Michael Strasser

Submarine mass movements and their consequences : 6th International Symposium

We present a short review of the state-of-the-art numerical tools that have been used for modeling landslide-generated waves. A comparative study is conducted on the physical properties of earthquake- and landslide-generated waves suggesting that both dispersion and nonlinearity effects may be neglected for the former waves whereas they may be considered for the latter ones. We introduce landslide tsunami models and group them into three classes: (1) models treating the moving mass as a fluid, (2) models estimating the initial water surface, and (3) models fed by the transient seafloor deformation. Selection of a particular model from the list of models introduced here depends on: (1) the dimensions of the source, (2) the available computing capacities, (3) availability of fine bathymetric grid, and (4) the purposes of the modeling.

Assessing the internal character, reservoir potential, and seal competence of mass-transport deposits using seismic texture: A geophysical and petrophysical approach

Three-dimensional (3-D) seismic volumes from southeast Brazil, southeast Japan, and borehole data from the Ocean Drilling and Integrated Ocean Drilling Programs are used to demonstrate a new method to distinguish mass-transport deposits (MTDs) from confining hemipelagites, quantify MTDs internal architecture, and assess their reservoir potential or seal competence—the contrast, directionality, energy (CDE) method. The CDE values extracted from 3-D seismic data can be tied to any ground-truthed property of strata regardless of their depositional history, age, and lithology. The application of the CDE method is, however, dependent on seismic-data acquisition parameters and selected processing sequences and should be independently applied to different seismic volumes. Borehole data indicate contrast (C) to reflect MTDs lithological heterogeneity and degree of disaggregation, which increase proportionally to the absolute value of C. More uniform values of P-wave velocity (Vp) and peak shear strength are recorded in strata with lower contrast. Directionality (D) relates to the existence of syn- or postdepositional fabric such as compressional ridges, imbricated strata or faults. Energy (E) relates to the acoustic impedance of strata, with high-amplitude reflections correlating with strata with higher shear strength, i.e., high Vp and shear-wave velocity (Vs) values, or with abrupt contrasts in density (bright spots). This work shows that distinct values of C, D, and E reflect variable degrees of vertical and horizontal connectivity in strata and, consequently, their seal and reservoir potential. The CDE values are thus subdivided in nine classes, which are represented in ternary plots to cover the full spectrum of MTDs and any confining strata. As a result, the data in this article confirm that lower seal competence, and higher reservoir potential, is recorded in strata with large D or moderate CDE values.

Significance of amplitude variations in shaley mass-transport deposits - a petrophysical-geophysical correlation

For this work were used three high-quality 3D seismic volumes from SE Japan and SE Brazil, together with borehole data from the Nankai Trough. We show that, on 3D seismic data, seismic texture is defined as a reflection amplitude pattern that is characterised by the magnitude and variation of neighbouring data in a seismic volume (Chopra and Marfurt, 2007). We show the importance of seismic amplitude variations to assess the seal competence and reservoir potential of MTDs.