Statistical modeling of ground motion relations for seismic hazard analysis   总被引：1，自引：0，他引：1  

Mathias Raschke 《Journal of Seismology》2013,17(4):1157-1182

We introduce a new approach for ground motion relations (GMR) in the probabilistic seismic hazard analysis (PSHA), being influenced by the extreme value theory of mathematical statistics. Therein, we understand a GMR as a random function. We derive mathematically the principle of area equivalence, wherein two alternative GMRs have an equivalent influence on the hazard if these GMRs have equivalent area functions. This includes local biases. An interpretation of the difference between these GMRs (an actual and a modeled one) as a random component leads to a general overestimation of residual variance and hazard. Beside this, we discuss important aspects of classical approaches and discover discrepancies with the state of the art of stochastics and statistics (model selection and significance, test of distribution assumptions, extreme value statistics). We criticize especially the assumption of logarithmic normally distributed residuals of maxima like the peak ground acceleration (PGA). The natural distribution of its individual random component (equivalent to exp(ε ₀) of Joyner and Boore, Bull Seism Soc Am 83(2):469–487, 1993) is the generalized extreme value. We show by numerical researches that the actual distribution can be hidden and a wrong distribution assumption can influence the PSHA negatively as the negligence of area equivalence does. Finally, we suggest an estimation concept for GMRs of PSHA with a regression-free variance estimation of the individual random component. We demonstrate the advantages of event-specific GMRs by analyzing data sets from the PEER strong motion database and estimate event-specific GMRs. Therein, the majority of the best models base on an anisotropic point source approach. The residual variance of logarithmized PGA is significantly smaller than in previous models. We validate the estimations for the event with the largest sample by empirical area functions, which indicate the appropriate modeling of the GMR by an anisotropic point source model. The constructed distances like the Joyner–Boore distance do not work well for event-specific GMRs. We discover also a strong relation between magnitude and the squared expectation of the PGAs being integrated in the geo-space for the event-specific GMRs. One of our secondary contributions is the simple modeling of anisotropy for a point source model.  相似文献   

Late Pleistocene and Holocene terrestrial geomorphodynamics and soil formation in northeastern Germany: a review of geochronological data     

Christoph Kappler  Knut Kaiser  Mathias Küster  Alexander Nicolay  Alexander Fülling  Oliver Bens 《自然地理学》2013,34(5):405-432

ABSTRACT

This study is based on 616 geochronological ages from aeolian and colluvial sediments as well as paleosols, representing the largest database of geochronological data from northeastern Germany available to date. Cumulative probability density functions for radiocarbon data and kernel density estimates for luminescence data were created covering the last 15 ka. The data analysis aimed at the identification of changes and their drivers in geomorphodynamics and soil formation. The ages representing aeolian activity cluster in the Late Glacial, the Early Holocene, and the Late Holocene, where the first two clusters are assumed to result mostly from climatic impact with only a minor share of human impact triggering the mobilization of aeolian sediments. The third cluster is considered to result mainly from human impact. The Late Glacial to Early Holocene activity phase is interrupted by a phase of surface stability around 11.5–12.7 ka, which is indicated by the occurrence of initial soil formations of Finow and Usselo types. Colluvial sedimentation predominantly occurred during the last 7 ka and clearly accelerated since the last 1000 a. According to the ages of specific paleosol types, related soil-forming processes started already in the Late Glacial and were completed in the Holocene.  相似文献   

Global warming and South Indian monsoon rainfall—lessons from the Mid-Miocene     

Markus Reuter  Andrea K. Kern  Mathias Harzhauser  Andreas Kroh  Werner E. Piller 《Gondwana Research》2013,23(3):1172-1177

Precipitation over India is driven by the Indian monsoon. Although changes in this atmospheric circulation are caused by the differential seasonal diabatic heating of Asia and the Indo-Pacific Ocean, it is so far unknown how global warming influences the monsoon rainfalls regionally. Herein, we present a Miocene pollen flora as the first direct proxy for monsoon over southern India during the Middle Miocene Climate Optimum. To identify climatic key parameters, such as mean annual temperature, warmest month temperature, coldest month temperature, mean annual precipitation, mean precipitation during the driest month, mean precipitation during the wettest month and mean precipitation during the warmest month the Coexistence Approach is applied. Irrespective of a ~ 3–4 °C higher global temperature during the Middle Miocene Climate Optimum, the results indicate a modern-like monsoonal precipitation pattern contrasting marine proxies which point to a strong decline of Indian monsoon in the Himalaya at this time. Therefore, the strength of monsoon rainfall in tropical India appears neither to be related to global warming nor to be linked with the atmospheric conditions over the Tibetan Plateau. For the future it implies that increased global warming does not necessarily entail changes in the South Indian monsoon rainfall.  相似文献   

