强震地面运动的超随机特性研究

简述了几种常用的地震动平稳随机模型，这几种地震动平稳随机模型的功率谱是一组光滑的函数，相应的自相关函数基本上是指数衰减的振荡函数，且很快衰减到零；但是真实地震动的归一化自相关函数则有一较显著的随机噪声项，这个随机噪声的幅值为0．15左右，这就是本文中所说的超随机特性。目前常用的地震动平稳随机模型没有考虑这个随机噪声项及其对结构反应的影响。本文将真实地震动的自相关函数分解为一确定性函数和一随机噪声的叠加，并对自相关函数中的噪声部分进行了分析，得出两条重要性质。本文的研究结果表明地震动加速度时程的平方和(SS)比峰值加速度(PGA)更好地量度了地震地面运动强度。由于归一化自相关函数的随机噪声部分所对应的功率谱的随机波动成分对频率的积分为零，即归一化自相关函数的噪声部分对地震动总功率或平方和的贡献为零，因此自相关函数的随机噪声项对地震动的幅值影响不大，但自相关函数的随机噪声项明显改变了地震动功率谱在频域上的分布特征，因此会对结构反应产生一定的影响。由于篇幅所限详细内容将在下一篇文章中作进一步探讨。     

Petrology and 40Ar–39Ar dating of shear zones in the Lanterman Range (northern Victoria Land, Antarctica): implications for metamorphic and temporal evolution at terrane boundaries

Summary The Lanterman Fault Zone, a major terrane boundary in northern Victoria Land, displays a polyphase structural evolution. After west-over-east thrusting, it experienced sinistral strike-slip shearing. Sheared metabasites from the Wilson Terrane (inboard terrane) preserve a record of retrograde metamorphic evolution. Shearing took place under amphibolite-facies metamorphic conditions (roughly comparable to those reached during regional metamorphism) which later evolved to greenschist-facies conditions. In contrast, the Bowers Terrane (outboard terrane) preserves a prograde metamorphic evolution which developed from greenschist-facies to amphibolite-facies metamorphism during shearing, followed by greenschist-facies metamorphism during the late deformational stages. Laser step-heating ⁴⁰Ar–³⁹Ar analyses of syn-shear amphibolite-facies amphiboles yielded ages of 480–460 Ma, in agreement with a ∼480-Ma age obtained from a biotite aligned along the mylonitic foliation. These ages are younger than those (∼492 to ∼495 Ma) obtained from pre-shear amphibole relics linked to regional metamorphism of the Wilson Terrane. Results attribute the structural and metamorphic reworking during shearing to the late stages of the Cambrian-Ordovician Ross Orogeny and to the Middle-Late Ordovician probably in relation to the beginning of deformation in the Lachlan Orogen, thus precluding any appreciable impact of the Devonian-Carboniferous Borchgrevink event in the study area.     

Analysis of sustained long-period activity at Etna Volcano, Italy

Following the installation of a broadband network on Mt. Etna, sustained Long-Period (LP) activity was recorded accompanying a period of total quiescence and the subsequent onset of the 2004–2005 effusive episode. From about 56000 events detected by an automatic classification procedure, we analyse a subset of about 3000 signals spanning the December 17th, 2003–September 25th, 2004, time interval. LP spectra are characterised by several, unevenly-spaced narrow peaks spanning the 0.5–10 Hz frequency band. These peaks are common to all the recording sites of the network, and different from those associated with tremor signals. Throughout the analysed time interval, LP spectra and waveforms maintain significant similarity, thus indicating the involvement of a non-destructive source process that we interpret in terms of the resonance of a fluid-filled buried cavity. Polarisation analysis indicates radiation from a non-isotropic source involving large amounts of shear. Concurrently with LP signals, recordings from the summit station also depict Very-Long-Period (VLP) pulses whose rectilinear motion points to a region located beneath the summit craters at depths ranging between 800 and 1100 m beneath the surface. Based on a refined repicking of similar waveforms, we obtain robust locations for a selected subset of the most energetic LP events from probabilistic inversion of travel-times calculated for a 3D heterogenous structure. LP sources cluster in a narrow volume located beneath the summit craters, and extending to a maximum depth of ≈ 800 m beneath the surface. No causal relationships are observed between LP, VLP and tremor activities and the onset of the 2004–2005 lava effusions, thus indicating that magmatic overpressure played a limited role in triggering this eruption. These data represent the very first observation of LP and VLP activity at Etna during non-eruptive periods, and open the way to the quantitative modelling of the geometry and dynamics of the shallow plumbing system.     

