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1.
Information concerning a total number of 13700 instrumentally recorded earthquakes is used to study the geographical and the vertical distribution of the Earth's seismicity. From these earthquakes, which form four complete samples of data (M 7.0, 1894–1992; M 6.5, 1930–1992; M 6.0, 1953–1992; M 5.5, 1966–1992), 11511 are shallow (h 60 km), 2085 are of intermediate focal depth (61 h 300 km) and 564 are deep focus earthquakes (301 h 720 km). The parameters a and b of the frequency-magnitude relationship were calculated in a grid of equally spaced points at 1° by using the data of earthquakes located inside circles centered at each point. The radius of the circles increased from 30 km with a step of 10 km until the information for the earthquakes located inside the circle fulfil three criteria which concern the size of the sample used to compute these parameters at each point of the grid. The results are given in a qualitative way (epicenter maps) as well as in a quantitative way (mean return periods).  相似文献   

2.
The regional variation of the seismic velocity-ratio () over a 200 km long traverse has been studied by means of microearthquake surveys. The Wadati-plot method is used with a minimum of four P and S arrivals for each of 49 earthquakes. The area as a whole is found to be characterized by a value of 1.74–1.76 for earthquakes of depth 12–40 km, except in a 50 km long section near Wellington, where is low at 1.60. This low has been attributed to the fault zones in the region. A small change of is observed between the upper crust (5 km) and lower crust (12 km), but there is no change of between the lower crust and uppermost mantle.  相似文献   

3.
The amplitude response of a LCR gravimeter with the SRW-E feedback was determined on a vertical vibrating platform. The ink-pen recorder was connected parallel with the digital voltmeter input to obtain an analog response of the gravimeter to the harmonic motion of the base with a peak-to-peak amplitude of 10 m and periods excited in an interval of 4 - 10 s as by the ground motion of meteorological microseisms, and in the interval 10 -100 s as by surface waves of distant strong earthquakes. In the first interval, an unexpected maximum of the amplitude response was observed with the double amplitude of apparent 6,5 Gal (6.5 × 10 –8 m/s 2 ) at a period of 4.8 s, and a baseline shift with the amplitude of–64Gal was observed at the same period. The value of this direct component cannot be separated from the effect of the Earth's gravity field. In the second interval, the amplitude response of the gravimeter displayed one expected maximum at a period of 40 s with the double amplitude of 8.1Gal. At the usual level of microseisms with a peak-to-peak amplitude of up to 2 m the fluctuation of the gravimeter on the direct baseline shifted by –4.9 Gal was estimated at 1 Gal. With typical Rayleigh surface waves with periods of 20 s and double amplitudes of up to 100 m, the fluctuation reached 67 Gal.  相似文献   

4.
We review earthquake distributions associated with hydrocarbon fields in the context of pore pressure diffusion models, poroelastic stress transfer and isostasy theory. These three mechanisms trigger or induce seismic instabilities at both local scale (D5 km) and at regional scale (D20 km). The modeled changes in stress are small (1 MPa), whatever the tectonic setting. Each mechanism corresponds to different production processes. (1) Local hydraulic fracturing due to fluid injection induces seismic-slip on cracks (M L3) within the injected reservoir through decreasing the effective stress. (2) Pure fluid withdrawal causes pore pressure to decrease within the reservoir. It triggers adjustments of the geological structure to perturbations related to the reservoir response to depletion. Poroelastic mechanisms transfer this stress change from the reservoir to the surrounding levels whereM L5 seismic instabilities occur either above or below the reservoir. (3) Massive hydrocarbon recovery induces crustal readjustments due to the removal of load from the upper crust. It can induce larger earthquakes (M L6) at greater distance from the hydrocarbon fields than the two other mechanisms.Due to the mechanical properties of the shallow rock matrices involved, seismic slip triggered either by mechanism (1) or (2), is a second-order process of the main elastoplastic deformation. for a minimum of 80% of commercially productive basins, most of the local deformation is reported as aseismic, i.e., there is no evidence forM L3 earthquakes. Nevertheless, the induced stresses vary as a function of time in a manner that depends on the hydraulic diffusivity (i.e., permeability) of the reservoir and surrounding rocks. Because small earthquakes (M L3) indicate changes in stress and pore pressure, monitoring of seismicity is a means of assessingin situ reservoir behavior.The less constrained seismic response to hydrocarbon recovery is the possible connection between local fluid manipulations, triggered earthquakes and major regional earthquakes. Positive feedback mechanisms suggest that the region of seismic hazard changes is much larger than the area where hydrocarbons are extracted. These observations and models testify that fluid movement and pore pressure changes (increase or decrease) play important roles in the mechanics of earthquakes and in the triggering of natural earthquakes.  相似文献   

