Simultaneous response of high-frequency geoacoustic emission and atmospheric electric field to strain of near-surface sedimentary rocks

During the period of October 1–18, 2009, 41 km southwest of Petropavlovsk-Kamchatsky, in the intersection zone of tectonic faults of various orders, simultaneous recording of the geoacoustic emission, gradient of the atmospheric electric field’s potential, strains of the Earth’s surface, atmospheric pressure, wind speed, and rain intensity was made. It was found for the first time that anomalous disturbances of high-frequency geoacoustic emission and atmospheric electric field near the Earth’s surface originate as a simultaneous response to extension of near-surface sedimentary rocks. In the case of compression, only disturbances of geoacoustic emission occur. Anomalies were recorded under quiet weather conditions and with rocks strains being two orders greater than those of tidal ones.     

Numerical hindcast of extreme waves

The cyclone wave parameters are predicted using Young’s parametric hurricane wave prediction model. The input cyclone tracks for this work are obtained from Fleet Naval Meteorology and Oceanography Center, USA. Extreme value analysis is carried out to obtain the wave heights and periods for 1 in 5, 10, 50 and 100 years return periods, respectively. The deep-water hindcast wave corresponding to 100 years from probable directions are allowed to propagate to Visakhapatnam coastal waters using nearshore spectral wind-wave mode. The offshore wave height for one in 100-year return period is 11.9 m, and the corresponding nearshore wave height at 10-m water depth varies between 4.6 and 5.6 m depending on the directional spreading. Weibull distribution is chosen to fit the 24 cyclonic data sets over a total period of 30 years (September 1972 to November 2002). This paper demonstrates usefulness of Young’s wave model for deep-water extreme wave hindcasting. Further, the results of the present study would be highly useful for assessing the design wave height for Visakhapatnam coast.     

Estimation of Vertical Continuous Stochastic Parameters from Seismic Reflection Data

This paper presents a scheme to invert reflected seismic wave fields for vertical spatial statistics of the Earth’s continuous stochastic velocity distribution. The forward model is based on a single scattering theory, where a seismogram is modeled as a convolution of a source wavelet and stochastic reflectivity, which obeys a von Kármán autocorrelation function. Tests with synthetic data indicate that the method presented here recovers vertical characteristic length from seismic reflection data that is similar to that of the original velocity model; however, the inversion does not reliably recover the Hurst exponent, ν. The input wavelet’s power spectrum is a free parameter in the inversion and is estimated as well, but is band-limited relative to the original source wavelet. Noise degrades the quality of the estimates of the stochastic parameters such that the recovered stochastic parameters are biased according to the power spectrum of the noise.     

Impact of various synthetic vortices on cyclone track prediction

Sensitivity experiments are conducted for three cases of cyclones for investigating the impact of different vortex initialization schemes on the structure and track prediction of the cyclone using India Meteorological Department’s Limited Area Model. The surface wind and pressure profiles generated using Holland and Rankine initialization schemes differ from each other. These different generated profiles are compared with the actual data and the root mean square error (RMSE) was calculated between them. In case of the Holland vortex, ‘b’ is found to be equal to 1.5 and 2.0 respectively for two cases of very severe cyclonic storms in the Arabian Sea, namely 6–10 June 1998 and 16–20 May 1999 and 2.25 for the severe cyclonic storm in the Bay of Bengal. The ‘α’ parameter in Rankine’s scheme was found to be 0.5 for two cases and 0.4 for the third system. This shows that cyclones differ even if they attain the same intensity. The values of these parameters i.e. ‘b’ and ‘α’ are used for generating the synthetic wind data for individual cyclones and the same is used in the data assimilation system. The analysis and forecast generated for the above cases using the Holland scheme show that the simulated structure has characteristics closer to the actual storm; however, the Rankine scheme shows a weaker circulation. The mean track error for three cases in the Holland scheme is 93, 149, 257 and 307 km in 12-, 24-, 36- and 48-h forecast. The mean track errors for the Rankine scheme are 152, 274, 345 and 327 km, respectively, for the same period.     

