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1.
Soil samples are collected from 74 sites in Shenyang city, northeast China, and the concentrations, spatial distribution, enrichment factors (EF), and potential ecological and human health risk (Er) of potentially toxic metals (Sr, Zn, Cr, Pb, Cu, Ni, and As) are investigated. The mean concentrations of potentially toxic metals in topsoil follow the order Sr > Zn > Cr > Pb > Cu > Ni > As. Compared with 2011, the contamination magnitude has improved in 2017, but the pollution status still exists, especially for As and Cr. EF and the mean Er of potentially toxic metals decrease following the order As > Pb > Cu > Ni > Zn > Cr > Sr and As > Cu > Zn > Pb > Sr > Ni > Cr, suggesting that the potentially toxic metals in the topsoil of Shenyang city mainly come from natural sources, and the potential ecological risk for potentially toxic metals is low. There are potentially non‐carcinogenic and carcinogenic health risks, but they are not considered significant. For non‐carcinogenic health risks, oral ingestion is the main exposure pathway, and Cr and Pb are the major pollutants. Finally, As is found to be the main carcinogenic contamination metal.  相似文献   

2.
In this study, closed form equations as functions of the isolator, bridge and ground motion properties are formulated to calculate the optimum characteristic strength, Qd and post-elastic stiffness, kd, of the isolator to minimize the maximum isolator displacement (MID) and force (MIF) for seismic isolated bridges (SIBs). For this purpose, first, sensitivity analyses are conducted to identify the bridge, isolator and ground motion parameters that affect the optimum values of Qd and kd. Next, for the identified parameters, nonlinear time history analyses of typical SIBs are conducted to determine the optimum values of Qd and kd for a wide range of values of the parameters. Next, nonlinear regression analyses of the available data are conducted to obtain closed form equations for the optimum values of Qd and kd, to minimize the MID and MIF. The equations are then simplified for various site soil conditions. It is observed that the optimum Qd and kd are highly dependent on the site soil condition. Furthermore, the optimum Qd is found to be a linear function of the peak ground acceleration.  相似文献   

3.
Tsunamis are most destructive at near to regional distances, arriving within 20–30 min after a causative earthquake; effective early warning at these distances requires notification within 15 min or less. The size and impact of a tsunami also depend on sea floor displacement, which is related to the length, L, width, W, mean slip, D, and depth, z, of the earthquake rupture. Currently, the primary seismic discriminant for tsunami potential is the centroid-moment tensor magnitude, M w CMT , representing the product LWD and estimated via an indirect inversion procedure. However, the obtained M w CMT and the implied LWD value vary with rupture depth, earth model, and other factors, and are only available 20–30 min or more after an earthquake. The use of more direct discriminants for tsunami potential could avoid these problems and aid in effective early warning, especially for near to regional distances. Previously, we presented a direct procedure for rapid assessment of earthquake tsunami potential using two, simple measurements on P-wave seismograms—the predominant period on velocity records, T d , and the likelihood, T 50 Ex , that the high-frequency, apparent rupture-duration, T 0, exceeds 50–55 s. We have shown that T d and T 0 are related to the critical rupture parameters L, W, D, and z, and that either of the period–duration products T d T 0 or T d T 50 Ex gives more information on tsunami impact and size than M w CMT , M wp, and other currently used discriminants. These results imply that tsunami potential is not directly related to the product LWD from the “seismic” faulting model, as is assumed with the use of the M w CMT discriminant. Instead, information on rupture length, L, and depth, z, as provided by T d T 0 or T d T 50 Ex , can constrain well the tsunami potential of an earthquake. We introduce here special treatment of the signal around the S arrival at close stations, a modified, real-time, M wpd(RT) magnitude, and other procedures to enable early estimation of event parameters and tsunami discriminants. We show that with real-time data currently available in most regions of tsunami hazard, event locations, m b and M wp magnitudes, and the direct, period–duration discriminant, T d T 50 Ex can be determined within 5 min after an earthquake occurs, and T 0, T d T 0, and M wpd(RT) within approximately 10 min. This processing is implemented and running continuously in real-time within the Early-est earthquake monitor at INGV-Rome (http://early-est.rm.ingv.it). We also show that the difference m b  ? log10(T d T 0) forms a rapid discriminant for slow, tsunami earthquakes. The rapid availability of these measurements can aid in faster and more reliable tsunami early warning for near to regional distances.  相似文献   