5.
nua u mam n ma aa ¶rt;mn ¶rt;u aa, ma a n¶rt;a [1]. mma m ¶rt;u aa a ¶rt;auu nauMi (uuuu n) uMa (¶rt;uauu anm), m amm u nu [2–5]. u¶rt;m mam u nu ¶rt;u ¶rt; u¶rt; mu ¶rt; u a ¶rt; ¶rt;a. mu a aa, n¶rt;ua m a aa, nua a¶rt; u u i uu a a¶rt; zi nu nu aa ¶rt; ¶rt;a, m ¶rt;um mua m, a¶rt;u ¶rt; a, ¶rt;m, mnam, anu ¶rt; naa, nm a an u nu. a ¶rt;mn ¶rt;u m n a nu u ¶rt;mn ¶rt;u, ma a ma n¶rt;a [1].  相似文献   

6.
Reservoir induced earthquakes began to occur in the vicinity of Shivajisagar Lake formed by Koyna Dam in Maharashtra state, western India, soon after its filling started in 1962. Induced earthquakes have continued to occur for the past 34 years in the vicinity of this reservoir, and so far a total of 10 earthquakes of M 5.0, over 100 of M 4 and about 100,000 of M 0.0 have occurred. Every year, following the rainy season, the water level in the reservoir rises and induced earthquakes occur. Seismic activity during 1967–68 was most intense when globally, the largest reservoir induced earthquake occurred on 10 December, 1967. Other years of intense seismic activity are 1973 and 1980. During 1986 another reservoir, Warna, some 20 km south of Koyna, began to be filled. The recent burst of seismic activity in Koyna-Warna region began in August, 1993, and was monitored with a close network of digital and analog seismographs. During August, 1993–December, 1995, 1,272 shocks of magnitude 2 were located, including two earthquakes of M 5.0 and M 5.4 on 8 December, 1993 and 1 February, 1994, respectively. Two parallel epicentral trends in NNE-SSW direction, one passing through Koyna and the other through Warna reservoir are delineated. The 1993 increase in seismicity has followed a loading of 44.15 m in Warna reservoir during 11 June 11, 1993 through August 4, 1993, with a maximum rate of filling being 16 m/week. The larger shocks have been found to be preceded by a precursory nucleation process.  相似文献   

