Publication year: 2009
Source: Computers & Geosciences, In Press, Accepted Manuscript, Available online 14 November 2009
Hussein, Mustapha , Roussos, Dimitrakopoulos

Spatially distributed natural phenomena represent complex non-linear and non-Gaussian systems. Currently, their spatial distributions are typically studied using second-order spatial statistical models, which are limiting considering the spatial complexity of natural phenomena such as geological applications. High-order geostatistics is a new area of research based on higher-order spatial connectivity measures, especially spatial cumulants as suitable for non-Gaussian and non-linear phenomena. This paper presents HOSC or “High-order spatial cumulants”, an algorithm for calculating spatial cumulants, including anisotropic experimental cumulants based on spatial templates. High-order cumulants are calculated on two- and three-dimensional synthetic training images so as to elaborate on their characteristics....

Publication year: 2009
Source: Computers & Geosciences, In Press, Accepted Manuscript, Available online 12 November 2009
G., Toxopeus , J., Thorbecke , S., Petersen , K., Wapenaar , E., Slob

An earth model is used in a collaborative environment in which some members provide information for its construction and others utilize the result. Validating an earth model by simulating a migration image is an important step. However, the high computational cost of generating 3D synthetic data, followed by the process of migration, limits the number of scenarios that can be validated. To overcome this computational cost, a novel strategy is used where a migration image is simulated by filtering a model with a spatial resolution filter. One of the key properties of this approach is that the model that describes...

Publication year: 2009
Source: Computers & Geosciences, In Press, Accepted Manuscript, Available online 10 November 2009
O.K., Mahabadi , G., Grasselli , A., Munjiza

Numerical modelling of discontinuous medium has gained much popularity in recent decades. The combined finite-discrete element method (FEM/DEM) is a state-of-the-art numerical modelling technique pioneered in the mid-1990s. Y2D is a robust two-dimensional FEM/DEM research code developed by A. Munjiza in 2004. The major limitations of this code are (1) the lack of a graphical user interface (GUI) meaning that all pre-processing has to be made directly on an ASCII input file and (2) the inability of dealing with heterogeneous media. This contribution presents the first GUI and pre-processor, known as Y-GUI, developed for Y2D, and the implementation of a...

Publication year: 2009
Source: Computers & Geosciences, In Press, Accepted Manuscript, Available online 5 November 2009
Paul, Wessel

I present a new set of tools for detection of intersections among tracks in 2-D Cartesian or geographic coordinates. These tools allow for evaluation of crossover errors at intersections, analysis of such crossover errors to determine appropriate linear models of systematic corrections for each track, and application of these corrections and further adjustments to data that completely eliminates crossover discrepancies from final 2-D data compilations. Unlike my older x_system tools, the new x2sys tools implement modern algorithms for detecting track intersections and are capable of reading a wide range of data file formats, including data files following the netCDF COARDS...

Publication year: 2009
Source: Computers & Geosciences, In Press, Accepted Manuscript, Available online 5 November 2009
H., Mustapha , A., Ghorayeb , K.A., Mustapha

Advanced algorithms in parallel computing can be employed for a better understanding of groundwater flow fluids. Water flows in very heterogeneous geological media which contain complex structures. Decomposing these structures into approximately equivalent sub-structures for a load-balancing is a major challenge. This paper proposes and analyzes a new algorithm using finite element methods to simulate parallel flow fluid in such complex media. Fully parallel software is developed and numerical examples are presented to show the efficiency and robustness of the algorithm proposed.

Publication year: 2009
Source: Computers & Geosciences, In Press, Accepted Manuscript, Available online 5 November 2009
André J.A., Unger

This work is the first installment in a two-part series, and focuses on the development of a numerical PDE approach to price components of a Bermudan-style callable catastrophe (CAT) bond. The bond is based on two underlying stochastic variables; the PCS index which posts quarterly estimates of industry-wide hurricane losses, as well as a single-factor CIR interest rate model for the three-month LIBOR. The aggregate PCS index is analogous to losses claimed under traditional reinsurance in that it is used to specify a reinsurance layer. The proposed CAT bond model contains a Bermudan-style call feature designed to allow the reinsurer...