Glacier mass balance variability in the Cordillera Blanca, Peru and its relationship with climate and the large-scale circulation   总被引：1，自引：0，他引：1  

Mathias Vuille  Georg Kaser  Irmgard Juen 《Global and Planetary Change》2008,62(1-2):14-28

A 41-year-long reconstructed annual mean glacier mass balance record from the Cordillera Blanca, Peru, was investigated for its climate sensitivity toward temperature, humidity and precipitation, and its links with the large-scale atmospheric circulation. On interannual timescales precipitation variability appears to be the main driver for glacier mass balance fluctuations in the Cordillera Blanca. This is corroborated by an analysis of the relationship between mass balance variations and local- to regional-scale precipitation variability. Temperature tends to enhance precipitation in driving the mass balance signal, as dry years are often characterized by warm conditions, while wet years usually coincide with cold anomalies. In some years, however, warm and wet or cold and dry conditions coincide, under which circumstances temperature minimizes or even neutralizes the effects of precipitation. Surface energy balance studies have shown that changes in atmospheric humidity significantly affect the melt rates of tropical glaciers, but the lack of long and high-quality in-situ measurements precludes a detailed quantitative assessment of its role on interannual timescales in the Cordillera Blanca. Sea surface temperature anomalies (SSTA) in the tropical Pacific exert the dominant large-scale forcing on interannual time scales, leading to negative mass balance anomalies during El Niño and above average mass balance during La Niña episodes. In general the teleconnection mechanism linking ENSO with glacier mass balance is similar to what has previously been described for the Bolivian Altiplano region. Changes in the upper-tropospheric zonal flow aloft associated with ENSO conditions determine the amount of snowfall during the wet season and thereby significantly affect the glacier mass balance. Because this teleconnection mechanism is spatially unstable and oscillates latitudinally along the subtropical Andes, it affects the Cordillera Blanca in most, but not all years. The relationship between ENSO and glacier mass balance is therefore characterized by occasional ‘break downs’, more common since the mid-1970's, when El Niño years with above average mass balance and La Niña events with negative mass balance have been observed.  相似文献   

Fish remains as a source to reconstruct long-term changes of fish communities in the Austrian and Hungarian Danube     

Alfred Galik  Gertrud Haidvogl  Laszlo Bartosiewicz  Gabor Guti  Mathias Jungwirth 《Aquatic Sciences - Research Across Boundaries》2015,77(3):337-354

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Paleotemperature reconstruction in tropical Africa using fossil Chironomidae (Insecta: Diptera)     

Hilde Eggermont  Oliver Heiri  James Russell  Mathias Vuille  Leen Audenaert  Dirk Verschuren 《Journal of Paleolimnology》2010,43(3):413-435

Fossil assemblages of chironomid larvae (non-biting midges) preserved in lake sediments are well-established paleothermometers in north-temperate and boreal regions, but their potential for temperature reconstruction in tropical regions has never before been assessed. In this study, we surveyed sub-fossil chironomid assemblages in the surface sediments of 65 lakes and permanent pools in southwestern Uganda (including the Rwenzori Mountains) and central and southern Kenya (including Mount Kenya) to document the modern distribution of African chironomid communities along the regional temperature gradient covered by lakes situated between 489 and 4,575 m above sea level (a.s.l). We then combined these faunal data with linked Surface-Water Temperature (SWTemp: range 2.1–28.1°C) and Mean Annual Air Temperature (MATemp: range 1.1–24.9°C) data to develop inference models for quantitative paleotemperature reconstruction. Here we compare and discuss the performance of models based on different numerical techniques [weighted-averaging (WA), weighted-averaging partial-least-squares (WA-PLS) and a weighted modern analogue technique (WMAT)], and on subsets of lakes with varying gradient lengths of temperature and other environmental variables. All inference models calibrated against MATemp have a high coefficient of determination ( r_\textjack² r_{\text{jack}}^{2}  = 0.81–0.97), low maximum bias (0.84–2.59°C), and low root-mean-squared error of prediction (RMSEP = 0.61–1.50°C). The statistical power of SWTemp models is generally weaker ( r_\textjack² r_{\text{jack}}^{2}  = 0.77–0.95; maximum bias 1.55–3.73°C; RMSEP = 1.39–1.98°C), likely because the surface-water temperature data are spot measurements failing to catch significant daily and seasonal variation. Models based on calibration over the full temperature gradient suffer slightly from the limited number of study sites at intermediate elevation (2,000–3,000 m), and from the presence of morphologically indistinguishable but ecologically distinct taxa. Calibration confined to high-elevation sites (>3,000 m) has poorer error statistics, but is less susceptible to biogeographical and taxonomic complexities. Our results compare favourably with chironomid-based temperature inferences in temperate regions, indicating that chironomid-based temperature reconstruction in tropical Africa can be achieved.  相似文献   

