Fall 2014

October 3, 2014

Stephen Kane, San Francisco State Univeristy

Title: Dispelling the Myths and Legends of the Habitable Zone

Abstract: The field of exoplanets has rapidly expanded from the exclusivity of exoplanet detection to include exoplanet characterization. A key step towards this characterization is the determination of which planets occupy the Habitable Zone (HZ) of their host stars. As the Kepler data continues to be processed, the orbital
period sensitivity is increasing and there are now numerous exoplanets known to occupy the HZ of their host stars. In this talk I will describe the properties of the HZ, the dependence on the spectral type properties, and the current state of exoplanet detections in the HZ. Along the way I will attempt to dispel some common misconceptions regarding the Habitable Zone. I will relate HZ results to the calculation of eta_Earth and eta_Venus. Finally, I will present several case studies of HZ Kepler planets, including circumbinary planets for which the HZ is a time-dependent function.


October 10, 2014

Marianne Conin, University of Lorraine

Title: Stress analysis in a medium containing mechanical discontinuities


October 17, 2014

Gerardo Dominguez, California State University, San Marcos

Title: Modern Approaches to Classical Problems in Diffusion and Isotopic Fractionation


October 24, 2014

Alain Plattner, California State University, Fresno

Title: A close look at the magnetic field of the Martian south pole - Localized planetary magnetic field analysis, application to Mars


October 31, 2014

Christodoulos Kyriakopoulos, University of California, Riverside

Title: Topography of the Subduction Interface across Nicoya, Costa Rica: Implications for Interseismic Locking


November 7, 2014

Roxana Lupu, SETI/NASA Ames Research Center

Title: The Atmospheres of Earth-like Planets after Giant Impact Events


November 14, 2014

Taka'aki Taira, University of California, Berkeley

Title: Monitoring seismic velocity changes associated with the 2014 Mw 6.0 South Napa earthquake


November 21, 2014

Eric Dunham, Stanford University

Title: Seismicity and Waves in Volcanoes


December 5, 2014

Sonia Tikoo, University of California, Berkeley

Title: The Lunar Dynamo


 December 12, 2014

Shalev Siman Tov, Hebrew University of Jerusalem

Title: The Dynamic Evolution of Carbonate Faults

Abstract:

Carbonate faults are ubiquitous around the world. Their structure and mechanics play an important role in controlling fluid-flow in the upper crust and in the physics of earthquakes occurring on them. Yet their structural evolution, the mechanism of formation of the principal slip zone, and the physics of earthquakes occurring on them, are still not well understood. In addition, field geologists still lack the knowledge to identify which carbonate faults slid seismically and which didn’t.

This talk presents three main new results, from experiments and field-work:

1)    Field data combined with experiments suggesting that the majority of sliding within a fault occurs on a micro-meter thick layer that we termed “fault mirror” (FM). Imaging of the FM structure revealed a thin layer, composed of tightly packed nanograins, coating a rougher layer composed of highly twinned micron-size calcite crystals. Observations on these structures suggest a new brittle-ductile mechanism for nano-grain formation. The observed structures also suggest that significant plastic deformation occurs within the nanograin layer during rapid frictional sliding.

2)    Laboratory experiments suggesting that FMs form only during rapid sliding (earthquakes), and are destroyed during slow sliding, so that their field-appearance may be indicative of past seismic fault activity. In addition, our modeled temperature evolution during shear suggests that plastic deformation may control the creation of these FMs.

3)    A possible new application of the clumped isotopes method as a paleothermometry method for assessing the thermal history of carbonate faults.

These field and experimental observations on carbonate faults contribute to our understanding of several open questions in the field of earthquakes and faulting. Although faulting is usually automatically connected with brittle deformation, our observations suggest that ductility could play a major rule in the formation of the fault nano-structures and in upper crustal slip behavior. Thanks to the new possibility to experimentally create fault mirror surfaces, we can now investigate the conditions by which these slip surfaces form in nature.