4.
Résumé Lors des révisions d'aménagements de ces dernières années, bien des forestiers suisses ont constaté que le capital-bois de leurs forêts ne s'était pas développé selon les prévisions. D'aucuns ont imputé cette déficience de dévoloppement à la sécheresse de ces dernières années. Pour contrôler ces allégations, l'auteur a examiné le développement de 5 peuplements situés dans des climats très différent: l'un se trouve dans l'est du Plateau, dans un climat tempéré et relativement sec, deux dans les Préalpes où la température est plus rude mais les précipitations abondantes et deux en Engadine dans un climat sec et froid.L'accroissement forestier a été donné par la mesure de la largeur des cernes annuelles. L'auteur n'a examiné qu'une essence: l'épicéa.Les éléments météorologiques furent tirés des tables originales de postes d'observations climatologiques que la Station centrale suisse de Météorologie entretient à proximité des peuplements considérés. Les extraits en ont été faits séparément pour la longueur de la période de végétation, la température moyenne, la somme des températures et la somme des précipitations. On a tiré ces valeurs pour le printemps, l'automne et l'année de végétation, celle-ci étant composée d'un printemps et de l'automne précédent. La période de végétation a été définie comme celle où la température journalière moyenne dépassait 5°C.De la comparaison des courbes d'accroissement avec celles des éléments météorologiques, l'auteur tire la conclusion que la forêt ne réagit aux fluctuations de la somme des précipitations que dans les régions sèches. Dans les Préalpes par contre c'est la température du printemps qui joue le rôle principal.Pour éviter des surprises lors des révisions d'aménagement, l'auteur propose d'adapter les exploitations aux variations du climat tout en maintenant le procédé actuel de détermination de la possibilité.Il rend le forestier attentif au fait que l'influence des précipitations diminue avec la latitude et l'altitude mais augmente en raison inverse de l'indice d'aridité. Il propose enfin une méthode graphique pour la détermination du facteur météorologique minimum.
Summary By controlling the managements of the forests, many swiss foresters noticed that the trees had not developed as forseen. Some foresters attributed this lack of development to the dryness of the least years. In order to control this allegations, the author has examined the development of five series of stocks situated in different climatic conditions: one resies in the East of the Swiss Plateau, in a temperate and relatively dry climate, two in the Prealps, where the temperature is rough and rain plentiful and two in the Engadin, in a dry and cold climate.The treegrowth as been measured through the width of annual rings. The author has examined just one species: Spruce.The meteorological elements have been taken from the original tables of climatological stations, which the Swiss Meteorological Office maintain in the neighbourhood of the examinated forests. The extracts have been made separately for the length of the vegetation period, for the mean temperature, for the sums of rainfalls and temperatures. These values have been extracted for spring, autumn and the vegatation year, this last one being composed of one spring and the preceding autumn. The vegetation period has been defined as a period where the daily mean temperature exceeds 5°C.From the comparison of the graphic curves of treegrowth with those of the meteorological elements, the author comes to the conclusion that the forest reacts to the fluctuations of the sum of rainfall only in dry regions. In the Prealps, it is the spring temperature which is most important.In order to avoid surprises by controlling the managements of forests, the author proposes to adapt the fellings to the climatic variations, but to maintain the present proceeding of determination of the possibility.He drais the attention of the forester to the fact that the influence of rainfall decreases with the latitude and the altitude, but increases in inverse ratio to the aridity. At last, he proposes a graphic method for the determination of the minimum meteorological factor.
Zusammenfassung Anlässlich von Wirtschaftsplanrevisionen sind in den letzten Jahren in schweizerischen Wälder bedeutende Zuwachsrückgänge festgestellt worden die von manchen Forstleuten auf die Trockenheit der 1940-er Jahre zurückgeführt werden. Um die Richtigkeit dieser Vermutung zu prüfen, hat der Verfasser die Entwicklung von fünf Beständen in Gegenden mit verschiedenem Klima untersucht. Der erste Bestand liegt im ostschweizerischen Mittelland d.h. in einer Gegend mit mildem, verhältnismässig trockenem Klima; zwei Bestände befinden sich im kühlen, niederschlagsreichen Voralpengebiet und zwei im trockenen, rauhen Engadin.Der Zuwachs wurde durch Messung der Jahrringbreiten an Fichten (Picea excelsa Link) bestimmt.Die meteorologischen Angaben sind den Originaltabellen benachbarter klimatologischer Beobachtungsposten der Meteorologischen Zentralanstalt entnommen, und zwar erstrecken sich die Auszüge auf die Dauer der Vegetationsperiode, die mittlere Temperatur, die Temperatursumme und die Niederschlagsmenge. Diese Angaben wurden jeweils für den Frühling, den Herbst und das Vegetationsjahr berechnet. Letzteres setzt sich aus einem Frühling und den vorausgegangenen Herbst zusammen. Die Vegetationsperiode wurde mit Hilfe der Temperatur definiert (Tagesmittel: 5°).Durch Vergleichuug der Zuwachskurven mit den Kurven der meteorologischen Elemente stellt der Verfasser fest, dass der Wald nur in den trockenen Regionen auf die Niederschlagsmenge reagiert. In den Voralpen spielt dagegen die Frühlingstemperatur die Hauptrolle.Um Ueberraschungen bei den Wirtschaftsplanrevisionen zu vermeiden, schlägt der Verfasser vor, die jetzt übliche Methode der Etatberechnug zu behalten, die Nutzung den Klimaschwankungen aber anzupassen.Er macht darauf aufmerksam, dass der Einfluss des Niederschlages mit zunehmender geographischen Breite und Höhe über Meer abnimmt, dagegen bei steigendem Trockenheitsindex zunimmt. Er schlägt schliesslich ein graphisches Verfahren zur Bestimmung des meteorologischen Minimumfaktors vor.
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5.
ＴｈｅｒｅｇｉｏｎａｌｃｈａｒａｃｔｅｒｉｓｔｉｃｓｏｆｓｅｉｓｍｉｃａｃｔｉｖｉｔｙｉｎＣｈｉｎａＺｈｅｎ－ＬｉａｎｇＳＨＩ，ＪｉａｎＷＡＮＧａｎｄＸｉａｏ－ＤｏｎｇＺＨＡＮＧ（时振梁，王健，张晓东）（ＩｎｓｔｉｔｕｔｅｏｆＧｅｏｐｈｙｓｉｃｓ，Ｓ...  相似文献   

6.
The paper presents an analysis of the crust and upper mantle structure in the central Fennoscandian shield based on new P- and S-wave 2D velocity models of the BALTIC wide-angle reflection and refraction profiles. Using reprocessing of the old data, new P- and S-wave velocity models and V P /V S ratio distribution were developed. Moving from SW to NE, the thickness of the crust varies strongly, from ∼36 km to extremely thick, 58–64 km, crossing Wiborg rapakivi massif, Saimaa and Outokumpu areas, and Eastern Finland complex. Based on the lateral variations of V P , V P /V S and thickness of the crust, three main blocks of the crust and upper mantle were distinguished from SW to NE: southwestern, associated with Wiborg rapakivi massif; the central, having the highest thickness of the crust; and the northeastern, not well documented, with Archaean basement.  相似文献   

