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1.
Yan B. Radziminovich 《Journal of Seismology》2014,18(1):93-107
The parametric catalogues of historical earthquakes in East Siberia contain large data gaps. Among these is a 15-year period in the late nineteenth century (1886–1901). This period was not covered by any of macroseismic catalogues known; neither acquisition nor systematization of macroseismic data was ever performed for that purpose. However, 15 years is a rather long period in which large seismic events may have occurred. The present paper deals with the previously unknown earthquake that occurred on November 13, 1898. The primary macroseismic data were taken from regional periodicals. On the strength of all the evidence obtained, the earthquake epicenter is localized in Western Transbaikalia, near the western end of the Malkhansky Range; the magnitude is estimated at M?=?5.9. The information about the large earthquake of November 13, 1898 provides filling significant gaps in knowledge for seismicity in Western Transbaikalia and a better understanding of seismic potential of faults therein. The obtained results show that the periods of seismic quiescence in catalogues may be related to insufficient information on seismicity of Eastern Siberia in the historical past rather than to the absence of large earthquakes. 相似文献
2.
Fourier reconstruction with sparse inversion 总被引：2，自引：0，他引：2
The problem of seismic data reconstruction is posed as an inverse problem where the objective is to obtain the Fourier coefficients that synthesize the signal. Once the coefficients have been found, they are used to reconstruct the data on a uniformly spaced grid. A non‐quadratic model weight function is included to stabilize the inversion and to provide the additional information required to interpolate through gaps. In the reconstruction of a non‐uniformly sampled trace, an image and a marine 3D VSP shot‐record, the method shows improved reconstruction in large gaps and is less sensitive to the spatial bandwidth used in the inversion compared to Fourier reconstruction without the non‐quadratic model weight function. 相似文献
3.
本文通过分析一些强震和中强震震例,指出通常所说的地震空区可分为两类。除了震前大范围、长时间、大震级的空区,这里称之为背景空区之外,还有可能出现震前较小范围、较短时间、较小震级的空区,这里称之为孕震空区.对这两类空区作了比较.我们发现在孕震空区的后期,孕震空区边缘往往会发生一个或一组较为引人注目的地震,本文称之为逼近地震.文中初步归纳了逼近地震的某些特征与主震的关系,讨论了用于地震预报的可能性.最后从断裂力学的观点初步探讨了孕震空区与逼近地震的成因机制。 相似文献
4.
以MAPSIS为平台, 用统一目录对新疆及周边和川、 滇、 青地区17次大地震前的地震分布进行大范围、 长时间扫描, 勾画椭圆形围空区。 除1970年代初期的3次地震外, 大多有较好的围空区。 包括2008年5月汶川8.0级地震和2010年4月玉树7.1级地震。 结果表明, 大震震级与空区长度有一定正相关关系, 但与空区起始时长及空区成形时长没有关系。 讨论认为, 椭圆围空区的确定条件较松, 在复杂情况下用来勾画空区容易出现多维性, 使围空区的可信性下降, 导致地震虚报增加。 相似文献
5.
The paper discusses model results and then reviews observational data concerning some aspects of the mechanics of mature seismic gaps in coupled subduction zones. The concern is with space-and time-varying stresses, as signalled by the presence and mechanisms of earthquakes in the outer-rise zones adjacent to main thrust areas of large subduction events, and down-dip from such areas, in the downgoing slab. Observations are shown to be consistent with the expectation that in mature seismic gaps, as a result of interplate boundary locking in presence of sustained gravitational driving forces, at least the deeper portions of the ocean plate in the outer-rise zones are under increased compression, and the downgoing slab is under increased tension. The observational data cover two cases of closed seismic gaps, namely the region of the Chilean Valparaiso earthquake of March 3, 1985, and the earthquake of October 4, 1983. Four other cases concern still to-be-closed gaps in northern Chile and along the coast of Guatemala, and also the Kurile Islands Trench gap and the northern New Hebrides gap. It is concluded that the intermediate-term precursor, consisting of a combination of compressional outer-rise earthquake(s) and tensional intermediate-depth, intra-plate events in the downgoing slab, which mechanically signals the latter part of the earthquake cycle, could be useful in evaluating the maturity, and hence great earthquake potential of a seismic gap. 相似文献
6.
The estimation of carbon exchange between ecosystems and the atmosphere suffers unavoidable data gaps in eddy-covariance technique, especially for short-living and fast-growing croplands. In this study we developed a modified gap-filling scheme introducing a leaf area index factor as the vegetation status information based on the conventional light response function for two East-Asian cropland sites (rice and potatoes). This scheme’s performance is comparable to the conventional time window scheme, but has the advantage when the gaps are large compared to the total length of the time series. To investigate how the time binning approach performs for fast-growing croplands, we tested different widths of the time window, showing that a four-day window for the potato field and an eight-day time window for the rice field perform the best. The insufficiency of the conventional temperature binning approach was explained as well as the influence of vapor pressure deficit. We found that vapor pressure deficit plays a minor role in both the potato and the rice fields under Asian monsoon weather conditions with the exception of the early pre-monsoon growing stage of the potatoes. Consequently, we recommend using the conventional time-window scheme together with our new leaf-light response function to fill data gaps of net ecosystem exchange in fast-growing croplands. 相似文献
7.
