Temporal correlations and clustering of landslides     

Annette Witt  Bruce D. Malamud  Mauro Rossi  Fausto Guzzetti  Silvia Peruccacci 《地球表面变化过程与地形》2010,35(10):1138-1156

This paper examines temporal correlations and temporal clustering of a proxy historical landslide time series, 2255 reported landslides 1951–2002, for an area in the Emilia‐Romagna Region, Italy. Landslide intensity is measured by the number of reported landslides in a day (D_L) and in an ‘event’ (S_event) of consecutive days with landsliding. The non‐zero values in both time series D_L and S_event are unequally spaced in time, and have heavy‐tailed frequency‐size distributions. To examine temporal correlations, we use power‐spectral analysis (Lomb periodogram) and surrogate data analysis, confronting our original D_L and S_event time series with 1000 shuffled (uncorrelated) versions. We conclude that the landslide intensity series D_L has strong temporal correlations and S_event has likely temporal correlations. To examine temporal clustering in D_L and S_event, we consider extremes over different landslide intensity thresholds. We first examine the statistical distribution of interextreme occurrence times, τ, and find Weibull distributions with parameter γ << 1·0 [D_L] and γ < 1·0 [S_event]; thus D_L and S_event each have temporal correlations, but S_event to a lesser degree. We next examine correlations between successive interextreme occurrence times, τ. Using autocorrelation analysis applied to τ, combined with surrogate data analysis, we find for D_L linear correlations in τ, but for S_event inconclusive results. However, using Kendall's rank correlation analysis we find for both D_L and S_event the series of τ are strongly correlated. Finally, we apply Fano Factor analysis, finding for both D_L and S_event the timings of extremes over a given threshold exhibit a fractal structure and are clustered in time. In this paper, we provide a framework for examining time series where the non‐zero values are strongly unequally spaced and heavy‐tailed, particularly important in the Earth Sciences due to their common occurrence, and find that landslide intensity time series exhibit temporal correlations and clustering. Many landslide models currently are designed under the assumption that landslides are uncorrelated in time, which we show is false. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Whole-stream metabolism in nutrient-poor calcareous streams on Öland,Sweden     

Anette B. Alnoee  Tenna Riis  Mikkel R. Andersen  Annette Baattrup-Pedersen  Kaj Sand-Jensen 《Aquatic Sciences - Research Across Boundaries》2015,77(2):207-219

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绿色杜氏藻被膜泡囊的超微结构研究   总被引：3，自引：0，他引：3  

黄晓航  张小庆  吴超元  Alfsen Annette 《海洋与湖沼》1998,29(6):565-569

于１９９０年５月－１９９１年５月,运用透射电镜观察绿色杜氏藻,对该氏藻被膜泡囊的形态结构及其在细胞内的分布和形成过程进行研究。观察表明,绿色杜氏藻细胞的高尔基体和细胞膜有许多大小不等的被膜泡囊;这些被膜泡囊由泡囊及其表面的网状结构构成,其直径在４５－１２０ｎｍ之间;在细胞膜附近的被膜泡囊直径较大;在高尔基体和细胞膜上还观察到被膜泡囊的形成过程。  相似文献   

Significance of an In Vivo Genotoxicity Test for Surface Waters Is Increased when the Physiological Characteristics of the Test Organism (Bivalvia: Mollusca) Are Taken into Account?     

M. Kramer  I. Hübner 《洁净——土壤、空气、水》2000,28(2):83-91

The alkaline filter elution assay using the gills of the freshwater clam species Corbicula fluminea detects breaks in single‐stranded DNA and is thus a good method for determining the genotoxic potential of surface waters. In attempting to standardize the procedure, a wide range of factors which could have an influence on the uptake of genotoxic substances by the exposed clams were studied. The most important parameters of the static exposure in relation to the rate of filtration by the animals turned out to be the temperature, the volume of the water, and the exposure time. Differences in body size and in the amount of suspended particles in surface waters did not play a significant role. The results demonstrate that the in vivo test system can be quite sensitive and its results reproducible when the relevant species‐specific characteristics of the test organisms are brought into consideration, even if the test organism belongs to a biologically more advanced group. A clear dose‐response relationship to the reference substances 4‐nitroquinoline‐1‐oxide (NQO) and N‐methyl‐N‐nitro‐N‐nitrosoguanidine (MNNG) can be observed even after a short exposure time of between four and twenty hours. No genotoxic effects were observed when using this method on surface waters from the area of Cologne (including water from the Rhine River and within the protection zone 2 of the Cologne waterworks).  相似文献   

Tsunami detection by high-frequency radar in British Columbia: performance assessment of the time-correlation algorithm for synthetic and real events     

Charles-Antoine Guérin  Stéphan T. Grilli  Patrick Moran  Annette R. Grilli  Tania L. Insua 《Ocean Dynamics》2018,68(4-5):423-438