Capturing critical behaviour in soil moisture spatio-temporal dynamics

A physical system is subject to a phase transition process when it shows a discontinuous change of a macroscopic feature of the system under a continuous change of a system’s state variable.     

Evaluation of the SEDD model for predicting sediment yield at the Sicilian experimental SPA2 basin

In this paper a spatially distributed model of the hillslope sediment delivery processes, named the sediment delivery distributed (SEDD) model, is initially reviewed; the model takes into account the sediment delivery processes due to both the hillslope sediment transport and the effects of slope curvature. Then the rainfall and sediment yield events measured at the experimental SPA2 basin, in Sicily, are used both to calibrate the SEDD model and to verify the predictive capability of the distributed sediment delivery approach at event scale. For the SPA2 basin discretized into morphological units and stream tubes, the SEDD model is calibrated at event scale using the measurements carried out at the outlet of the experimental basin in the period December 2000–January 2001. The model calibration is used to determine a relationship useful for estimating the unique coefficient β_e of the model by rainfall erosivity factor R_e at event scale. To test the predictive capability of the β_e = f(R_e) relationship, 20 events measured in the period September 2002–December 2005 are used; the comparison between measured sediment yield values and calculated ones for all monitored events shows that the sediment delivery distributed approach has a good predictive ability at event scale. The analysis also shows that estimating β_e by the relationship β_e = f(R_e) gives a better agreement between measured and calculated sediment yields than obtained with the median value β_e,m of all 27 calculated β_e values. Finally the analysis at annual scale, for the period 2000–2005, allows the estimation of the median value β_a,m representative of the annual behaviour. This analysis shows that the sediment delivery distributed approach also has a good predictive ability at annual scale. Copyright © 2006 John Wiley & Sons, Ltd.     

南通地区新构造运动特征

从盆地沉积及其演变特征入手，总结了该区新构造运动特征；运用新构造运动理论对海岸线的变迁、长江的迁移及旋扭变形现象进行了探讨，并提出建立第四系各年代的地层沉降速率数学模型、用升降运动速率划分和对比第四纪地层的见解。     

Fall vs flow activity during the 1991 climactic eruption of Pinatubo Volcano (Philippines)

Six years after the 1991 Mt. Pinatubo eruption, deep erosion incisions into the pyroclastic deposits accumulated around the volcano enabled us to investigate the stratigraphy of the climactic deposits both in valley bottoms and on contiguous ridges. Stratigraphic relationships between fall, flow, and surge deposits in the Marella drainage system indicate that during the climactic eruption a progressive shift occurred from an early convective regime, to a transitional regime feeding both the plinian convective column and mostly dilute density currents, to a fully collapsing regime producing mostly dense pyroclastic flows. Syn-plinian dilute density currents (surges) propagated up to ~10 km from the crater, both along valley bottoms and on contiguous ridges of the Marella Valley, whereas post-plinian pyroclastic flows had greater runout (~13 km), were confined to valleys and were not associated with significant surges. Stratigraphic study and grain-size analyses allow the identification of three types of intra-plinian deposits: (a) lower and often coarse-grained surge deposits, emplaced during the accumulation of the coarsest portion of the fallout bed at time intervals of ~16-24 min; (b) upper fine-grained surge deposits, interstratified with the fine-grained portion of the fall bed and emplaced at shorter time intervals of ~3-13 min; and (c) small-volume, channel-confined, massive pumiceous flow deposits interbedded with the upper surges in the upper fine-grained fall bed. Maximum clast size isopleths of 1.6 and 0.8 cm for lithics (ML) and 2.0 and 4.0 cm for pumices (MP) show almost symmetrical distribution around the vent, indicating that the passing of the typhoon Yunya during the climactic eruption had little effect on trajectories of high-Reynold-number clasts. Significant distortion was, however, observed for the 3.2-cm ML and 6.0-cm MP proximal isopleths, whose patterns were probably influenced by the interaction of the clasts falling from column margins with the uprising co-ignimbrite ash plumes. Application of the Carey and Sparks (1986) model to the undisturbed isopleths generated by the umbrella cloud yields a maximum column height of ~42 km, in good agreement with satellite measurements. Systematic stratigraphic and vertical grain-size studies of the plinian fall deposit in the Marella Valley, combined with satellite data and eyewitness accounts, reveal that the carrying capacity of the convective column and related fallout activity peaked in the early phase of the eruption, beginning slightly before 13:41 and gradually declined until its cessation 3 h later. Most of the pumiceous pyroclastic flow deposits were emplaced after the end of the fallout activity at ~16:30 but before the summit caldera collapse at approximately 19:11. Only a small volume of pumiceous flow deposits accumulated after the final caldera collapse. In contrast to the previous reconstruction of Holasek et al. (1996), which interpreted the progressive lowering of the column, documented by satellite data, as due to a decreasing mass eruption rate, we suggest that a progressive shift from a plinian column to a large co-ignimbrite column could also account for such a variation.     