Relationship of high-frequency geoacoustic emission and electric field in the atmosphere in seismotectonic process

In July–October 2006 and 2007, combined measurements of geoacoustic emission in the range of 2.0–6.5 kHz, the electric field in the atmosphere near the ground, and meteorological values were carried out in Kamchatka. Using the nonparametric method of Spearman’s correlation analysis, the relationship between their average hourly values was examined. After excluding results of bad weather (rain, strong and moderate wind, low atmospheric pressure), a highly important negative relation between disturbances in geoacoustic emission and the electric field were detected. Most probably, it was caused by amplification of the strain of near-surface sedimentary rocks at the observation point during a seismotectonic process. The revealed relation is evidence for another manifestation of the lithosphere’s influence on surface atmosphere in a seismoactive region.     

A direct inversion scheme for deep resistivity sounding data using artificial neural networks

Initialization of model parameters is crucial in the conventional 1D inversion of DC electrical data, since a poor guess may result in undesired parameter estimations. In the present work, we investigate the performance of neural networks in the direct inversion of DC sounding data, without the need ofa priori information. We introduce a two-step network approach where the first network identifies the curve type, followed by the model parameter estimation using the second network. This approach provides the flexibility to accommodate all the characteristic sounding curve types with a wide range of resistivity and thickness. Here we realize a three layer feed-forward neural network with fast back propagation learning algorithms performing well. The basic data sets for training and testing were simulated on the basis of available deep resistivity sounding (DRS) data from the crystalline terrains of south India. The optimum network parameters and performance were decided as a function of the testing error convergence with respect to the network training error. On adequate training, the final weights simulate faithfully to recover resistivity and thickness on new data. The small discrepancies noticed, however, are well within the resolvability of resistivity sounding curve interpretations.     

基于RNN模型的坝体和岩基区间参数反演方法研究

针对混凝土大坝坝体和岩基参数的区间不确定性,构造具有区间分析功能的RNN（粗糙神经网络）模型,并运用该模型反演坝体和岩基区间参数值。应用区间有限元对结构进行正分析,根据区间参数反演的需要选取相应的区间学习样本,利用RNN模型对样本进行模式学习直至网络收敛,最后通过网络回想和反归一法得到坝体和岩基力学参数的区间值。研究结果表明,该方法可用于反演混凝土坝坝体和岩基区间力学参数,反演得到的区间参数值是合理的。此外,基于RNN模型的区间参数反演方法经过一定的拓展和改进,理论上可应用于反演其他类型的区间参数。     

Residual and Fully Softened Strength Evaluation of Soils using Artificial Neural Networks

A backpropagation artificial neural network (ANN) model is developed to predict the secant friction angle of residual and fully softened soils, using data reported by Stark et al. (J Geotech Geoenviron Eng ASCE 131:575–588, 2005). In the ANN model, index properties such as liquid limit, plastic limit, activity, clay fraction and effective normal stress are used as input variables while secant residual friction angle is used as output variable. The model is verified using data that were not used for model training and testing. The results also indicate that the secant residual friction angle of cohesive soils can be predicted quite accurately using liquid limit, clay fraction and effective normal stress as input variables with R ² = 0.93. The sensitivity analysis results indicate that plastic limit and activity have no appreciable effect on ANN predicted secant friction angles. The secant friction angle predictions of the ANN model were also compared with those of Stark’s et al. (2005) curves and the empirical formulas suggested for the same data sets by Wright (Evaluation of soil shear strengths for slope and retaining wall stability with emphasis on high plasticity clays, 2005). The comparison shows that the ANN model predictions are very close to those suggested by the Stark et al. (2005) curves but much better than the prediction of Wright’s (2005) empirical equations. The results also show that ANN is an alternative powerful tool to predict the secant friction angle of soils.     

Lemniscate representation for inversion of gravity and magnetic data through nonlocal optimization

A method of representing surfaces and volumes by a set of geometric points and a small set of auxiliary parameters, based on generalization of Bernoulli’s notion of lemniscates is introduced. It provides for easy generation and modification of surfaces and volumes, which could be connected, disjoint or even with very irregular boundaries. This allows solving geophysical inversion problems, without constraining the anomalous volumes to some ideal or simple forms. This is illustrated by the example of joint inversion of gravity and magnetic data sets attributable to two-dimensional anomalous bodies. A nonlocal optimization algorithm calledsegmented Hamming scan is used for inversion. Comparison with nonlinear least-squares algorithm shows the advantages of the chosen approach. The concepts ofdesideratal andprocedural detours are illustrated.     

