Dependence of earthquake recurrence times and independence of magnitudes on seismicity history     

lvaro Corral 《Tectonophysics》2006,424(3-4):177

The fulfillment of a scaling law for earthquake recurrence–time distributions is a clear indication of the importance of correlations in the structure of seismicity. In order to characterize these correlations we measure conditional recurrence–time and magnitude distributions for worldwide seismicity as well as for Southern California during stationary periods. Disregarding the spatial structure, we conclude that the relevant correlations in seismicity are those of the recurrence time with previous recurrence times and magnitudes; in the latter case, the conditional distribution verifies a scaling relation depending on the difference between the magnitudes of the two events defining the recurrence time. In contrast, with our present resolution, magnitude seems to be independent on the history contained in the seismic catalogs (except perhaps for Southern California for very short time scales, less than about 30 min for the magnitude ranges analyzed).  相似文献   

A record of pre-Variscan Barrovian regional metamorphism in the eastern part of the Slavonian Mountains (NE Croatia)     

D. Balen  P. Horváth  B. Tomljenović  F. Finger  B. Humer  J. Pamic  P. Árkai 《Mineralogy and Petrology》2006,87(1-2):143-162

Summary Petrological investigations and monazite dating are carried out on medium-grade metamorphic rocks (micaschist, gneiss and amphibolite) from the Kutjevačka Rijeka transect in the Slavonian Mts., Tisia Unit (NE Croatia). Field, mesoscopic and microstructural observations, as well as the preserved mineral chemistry, point to a single metamorphic event during peak assemblage growth reaching amphibolite facies conditions of ca. 600–650 °C and 8–11 kbar. Th, U and Pb contents of yttrium-rich accessory monazites indicate a pre-Variscan, i.e. Ordovician-Silurian age (444 ± 19 and 428 ± 25 Ma) for the medium-grade metamorphism of garnet-bearing micaschist.  相似文献   

Functional and Physical Parameters of HII Galaxies     

Ángeles I. Díaz 《Astrophysics and Space Science》1998,263(1-4):143-146

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Petrology of a new basalt occurrence in Hungary     

Dr. A. Embey-Isztin  G. Dobosi  Dr. G. Noske-Fazekas  E. Árva-Sós 《Mineralogy and Petrology》1989,40(3):183-196

Summary A new occurrence of basalt (minimum K/Ar age 57.9 ± 2.2 m.y.) is reported from Budaliget, near Budapest. Major and minor element concentrations show that the basalts are alkaline and potassic in nature ranging from olivine tholeiite to moderately undersaturated basanite. High mg-values and concentrations of Ni and Cr indicate that some of the samples may represent primary compositions. High pressure accidental xenoliths, xenocrysts and cognate megacrysts are frequent and the chemical zoning patterns of olivine and pyroxene phenocrysts indicate a complex evolution and polibaric conditions for the crystallization. The discovery of the new basalt occurrence is important from a geodynamical point of view: prior to the last two major geodynamical events (Plio-Pleistocene rifting with associated alkali basaltic volcanism and collision of microplates with associated Miocene calk-alkaline volcanism) the continental lithosphere below NE Transdanubia may have experienced another rifting period in the Paleocene or Upper Cretaceous.With 7 Figures  相似文献   

FRACTURES AS CONDUCTING DYKES AND CORRESPONDING TWO-DIMENSIONAL MODELS*     

A. ÁDÁM 《Geophysical Prospecting》1984,32(4):543-553

A statistical treatment of MT data from the Pannonian Basin, Hungary, based on the distortion theory of the S-effect suggests that the local increase in crustal conductivity is connected with deep fractures. Field model measurements have recently been carried out in a shallow, quasi two-dimensional basin of well known tectonics using MT station distances of 1–3 km. The results of the investigation and numerical modelling of near surface distortions, support the idea that deep fractures (faults) contain the conducting formations. According to 2-D model computations, several conducting dykes at considerable depths can cause anomalies which are indiscernible from an anomaly due to a conducting layer. The significance of these results is discussed from the point of view of geothermal energy exploitation.  相似文献   

Remarks on the one-photon-pair annihilation in strong magnetic fields     

Jorge PÁez  L. Semionova  J. Bonatti 《Astrophysics and Space Science》1994,214(1-2):89-92

We report specifically on a quantum electrodynamic feature of the one-photon-pair annihilation. Most of the calculation related with this process (not excluding other ones) have been carried out usually utilizing the wave functions obtained from the Dirac equation in the Landau gauge A = (0,Bx, 0), where B is oriented along the z-axis (Johnson and Lippman, 1949). Although, the eigenstates of the Dirac Hamiltonian as it was introduced by Johnson and Lippman, do not consider the coupling to the radiation field and consequently they reflect only forp _z = 0 the same linear combination of the two degenerate polarization states.We report the transition rate function for the one-photon-pair annihilation in a strong magnetic field by using the Sokolov and Ternov eigenstate |± as far asp _z = 0 andN > 0 is concerned. The difference between the expression for the transition rate by using the Sokolov and Ternov eigenstates and the one calculated by (Wunneret al., 1986), is just the functionI _s,s which corresponds to the degeneracy of the orbit center of the electrons characterized by the quantum numberss ands. Presented at the 2nd UN/ESA Workshop, held in Bogotá, Colombia, 9-13 November, 1992.  相似文献   