MAPGIS下重磁数据直接成图的实现及意义

作者在文中介绍了通过编制QBASIC小程序实现两种常见格式重磁数据直接生成MAPGIS图形文件的方法，为其它类似格式数据在MAPGIS下成图及建库提供可借鉴的思路和途径。     

Analysis of the vortivity and divergence of the thermal wind in pure geostrophic flow

By applying the horizontal del operator to the thermal wind equation in vectorial form and considering only horizontal geostrophic motion, expressions are found for the vorticity and divergence of thermal wind. It is shown that vorticity, in the case of pure geostrophic flow at all levels, depends upon four factors, namely: latitude, horizontal distribution of temperature, temperature lapse rate and divergence of horizontal temperature gradient. The divergence of the thermal wind, on the other hand, depends only upon the orientation of the mean isotherms of an isobaric layer relative to the parallel circles. These terms are evaluated and it is shown that the latitude term and the lapse rate term are far greater than the remaining terms of the vorticity equation for geostrophic flow. A criterion is then given which enables to determine the conditions for irrotational horizontal motion with vertical geostrophic wind shear.

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Zusammenfassung Durch Anwendung des horizontalenNabla-Operators auf die thermische Windgleichung in vektorieller Form und bei ausschließlicher Berücksichtigung der geostrophischen Horizontalbewegung lassen sich Ausdrücke für die vorticity und die Divergenz des thermischen Windes herleiten. Es wird gezeigt, daß die vorticity im Falle einer rein geostrophischen Strömung in allen Niveaus von folgenden vier Faktoren bedingt ist: Breite, horizontale Temperaturverteilung, vertikaler Temperaturgradient und Divergenz des horizontalen Temperaturgradienten. Andrerseits hängt die Divergenz des thermischen Windes nur von der Orientierung der mittleren Isothermen einer in Bezug auf die Parallelkreise isobaren Schicht ab. Diese vier Terme werden ausgewertet und es wird gezeigt, daß das Breitenglied und der Term für den Vertikalgradienten viel größer sind als die übrigen Terme der vorticity-Gleichung für geostrophische Strömung. Schließlich wird ein Kriterium entwickelt, das gestattet, die Bedingungen für rotorfreie Horizontalbewegung mit vertikaler geostrophischer Windscherung zu bestimmen.

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Résumé On peut déduire des équations sur la rotationelle et la divergence du vent thermique en appliquant l'opérateur nabla horizontal à l'équation du vent thermique sous une forme vectorielle et en ne considérant que le mouvement géostrophique horizontal. On démontre que la rotationelle, dans le cas d'un courant géostrophique pur, dépend dans tous les niveaux des quatre facteurs suivants: latitude, répartition horizontale de la température, gradient vertical de la température et divergence du gradient horizontal de température. D'autre part, la divergence du vent thermique ne dépend que de l'orientation des isothermes moyennes d'une couche isobare par rapport aux parallèles. En évaluant ces quatre termes, on montre que les termes relatifs à la latitude et au gradient vertical sont beaucoup plus grands que les autres termes de l'équation de la rotationelle pour un courant géostrophique. Pour terminer, l'auteur développe un critère qui permet de déterminer les conditions pour un mouvement horizontal irrotationel mais avec un cisaillement vertical géostrophique du vent.