7.
Résumé Dans le premier Chapitre, l'auteur détermine expérimentalement l'altitude à laquelle se manifeste l'interruption aubale de la propagation des ondes longues (27 kc/sec) émanant des sources orageuses troposphériques, en analysant les enregistrements du radiogoniographe à secteur étroit de l'Institut Suisse de Météorologie. Les différences de temps entre les interruptions des enregistrements des foyers et le lever astronomique du soleil à Zurich, pris comme temps de référence, sont groupées par direction azimutale entre 160° et 300° et portées en fonction de l'azimut du soleil à son lever à Zurich. A l'aide des Tables Crépusculaires deLugeon, l'auteur localise dans l'espace des pointsM tels que les différences respectives des temps entre les levers astronomiques du soleil à chacun des dits points et à Zurich donnent des courbes (par direction azimutale et en fonction de l'azimut du soleil à son lever à Zurich) semblables aux fonctions empiriques (mesures). Il en résulte que l'interruption de la propagation coïncide sensiblement avec le moment du lever du soleil à l'altitude de 75 km sur la trajectoire de l'onde, compte tenu du retard de l'ordre de 10 min dû à la zone d'influence de la couche d'ozone. L'altitude de cette zone d'influence est évaluée à 28 km. Les positions moyennes des foyers orageux ont été déduites de la distribution des nombres de jours d'orages dans les deux hémisphères. Pour terminer, l'auteur vérifie si ce modèle est conforme à la réalité, en faisant intervenir les distances angulaires des foyers.Le deuxième Chapitre traite du problème du «satellite» ou du «petit nez» qui apparaît souvent sur les enregistrements des compteurs d'impulsions (atmoradiographe) après le lever du soleil. La théorie proposée est fondée sur une conception géométrique simple de la propagation, compte tenu des résultats du premier Chapitre. Elle est ensuite appliquée à dix cas particuliers, dont les enregistrements ont été obtenus comme suit: Quelques heures avant le lever du soleil, les cadres récepteurs du radiogoniographe à secteur étroit sont bloqués dans une direction «privilégiée» et les impulsions reçues sont commutées sur l'atmoradiographe. Les enregistrements obtenus permettent d'illustrer de façon satisfaisante le processus de la propagation transitoire, les positions des foyers étant connues d'autre part. Parfois, deux ou trois «satellites» ou «nez» sont discernables; tous ont pu être justifiés. L auteur conclut que le «satellite» se forme au moment où la dernière réflexion se produit sur la coucheD, toutes les autres ayant encore lieu sur la base de la régionE dans la partie obscure. Le satellite se termine quand les rayons ionisants du soleil coupent la trajectoire de l'onde aux environs de 75 km, dans le voisinage de l'avant-dernier point de réflexion.Dans le troisième Chapitre, l'auteur améliore le modèle initial développé dans les deux premiers, en l'adaptant aux connaissances actuelles de l'ionosphère. La densité électronique devant être envisagée comme une fonction continue de l'altitude, l'auteur montre que si les réflexions diurne et nocturne obéissent aux lois de la réflexion métallique, on doit assister à un phénomène de réfraction sur la surface du lieu des levers des rayons ionisants du soleil dans la région séparant les couchesD etE, le modèle initial conservant malgré cette nouvelle conception toute sa raison d'être.
Summary In the first Chapter, the author determines experimentally the altitude at which occurs the early morning fading of the propagation of the long waves (27 kc/sec) originating in the tropospheric thunderstorms, on the basis of the records of the narrow sector radiogoniograph of the Swiss Meteorological Office. The time differences between the interruptions of the recordings of the thunderstorm sources and the astronomical sunrise at Zurich — adopted as reference time — are grouped according to the azimut between 160° and 300° and represented as function of the azimut of the rising sun at Zurich. By means ofLugeon's «Tables Crépusculaires», the author searches in space for pointsM being such that the respective time differences between the astronomical sunrise at each of them and at Zurich give curves which are comparable to the empirical functions defined above. It follows that the interruption of the propagation coincides sensibly with the time of sunrise at the altitude of 75 km on the wave trajectory, bearing in mind the delay of about 10 minutes due to the active part of the ozone layer; the height of this active part has been found at about 28 km. The average positions of the thunderstorm sources have been deduced from the distribution of the numbers of thunderstorm days all over the world. Finally, the author verifies that this model corresponds to the reality, taking account of the angular distances of the sources.The second Chapter deals with the sun-rise-effect — particularly the «nose» —often to be seen on the records of the impulse counter (atmoradiograph). The theory exposed is based upon a simple geometrical model of the propagation and on the results of First Chapter. This theory is then applied to 10 special cases, the recordings of which have been obtained as follows: Some hours before sunrise, the reception frames of the narrow sector radiogoniograph are stopped in a «privileged» direction and the received impulses are fed into the atmoradiograph. The obtained recordings are in satisfactory accord with the process of the «transitory» propagation, provided that the sources are known. Sometimes, two or three «satellites» or «noses» are to be seen; they have all been explaned. The author is lead to the conclusion that the «nose» is beginning in the very moment, when the last reflection occurs on theD-layer, all the others taking place on the lower part of theE-region in the dark zone. The «nose» ends when the first ionising sunrays intersect the wave trajectory at about 75 km in the neighbourhood of the last but one reflection point.In the third Chapter, the author improves the first model developped in the Chapters I and II, adapting it to the present knowledge of the ionosphere. The electronic density having to be considered as a continuous function of the height, the author shows that there must be a phenomenon of refraction on the surface formed by the first ionising rays of the rising sun in the region between theD- andE-layers, if the reflections obey to the law of metallic reflection. The first model keeps its whole value in spite of the new conception.
Zusammenfassung Im ersten Kapitel bestimmt der Autor die Höhe, in welcher der Unterbruch in der Ausbreitung langer Wellen (27 kHz) beim Sonnenaufgang stattfindet. Dabei handelt es sich um Wellen, die von troposphärischen Gewitterherden ausgehen; die Untersuchung stützt sich auf die Registrierungen des Radiogoniographen mit schmalem Sektor der Schweizerischen Meteorologischen Zentralanstalt. Die Zeitdifferenz zwischen den Unterbrüchen der Herdregistrierungen und dem astronomischen Sonnenaufgang in Zürich, letzterer als Ausgangspunkt der Zeitmessung genommen, werden nach Azimuth-Werten zwischen 160 und 300 Grad gruppiert und als Funktion des Azimuths der Sonne beim Sonnenaufgang in Zürich, aufgetragen. Mit Hilfe derLugeon'schen Dämmerungstafeln sucht der Autor PunkteM im Raum auf, derart, dass die Zeitdifferenz der Sonnenaufgänge in jedem von ihnen und in Zürich Kurven ergeben, die mit den Messwerten vergleichbar sind (Zeitdifferenz als Funktion des Sonnenazimuths bei Sonnenaufgang in Zürich, gruppiert nach der Empfangsrichtung). Es ergibt sich daraus, dass der Ausbreitungsunterbruch fühlbar mit dem Moment des Sonnenaufgangs in 75 km Höhe auf dem Wellenstrahl zusammenfällt. Hierbei ist die Verzögerung in der Grössenordnung von 10 Minuten berücksichtigt, die durch die Einflusszone der Ozonschicht (deren Höhe zu 28 km ermittelt wurde) bedingt ist. Die mittleren Gewitterherdlagen wurden aus der Verteilung der Anzahl Gewittertage auf beiden Hemisphären ermittelt. Zum Schluss prüft der Autor nach, ob dieses Modell der Wirklichkeit entspricht, indem er die Winkeldistanzen der Herde einführt.Das zweite Kapitel befasst sich mit dem Problem der in den Registrierungen des Impulszählers (Atmoradiograph) häufig nach Sonnenaufgang auftretenden als «Satellit» bezeichneten kleinen Nase. Die vorgeschlagene Theorie gründet sich auf eine einfache geometrische Auffassung der Ausbreitung und stützt sich auf die Ergebnisse des ersten Kapitels. Sie wird sodann auf 10 besondere Fälle angewendet, deren Registrierungen folgendermassen erhalten wurden: Einige Stunden nach Sonnenaufgang werden die Rahmenempfangsantennen des Radiogoniographen in einer «bevorzugten» Richtung festgelegt und die eingehenden Impulse werden auf den Atmoradiographen geleitet. Die erhaltenen Registrierungen bestätigen in befriedigender Weise, den Ausbreitungsvorgang voraussgesetzt, dass die Lage der Herde bekannt ist. Sehr oft sind zwei oder drei kleine «Satelliten» oder «Nasen» zu unterscheiden, alle konnten als zutreffend nachgewiesen werden. Der Autor schliesst daraus, dass der Satellit sich in dem Augenblick bildet, indem die letzte Reflexion an derD-Schicht auftritt, während alle andern noch im beschatteten Teil der Basis derE-Schicht liegen. Der «Satellit» hört auf, wenn die ionisierenden Sonnenstrahlen in der Umgebung des vorletzten Reflexionspunktes den Wellenstrahl (bei ungefähr 75 km Höhe) schneiden.Im dritten Kapitel wird das bisher entwickelte Modell mit Rücksicht auf die Struktur der Ionosphäre, soweit sie bis heute bekannt ist, verfeinert. Da sich die Elektronendichte in Funktion der Höhe stetig ändert, folgert der Autor, dass eine Brechung zwischen derD- undE-Schicht an der Schattengrenze der ionisierenden Sonnenstrahlen auftritt, vorausgesetzt, dass sowohl nachts wie tagesüber die Gesetze der metallischen Reflexion anwendbar sind. Dabei behält das ursprüngliche Modell trotz dieser neuen Interpretation seine Gültigkeit im wesentlichen bei.
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8.