Disentangling Shallow and Deep Processes Causing Surface Movement

Understanding and predicting surface movement is important both technically and for social reasons. The shallow processes contributing to subsidence include construction works, peat oxidation, clay compaction, and groundwater withdrawal; deep causes are hydrocarbon and salt production. We describe an inversion procedure we have devised to disentangle the deep and shallow causes of surface movement. It employs a Bayesian inversion scheme, using forward models and other ‘a priori’ information about shallow and deep compaction. Parameter estimation thus takes place at two different depths, thereby disentangling the deep and shallow compaction processes responsible for surface movement. The uncertainty in the surface measurements and ‘a priori’ estimates is naturally incorporated. Furthermore, spatial and temporal correlations can be taken into account through inclusion of the covariance matrix. The inversion scheme is demonstrated for two synthetic cases. The first combines a compacting gas field and a compacting shallow peat layer. We demonstrate that assumptions on the shape of the subsidence bowl are not necessary. We also show how neglecting either deep or shallow causes of subsidence can produce spurious results. The advantage of using the ‘a priori’ estimates of the compaction and the covariance matrix obtained by Monte Carlo simulations is demonstrated with a second synthetic example involving two polders and different depths of their water table. A robust solution is obtained for each polder unit, while a simpler (and faster) ‘a priori’ estimate based on the expected average clay thickness fails to reproduce the actual compaction. Monte Carlo simulations can also be applied to compaction in depleting gas reservoirs. Information on spatial correlations is often available, even when the absolute values of the ‘a priori’ compaction data are quite uncertain. Explicitly incorporating such ‘a priori’ known spatial correlations improves the result significantly.     

A mathematical framework for earth science data provenance tracing

This paper identifies three distinct data production paradigms for Earth science data, each having its own versioning structure:

Thermodynamic properties and equation of state of fcc aluminum and bcc iron, derived from a lattice vibrational method

We use a lattice vibrational technique to derive thermophysical and thermochemical properties of the pure elements aluminum and iron in pressure–temperature space. This semi-empirical technique is based on either the Mie–Grüneisen–Debye (MGD) approach or an extension of Kieffer’s model to incorporate details of the phonon spectrum. It includes treatment of intrinsic anharmonicity, electronic effects based on the free electron gas model, and magnetic effects based on the Calphad approach. We show that Keane’s equation of state for the static lattice is better suitable to represent thermodynamic data for aluminum from 1 bar to pressures in the multi-megabar region relative to Vinet’s universal and the Birch–Murnaghan equation of state. It appears that the MGD and Mie–Grüneisen–Kieffer approach produce similar results, but that the last one better represents heat capacity below room temperature. For iron we show that the high temperature behavior of thermal expansivity can be explained within the Calphad approach by a pressure-dependent Curie temperature with a slope between –1 and 0 K/GPa.     

Ancient eco-technology of qanats for engineering a sustainable water supply in the Mediterranean Island of Cyprus

The qanat water supply technology, which gravity drains mountain aquifers into valleys, is considered as a culturally appropriate and ecological sustainable design to meet northern Cyprus’ drinking water development needs. This research estimates the boundary and water budget for the proposed qanat recharge area of 370 km², which is in the upper elevations of the limestone dominated Five Finger Mountain Range. The mountain drainage was analyzed using global elevation data from the Shuttle Ranging Topography Mission (SRTM). Efforts to use Tropical Rainfall Measuring Mission (TRMM) annual precipitation for water budget inputs failed due to extreme error when tested against 10–30 years of meteorological station data; TRMM under-estimated depths on the narrow mountain peaks. Gage records, while few in number, were area averaged to set average annual precipitation inputs at 530 mm year⁻¹. Evaporation was estimated using a complementary relationship areal evapotranspiration (CRAE) model, setting average atmospheric outputs at 221 mm year⁻¹. Recharge to the qanat aquifer was set by subtracting evaporation from precipitation, and then allocating 50% of the remaining water to environmental services. At 25% development, the qanat system supplies 14 mm³ year⁻¹ of water, meeting the drinking water deficit of 13 mm³.     

