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641.
Automatic pickings in earthquake real-time monitoring systems often contain noise bursts and/or phases of different event(s)
occurring almost simultaneously. Typically, a locator uses these picks as P and S waves arrival times coming from a single
event and, therefore, should be complemented by a distinctive phase association logic. The method we propose manages to automatically
associate data related to different events and eliminates the influence of spoiled data from single events. The method is
based on “network beamforming”, a robust and stable algorithm, which utilizes a hypocenter grid search for the stack maximum
of a set of complex exponents applied to the P phase readings. The algorithm separates the residual outliers and then uses
them for location. If successful, a hypocenter is established for the interfering event. The solutions obtained are overall
robust and independent from the estimate of origin times. The preliminary epicenter for the grid search is provided by the
intersection of perpendicular bisectors in the modified “arrival order algorithm” or by the modified “Tnow” algorithm, which uses non-arrival information. We applied this method to automatic first arrival phase readings of 915 events
registered by the Hi-net Japan seismic network and our results are statistically promising. Here, we present two interesting
and complicated examples. 相似文献
642.
Comparison of Earth’s magnetospheric magnetic field models in the context of cosmic ray physics 总被引:1,自引:0,他引:1
Laurent Desorgher Karel Kudela Erwin O. Flückiger Rolf Bütikofer Marisa Storini Vladimir Kalegaev 《Acta Geophysica》2009,57(1):75-87
Over the last two decades, models of the Earth’s magnetospheric magnetic field have been continuously improved to describe
more precisely the different magnetospheric current systems (magnetopause current, symmetric and partial ring currents, tail
currents and field aligned currents). In this paper we compare the different Tsyganenko models and the Alexeev and Feldstein
model in the context of cosmic ray physics. We compare the vertical cutoff rigidity and asymptotic direction of vertical incidence
obtained with these models for the January 20, 2005, ground level enhancement and for the big magnetic storm of April 6, 2000.
For the event of January 20, 2005, we study the impact of the differences in asymptotic direction obtained with the models
on the radiation dose computation at aircraft altitude. For the magnetic storm of April 6, 2000, we discuss the importance
of the different magnetospheric current systems in causing cutoff rigidity variations. Finally we summarise the advantages
and drawbacks of the different models in the context of space weather. 相似文献
643.
Jean-Louis Le Mouël Vladimir Kossobokov Vincent Courtillot 《Journal of Atmospheric and Solar》2010,72(1):62-76
We analyze the longest temperature series from Prague, Bologna and Uccle. We partition daily minimum and maximum temperatures and their differences in two subsets as a function of high vs low solar activity, using the superimposed epochs method. Differences display patterns with significant amplitudes and time constants ~3 months. These are recognized in all stations and are stable against a change in the analyzed period. Amplitude of variations is ~1 °C. Differences between average annual values corresponding to high vs low activity periods are also ~1 °C. Solar activity may account for these long-term temperature variations. These variations also present local characteristics, which may render identification of a global correlation delicate. We discuss possible physical mechanisms by which solar variation could force climate changes (e.g. through solar activity itself, the EUV part of the solar flux, cosmic rays, the downward ionosphere-earth current density, etc.). 相似文献
644.
Vitaliy D. Rusov Vladimir N. Vaschenko Elena P. Linnik Оksana T. Myhalus Yuriy A. Bondartchuk Vladimir P. Smolyar Sergey I. Kosenko Strachimir Cht. Mavrodiev Boyko I. Vachev 《Journal of Atmospheric and Solar》2010,72(5-6):389-397
The solution of energy-balance model of the Earth global climate and the EPICA Dome C and Vostok experimental data of the Earth surface palaeotemperature evolution over past 420 and 740 kyr are compared.In the framework of proposed bifurcation model (i) the possible sharp warmings of the Dansgaard-Oeschger type during the last glacial period due to stochastic resonance is theoretically argued; (ii) the concept of climatic sensitivity of water in the atmosphere, whose temperature instability has the form of so-called hysteresis loop, is proposed, and based on this concept the time series of global ice volume over the past 1000 kyr, which is in good agreement with the time series of δ18O concentration in the sea sediments, is obtained; (iii) the so-called “CO2 doubling” problem is discussed. 相似文献
645.
Lidija Krstevska Ljubomir Tashkov Vladimir Gocevski Mihail Garevski 《Bulletin of Earthquake Engineering》2010,8(2):421-450
The seismic stability of the facade brick-masonry walls of the machinery building of the Beauharnois powerhouse near Montreal,
Quebec, Canada were investigated numerically by use of non-linear models and applying experimental methods on site and on
the IZIIS’ seismic shake-table. The dynamic properties of the machinery building were obtained by ambient vibration measurements.
Based on these results, a model of a representative part of the building, consisting of steel frames and brick masonry wall,
was designed and constructed to the reduced scale at the IZIIS’ Dynamic Testing Laboratory and then tested on the two-component
shake-table. The geometry of the original structure was completely scaled to 1/3, consisting of many realistically simulated
details such us: brick layers, steel columns, openings, window frames, steel connectors between brick layers, number of layers,
brick dimensions, etc. The material used for the model was: original steel for the frame structure and bricks of reduced mechanical
properties for the masonry wall, close to the similitude requirements according to the Backingham’s theorem, valuable for
adequate artificial—mass simulation model as well as true replica simulation model. More than 50 seismic tests were performed
considering the design earthquake Nahanni NWT, H1, with a time scaling factor of 31/2, and acceleration scaling factor 1, according to the model design rules. The intensity of the applied input earthquake excitation
was from 0.05 to 1.2 g. The design peak acceleration of Nahanni earthquake was 0.2 g. The cracks development was stated at
0.7 g input acceleration. These were concentrated around the openings. No collapse happened even under the strongest earthquake
input. The numerical part of this paper deals with formulation/application of the critical plane approach to seismic analysis
of masonry structures. Starting with the constituents, i.e. mortar and bricks, the macroscopic strength properties of masonry
were established based on numerical homogenization. Generally, based on all the performed experimental tests, considering
some simplifications and assumptions in the constructing details, as well as in the design of the model, the global conclusion
is that the existing wall is very well incorporated in the steel structure of the powerhouse. The complementary stiffness
of the steel frame and the brick masonry wall produces interactive deformation of the system. Only local cracking and relative
displacement between the wall and the steel frames could be expected in the case of a strong earthquake. 相似文献
646.