Contents of As, Cd, Co, Cr, Cu, Ni, Pb and Zn were determined in the material collected in sandboxes of seven spa resorts located in S Poland (CCE) and their results used to establish a health risk of children. After sieving out grains > 2 mm, the bulk samples were quantitatively separated into four grain fractions: 2000–1000, 1000–200, 200–63 and < 63 µm. In each of them were determined: the mineral composition, the total contents of the elements, and the distribution of the elements among the fractions distribution factor. In the bulk material < 2 mm, the totals of the elements are 5–64 times lower than in the finest fractions (< 63 µm). Considering that the finest fractions are enriched in clay minerals such as clinochlore, illite and kaolinite, which can adsorb and desorb metals, this material is most dangerous for children, staying both permanently and temporarily in the spas. The total health risks HI resulting from non-carcinogenic elements present in the fractions < 63 µm are 1.26 and 0.94, for the children-residents 3 and 6 years old, respectively. The figures are disturbing as one of them exceeds and the other is close to a permissible limit of 1. The highest contribution (93.4%) into the total HI is caused by inadvertent swallowing the soil “dirt”: the ingestion path HQ ing for the 3 years old residents is 1.17, and for the 6-year olds 0.88. With respect to the elements, the highest is the risk resulting from Pb: HQ in values of the residents are 4.71E−01 and 3.54E−01 for the 3-year olds and the 6-year olds. Slightly lower are the HQ ing values calculated for both age groups: in the case of Cr—3.12E−01 and 2.34E−01 and As—2.92E−01 and 2.19E−01). The dermal path (HQ dermal ) contributes to the total HI much less as it equals 6.5%, while the contribution of the inhalation path (HQ inhal ) is considerably the lowest and equals only 0.1%. The Risk indexes determined in the case of cancerogenic components for both age groups of the spa residents are lower than the permissible limit 10E−5 and equal 6.48E−06 and 9.72E−06, respectively. Considering the children that only visit the spas, all the calculated indexes, i.e., HI and Risk, are significantly lower than those determined for the children-residents.