7.
an¶rt;u am mu 15- an 1979. a auu a mumuu auu.  相似文献   

8.
Summary We search for the effects of the interplanetary magnetic field (IMF) sector boundary crossing (SBC) in upper stratospheric ozone. The SBUV data (Nimbus-7) at the 10, 3 and 1 hPa levels are analysed for latitudes 45° N and 55° N for winters of the period December 1979 to December 1982. An effect of the IMF SBC wos only found at the 10 hPa level. These first results concerning the IMF SBC effect in upper stratospheric ozone are rather preliminary.
¶rt;m uu nu mau () nam aum n () a mam. SBUV ¶rt;a (u-7) a nm ¶rt;au 10, 3 u 1a aauum ¶rt; um 45° u 55° . . ua nu¶rt;a ¶rt;a 1979 – ¶rt;a 1982. m uu a¶rt; m a 10a. mu n mam n uuu a mam m n¶rt;aumu.
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9.
Linear stacking procedures are used to retrieve the attenuation of 91 modes belonging to the 3rd, 4th and 5th Rayleigh overtones branches in the 80–160 s period range, and contributing to the so-called PhaseX wave group. Our data show in general slightly less attenuation than expected from available models. Data space inversion shows that, when combined with previously measured fundamental modeQ's, this new dataset improves resolution significantly in the 1000–2000 km depth range. Based on this remark, we carry out a number of parameter space inversions. Our results suggest a narrow (80–200 km) zone of high attenuation (Q =75–90), low attenuation in the intermediate mantle (670–1500 km); (Q 350), and lower values in the deeper mantle (Q 200).  相似文献   

10.
Summary A non-linear model of trochoidal waves is presented which represents a geometrical and kinematical generalization of Gerstner's waves and of the results of[2–4].
¶rt;aam ¶rt; mu¶rt;a , ma m u ma u am[2–4] mu umuu u uamu mm ¶rt;u.
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11.
Summary Based on the analysis of the occurrence ofSEC disturbances in the polar cap ionosphere under varying solar wind parameters, the relation between the generation ofSEC-type ionospheric disturbances and interplanetary and magnetospheric conditions is discussed. It is emphasized that the Farley-Buneman instability in the E-layer of the ionosphere, reflected in ionograms as anSEC disturbance, depends on the complex effect of the solar wind parameters, the orientation of the interplanetary magnetic field playing an important role.
a aaua nu u munaSEC n an u nu uu naama ma mam ¶rt; uu mu u, ¶rt; m, u namu u aumu uu, ¶rt;. ¶rt;uam, m maum au-aa, uaa u, u na a uaa a u munaSEC, auum m n uu naam ma, nu numau nam aum n uam aum .
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12.
¶rt;m uu n ¶rt;au m uu nu mau nam aum n. mu uu auam mmmuu uuu ¶rt;u u naam. a¶rt;am auu ¶rt; uuu n ¶rt;au m u u. a auu a¶rt;am nuu amm 245 . ¶rt;aam umnmau m a¶rt;a uu.  相似文献   

13.
Summary In the experiment described, we test the possibility of utilizing forecasts of the pressure field, contained in GRID reports, to solve the problem of horizontal boundary conditions of a local model of short-range forecast of meteorological elements. We prove that the assumption of a linear tendency of the prognostic variables in the boundary region yields good results, using the Perkey-Kreitzberg method[1], even if applied to period T=24 hrs. In the Perkey-Kreitzberg method the effect of the horizontal diffusion in the boundary region is suppressed[2]. However, considering the diffusive term apart from the procedure of the method mentioned proves detrimental to the forecast.
nua num n m unau n n ¶rt;au, ¶rt;au ¶rt; ¶rt; u numaau u a ¶rt;u am na muu m. aam, m n¶rt;nu u m¶rt;uu nmuu n au amu nu unauu m¶rt;a u- [1] ¶rt;am u mam ¶rt;a nu nuuu nu¶rt; T=24 a. m¶rt; u- nu¶rt;um n¶rt;au uuuma ¶rt;uuu au amu[2]. ama ¶rt;u a n¶rt; nu¶rt; m¶rt;a nu¶rt;um, ¶rt;a, ¶rt;u n.
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14.
We consider a general stochastic branching process,which is relevant to earthquakes as well as to many other systems, and we study the distributions of the total number of offsprings (direct and indirect aftershocks in seismicity) and of the total number of generations before extinction. We apply our results to a branching model of triggered seismicity, the ETAS (epidemic-type aftershock sequence) model. The ETAS model assumes that each earthquake can trigger other earthquakes (aftershocks). An aftershock sequence results in this model from the cascade of aftershocks of each past earthquake. Due to the large fluctuations of the number of aftershocks triggered directly by any earthquake (fertility), there is a large variability of the total number of aftershocks from one sequence to another, for the same mainshock magnitude. We study the regime in which the distribution of fertilities is characterized by a power law ~1/1+. For earthquakes we expect such a power-distribution of fertilities with =b/ based on the Gutenberg-Richter magnitude distribution ~ 10–bm and on the increase ~ 10–m of the number of aftershocks with the mainshock magnitude m. We derive the asymptotic distributions pr(r) and pg(g) of the total number r of offsprings and of the total number g of generations until extinction following a mainshock. In the regime < 2 for which the distribution of fertilities has an infinite variance, we find This should be compared with the distributions obtained for standard branching processes with finite variance. These predictions are checked by numerical simulations. Our results apply directly to the ETAS model whose preferred values =0.8–1 and b=1 puts it in the regime where the distribution of fertilities has an infinite variance. More generally, our results apply to any stochastic branching process with a power-law distribution of offsprings per mother  相似文献   

