LONG-TERM GOALS My long term goals are to develop, test, and clearly present new quantitative methods for evaluating ' stresses in the earth's crust and to through new field observations and new mechanical analyses to contribute to a better understanding of geologic fracture phenomena, especially faulting, landsliding, joint formation, and dike intrusion. OBJECTIVES The main scientific objectives of this project are to identify and better understand the factors controlling where submarine landslide failure surfaces nucleate, how they propagate, how deformation accumulates in the incipient stages of landsliding, and to develop methods for analyzing these phenomena. A second objective is to reconcile predictions of fracture mechanics theory with observations of secondary fractures around faults. The landslide and faulting studies are linked because they both involve shear fracture, albeitunder different environmental conditions. The work also is undertaken with the objective of developing my graduate students as well-grounded research scientists. APPROACH This study is primarily theoretical and utilizes numerical stress analyses to understand sliding processes. Landslide failure surfaces and faults are modeled as fractures in elastic media using displacement discontinuity boundary element codes (e.g., Crouch and Starfield, 1983; Thomas, 1993). Fleming and Johnson (1989) proposed viewing landslide failure surfaces as fractures, and this concept is tested quantitatively here. The mechanical analyses for landslides have been conducted in both two-and three-dimensions and account for topography and stresses due to gravity. The stresses in a slope without a failure surface are examined to see where failure might nucleate. Stresses and displacements within a slope containing different failure surface geometries are then examined to understand how a failure surface might propagate and how the slope deforms in response. The model results are compared with observations made by other investigators to test the model predictions. For the faults, stress analyses have been conducted in three-dimensions to indicate the location, orientation, and size of secondary fractures. The mechanical analyses are then tested against my field observations of faults, collected as part of another project. Development of mechanical analysis methods is a major component of this research. IJTIG QUALITY JEZr%&Wm 4 20000627 025

Due to the recent development of well-integrated surveying techniques of the sea floor, significant improvements were achieved in mapping and describing the morphology and architecture of submarine mass movements. Except for the occurrence of turbidity currents, the aquatic environment (marine and fresh water) experiences the same type of mass failure as that found on land. Submarine mass movements, however, can have run-out distances in excess of 100 km, so their impact on any offshore activity needs to be integrated over a wide area. This great mobility of submarine mass movements is still not very well understood, particularly for cases like the far-reaching debris flows mapped on the Mississippi Fan and the large submarine rock avalanches found around many volcanic islands. A major challenge ahead is the integration of mass movement mechanics in an appropriate evaluation of the hazard so that proper risk assessment methodologies can be developed and implemented for various human activities offshore, including the development of natural resources and the establishment of reliable communication corridors.Key words: submarine slides, hazards, risk assessment, morphology, mobility, tsunami.

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Fragmentation is one of the mechanisms involved in rock avalanches. Quantifying the associated energy during a rock avalanche can help to assess the influence of fragmentation on post-failure mass movements. In this paper, in situ block size distributions of the intact rock mass and the debris deposits are presented and analyzed for nine rock avalanches, five in the Canadian Rocky Mountains and four in the European Alps. Degrees of fragmentation are estimated from these data. Two methods are examined to assess fragmentation energy, one based on the comminution theory, and one on the blasting energy used in the mining industry. The results show that, for the studied rock avalanches, there is a relationship between the reduction in diameter ratio, Rr = D50/d50 (where D50 and d50 are the mean diameter of the intact rock mass and the mean diameter of the debris, respectively), and the potential energy per unit volume normalized with respect to the point load strength of rock (γHG/σc), where γ is the unit weight of the material, HG is the vertical distance between the centres of gravity of the mass at the start and end positions, and σc is the point load strength). For the cases studied, fragmentation energy calculations average 20% of the potential energy. An empirical relationship between Rr and γHG/σc has been established and is used in the definition of a disintegration index (ID). This index seems to reflect the physics of the disintegration process, since it accounts for the fact that the reduction in diameter ratio is a function of the dissipated energy and the strength of the rock. These factors have long been known to affect fragmentation but have never been presented in a coherent manner for rock avalanches.Key words: rock avalanches, disintegration, fragmentation energy, Canadian Rocky Mountains, European Alps.

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