Comment on “Revision of the age of the Qom Formation in the Central Iran Basin,Iran” by Zhu et al. (Journal of Asian Earth Sciences, 2007, vol. 29, 715–721)     

Markus Reuter  Werner E. Piller  Mathias Harzhauser 《Journal of Asian Earth Sciences》2009,34(5):699-701

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Boundary layer characteristics and turbulent exchange mechanisms in highly complex terrain   总被引：2，自引：0，他引：2  

Mathias W. Rotach  Marco Andretta  Pierluigi Calanca  Andreas P. Weigel  Alexandra Weiss 《Acta Geophysica》2008,56(1):194-219

The Mesoscale Alpine Programme’s Riviera project investigated the turbulence structure and related exchange processes in an Alpine valley by combining a detailed experimental campaign with high-resolution numerical modelling. The present contribution reviews published material on the Riviera Valley’s boundary layer structure and discusses new material on the near-surface turbulence structure. The general conclusion of the project is that despite the large spatial variability of turbulence characteristics and the crucial influence of topography at all scales, the physical processes can accurately be understood and modelled. Nevertheless, many of the “text book characteristics” like the interaction between the valley and slope wind systems or the erosion of the nocturnal valley inversion need reconsideration, at least for small non-ideal valleys like the Riviera Valley. The project has identified new areas of research such as post-processing methods for turbulence variables in complex terrain and new approaches for the surface energy balance when advection is non-negligible. The exchange of moisture and heat between the valley atmosphere and the free troposphere is dominated by local “secondary” circulations due to the curvature of the valley axis. Because many curved valleys exist, and operational models still have rather poor resolution, parameterization of these processes may be required.  相似文献   

A novel model and estimation method for the individual random component of earthquake ground-motion relations     

Mathias Raschke 《Journal of Seismology》2017,21(1):21-34

In this paper, I introduce a novel approach to modelling the individual random component (also called the intra-event uncertainty) of a ground-motion relation (GMR), as well as a novel approach to estimating the corresponding parameters. In essence, I contend that the individual random component is reproduced adequately by a simple stochastic mechanism of random impulses acting in the horizontal plane, with random directions. The random number of impulses was Poisson distributed. The parameters of the model were estimated according to a proposal by Raschke J Seismol 17(4):1157–1182, (2013a), with the sample of random difference ξ?=?ln(Y ₁ )-ln(Y ₂ ), in which Y ₁ and Y ₂ are the horizontal components of local ground-motion intensity. Any GMR element was eliminated by subtraction, except the individual random components. In the estimation procedure, the distribution of difference ξ was approximated by combining a large Monte Carlo simulated sample and Kernel smoothing. The estimated model satisfactorily fitted the difference ξ of the sample of peak ground accelerations, and the variance of the individual random components was considerably smaller than that of conventional GMRs. In addition, the dependence of variance on the epicentre distance was considered; however, a dependence of variance on the magnitude was not detected. Finally, the influence of the novel model and the corresponding approximations on PSHA was researched. The applied approximations of distribution of the individual random component were satisfactory for the researched example of PSHA.  相似文献   

Wave Propagation in Pulsating Stars     

P. Mathias 《Astrophysics and Space Science》1998,260(1-2):131-134

Lissajous diagrams are used to detect phase lags between radial velocity curves associated with different ions. Present in many kind of variable stars, this effect provides an important tool to study the atmosphere dynamics. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献