Publication year: 2009
Source: Computers & Geosciences, In Press, Accepted Manuscript, Available online 4 November 2009
Arrigo, Caserta , Massimo, Di Bona

Using a Monte Carlo method based on a random walk in ad hoc N-dimensional phase space, we construct N random time series having prescribed coherence spatial decay. We apply the method in seismology by designing a numerical experiment to investigate how the coherence of the bedrock motion relates to the coherence of the surface ground motion in a sedimentary valley. The main features of the coherence behavior in the valley are found to tie in with data analysis and field observations.

Publication year: 2009
Source: Computers & Geosciences, In Press, Accepted Manuscript, Available online 4 November 2009
André J.A., Unger

This work is the second installment in a two-part series, and focuses on object-oriented programming methods to implement an augmented-state variable approach to aggregate the PCS index and introduce the Bermudan-style call feature into the proposed CAT bond model. The PCS index is aggregated quarterly using a discrete Asian running-sum formulation. The resulting aggregate PCS index augmented-state variable is used to specify the payoff (principle) on the CAT bond based on reinsurance layers. The purpose of the Bermudan-style call option is to allow the reinsurer to minimize their interest rate risk exposure on making fixed coupon payments under prevailing interest...

Publication year: 2009
Source: Computers & Geosciences, In Press, Accepted Manuscript, Available online 4 November 2009
L., Ortega , A., Rueda

Drainage networks determination from Digital Elevation Models (DEM) has been a widely studied problem in the last three decades. During this time, satellite technology has been improving and optimizing digitalized images, and computers have been increasing their capabilities to manage such a huge quantity of information. The rapid growth of CPU power and memory size has concentrated the discussion of DEM algorithms on the accuracy of their results more than their running times.However obtaining improved running times remains crucial when DEMs dimensions and resolutions increase. Parallel computation provides an opportunity to reduce run times. Recently-developed Graphics Processing Units (GPUs) are...

Publication year: 2009
Source: Computers & Geosciences, In Press, Accepted Manuscript, Available online 3 November 2009
Florian, Centler , Haibing, Shao , Cecilia, De Biase , Chan-Hee, Park , Pierre, Regnier , ...

The description of reactive transport processes in subsurface environments requires a sound understanding of both the biogeochemical complexity of the system and the spatially resolved transport of reactive species. However, most existing reactive transport models, for example in the field of contaminant hydrology, are specialized either in the simulation of the reactive or of the flow and transport processes. In this paper, we present and test the coupling of two highly flexible codes for the simulation of reactive transport processes in the subsurface: the Biogeochemical Reaction Network Simulator (BRNS), which contains a solver for kinetically and thermodynamically constrained biogeochemical reactions,...

Publication year: 2009
Source: Computers & Geosciences, In Press, Accepted Manuscript, Available online 31 October 2009
Yalçın, Ersoy , Cahit, Helvacı

Several petrological processes, such as (1) fractional crystallization (FC), (2) combined and decoupled fractional crystallization and assimilation (AFC and FCA), and (3) mixing processes, which modify the geochemical composition of the magma, are graphically programmed using Microsoft® Excel© spreadsheet on the basis of differentiation equations. The FC-AFC-FCA and mixing modeler is an interactive Microsoft® Excel© spreadsheet program that models the consequent theoretical vectors of FC, AFC, FCA and mixing processes, which are frequently used in modern petrology. The program enables the user to export outputs of linear- or logarithmic-scaled bivariate diagrams and also rare earth elements (REE)- and multi element-spider...

Publication year: 2009
Source: Computers & Geosciences, In Press, Accepted Manuscript, Available online 29 October 2009
A., Al-Anazi , T., Babadagli

This paper presents a new methodology to continuously update and improve fracture network models. We begin with a hypothetical model whose fracture network parameters and geological information are known. After generating the “exact” fracture network with known characteristics, the data were exported to a reservoir simulator and simulations were run over a period of time. Intelligent wells equipped with downhole multiple pressure and flow sensors were placed throughout the reservoir and put into production. These producers were completed in different fracture zones to create a representative pressure and production response.We then considered a number of wells of which static (cores...