15.
Summary The distribution of radioactive(Th, U, K) and selected trace(Rb, Sr, Ba, Y, Zr, V, Cr, Ni) elements in volcanic rocks from the Opole and Jawor regions of the Lower Silesia has been studied. The behaviour of these elements in the studied rocks indicates that the Lower Silesian volcanic rocks are characterized by less differentiated type than other volcanic rocks of the Bohemian Massif, the Opole rock types probably having a less differentiated character than the Jawor rock types.
¶rt;a an¶rt;u a¶rt;uamu(Th, U, K) u m ¶rt;u(Rb, Sr, Ba, Y, Zr, V, Cr, Ni) m auu n¶rt;a am n u u uuu. a n mam n¶rt;num, m aum u uuu n¶rt;mam ¶rt; aamuu n¶rt; u ¶rt;uuau, aum u ana¶rt; uu. au a n¶rt;num, m auu n¶rt; amu n ¶rt;uuau ma ua n¶rt; u amu .
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16.
Summary It has been shown that dynamically, on the basis of the distribution of angular momenta, the Jovian system cannot be considered an analogue within the Solar system. The total tidal decrease in the angular momentum of Jupiter and in its angular velocity of rotation have been estimated, as well as the loss of mechanical energy due to tidal dissipation. It has been concluded that there are no dynamical contradictions with the hypothesis of the common cosmogonic origin of Jupiter and of its eight close satellites.
aam, m ¶rt;uauu, n an¶rt;u m uma ¶rt;uu, um numa umam aayu um. a a y au ma uma ¶rt;uu numa u z mu z au u—a nuuz mu, ma a nmu au yuu um u—a ¶rt;uunauu. a au, m m ¶rt;uauu azau zunm m zuu aaa numa u z uau u nmu.
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17.
We analyzed the broadband body waves of the 1992 Nicaragua earthquake to determine the nature of rupture. The rupture propagation was represented by the distribution of point sources with moment-rate functions at 9 grid points with uniform spacing of 20 km along the fault strike. The moment-rate functions were then parameterized, and the parameters were determined with the least squares method with some constraints. The centroid times of the individual moment-rate functions indicate slow and smooth rupture propagation at a velocity of 1.5 km/s toward NW and 1.0 km/s toward SE. Including a small initial break which precedes the main rupture by about 10 s, we obtained a total source duration of 110 s. The total seismic moment isM o =3.4×1020 Nm, which is consistent with the value determined from long-period surface waves,M o =3.7×1020 Nm. The average rise time of dislocation is determined to be 10 s. The major moment release occurred along a fault length of 160 km. With the assumption of a fault widthW=50 km, we obtained the dislocationD=1.3 m. From andD the dislocation velocity isD=D/0.1 m/s, significantly smaller than the typical value for ordinary earthquakes. The stress drop =1.1 MPa is also less than the typical value for subduction zone earthquakes by a factor of 2–3. On the other hand, the apparent stress defined by 2E s /M o , where andE s are respectively the rigidity and the seismic wave energy, is 0.037 MPa, more than an order of magnitude smaller than . The Nicaragua tsunami earthquake is characterized by the following three properties: 1) slow rupture propagation; 2) smooth rupture; 3) slow dislocation motion.  相似文献   