The authors recently proposed a new method for detecting tsunamis using high-frequency (HF) radar observations, referred to as “time-correlation algorithm” (TCA; Grilli et al. Pure Appl Geophys 173(12):3895–3934, 2016a, 174(1): 3003–3028, 2017). Unlike standard algorithms that detect surface current patterns, the TCA is based on analyzing space-time correlations of radar signal time series in pairs of radar cells, which does not require inverting radial surface currents. This was done by calculating a contrast function, which quantifies the change in pattern of the mean correlation between pairs of neighboring cells upon tsunami arrival, with respect to a reference correlation computed in the recent past. In earlier work, the TCA was successfully validated based on realistic numerical simulations of both the radar signal and tsunami wave trains. Here, this algorithm is adapted to apply to actual data from a HF radar installed in Tofino, BC, for three test cases: (1) a simulated far-field tsunami generated in the Semidi Subduction Zone in the Aleutian Arc; (2) a simulated near-field tsunami from a submarine mass failure on the continental slope off of Tofino; and (3) an event believed to be a meteotsunami, which occurred on October 14th, 2016, off of the Pacific West Coast and was measured by the radar. In the first two cases, the synthetic tsunami signal is superimposed onto the radar signal by way of a current memory term; in the third case, the tsunami signature is present within the radar data. In light of these test cases, we develop a detection methodology based on the TCA, using a correlation contrast function, and show that in all three cases the algorithm is able to trigger a timely early warning.  相似文献   

Evidence for alignment of the rotation and velocity vectors in pulsars – II. Further data and emission heights     

Simon Johnston  M. Kramer  A. Karastergiou  G. Hobbs  S. Ord  J. Wallman 《Monthly notices of the Royal Astronomical Society》2007,381(4):1625-1637

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The Parkes Multibeam Pulsar Survey – II. Discovery and timing of 120 pulsars     

D. J. Morris  G. Hobbs  A. G. Lyne  I. H. Stairs  F. Camilo  R. N. Manchester  A. Possenti  J. F. Bell  V. M. Kaspi  N. D' Amico  N. P. F. McKay  F. Crawford  M. Kramer 《Monthly notices of the Royal Astronomical Society》2002,335(2):275-290

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Invertebrate p53-like mRNA isoforms are differentially expressed in mussel haemic neoplasia     

Muttray AF  Schulte PM  Baldwin SA 《Marine environmental research》2008,66(4):412-421

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Velocity interpolation and streamline tracing on irregular geometries     

Runhild A. Klausen  Atgeirr F. Rasmussen  Annette F. Stephansen 《Computational Geosciences》2012,16(2):261-276

Streamline tracing on irregular grids requires reliable interpolation of velocity fields. We propose a new method for direct streamline tracing on polygon and polytope cells. While some numerical methods provide a basis function that can be used for interpolation, other methods provide only the fluxes at the faces of the elements. We introduce the concept of full- and raw-field methods. Full-field methods have built-in interpolation but are often not defined on general grids such as polygonal and polyhedral grids which we examine here. Also, reliability issues may arise on non-simplicial meshes in terms of not being able to reproduce constant velocity fields. We propose an interpolation in H(div) and H(curl) valid on general grids that is based on barycentric coordinates and that reproduces uniform flow. The interpolation can be used to compute the streamline directly on the complex cell geometry. The method generalizes to convex polytopes in 3D, with a restriction on the polytope topology near corners that is shown to be satisfied by several popular grid types. Numerical results confirm that the method is applicable to general grids and preserves uniform flow.  相似文献   

Semi-analytical solutions for stream–aquifer interactions under triangular stream-stage variations and its application to study urbanization impacts in an ungaged watershed of south Texas     

E. Annette Hernandez  Venkatesh Uddameri 《Environmental Earth Sciences》2014,71(6):2547-2557

Simple yet physically based models to evaluate stream–aquifer interactions during a flooding event subject to triangular stream stage variation were developed in this study. The results from the developed models were compared with other analytical and numerical solutions and noted to be very accurate. The study fills an important gap with regard to available analytical and semi-analytical solutions for modeling stream–aquifer interactions, which can be used for evaluating numerical codes. In particular, the developed models are very useful to obtain preliminary insights with regard to bank storage in ungaged watersheds as required for watershed management and planning studies in rapidly urbanizing watersheds. The utility of the model is illustrated by applying it to study the effects of urbanization on stream–aquifer interactions in the Arroyo Colorado River Watershed along the US–Mexico border region. The results indicate that increased urbanization reduces the amount of influx into the banks. The reduction in flood passage time was noted to have a greater impact than the associated rise in stage. The presence of a semi-permeable barrier was seen to mask the effects of urbanization. The model results also implicitly highlight the importance of how water quality variations caused due to urbanization can affect stream–aquifer interactions.  相似文献