Unraveling reservoir compaction parameters through the inversion of surface subsidence observations

In an attempt to derive more information on the parameters driving compaction, this paper explores the feasibility of a method utilizing data on compaction-induced subsidence. We commence by using a Bayesian inversion scheme to infer the reservoir compaction from subsidence observations. The method’s strength is that it incorporates all the spatial and temporal correlations imposed by the geology and reservoir data. Subsequently, the contributions of the driving parameters are unravelled. We apply the approach to a synthetic model of an upscaled gas field in the northern Netherlands. We find that the inversion procedure leads to coupling between the driving parameters, as it does not discriminate between the individual contributions to the compaction. The provisional assessment of the parameter values shows that, in order to identify adequate estimate ranges for the driving parameters, a proper parameter estimation procedure (Markov Chain Monte Carlo, data assimilation) is necessary.     

Influence of Stochastic Discontinuity Network Parameters on the Formation of Removable Blocks in Rock Slopes

Summary  We study the effects of discontinuity network parameters on the formation of removable wedges in rock slopes. Discontinuities are simulated using the Poisson disk model, and removable wedges are identified using block theory. The formation of removable wedges of different sizes is assumed to follow a Poisson process. Poisson regression and Monte Carlo simulation are then used to identify statistically relevant parameters of the model, and to study the effects that variations in their values have on formation of removable blocks. The sensitivity of the results as a function of the mean orientations of the discontinuity sets forming the blocks is also studied by means of a parametric study. The volumetric intensity of discontinuities in the rock mass is found to have a significant impact on the computed estimates of removable block formation. As predicted by theory, our results indicate that, everything else being equal, the expected rate of formation of removable wedges is proportional to the square of the intensity measure. Estimates are also sensitive to changes in discontinuity size, especially in cases in which discontinuities are smaller than one to two times the height of the slope. The interaction between the mean size of discontinuities and the coefficient of variation of discontinuity sizes is found to be significant as well. Finally, results of our sensitivity analysis suggest that the orientation of discontinuity sets significantly affects the rate of formation of removable blocks in rock slopes. Author’s address: Dr. Rafael Jimenez-Rodriguez, ETS Ing. de Caminos, Canales y Puertos. Universidad Politecnica de Madrid, Spain     

Identifying China’s leading world city: a network approach

This paper reports our research on China’s world cities. Formal network analysis of air passenger linkages for recent years among China’s most populous cities and among many of the world’s largest cities allows us to identify the country’s leading world city from among the leading Mainland candidates, Beijing, Shanghai and Guangzhou. We theorize our findings about China’s world cities in relation to both global forces (and China’s increasing entanglement with them) and the policies and actions of the national state. We examine the national and global urban network through a longitudinal, two-level analysis of airline passenger travel for four time points between about 1990 and 2005. We show that Beijing was China’s leading world city at the beginning of the time period, a status it lost nationally in as early as 1995, and then globally 10 years later. On the other hand Shanghai became China’s leading world city, and it acquired this status first nationally in 2000, and then globally in 2005. The changing status of the Chinese capital corresponds to the country’s increasing involvement with the capitalist world economy. Shanghai’s ascendance as the leading world city in China may indicate that global forces have come to play an increasingly important role relative to that of the developmental state.

基于逐减随机震源采样法的频率域二维黏滞声波方程全波形反演

全波形反演方法利用叠前地震波场的运动学和动力学信息重建地下速度结构,具有揭示复杂地质背景下构造与岩性细节信息的潜力。然而,巨大的计算量是阻碍其发展的一个瓶颈问题。为此,研究者们提出了震源编码技术来减少计算量,但是此方法在模型更新过程中会引进随机串扰噪声,降低反演结果准确性。所以,在保证计算精度的情况下,本文提出了采用逐减随机震源采样的方法来高效计算全波形反演问题。笔者将此方法应用于频率域二维黏滞声波波动方程全波形反演,开始了在频率域进行随机震源采样类方法的研究,计算过程中共使用了依次增大的8个频率段;并应用Overthrust模型来验证此类随机震源采样法的正确性。实验结果表明：基于逐减随机震源采样法的反演结果与实际Overthrust模型的拟合误差为0.065 65,而应用基于全部震源的全波形反演方法得到的反演结果与实际Overthrust模型的拟合误差为0.064 64,两者差别不大;但计算用时由740 min减少到291.2 min,即计算效率提高了2.54倍。为了更好地确定方法的有效性,将其应用于Marmousi模型进行试算。模型试算结果表明：基于逐减随机震源和基于全部震源得到的反演结果与实际Marmousi模型的拟合误差分别为0.080 12和0.078 97,相差不大;但计算用时由1 218.9 min减少到274.4 min,计算效率提高了4.44倍。综上,在保证反演精度的情况下,基于逐减随机震源采样法的频率域全波形反演方法大大减少了计算量,具有不可替代的计算优势,并且没有引进随机串扰噪声。     