18.
Summary Upgoing and downgoing deuteron whistlers were found on VLF records made by Interkosmos 5, 14 and 19 satellites even at heights below 1000 km. To account for them, a slight admixture ofD + ions has been introduced into the ionospheric plasma model with the usual content of only three ion speciesH +,He + andO +. Relations derived for the calculation of characteristic frequencies in a five-component plasma (e,H +,D +,He +,O +) are given as well as the values of characteristic frequencies calculated on this basis. The observed features of upgoing and downgoing deuteron whistlers could be explained by the calculation results, and it is also possible to formulate some conclusions for the purposes of plasma diagnostics.
mu um, anmau a ma u u, u a a nmua m 5, 14 u 19 a ma ¶rt;a 1000 . u u a ¶rt;a ¶rt; u na ¶rt;au uH +,He +,O + aa nuD + u. m mm ua nma ¶rt;a ¶rt; aamumuu amm ¶rt;a ¶rt;u na. uu aamumuu amm nuu um a¶rt;a mu ¶rt;mu um. a m ¶rt; unam aamumuu ¶rt;mu um ¶rt; u¶rt;au naam na.
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19.
Summary According to Newton's law of viscosity y = Dvy/dy. But experiments have shown that y is indeed proportional to –dv x/dy for all gases and for homogeneous nonpolymeric liquids. There are however, a few industrially important materials, e.g. plastics, asphalts, crystalline materials that are not described by the equation given by Newton's law of viscosity and they are referred to as non-Newtonian fluids. The steady state rheological behaviour of most fluids can be expressed by the generalised form, y = –(dvy/dy) where may be expressed as a function of eitherdv x/dy or y (where is independent of the rate of shear, the behaviour is Newtonian with =). Numerous empirical equations or models have been proposed to express the steady-state relation between y anddv x/dy. The flow of Newtonian fluids through circular tubes have been discussed before by many. Here we shall discuss the case of two such models of non-Newtonian fluids through circular tubes. The flow of fluids in circular tubes is encountered frequently in Physics, Chemistry, Biology and Engineering.  相似文献   

20.
Zusammenfassung Die atmosphärische Aerosolstreuung wird im Bereich 0.52.1 m und 4°40° experimentell untersucht. Sie scheint im Infraroten weitgehend durch die Verhältnisse im Sichtbaren charakterisierbar zu sein, wenn auch die Streudispersion ein unerwartet gegensätzliches Verhalten zeigt. BeiA-ähnlichen, visuellen Streutypen (oder Typen nahe 1) verschwindet diese ab etwa 1.1 m fast vollständig. DieB-ähnlichen, visuellen Streutypen (oder Typen nahe 2) tritt in einem Zwischenbereich (etwa 0.8 bis 1.3 m) starke Streudispersion auf. Für den Gesamtstreutyp wird eine Klassifizierung in Anlehnung an die im Sichtbaren gebräuchliche [11–14]2) vorgeschlagen.
Summary The scattering by the atmospheric aerosol of radiation in the region 0.52.1 m and 4°40° is investigated experimentally. The features in the infrared can be characterized by that in the visible, but the scattering dispersion is found to be different to that expected. At scattering types nearA (or 1) in the visible there is almost no scattering dispersion for 1.1 m. At types nearB (or 2) in the visible a high scattering dispersion in the region between 0.8 m and 1.3 m was observed. For the whole region of wavelength including the infrared a classification similar to that used in the visible [11–14]2) is suggested.

Mitteilungen des Astronomischen Instituts der Universität Tübingen Nr. 77  相似文献   

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