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9.
Hong Xie  Xuan Zhu 《水文研究》2013,27(25):3685-3693
Evapotranspiration is an important component of the water and energy balance. It is dependent on climate. Precipitation, solar radiation, temperature, humidity, and wind all contribute to the rate of evapotranspiration. In this study, the temporal trends of reference evapotranspiration (ETref) and four main ETref drivers, namely, mean air temperature (Ta), wind speed (u2), net radiation (Rn) and actual vapour pressure (ea) from 1970 to 2009, were calculated based on 75 meteorological stations on the Tibetan Plateau. The results showed that the ETref on the Tibetan Plateau decreased on average by 0.6909 mm a‐1a‐1 from 1970 to 2009. Ta and ea showed an increasing trend, whereas u2 and Rn exhibited a decreasing trend. To explore the underlying causes of the ETref variation, an attribution analysis was performed to quantify the contribution of Ta, u2, Rn and ea, which showed that the changes in u2, Rn and ea produced the negative effect, whereas Ta produced the positive effect on ETref rates. The changes in u2 were found to produce the largest decrease (?0.7 mm) in ETref, followed by ea (?0.4 mm) and Rn (?0.1 mm). Although the significant increase in Ta had a large positive effect (0.51 mm) on ETref rates, changes in the other three variables each reduced ETref rates, resulting in an overall negative trend in ETref. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

10.
Ambiguity in the inverse problem of retrieval of the mechanical parameters of the Earth’s shell and core from the set of data on the velocities V p and V S , of longitudinal and transverse seismic body waves, the frequencies f i and quality factors Q i , of free oscillations, and the amplitudes and phases of forced nutation is considered. The numerical experiments show that the inverse problem of simultaneous retrieval of the density profile ρ in the mantle-liquid core system and the mechanical quality factor Q μ of the mantle (if the total mass M and the total mean moment of inertia I of the Earth, and V p and V S are constant at all depths) has most unstable solutions. An example of depth distributions of ρ and Q μ which are alternative to the well-known PREM model is given. In these distributions, the values of M and I and the velocities V p and V S at all depths for the period of oscillations T = 1 s exactly coincide with their counterparts yielded by PREM model (T = 1 s); however, the maximum deviations of the ρ and Q μ profiles from those in the PREM model are about 3% and 40%, respectively; the mass and the moment of inertia of the liquid core are smaller than those for the PREM model by 0.75% and 0.63%, respectively. In this model, the root mean square (rms) deviations of all the measured values of f i and Q i from their values predicted by theory are half to third the corresponding values in the PREM model; the values of Δ for natural frequencies of the fundamental tone and overtones of radial oscillations, the fundamental tones of torsional oscillations, and the fundamental tones of spheroidal oscillations, which are measured with the highest relative accuracy, are smaller by a factor of 30, 6.6, and 2 than those in the PREM model, respectively. Such a large ambiguity in the solution of the inverse problem indicates that the current models of the depth distribution of density have relatively low accuracy, and the models of the depth distribution of the mechanical Q in the mantle are extremely unreliable. It is shown that the ambiguity in the models of depth distribution of density considerably decreases after the new data on the amplitudes and phases of the forced nutation of the Earth are taken into account. Using the same data, one may also refine by several times the recent estimates of the creep function for the lower mantle within a wide interval of periods ranging from a second to a day.  相似文献   

11.
On May 21, 2021, an MS6.4 earthquake occurred in Yangbi, Yunnan province, China, which exhibited typical foreshock-mainshock-aftershock characteristics. To better understand the velocity structure of the focal area and adjacent fault zones, Pg/Sg travel times at 12 seismic stations for the local earthquakes with ML ≥ 1.5 from 2009–2019 and the Yangbi sequence in May of 2021 were used to invert the three-dimensional (3D) structures for both vP and vP/vS. The obtained structure extends deeply to 15 km for area (25°N–26.5°N, 99.5°E–101°E) at a horizontal resolution of 10× 10 km, and the accuracy of the vP velocity was verified using airgun signals excited by the Binchuan Airgun Transmitting Seismic Station (BATSS). The resulting vP and vP/vS images correlate with existing fault zones and the Yangbi sequence, including: (1) The shallow velocity structure at 0 km agrees with local topography, where the Binchuan basin exhibits low-vP and high-vP/vS values. From 3–15 km, vP and vP/vS show variations, and the boundaries are consistent with the main faults (e.g., the Weixi-Qiaohou-Weishan, Honghe, and Chenghai faults). (2) The largest foreshock (MS5.6), mainshock (MS6.4), and largest aftershock (MS5.2) occurred near the boundaries where both vP and vP/vS have clear contrasts. (3) Small earthquakes are also concentrated in the transition zone between high- and low-vP and vP/vS anomalies, and are biased toward low-vP/vS zones. (4) Boundaries in vP and vP/vS are observed at 20 km west of the Weixi-Qiaohou-Weishan fault, indicating that there may exist one hidden fault.  相似文献   