Publication year: 2009
Source: Computers & Geosciences, In Press, Accepted Manuscript, Available online 28 October 2009
Sheng, Yang , Jun-Hai, Yong , Jiaguang, Sun , Hejin, Gu , Jean-Claude, Paul

This paper presents a numerically stable solution to a point-in-polygon problem by combining the orientation method and the uniform subdivision technique. We define first a quasi-closest point that can be locally found through the uniform subdivision cells, and then we provide the criteria for determining whether a point lies inside a polygon according to the quasi-closest point. For a large number of points to be tested against the same polygon, the criteria are employed to determine the inclusion property of an empty cell as well as a test point. The experimental tests show that the new method resolves the singularity...

Publication year: 2009
Source: Computers & Geosciences, In Press, Accepted Manuscript, Available online 23 October 2009
Mauro, Alberti

The kinematic correlation between faults and focal mechanisms can be quantified using scalar (vector and tensor product) or geometric (rotation pole and angle) measures of the similarity of their orientations. The statistical properties of the correlation may help characterise the spatio-temporal properties of natural datasets and test their congruence with theoretical models. This paper describes GIS and Fortran 90/95 tools for analysing the kinematic correlation of faults, and for simulating fault movements in a homogeneous stress field. As an example, we analyse the Umbria-Marche 1997 seismic sequence with these tools; our results show a positive spatial correlation of seismic events...

Publication year: 2009
Source: Computers & Geosciences, In Press, Accepted Manuscript, Available online 23 October 2009
Hiroyoshi, Arai

Publication year: 2009
Source: Computers & Geosciences, In Press, Accepted Manuscript, Available online 23 October 2009
Chi, Zhang , Zhenhao, Duan

Publication year: 2009
Source: Computers & Geosciences, In Press, Accepted Manuscript, Available online 17 October 2009
Niksa, Orlic , Sven, Loncaric

An important and challenging problem in seismic data processing is to discriminate between natural seismic events such as earthquakes and artificial seismic events such as explosions. Many automatic techniques for seismogram classification have been proposed in the literature. Most of these methods have a similar approach to seismogram classification: a predefined set of features based on ad-hoc feature selection criteria is extracted from the seismogram waveform or spectral data and these features are used for signal classification. In this paper we propose a novel approach for seismogram classification. A specially formulated genetic algorithm has been employed to automatically search for...

Publication year: 2009
Source: Computers & Geosciences, In Press, Accepted Manuscript, Available online 14 October 2009
E.W., Llewellin

lbflow is a flexible, extensible implementation of the lattice Boltzmann method, developed with geophysical applications in mind. The theoretical basis for lbflow, and its implementation, are presented in the companion paper, ‘Part I’. This article covers the practical usage of lbflow and presents guidelines for obtaining optimal results from available computing power. The relationships between simulation resolution, accuracy, runtime and memory requirements are investigated in detail. Particular attention is paid to the origin, quantification and minimization of errors. lbflow is validated against analytical, numerical and experimental results for a range of three-dimensional flow geometries. The fluid conductance of prismatic pipes...

Publication year: 2009
Source: Computers & Geosciences, In Press, Accepted Manuscript, Available online 14 October 2009
Weirong, Chen , Geoffrey M., Henebry

How does the observed spatial structure change as a function of spectral wavelength and resolution? Fine spectral resolution bands of a Hyperion image acquired over agricultural research fields in eastern Nebraska, USA, were analyzed using variography to characterize spatial pattern. Analysis was repeated using Landsat TM/ETM+ bands simulated from the Hyperion data. Significant changes in spatio-spectral heterogeneity were observed across the red edge. Total amount of spatial variability is closely correlated to the difference in reflectance of underlying targets, which to a lesser extent is also the case for spatial dependence. Increasing bandwidth may blur spatial structure that occurs at...

Publication year: 2009
Source: Computers & Geosciences, In Press, Accepted Manuscript, Available online 14 October 2009
Lyndon M., Pease , P., Oduor , G., Padmanabhan

Agricultural pollution is a significant problem in North Dakota. Water quality in the Pipestem Creek watershed above Pingree in North Dakota, USA, has been a major environmental concern amongst other adjacent watersheds within the region. The Annualized Agricultural Non-Point Source Model (AnnAGNPS), a large scale watershed model designed to predict sediment and nutrient loads was used to evaluate non-point source pollution in a typical agricultural watershed. Best available data was assembled and used in the analysis. The model developed predicted runoff was 0.31 m3/s compared to an observed value of 0.46 m3/s. Poor correlation was seen when comparing the model...