Synopsis: Seminar meeting #2

Though our primary topic was the reading (detailed below), we also briefly discussed strategies for reading scientific papers, including (1) focus on the unknown questions addressed, the data used, and whether the questions were resolved and (2) focus on the figures.

Reading: O. Katz and E. Aharanov, Landslides in vibrating sand box: What controls types of slope failure and frequency magnitude relations? EPSL, 247, 280–294, 2006.

Our primary points of discussion:

· Frequency magnitude distributions in landslides. Al and Georgie gave a concise summary of the background on these distributions, describing the characteristic rollover and inverse power law decay. Power law exponent can vary among different inventories, but many landslides with different triggering mechanisms have similar distributions (shown in Figure 1). We discussed the physical meaning of the rollover and generally agree with the authors’ assertion that this corresponds to a characteristic size of shallow landslides.

· Specifics of the experimental design. We spent some time discussing the role of water in the experiment, particularly why pore pressure is negative (due to the curvature of the water-air interface) and that the experiment viability is very sensitive to %weight water. We also talked about grain angularity and whether the results would be different with perfectly spherical grains.

· Ideas for further experiments. We had a few questions about the experimental design that we thought could be addressed in additional experiments, such as:

o What is the depth distribution of failures? How could this be measured (photoelectric particles, lasers)? Does the heterogeneity introduced by tension cracks penetrate far below the surface?

o How sensitive are the results to slope angle?

· Relevance to natural systems. How well do these experiments reproduce failures that are hydrologically triggered? We discussed whether the difference in triggering mechanism explains why the power law exponent for the experiments is lower than for many natural systems and agreed that it’s not clear from past literature that the distribution is tied to triggering mechanism.