12.
The 3-d coupled physical–biogeochemical model ECOHAM (version 3) was applied to the Northwest-European Shelf (47°41′–63°53′N, 15°5′W–13°55′E) for the years 1993–1996. Carbon fluxes were calculated for the years 1995 and 1996 for the inner shelf region, the North Sea (511,725 km2). This period was chosen because it corresponds to a shift from a very high winter-time North Atlantic Oscillation Index (NAOI) in 1994/1995, to an extremely low one in 1995/1996, with consequences for the North Sea physics and biogeochemistry. During the first half of 1996, the observed mean SST was about 1 °C lower than in 1995; in the southern part of the North Sea the difference was even larger (up to 3 °C). Due to a different wind regime, the normally prevailing anti-clockwise circulation, as found in winter 1995, was replaced by more complicated circulation patterns in winter 1996. Decreased precipitation over the drainage area of the continental rivers led to a reduction in the total (inorganic and organic) riverine carbon load to the North Sea from 476 Gmol C yr−1 in 1995 to 340 Gmol C yr−1 in 1996. In addition, the North Sea took up 503 Gmol C yr−1 of CO2 from the atmosphere. According to our calculations, the North Sea was a sink for atmospheric CO2, at a rate of 0.98 mol C m−2 yr−1, for both years. The North Sea is divided into two sub-systems: the shallow southern North Sea (SNS; 190,765 km2) and the deeper northern North Sea (NNS; 320,960 km2). According to our findings the SNS is a net-autotrophic system (net ecosystem production NEP>0) but released CO2 to the atmosphere: 159 Gmol C yr−1 in 1995 and 59 Gmol C yr−1 in 1996. There, the temperature-driven release of CO2 outcompetes the biological CO2 drawdown. In the NNS, where respiratory processes prevail (NEP<0), 662 and 562 Gmol C yr−1 were taken up from the atmosphere in 1995 and 1996, respectively. Stratification separates the productive, upper layer from the deeper layers of the water column where respiration/remineralization takes place. Duration and stability of the stratification are determined by the meteorological conditions, in relation to the NAO. Our results suggest that this mechanism controlling the nutrient supply to the upper layer in the northern and central North Sea has a larger impact on the carbon fluxes than changes in lateral transport due to NAOI variations. The North Sea as a whole imports organic carbon and exports inorganic carbon across the outer boundaries, and was found to be net-heterotrophic, more markedly in 1996 than in 1995.  相似文献   

13.
Summary Since November 1984 a regional study of the Earth's magnetic field has been carried out, measuring absolute values ofF, D, andI. The aim is to find the behaviour of the secular variation at about 40 field sites with maximum distances of 50 km from Göttingen. After a long search for the least disturbed points, the first set of measurements was taken in 1987. For the reduction according to the normal 2h UT level the Göttingen observatory (GTT) records are used for each field point. However, by comparing the simultaneously registered magnetic values of the observatories Wingst (WNG) and GTT it turned out that there is an annual periodic drift in the GTT registrations. Besides the temperature coefficients of the variometers the whole micro-climate of temperature and humidity inside and outside the building and of the underground has to be considered. It causes a motion of the bottom plate (on which the variometers are standing) relative to the foundations of the walls (which house the camera and the lamps for the photographic registration). These motions can be misinterpreted as long period magnetic variations. Variations of the micro-climate and consequently the time dependence of the motions cannot be predicted. Apparently the long-term stability of the whole recording system, which is essential for reducing regional measurements and for the investigation of the secular variation, had not been considered important as the building was set-up. To overcome that lack of stability two ways are necessary: firstly, to perform regular absolute measurements at the observatory (more than once a week) to get a better knowledge of the base line of each component, secondly, to refer the GTT registrations to the momentary values of WNG which are assumed to be stable, to get by this way a proper reduction of the field measurements.
Die Stabilität der Basiswerte der magnetischen Hauptregistrierung des Observatoriums Göttingen
Zusammenfassung Seit November 1984 wird das regionale Erdmagnetfeld in der Umgebung von Göttingen mit Absolutinstrumenten fürF, D undI vermessen. Das Ziel einer solchen Vermessung ist die Untersuchung der Säkularvariation an 40 Punkten mit einer maximalen Entfernung von 50 km von Göttingen. Nach einer längeren Suche nach den am wenigsten gestörten Punkten wurde 1987 mit den Messungen begonnen. Für die Reduktion aller Meßwerte auf 2h UT und auf einen bestimmten Tag im Jahr wurden die photographischen Registrierungen des Observatoriums Göttingen (GTT) benutzt. Durch Vergleich der gleichzeitig in den Observatorien Wingst (WNG) und GTT abgelesenen Momentanbeobachtungen der Magnetfeldkomponenten zeigte sich aber, daß der Säkularvariation in GTT eine starke Jahreswelle überlagert ist. Verursacht wird diese Jahreswelle offenbar durch eine Relativbewegung der zwei Fundamente der Meßhütte: Die Fundamentplatte (auf der die Variometer stehen) bewegt sich gegenüber dem Fundament der Wände (in die Registrierkamera und die Lampen eingelassen sind). Auf der Registrierung können diese Bewegungen fälschlicherweise als Magnetfeldvariation mit langer Periode gedeutet werden. Änderungen des Mikroklimas (Temperatur und Feuchte) innerhalb und außerhalb der Meßhütte, das für diese Bewegungen verantwortlich ist, sind nicht vorhersehbar. Offenbar ist die Langzeitstabilität der Aufzeichnungsapparatur, die auch eine Untersuchung der Säkularvariation ermöglichen würde, bei der Konstruktion der Meßhütte noch nicht wichtig gewesen. Um dennoch eine vernünftige Reduktion zu erzielen, ist es nötig, öfter als einmal wöchentlich die Absolutwertbestimmung in GTT durchzuführen und damit die Basis jeder Magnetfeldkomponente zu bestimmen, und zweitens zu versuchen, die Zeiten zwischen zwei Absolutwertbestimmungen mit den Momentanwerten aus WNG zu überbrücken.
La stabilité des valeurs de base de l'enregistrement principal de l'observatoire à Göttingen
Résumé Depuis novembre 1984, une étude régionale du champ magnétique terrestre a été menée afin de déterminer les valeurs absolues deF, D etI. le but visé est de déterminer l'évolution de la variation séculaire sur environ quarante sites situés à une distance maximale de 50 km de Göttingen. Après une longue recherche des points les moins perurbés une première série de mesures a pu être effectuée en 1987. Pour la réduction rapportée à la valeur normale à 2h UT, les enregistrements de l'observatoire de Göttingen (GTT) furent utilisés pour chaque site.En comparant les valeurs magnétiques enregistrées simultanément à l'observatoire de Wingst (WNG) et à GTT, il apparut qu'il existait une dérive annuelle périodique dans les enregistrements de GTT. Outre les coefficients de température des variomètres, l'ensemble des paramètres température et humidité du micro-climat, à l'intérieur et à l'extérieur de la station ainsi qu'en sous-sol dut être pris en compte. Ces derniers causent un déplacement de l'embase (sur laquelle les variomètres sont installés) par rapport aux fondations des murs (qui abritent la caméra et les flashs pour l'enregistrement photographique): Ces mouvements peuvent être interprétrés à tort comme des variations à longue période du champ magnétique.Les variations du micro-climat et partant, la dépendance de ces mouvements en fonction du temps, ne peuvent se prévoir. Apparemment la stabilité á long terme de l'ensemble du système d'enregistrement, qui est essentielle pour la réduction des mesures régionales et pour l'étude de la variation séculaire, n'avait pas été condiérée comme importante au moment de la construction de la station.Pour palier ce manque de stabilité deux solutions sont possibles: Tout d'abord réaliser régulièrement des mesures absolues à l'observatoire (plus d'une par semaine) afin d'obtenir une meilleure connaissance de la valeur instantanée de la direction de chaque composante, ensuite rattacher les enregistrements de GTT aux valeurs déterminées à WNG, supposées stables, pour obtenir ainsi une réduction correcte des mesures de champs.
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14.