Alpine metamorphism of organic matter in metasedimentary rocks from Mt. Medvednica (Croatia)     

Katalin Judik  Gerd Rantitsch  Thomas M. Rainer  Péter Árkai  Bruno Tomljenović 《Swiss Journal of Geoscience》2008,101(3):605-616

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Variations in the dynamic response of structures founded on piles induced by obliquely incident SV waves     

Cristina Medina  Guillermo M. Álamo  Juan J. Aznárez  Luis A. Padrón  Orlando Maeso 《地震工程与结构动力学》2019,48(7):772-791

Although the seismic actions generally consist of a combination of waves, which propagates with an angle of incidence not necessarily vertical, the common practice when analyzing the dynamic behavior of pile groups is based on the assumption of vertically incident wave fields. The aim of this paper is to analyze how the angle of incidence of SV waves affects the dynamic response of pile foundations and piled structures. A three-dimensional boundary element-finite element coupling formulation is used to compute impedances and kinematic interaction factors corresponding to several configurations of vertical pile groups embedded in an isotropic homogeneous linear viscoelastic half-space. These results, which are provided in ready-to-use dimensionless graphs, are used to determine the effective dynamic properties of an equivalent single-degree-of-freedom oscillator that reproduces, within the range where the peak response occurs, the response of slender and nonslender superstructures through a procedure based on a substructuring model. Results are expressed in terms of effective flexible-base period and damping as well as maximum shear force at the base of the structure. The relevance and main trends observed in the influence of the wavefront angle of incidence on the dynamic behavior of the superstructure are inferred from the presented results. It is found that effective damping is significantly affected by the variations of the wave angle of incidence. Furthermore, it comes out that the vertical incidence is not always the worst-case scenario.  相似文献   

Structure of earthquake occurrence in space,time and magnitude     

lvaro Corral 《地学学报》2007,19(5):337-343

Distributions of time between consecutive earthquakes verify an approximately universal scaling law for stationary seismicity. The shape of these distributions is shown to arise as a mixture of one distribution for short‐distance events and an exponential distribution for far‐off events, the distinction from short and long distances being relative to the size of the region studied. The distributions of consecutive distances show a double power law decay and verify an approximate scaling law which guarantees the simultaneous fulfillment of the scaling laws for time. The interplay between space and time can be seen as well by looking at the distribution of distances for a fixed time separation. These results suggest that seismicity can be understood as a series of intertwined independent continuous‐time random walks, with power law‐distributed waiting times and Lévy‐flight jumps. However, a simple model based on these ideas does not capture the invariance of seismicity under renormalization.  相似文献   

Anomalous Emissions of SO2 During the Recent Eruption of Santa Ana Volcano, El Salvador, Central America   总被引：1，自引：0，他引：1  

Rodolfo Olmos  José Barrancos  Claudia Rivera  Francisco Barahona  Dina L. López  Benancio Henriquez  Agustín Hernández  Efrain Benitez  Pedro A. Hernández  Nemesio M. Pérez  Bo Galle 《Pure and Applied Geophysics》2007,164(12):2489-2506

Santa Ana volcano in western El Salvador, Central America, had a phreatic eruption at 8:05 am (local time) on October 1, 2005, 101 years after its last eruption. However, during the last one hundred years this volcano has presented periods of quiet degassing with fumarolic activity and an acidic lake within its crater. This paper presents results of frequent measurements of SO₂ degassing using the MiniDOAS (Differential Optical Absorption Spectroscopy) system and a comparison with the volcanic seismicity prior to the eruption, during, and after the eruption. Vehicle measurements of SO₂ flux were taken every hour during the first nine days of the eruption and daily after that. The period of time reported here is from August to December, 2005. Three periods of degassing are distinguished: pre-eruptive, eruptive, and post-eruptive periods. The intense activity at Santa Ana volcano started in July 2005. During the pre-eruptive period up to 4306 and 5154 ton/day of SO₂ flux were recorded on October 24 and September 9, 2005, respectively. These values were of the same order of magnitude as the recorded values just after the October 1^st eruption (2925 ton/day at 10:01 am). Hourly measurements of SO₂ flux taken during the first nine days after the main eruptive event indicate that explosions are preceded by an increase in SO₂ flux and that this parameter reaches a peak after the explosion took place. This behavior suggests that increasing accumulation of exsolved magmatic gases occurs within the magmatic chamber before the explosions, increasing the pressure until the point of explosion. A correlation between SO₂ fluxes and RSAM (Real Time Seismic Amplitude Measurements) is observed during the complete sampling period. Periodic fluctuations in the SO₂ and RSAM values during the entire study period are observed. One possible mechanism explaining these fluctuations it that convective circulation within the magmatic chamber can bring fresh magma periodically to shallow levels, allowing increasing degasification and then decreasing degasification as the batch of magma lowers its gas content, becomes denser, and sinks to give space to a new magma pulse. These results illustrate that the measurements of SO₂ flux can provide important warning signals for incoming explosive activity in active volcanoes.  相似文献