Joachim Miksat Kuo-Liang Wen Vladimir Sokolov Chun-Te Chen Friedemann Wenzel 《Bulletin of Earthquake Engineering》2010,8(4):847-858
Taipei, the capital of Taiwan, suffered from destructive earthquakes four times during the 20th century (M
L = 7.3 on April 15, 1909; M
L = 6.8 on November 15, 1986; the Chi–Chi M
L = 7.3 earthquake on September 21, 1999; and M
L = 6.8 on March 31, 2002). Analysis of recorded data shows a strong dependence of spectral amplification in the Taipei Basin
on earthquake depth and azimuth. At low frequencies (f < 3 Hz) significant larger amplifications are observed for shallow earthquakes as compared to intermediate depth events.
The former ones also display strong azimuthal dependence. As structures with large response periods such as bridges and tall
buildings are sensitive to these low frequencies the understanding of the associated wave effects within the basin and their
role for site effect amplification is critical. The tool we employ is 3D finite-difference modeling of wave propagation of
incident wave fronts. The available detailed model of the basin allows studying the wave effects. Modeling clearly reveals
that basin edge effects as observed in data are related to surface wave generation at the basin edges with a high degree of
azimuthal dependency. The reproduced site amplification effects are in qualitative agreement with the observations from strong
motion data. 相似文献
647.
Determination of impedances is necessary in order to eliminate some shortcoming of our knowledge about structures of the exciting
source fields and their fickleness. The experimental impedances for induction soundings result from the impedance boundary
conditions or heuristic models. The simplified models give just a rough idea of their domain of applicability. Impedances
can depend on many factors, including the exciting field structures of several source types which are present in the period
range of the mantle soundings (104−4×108 s). The problem in the mantle investigations arises if impedances measured by different methods have to be jointly inverted
in order to essentially prolongate the analyzed period range and hence to increase the reliability and depth of induction
soundings on land. The subject of our work is an analysis of the known magnetotelluric and magnetovariation impedances to
suggest a physically substantiated approach for their joint inversions. 相似文献
648.
Mauricio Parra Andrés Mora Carlos Jaramillo Vladimir Torres Gerold Zeilinger Manfred R. Strecker 《Basin Research》2010,22(6):874-903
In order to evaluate the relationship between thrust loading and sedimentary facies evolution, we analyse the progradation of fluvial coarse‐grained deposits in the retroarc foreland basin system of the northern Andes of Colombia. We compare the observed sedimentary facies distribution with the calculated one‐dimensional (1D) Eocene to Quaternary sediment‐accumulation rates in the Medina wedge‐top basin and with a three‐dimensional (3D) sedimentary budget based on the interpretation of ~1800 km of industry‐style seismic reflection profiles and borehole data. Age constraints are derived from a new chronostratigraphic framework based on extensive fossil palynological assemblages. The sedimentological data from the Medina Basin reveal rapid accumulation of fluvial and lacustrine sediments at rates of up to ~500 m my?1 during the Miocene. Provenance data based on gravel petrography and paleocurrents reveal that these Miocene fluvial systems were sourced from Upper Cretaceous and Paleocene sedimentary units exposed to the west in the Eastern Cordillera. Peak sediment‐accumulation rates in the upper Carbonera Formation and the Guayabo Group occur during episodes of coarse‐grained facies progradation in the early and late Miocene proximal foredeep. We interpret this positive correlation between sediment accumulation and gravel deposition as the direct consequence of thrust activity along the Servitá–Lengupá faults. This contrasts with one class of models relating gravel progradation in more distal portions of foreland basin systems to episodes of tectonic quiescence. 相似文献
649.
Species of freshwater bryozoans are newly recognized in the fauna of aquatic invertebrates in Serbia. This first record includes a total of five species of class Phylactolaemata found at eight localities during limnological investigations in the period from 2002 to 2006. Four species are assigned to family Plumatellidae (Plumatella casmiana, P. emarginata, P. geimermassardi and Hyalinella punctata). Family Cristatellidae is represented by one species (Cristatella mucedo). The freshwater bryozoans in the form of intact colonies and especially as dormant bodies were identified to the species level. The identification was done using scanning electron microscopy, analyzing resting bodies’ morphological ultrastructure. 相似文献
650.
V. A. Petrov M. Lespinasse V. V. Poluektov S. A. Ustinov V. A. Minaev 《Doklady Earth Sciences》2017,472(2):130-133
The interrelation between geometric parameters (density and length) of the fault systems of four scale levels (kilometers, meters, centimeters, and millimeters) was established for the first time by detailed structural study of the rocks of the Urtui granite massif located in the western framework of the Strel’tsovskii uranium caldera in the Southeastern Transbaikalia. The further use of these geostructural data for conceptual and numerical modeling of the fluid filtration processes and transport of radionuclides in a three-dimensional crack and pore space in the variably deformed and metasomatically altered crystalline rocks was substantiated. 相似文献