利用地震活动图像演化动态跟踪、地震活动参数时间扫描及震群判定等目前较为成熟的地震预测方法,研究了2001年昆仑山口西8.1级地震前地震活动性异常.结果显示8.1级地震前地震活动性异常有序性明显,地震空区、地震条带、震群活动异常突出,且呈现配套特征.研究认为地震空区图像演化对揭示特大地震的孕育场有所帮助;大范围前兆震群活动是特大地震前多点应力积累、释放的前兆反应;结合地震活动参数扫描异常综合分析,特大地震前可能做出一定的中期-短期预测. 相似文献
8.
渤海地区的地震活动特征 总被引：1，自引：0，他引：1
对渤海地区３级以上地震的扫描分析表明,自１９７０年以来,该区不断出出３级地震条带或空区等特殊地震活动图像,反映了该区应力场的演化过程。同时,这些条带或空区图像的出现,与外围附近地区的中强地震发生、大区域应力场的调整有关。 相似文献
9.
中强地震平静图像已被许多研究者认为是强震前的一个典型异常指标。近期中国大陆西部2次8级地震前地震活动图像的研究认为,8级特大地震前不仅中强震出现大面积平静,而且中小地震也会出现大规模平静现象,形成地震空区。震前依据震级由大而小逐级形成配套出现的地震空区,可作为中国大陆西部8级特大地震的中短期预测与8级地震发生地区的判定的一项有实际意义的指标。 相似文献
10.
We examine ion flux dropouts detected by INTERBALL-Auroral upon traversal of the auroral zone at altitudes of ≈13 000 up to 20 000 km. These dropouts which we refer to as “gaps”, are frequently observed irrespectively of longitudinal sector and appear characteristic of INTERBALL-Auroral ion spectrograms. Whereas some of these gaps display a nearly monoenergetic character (≈12 keV), others occur at energies of a few hundreds of eV up to several keV. INTERBALL-Auroral data exhibit the former monoenergetic gap variety essentially in the evening sector. As examined in previous studies, these gaps appear related to transition from particle orbits that are connected with the magnetotail plasma source to closed orbits encircling the Earth. The latter gap variety, which spreads over several hundreds of eV to a few keV is often observed in the dayside magnetosphere. It is argued that such gaps are due to magnetospheric residence times well above the ion lifetime. This interpretation is supported by numerical orbit calculations which reveal extremely large (up to several tens of hours) times of flight in a limited energy range as a result of conflicting E × B and gradient-curvature drifts. The characteristic energies obtained numerically depend upon both longitude and latitude and are quite consistent with those measured in-situ. 相似文献
11.
12.
The hyperbolic Radon transform has a long history of applications in seismic data processing because of its ability to focus/sparsify the data in the transform domain. Recently, deconvolutive Radon transform has also been proposed with an improved time resolution which provides improved processing results. The basis functions of the (deconvolutive) Radon transform, however, are time-variant, making the classical Fourier based algorithms ineffective to carry out the required computations. A direct implementation of the associated summations in the time–space domain is also computationally expensive, thus limiting the application of the transform on large data sets. In this paper, we present a new method for fast computation of the hyperbolic (deconvolutive) Radon transform. The method is based on the recently proposed generalized Fourier slice theorem which establishes an analytic expression between the Fourier transforms associated with the data and Radon plane. This allows very fast computations of the forward and inverse transforms simply using fast Fourier transform and interpolation procedures. These canonical transforms are used within an efficient iterative method for sparse solution of (deconvolutive) Radon transform. Numerical examples from synthetic and field seismic data confirm high performance of the proposed fast algorithm for filling in the large gaps in seismic data, separating primaries from multiple reflections, and performing high-quality stretch-free stacking. 相似文献
13.
大地测量和地震观测都是地震监测预报的重要手段。大地测量是一种物理意义十分明确的观测方法，它不仅能够监测大区域、大幅度的地壳变化，而且能够监视地球的微小变化，甚至能观测到慢地震。地震观测与大地测量之间目前还存在着观测频段空间，应尽力缝合两者之间的频段空间，以推动地震预报研究。该文提出了缝合的一些设想。 相似文献
14.
