Geophysics and Tectonics Seminar - fall-2013

Oct. 4, 2013
noon - 1 p.m.
3814 Geology

Presented By:

• Masateru Ishiguro - Seoul National University/ UCLA visiting professor

Seminar Description coming soon.

Oct. 18, 2013
noon - 1 p.m.
3814 Geology

Presented By:

• Renyu Hu - Caltech

Seminar Description coming soon.

Oct. 25, 2013
noon - 1 p.m.
Geology 3814

Presented By:

• Colette Salyk - National Optical Astronomy Observatory

We have long known about the great diversity of types of planets found within the solar system. Thanks to the continuing discovery and characterization of exoplanets, we now know that bulk planetary properties and system architectures also vary significantly between planetary systems. In this talk, I will discuss some of the possible origins of both intra- and inter-system planetary diversity, and explain how protoplanetary disk observations can be used to directly observe these origins. In particular, I’ll focus on how spectroscopic observations across a wide range of wavelengths are allowing us for the first time to study the chemical make-up of disks, and to test our understanding of processes such as the condensation sequence and the freeze-out of ices at snow lines.

Nov. 1, 2013
noon - 1 a.m.
3814 Geology

Presented By:

• An Yin - UCLA

"A bookshelf-faulting model for the mechanical origin of the tiger-stripe fracture system in the South Polar Terrain of Saturn’s moon Enceladus" The semi-square-shaped South Polar Terrain (SPT) of Saturn’s small moon Enceladus (500 km diameter) hosts five regularly spaced (~35 km) and similar-length (~130-150 km) linear structural zones informally named as the tiger-stripe fractures. Although the tiger-stripe fractures are geologically active and serve as conduits of erupting water vapor, their mechanical origin remains uncertain. Existing hypotheses invoke both tidal stress and internal heating and predict the tiger-stripe fractures to be extensional cracks, propagating spreading ridges, faults with alternating opening, closing, right-slip and left-slip kinematics, and transpressional shear zones. The main issue leading to such diverse views on the mechanical origin and the kinematic development of the tiger-stripe fractures is a lack of systematic determination of the geometric and kinematic relationships among diverse geologic structures in the South Polar Terrain. To address this question, a first detailed tectonic map of the South Polar Terrain is constructed based on a detailed analysis of the most recently released CASSINI images of the SPT. The structural analysis taken in this study differs from the early work in that it does not rely on the use of fracture offsets as a mean of determining fault kinematics, as termination and overstepping of younger fractures at and across older fractures can lead to erroneous interpretations on the timing and kinematics of fracture formation. Instead, the new approach used in this study emphasizes the use of geometrically linked and kinematically related secondary and termination structures to establish the kinematics of the tiger-stripe faults. Based on this new approach and guides from terrestrial examples, we show that (1) the tiger-stripe fractures are left-slip faults and (2) the SPT is bounded by an extensional zone along its leading edge, a thrust-fold belt along its trailing edge, a right-slip shear zone along its eastern edge, and a left-slip shear zone along its western edge. A westward increase in the width of the leading-edge extensional zone requires that the SPT deformation be partitioned by translation towards the trailing-edge and clockwise rotation of the SPT. The translation of the SPT is accommodated by contraction along the trailing edge and strike-slip shear along the eastern and western edges. Meanwhile, clockwise rotation of the SPT is accommodated first by initiation of the tiger-stripe fractures as conjugate Riedel faults that was followed by bookshelf faulting. Based on the topography data we attribute the lateral translation of the SPT to gravitational sliding along an inclined brittle-ductile transition zone dipping towards the trailing-edge direction. Clockwise rotation of the SPT relative to its surrounding region could either be related to internal deformation induced by gravitational sliding or by non-synchronous rotation of the SPT above a local ocean.

Nov. 8, 2013
noon - 1 a.m.
3814 Geology

Presented By:

• Daniel Perez-Becker - UC Berkeley

Seminar Description coming soon.

Nov. 15, 2013
noon - 1 a.m.
3814 Geology

Presented By:

• Joshua Pepper - Lehigh University

The past two decades have seen an explosion of discovery of extrasolar planets. We are now assembling a picture of the variety of planetary systems in our galaxy, detecting planets in previously unexpected configurations and types. I will describe the results from recent exoplanet surveys, including the Kepler space mission, and the ways in which our understandings of planet formation and evolution have been revolutionized. I will describe the next steps in exoplanet discovery, including the work of low-cost small telescopes, and the future NASA missions that will move us toward the direct detection of biomarkers in the atmospheres of habitable exoplanets.

Nov. 22, 2013
noon - 1 p.m.
3814 Geology

Presented By:

• Brendan Bowler - Jet Propulsion Laboratory (JPL) - NASA

Seminar Description coming soon.

Dec. 6, 2013
noon - 1 p.m.
3814 Geology

Presented By:

• Steve Chesley - Jet Propulsion Laboratory (JPL) - NASA

Seminar Description coming soon.