Rank statistical analysis of nickel sulphide resources of the Norseman-Wiluna Greenstone Belt,Western Australia

Estimating the undiscovered mineral resources of a terrane is a challenging, yet essential, task in mineral exploration. We apply Zipf’s law rank statistical analysis to estimate the undiscovered nickel sulphide resources in the Norseman-Wiluna Greenstone Belt, Western Australia. The analysis suggests that about 3.0 to 10.0 Mt of nickel sulphide resources are yet to be discovered in this belt, compared to the currently known total nickel sulphide endowment of 10.8 Mt. This undiscovered nickel sulphide endowment is likely to be hosted by incompletely delineated deposits and undiscovered deposits in less explored komatiites in the belt. Using the more detailed data subset of the Kambalda domain, this study manipulates Zipf’s law to estimate the sizes of undiscovered deposits, in addition to the domain’s total nickel sulphide endowment estimate. Importantly, regression analysis shows that the gradient of the line of best fit through the logarithmic rank-size plot for the detailed Kambalda data subset is −1. This gradient, which is the key Zipf’s law constant k, has the value of −0.92 for the Norseman-Wiluna Greenstone Belt which is collectively less mature than the Kambalda domain. This result corroborates the use of k = −1 in Zipf’s law predictive analyses of mineral resources for deposit populations for which the value of k = −1 has not yet been attained due to exploration immaturity.     

Overbank block-and-ash flow deposits and the impact of valley-derived, unconfined flows on populated areas at Merapi volcano, Java, Indonesia

Merapi, an andesitic volcanic complex in Central Java, is one of the most frequently erupting volcanoes in Indonesia and poses a permanent threat to the surrounding population of over 1 million people. With frequently recurring volcanic activity, the sixty or so reported eruptions since the mid-1500s have caused ~7,000 fatalities and destroyed numerous villages in the region. In June 2006, an eruption affected the densely populated area on the volcano’s southern and south-eastern flanks for the first time in almost a century. The resultant block-and-ash flows (BAFs) travelled down an incised river valley (Kali Gendol) to a distance of 7 km from the source, breaking out of the main channel at four main locations. Unconfined (overbank) BAFs were generated, which covered the interfluve regions on either side of the main valley and buried buildings and other infrastructure features in the village of Kaliadem, situated on the western bank of the Gendol valley ~5 km from the summit of Merapi. Using traditional volcanological field-based methods and non-invasive, high-resolution ground-penetrating radar techniques, the morphology and internal architecture of these overbank deposits were studied in detail in order to evaluate the destructive impact of these flows in a local context. The results show that complex, local-scale variations in flow dynamics and deposit architectures are apparent and that BAFs are capable of transporting significant numbers of large blocks (>1–2 m) out of the valley confines. We propose a conceptual model for the escape of these channelised BAFs onto the interfluvial terrace at Kaliadem and show, through a stratigraphic analysis of the pyroclastic successions underlying the village and adjacent areas on the volcano’s southern flank, that the area has been affected repeatedly by overbank BAFs and explosive eruptions over the past few 100 years (and more).     

Dempster–Shafer Theory Applied to Uncertainty Surrounding Permeability

Typically, if uncertainty in subsurface parameters is addressed, it is done so using probability theory. Probability theory is capable of only handling one of the two types of uncertainty (aleatory), hence epistemic uncertainty is neglected. Dempster–Shafer evidence theory (DST) is an approach that allows analysis of both epistemic and aleatory uncertainty. In this paper, DST combination rules are used to combine measured field data on permeability, along with the expert opinions of hydrogeologists (subjective information) to examine uncertainty. Dempster’s rule of combination is chosen as the combination rule of choice primarily due to the theoretical development that exists and the simplicity of the data. Since Dempster’s rule does have some criticisms, two other combination rules (Yager’s rule and the Hau–Kashyap method) were examined which attempt to correct the problems that can be encountered using Dempster’s rule. With the particular data sets used here, there was not a clear superior combination rule. Dempster’s rule appears to suffice when the conflict amongst the evidence is low.