Events at Physics |
Events on Tuesday, May 5th, 2009
- Chaos & Complex Systems Seminar
- Earthquakes beneath the sea: Understanding the mechanics of fault zones through subsurface imaging and scientific drilling
- Time: 12:05 pm
- Place: 4274 Chamberlin
- Speaker: Harold Tobin, UW Department of Geology and Geophysics
- Abstract: Understanding of the processes by which earthquakes occur remains one of the great challenges of geophysics. The complex interplay among frictional processes, stress, pore fluid pressure, temperature, and other factors means that a comprehensive model for fault physics has not been achieved. One reason for this is the lack of in situ observations and samples from within the faults deep beneath the earth's surface. To address this problem, several major projects have been launched to drill into fault zones. The massive subduction earthquakes which occur at the boundary between two tectonic plates at subduction zones are especially of interest because they cause devastating tsunami, and occur with repeating characteristics. Off the Pacific coast of Japan, the NanTroSEIZE (Nankai Trough Seismogenic Zone Experiment) project targets a subduction zone for drilling to sample and place instruments into and around the fault zone responsible for these tsunami-generating earthquakes. Three-dimensional seismic reflection surveys image the plate boundary zone and provide evidence for fault properties. Drilling provides evidence on the rock composition, chemistry, stress, and other parameters. These unique new datasets are helping to test theoretical and laboratory-derived models for fault physics. I will discuss the overall challenge and present results from the first phase of drilling in 2007-2008.
- Astronomy Colloquium
- The Power of Cooling Cores in Clusters in Galaxies
- Time: 3:30 pm
- Place: 6515 Sterling Hall
- Speaker: Mateusz Ruszkowski, University of Michigan
- Abstract: A significant fraction of clusters of galaxies possess cool cores. If uninhibited, the cooling of the intracluster medium (ICM) will result in extreme mass accretion rates which is contrary to observations. It is widely accepted now that active galactic nuclei (AGN), and possibly other processes, "conspire" to heat the cluster plasma and prevent such "cooling catastrophes". However, several aspects of this process are not understood. I will discuss some of the outstanding problems of the energetics of cool cores in clusters of galaxies. More specifically, I will discuss (1) the role of the brightest cluster galaxy and the mass of its central black hole in supplying the energy, (2) the impact of the energy transfer by thermal conduction, (3) the role of the magnetic fields in slowing the mixing of the hot AGN-inflated bubbles with the ICM and, finally, (4) I will briefly comment on our ongoing efforts to understand the role of anisotropic conduction in cosmological simulations of cluster formation. <br>
- Host: Professor Sebastian Heinz