The paper discusses quantitatively the influence of the Yutian MS7.4 earthquake of March 21, 2008 and Wuqia MS6.9 earthquake of October 5, 2008 on regional seismicity in Xinjiang, and explains primarily the possible reason of earthquake activity feature in Xinjiang after the Yutian MS7.4 earthquake by analyzing the static Coulomb failure stress change produced by the Yutian MS7.4 earthquake and Wuqia MS6.9 earthquake, and the seismicity feature of MS?≥3 earthquakes in the positive Coulomb stress change region of Kashi-Wuqia joint region, the central segment of Tianshan Mountain and Kalpin block. The result shows that the Yutian MS7.4 earthquake of March 21, 2008, may encourage the Wuqia MS6.9 earthquake of October 5, 2008, and the Yutian MS7.4 earthquake and Wuqia MS6.9 earthquake may change the seismicity state in the central segment of Tianshan Mountain, Kalpin block and Kashi-Wuqia joint region, and encourage the subsequent MS?≥3 earthquakes.

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15.
Samples of the polychaete Chaetopterus variopedatus, worm tubes, commensal crab Polyonyx gibbesi and sediments were collected in eight sites in Todos os Santos Bay, Brazil, in order to evaluate the potential use of the polychaetes and crabs as biomonitors and to assess the relationships and accumulation of trace and major elements in different benthic compartments. Trace and major elements were determined by ICP OES. Organic carbon, total nitrogen and sulfur were determined by CNS elemental analyser. Tubes, crabs and polychaetes were important in the retention of trace and major elements. Metals that presented the highest accumulation in polychaetes (i.e. Mg > Al > Fe > Zn > Mn > Co > Cu > Ba > Cr) where the same for crabs (i.e. Mg > Al > Fe > Mn > Co > Zn > Cu > Ba > Cr). High concentrations of Al, Ba, Cr, Mn and Fe, from terrigenous sources, were observed in tubes, which presented accumulation factors up to 81.5 for Mn. Sedentary polychaetes are seen as good biomonitor alternatives for metal contamination studies, because they are one of the most abundant taxon in the benthic system, live in direct contact with sediments, are present in broad distributions and can also handle relatively high concentrations of metals ensuring chronic exposition. The possibility to work with not only the polychaete but also its tube offers advantages compared to bivalves that generally do not accumulate certain metals in very high levels.  相似文献   

16.
Summary Approximate formulae (2,4) were derived for estimating the geometric parameters of a national triangular net, if its area P, in a certain way determined circumference O, and intended average length of the triangle side d are given. The formulae are given for nΔ triangles, nb points, nd sides, and for rg conditions with a trigonometrical net the bearings of which are measured, or rl conditions with a trilateral net. Other approximate formulae (7–10) serve for estimating the mean errors Mg and Ml of adjusted observations and the positional errors Mx,y,g and Mx,y,l of the points of the net. Equation (11) gives the relation between the mean errors of observations mg and ml, which leads to the same positional accuracy with both bearing and distance measuring methods. The effect of the relative error Rd of the estimate of distance d is only observed with the geometric parameters and it is given by equations (6).

