurrence times of earthquake precursors in a quasistatic electric field of the surface atmosphere on the Kamchatka Peninsula. The propagation velocity of the precursors and their occurrence time dependence on the earthquake source depth are estimated. A hypothesis on the possible correlation of the precursor propagation velocity with the diffusion rate of subsurface radon is proposed.  相似文献   

Nuclear activity of NGC 5548 from UBVRI observations during 1990–2000     

V. T. Doroshenko  V. M. Lyuty  N. G. Bochkarev  N. I. Merkulova  S. G. Sergeev  V. V. Vlasyuk  V. P. Mikhailov  O. I. Spiridonova  O. V. Ezhkova  K. N. Grankin  S. Yu. Mel’nikov 《Astronomy Letters》2001,27(11):691-702

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Isotopic Composition of Oxygen and Carbon and Formation Temperature of Accessory Minerals from Evaporitic Sediments in the Pripyat Trough     

Makhnach  A. A.  Kuleshov  V. N.  Pokrovskii  B. G.  Gulis  L. F.  Mikhailov  N. D.  Kolosov  I. L. 《Lithology and Mineral Resources》2002,37(6):536-545

The isotopic composition of oxygen and carbon was studied in accessory carbonates and quartz separated from salts in Upper Devonian halogenous formations of the Pripyat Trough (Belorus). It is established that isotopic characteristics vary in a wide range. Values of ¹⁸O vary in the following range (SMOW): from 18.2 to 29.2 in calcites, from 15.7 to 32.5 in dolomites, and from 17.4 to 27.2 in quartz. Values of ¹³C range from –13.4 to 1.4 in calcites and from –11.1 to 1.7 in dolomites (PDB). Results obtained indicate highly variable isotope-geochemical conditions of sedimentation and early diagenesis during the formation of evaporitic sediments. Accessory minerals were repeatedly formed in a wide temperature range and probably at various stages of the lithogenesis.  相似文献   

Hydrological Regime and Morphodynamics of the Yangtze River Mouth Area   总被引：1，自引：0，他引：1  

Mikhailov  V. N.  Korotaev  V. N.  Mikhailova  M. V.  Congxian  Li  Shuguang  Liu 《Water Resources》2001,28(4):351-363

The features of the hydrological regime, modern morphological structure, fluviomorphological processes, and the history of formation of the Yangtze River mouth area are discussed. The influence of the huge river water and sediment runoff and tides on the hydrological and morphological processes in the Yangtze River mouth is shown. The possible impact of construction of the large waterworks Three Gorges on the hydrological and morphological processes in the Yangtze River mouth is roughly evaluated.  相似文献   

Cenomanian florule of Nammoura, Lebanon     

Valentin Krassilov  Flavio Bacchia 《Cretaceous Research》2000,21(6):785

The mid-Cenomanian fish beds of Nammoura, Mont-Liban district, Lebanon contain a diverse fauna of aquatic and terrestrial vertebrates, a few crustaceans and moderately well-preserved plant remains of which a single species,Sapindopsis anhouryi , was previously described by Dilcher & Basson (1990). We add 11 species of ferns, gymnosperms and angiosperms of which Nammouria cretacea gen. et sp. nov, Nupharanthus cretacea gen. et sp. nov., Sapindopsis libanensis sp. nov. and Nammourophyllum altingioides gen. et sp. nov. are new taxa. The florule differs markedly from both Early Cretaceous and Turonian plant assemblages of the Middle East, thereby representing a distinct stage of the regional floristic evolution. Its phytogeographic affinities are with contemporaneous floras of North America, Central Europe and the Crimea. A combination of such features as xeromorphism, the prevalence of compound leaves, and the presence of deciduous angiosperm components and gymnosperms may indicate climatic conditions similar to those of the present day Mediterranean.  相似文献