Radiocarbon calibration beyond the extent of tree-ring records depends on U-series dating of fossil corals or speleothem, both of which can provide independent calendar ages. Less direct methods rely on layer counting and comparison with other well-dated records. In spite of considerable effort to provide a reliable radiocarbon calibration curve beyond 25,000 years, the majority of the data show large atmospheric radiocarbon peaks which are inconsistent both in magnitude and timing between different determinations. The results of the most recent work [Chiu, T.-C., Fairbanks, R.G., Mortlock, R.A., Bloom, A.L., 2005. Extending the radiocarbon calibration beyond 26,000 years before present using fossil corals. Quaternary Science Reviews 24 (16–17), 1797–1808], from Araki Island fossil corals, indicate a monotonic variation from about 33 to 49 ka, with no radiocarbon peaks, but with some gaps in the data. The difference between this and previous results, from fossil corals, has been attributed to selection of better-quality samples and rigorous analytical methods. However, previous results from Huon Peninsula [Yokoyama, Y., Esat, T.M., Lambeck, K., Fifield, L.K., 2000. Last ice age millennial scale climate changes recorded in Huon Peninsula corals. Radiocarbon 42 (3), 383–401; Cutler, K.B., Gray, S.C., Burr, G.S., Edwards, R.L., Taylor, F.W., Cabioch, G., Beck, J.W., Cheng, H., Moore, J., 2004. Radiocarbon calibration and comparison to 50 kyr BP with paired 14C and 230Th dating of corals from Vanuatu and Papua New Guinea. Radiocarbon 46 (3), 1127–1160] show radiocarbon peaks exclusively located within the gaps in the Araki data. The timing of the gaps are not random, but appear to be related to severe climate and sea-level variations associated with Heinrich events initiated in the North Atlantic. We propose that the Huon and Araki data sets are complementary rather than exclusive and that the absence of coral growth at Araki Island during Heinrich events presumably reflect local adverse conditions for coral growth. 相似文献
15.
The influence of cloud structure and droplet concentration on the reflectance of shortwave radiation
The effects of cloud shadowing, channelling, cloud side illumination and droplet concentration are investigated with regard to the reflection of shortwave solar radiation. Using simple geometric clouds, coupled with a Monte Carlo model the transmission properties of idealized cloud layers are found. The clouds are illuminated with direct solar radiation from above. The main conclusion reached is that the distribution of the cloud has a very large influence on the reflectivity of a cloud layer. In particular, if the cloud contains vertical gaps through the cloud layer in which the liquid water content is zero, then, smaller more numerous gaps are more influential on the radiation than fewer, larger gaps with equal cloud fraction. At very low solar zenith angles channelling of the radiation reduces the reflection expected on the basis of the percentage cloud cover. At high solar zenith angles the illumination of the cloud edges significantly increases the reflection despite the shadowing of one cloud by another when the width of the gaps is small. The impact of droplet concentration upon the reflection of cloud layers is also investigated. It is found that at low solar zenith angles where channelling is important, the lower concentrations increase the transmission. Conversely, when cloud edge illumination is dominant the cloud distribution is found to be more important for the higher concentrations. 相似文献
16.
Evaluating the functionality and streamflow impacts of explicitly modelling forest–snow interactions and canopy gaps in a distributed hydrologic model 
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下载免费PDF全文 Ning Sun Mark Wigmosta Tian Zhou Jessica Lundquist Susan Dickerson‐Lange Nicoleta Cristea 《水文研究》2018,32(13):2128-2140
Many plot‐scale studies have shown that snow‐cover dynamics in forest gaps are distinctly different from those in open and continuously forested areas, and forest gaps have the potential to alter the magnitude and timing of snowmelt. However, the watershed‐level impacts of canopy gap treatment on streamflows are largely unknown. Here, we present the first research that explicitly assesses the impact of canopy gaps on seasonal streamflows and particularly late‐season low flows at the watershed scale. To explicitly model forest–snow interactions in canopy gaps, we made major enhancements to a widely used distributed hydrologic model, distributed hydrology soil vegetation model, with a canopy gap component that represents physical processes of snowpack evolution in the forest gap separately from the surrounding forest on the subgrid scale (within a grid typically 10–150 m). The model predicted snow water equivalent using the enhanced distributed hydrology soil vegetation model showed good agreement (R2 > 0.9) with subhourly snow water equivalent measurements collected from open, forested, and canopy gap sites in Idaho, USA. Compared with the original model that does not account for interactions between gaps and surrounding forest, the enhanced model predicted notably later melt in small‐ to medium‐size canopy gaps (the ratio of gap radius (r) to canopy height (h) ≤ 1.2), and snow melt rates exhibited great sensitivity to changing gap size in medium‐size gaps (0.5 ≤ r/h ≤ 1.2). We demonstrated the watershed‐scale implications of canopy gaps on streamflow in the snow‐dominated Chiwawa watershed, WA, USA. With 24% of the watershed drainage area (about 446 km2) converted to gaps of 60 m diameter, the mean annual 7‐day low flow was increased by 19.4% (i.e., 0.37 m3/s), and the mean monthly 7‐day low flows were increased by 13.5% (i.e., 0.26 m3/s) to 40% (i.e., 1.76 m3/s) from late summer through fall. Lastly, in practical implementation of canopy gaps with the same total gap areas, a greater number of distributed small gaps can have greater potential for longer snow retention than a smaller number of large gaps. 相似文献
17.