Anschrift: Politickych vězňů 12, Praha 1-Nové Město.  相似文献   

17.
LaCe ages are reported for two sets of Finnish pegmatites, Lövböle and Mustikkamäki, and for an Amiˆtsoq gneiss, Greenland. When λβ138La value (2.29 × 10−12 yr−1) obtained by radioactivity measurement [1] is used for the chronological calculation, the LaCe ages (2129, 2325, 3271 Myr) evaluated for these rocks are 18–35% older than the SmNd ages for the same samples. To make the LaCe age fit to the SmNd age for the same sample, a new value of (2.77 ± 0.21) × 10−12 yr−1 is evaluated for λβ138La. In this calculation, the LaCe and SmNd ages reported for a Bushveld gabbro [2] have been also taken into account together with those for the Lövböle pegmatite and the Mustikkamäki pegmatite, while the Amiˆtsoq gneiss (GGU110999) has been omitted because of the complicated thermal history of this sample.  相似文献   

18.
Cruises to Bering Strait and the Chukchi Sea in US waters from late June in 2002 to early September in 2004 and the Russian–American Long-term Census of the Arctic (RUSALCA) research cruise in 2004 covered all major water masses and contributed to a better understanding of the regional physics, nutrient dynamics, and biological systems. The integrated concentration of the high nitrate pool in the central Chukchi Sea was greater in this study than in previous studies, although the highest nitrate concentration (∼22 μM) in the Anadyr Water mass passing through the western side of Bering Strait was consistent with prior observations. The chlorophyll-a concentrations near the western side of the Diomede Islands ranged from 200 to 400 mg chl-a m−2 and the range in the central Chukchi Sea was 200–500 mg chl-a m−2 for the 2002–2004 Alpha Helix (HX) cruises. Chlorophyll-a concentrations for the 2004 RUSALCA cruise were lower than those from previous studies. The mean annual primary production of phytoplankton from this study, using a 13C–15N dual-isotope technique, was 55 g C m−2 for the whole Chukchi Sea and 145 g C m−2 for the plume of Anadyr–Bering Shelf Water in the central Chukchi Sea. In contrast, the averages of annual total nitrogen production were 13.9 g N m−2 (S.D.=±16.2 g N m−2) and 33.8 g N m−2 (S.D.=±14.1 g N m−2) for the Chukchi Sea and the plume, respectively. These carbon and nitrogen production rates of phytoplankton were consistently two-or three-fold lower than those from previous studies. We suggest that the lower rates in this study, and consequently more unused nitrate in the water column, were caused by lower phytoplankton biomass in the Bering Strait and the Chukchi Sea. However, we do not know if the lower rate of production from this study is a general decreasing trend or simply temporal variations in the Chukchi Sea, since temporal and geographical variations are substantially large and presently unpredictable.  相似文献   

19.
Samples dredged from 2 localities near the crest of the Valu Fa ridge, an active back-arc basin spreading centre in the Lau Basin, consist of highly vesicular lava fragments of andesitic composition. The samples are characterized by rare, euhedral An85 plagioclase phenocrysts in a hypocrystalline groundmass of An60 plagioclase laths, brown glass and rare subhedral clinopyroxene. Samples from within and, to a lesser extent, between the dredge hauls show remarkable isotopic and chemical homogeneity, with: 87Sr/86Sr − 0.70330 ± 2; 143Nd/144Nd − 0.51303 ± 2; 206Pb/204Pb − 18.65 ± 2; 207Pb/204Pb − 15.55 ± 1; 208Pb/204Pb − 38.34 ± 4; Sr − 165 ppm; Rb − 7 ppm; Cs − 0.17 ppm; K − 3300 to 4200 ppm; Ba − 96 ppm; and REE — LREE depleted with 12–18 × chondritic abundances. On Sr-Nd, Pb-Pb and Sr-Pb plots the volcanics lie just within or on the edge of the MORB fields, overlapping with island-arc volcanics from the Marianas and Tonga. Compared with MORB and ocean-island basalts, the samples show alkali-element enrichment relative to REE and higher Cs relative to Rb. The isotopic and geochemical characteristics of the Valu Fa Ridge volcanics clearly indicate a minor, but significant, slab-derived component in the back-arc basin mantle source.  相似文献   

20.
Starting from the classical empirical magnitude-energy relationships, in this article, the derivation of the modern scales for moment magnitude M w and energy magnitude M e is outlined and critically discussed. The formulas for M w and M e calculation are presented in a way that reveals, besides the contributions of the physically defined measurement parameters seismic moment M 0 and radiated seismic energy E S, the role of the constants in the classical Gutenberg–Richter magnitude–energy relationship. Further, it is shown that M w and M e are linked via the parameter Θ = log(E S/M 0), and the formula for M e can be written as M e = M w + (Θ + 4.7)/1.5. This relationship directly links M e with M w via their common scaling to classical magnitudes and, at the same time, highlights the reason why M w and M e can significantly differ. In fact, Θ is assumed to be constant when calculating M w. However, variations over three to four orders of magnitude in stress drop Δσ (as well as related variations in rupture velocity V R and seismic wave radiation efficiency η R) are responsible for the large variability of actual Θ values of earthquakes. As a result, for the same earthquake, M e may sometimes differ by more than one magnitude unit from M w. Such a difference is highly relevant when assessing the actual damage potential associated with a given earthquake, because it expresses rather different static and dynamic source properties. While M w is most appropriate for estimating the earthquake size (i.e., the product of rupture area times average displacement) and thus the potential tsunami hazard posed by strong and great earthquakes in marine environs, M e is more suitable than M w for assessing the potential hazard of damage due to strong ground shaking, i.e., the earthquake strength. Therefore, whenever possible, these two magnitudes should be both independently determined and jointly considered. Usually, only M w is taken as a unified magnitude in many seismological applications (ShakeMap, seismic hazard studies, etc.) since procedures to calculate it are well developed and accepted to be stable with small uncertainty. For many reasons, procedures for E S and M e calculation are affected by a larger uncertainty and are currently not yet available for all global earthquakes. Thus, despite the physical importance of E S in characterizing the seismic source, the use of M e has been limited so far to the detriment of quicker and more complete rough estimates of both earthquake size and strength and their causal relationships. Further studies are needed to improve E S estimations in order to allow M e to be extensively used as an important complement to M w in common seismological practice and its applications.  相似文献   

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