William C. Haneberg

A Rational Probabilistic Method for Spatially Distributed Landslide Hazard Assessment

First-order, second-moment (FOSM) approximations of limit equilibrium slope stability equations can be combined with digital elevation models to perform spatially distributed probabilistic landslide hazard analyses. This is most easily accomplished using the infinite slope idealization, which is the basis of many published reconnaissance-level slope stability assessments. Comparisons of FOSM and Monte Carlo results show that FOSM approximations yield accurate results when input distributions are symmetric, or nearly symmetric, probability density functions. Contrary to the assumptions of previous authors, however, the Monte Carlo results suggest that factors of safety may be better represented by log-normal distributions than by normal distributions. A 3- × 2-km area near Wheeling, West Virginia, covered by a pre-existing landslide hazard map was used to illustrate the application of the spatially distributed FOSM approach. This area was chosen specifically because it includes active translational landslides as well as several map units that likely violate the infinite slope idealization to one degree or another: large dormant landslides, actively moving cove landforms, and areas deemed susceptible to sliding by virtue of underlying bedrock lithology. Using a 50 percent probability of sliding threshold to delineate unstable areas, the FOSM model predicted 74 percent of the mapped active landslide area to be unstable and 77 percent of the area without mapped slope hazards to be stable (both on a raster-by-raster basis). The overall degree of correspondence for all hazard map units was 54 percent if dormant landslides were considered to be unstable and 65 percent if considered to be stable. The degree of correspondence varies as a function of the threshold probability but is similar to values reported for pairs of landslide inventory maps prepared by different geologists.

Humans as Geologic Agents

Homo sapiens is the only known species to consciously effect change to the Earth’s geologic environment. We reshape the Earth; intensify erosion; modify rivers; change local climates; pollute water resources, soils, and geologic media; and alter soils and the biosphere. We dig holes in it, remove parts of it, and bury highly toxic materials in it. In this volume, the authors explore human impact on the Earth and attempt to answer the following questions. What have we done to Terra? How fast have we effected change? Are the changes permanent? Are they good, or have we inadvertently caused more damage? Can we, should we, repair some or all of these changes? These are important questions for the geoscience community because, as those most knowledgeable about the Earth and its resources, geologists play a major role in sustaining and preserving the Earth.

Evaluating the Effects of Input Cost Surface Uncertainty on Deep-Water Petroleum Pipeline Route Optimization

A resampling-based stochastic simulation approach was used to evaluate the uncertainty that may be associated with geologically constrained least-cost path pipeline route optimization. A smoothed version of a composite geocost surface from a deep-water pipeline routing project was resampled and the results used to generate a series of equally probable cost surface realizations, which were in turn used as the basis for the same number of route optimizations. Eighty percent of the simulated routes followed a 500–2,000 m wide corridor nearly parallel to the baseline route (based upon complete information) between two hypothetical pipeline termini located about 25 km apart. Twenty percent followed an alternate corridor of approximately the same width. These results suggest that, while the general method of geologically constrained pipeline route optimization is a relatively robust one, uncertainties in geological input will at the least create a least-cost route corridor rather than a single least-cost route and may suggest realistic alternatives that must be critically evaluated in light of the available geological information.

Incorporating Correlated Variables into GIS-Based Probabilistic Submarine Slope Stability Assessments

First-order, second-moment (FOSM) formulations are useful tools for assessing uncertainty in GIS based submarine slope stability models. In the simplest applications, variables are assumed to be uncorrelated. In some cases, however, correlation among variables may be significant enough to require inclusion. Correlations among variables can be incorporated by creating an empirical covariance matrix and combining it with analytically derived expressions for partial derivatives of the factor of safety equation. Example calculations show that ignoring correlated variables over-predicts the probability of sliding for gentle slopes and under-predicts the probability of sliding for steep slopes, with small differences for moderate slopes. GIS-based application is illustrated using a hypothetical example motivated by an actual deepwater geohazard assessment, showing areas in which the use of uncorrelated rather than correlated variables over-predicts the likelihood of instability.

Evolution of a Submarine Mass-Transport Complex in Space and Time

Submarine mass-transport deposits (MTDs) can be petroleum reservoirs, drilling hazards, or indicators of seafloor instability that need to be considered in deep-water engineering projects. In 3-D seismic reflection data, MTDs are typically characterized by laterally extensive but relatively thin layers of debris with weak and incoherent reflectors and, in many cases, little or no seafloor geomorphic expression. Because of their great lateral extent, it is unusual to see proximal and distal portions of large MTDs in a single data set. We infer that spatial variation in the geometry of a large and exceptionally well-imaged MTD can serve as a proxy for the temporal evolution of the mass transport event at a point. Near its source, the MTD is characterized by disaggregation of originally intact strata. As distance from the source increases, the complex becomes increasingly chaotic the manifestation of the original structure weakens. Each facies also has a characteristic seafloor geomorphologic expression. The spatio-temporal evolution is particularly evident when the fabric is visualized using 3-D seismic volume amplitude attributes that display the lateral continuity of reflectors.

Statistics of Earth Science Data

Statistics of Earth Science Data was published in 2003 by Springer and retails for

Nature and timing of large landslides in the Himalaya and Transhimalaya of northern India

79.95. It consists of eleven chapters and two appendices that begin by covering standard material such as sampling schemes, central tendency and dispersion, theoretical distributions (limited to binomial, Poisson, and normal), statistical inference and hypothesis testing, comparison of frequency distribution curves, linear regression, and correlation of variables. The final four chapters are more specific to geoscientists, and the final three are especially specific to geologists who deal with circular and spherical orientation data (which should include many engineering geologists). The two appendices cover errors in compound quantities (short but important) and the manual use of stereograms. A complete table of contents is available on the publishers web site (www.springeronline.com). One of the unique features of this book is an abbreviated glossary in the front matter. Although it is abbreviated in length, the definitions are unusually thorough, and many consist of short articles running to more than 200 words. Borradaile also goes to great lengths to discuss sampling in theory and reality, which is an important consideration to anyone working in the geosciences. …