Thomas Backhaus Rolf Altenburger sa Arrhenius Hans Blanck Michael Faust Antonio Finizio Paola Gramatica Matthias Grote Marion Junghans Wiebke Meyer Manuela Pavan Tobias Porsbring Martin Scholze Roberto Todeschini Marco Vighi Helge Walter L. Horst Grimme 《Continental Shelf Research》2003,23(17-19):1757
Freshwater and marine ecosystems are exposed to various multi-component mixtures of pollutants. Nevertheless, most ecotoxicological research and chemicals regulation focus on hazard and exposure assessment of individual substances only, the problem of chemical mixtures in the environment is ignored to a large extent. In contrast, the assessment of combination effects has a long tradition in pharmacology, where mixtures of chemicals are specifically designed to develop new products, e.g. human and veterinary drugs or agricultural and non-agricultural pesticides. In this area, two concepts are frequently used and are thought to describe fundamental relationships between single substance and mixture effects: Independent Action (Response Addition) and Concentration Addition. The question, to what extent these concepts may also be applied in an ecotoxicological and regulatory context may be considered a research topic of major importance, as the concepts would allow to make use of already existing single substance toxicity data for the predictive assessment of mixture toxicities. Two critical knowledge gaps are identified: (a) There is a lack of environmental realism, as a huge part of our current knowledge about the applicability of the concepts is restricted to artificial situations with respect to mixture composition or biological effect assessment. (b) The knowledge on what exactly is needed for using the concepts as tools for the predictive mixture toxicity assessment is insufficient. Both gaps seriously hamper the necessary, scientifically sound consideration of mixture toxicities in a regulatory context.In this paper, the two concepts will be briefly introduced, the necessity of considering the toxicities of chemical mixtures in the environment will be demonstrated and the applicability of Independent Action and Concentration Addition as tools for the prediction and assessment of mixture toxicities will be discussed. An overview of the specific aims and approaches of the BEAM project to fill in the identified knowledge gaps is given and first results are outlined. 相似文献
18.
本文使用四川台网地震目录全部资料,适当参考邻省地震目录,对于四川省从1970年下半年以来发生的15组5级以上地震(另有5组缺乏完整资料无法讨论),作 R-t 图、D-t 图寻找时间空区,并作相应的平面空区图.通过对比分析,发现6组6级以上和4组5级地震前震中附近出现空区现象.根据形成空区的变化过程可分为先扩(大)后缩(小)型和逐渐扩大的开放型两种类型.平面空区的位置和形状往往与构造展布有关.有5组5级震例,或因震前震中区小震不断,或因震中及其附近地区小震太少,看不出明显的空区.本文利用出现空区的10个震例,总结出空区参数与未来地震的震级的经验关系:M=5.50 lg Rmax-2.331.32 M=2.98 lgT+2.941.06 M=2.52lg(RmaxT)-0.510.96文中将上述结果与大竹政和的结果作了对比.空区不同变化形态可用金森博雄概括的突起点模式加以解释. 相似文献
19.
A major requirement for the assessment, development and sustainable use of water resources is the availability of good quality hydrological time series data of sufficiently long duration. However, it is not uncommon to find data that are riddled with gaps, characterized by questionable quality and short durations. Sometimes, the data are just not available. Such situations are most prevalent in developing countries and the consequence is a high degree of uncertainty in the assessed characteristics of water management schemes and ultimately its ineffectual performance. Thus dealing with these problems is an important exercise in hydrological analyses. This paper focuses on the multivariate infilling of gaps for rainfall and streamflow data in the Shire River basin in Malawi, using a self organizing map (SOM) approach, which is a form of unsupervised artificial neural networks. The results show that this approach can produce reliable estimates of hydro-meteorological data thus offering promise for reducing the uncertainties associated with the use of insufficient data for water resources assessment. 相似文献
20.
兴海6．6级地震前地震活动异常图像与序列主要特征 总被引：1，自引：1，他引：1
兴海6．6级地震异常特征典型，从背景空区、孕震空区、大面积震群活动到地震条带、前震序列，长、中、短期地震活动性异常配套。该地震序列无论从其能量释放比、震级差，还是序列参数计算均符合主震－余震型判断指标，根据全序列特征，该地震为前震－主震－余震型序列。 相似文献