EPSS Colloquium - winter-2014

Jan. 9, 2014
4 p.m. - 5 p.m.
Geology 3656

Presented By:

• Jon Keeley - UCLA

Seminar Description coming soon.

Jan. 16, 2014
4 p.m. - 5 p.m.
3656 Geology

Presented By:

• Terry Plank - Columbia

Why is there volcanism in the Basin and Range? Cinder cones have popped up from California to Utah, bringing mantle melts and xenoliths to the surface. Some of these volcanic vents are clearly related to active deformation in the Basin and Range, while others are not. Recent work points to small-scale convective phenomena in the mantle, such as lithospheric drips or edge-driven convection, to drive melting. What is the role of prior subduction and hydration of the lithosphere in generating magmas? These questions are fundamental to how the continent evolves in regions of active extension, and yet there are no consensus answers. The first data on the water contents of Basin and Range magmas are combined with mantle melt thermobarometers and seismic shear wave velocities to provide a new view of melting beneath the Western US.

Jan. 23, 2014
4 p.m. - 5 p.m.
Geology 3656

Presented By:

• Jon Stewart - UCLA

The Mw9.0 Tohoku-oki Japan earthquake produced approximately 2,000 ground motion recordings. We have considered 1,238 three-component accelerograms corrected with component-specific low-cut filters. The recordings have rupture distances between 44 km and 1,000 km, time-averaged shear wave velocities of VS30 = 90 m/s to 1,900 m/s, and usable response spectral periods of 0.01 sec to >10 sec. The data support the notion that the increase of ground motions with magnitude saturates at large magnitudes. High-frequency ground motions demonstrate faster attenuation with distance in backarc than in forearc regions, which is only captured by one of four considered ground motion prediction equations for subduction earthquakes. Recordings within 100 km of the fault are used to estimate event terms, which are generally positive (indicating model underprediction) at short periods and zero or negative (overprediction) at long periods. We find site amplification to scale minimally with VS30 at high frequencies, in contrast with other active tectonic regions, but to scale strongly with VS30 at low frequencies.

Jan. 30, 2014
4 p.m. - 5 p.m.
Geology 3656

Presented By:

• Jack Lissauer - NASA

Seminar Description coming soon.

Feb. 6, 2014
4 p.m. - 5 p.m.
3656 Geology

Presented By:

• Jack Wisdom - MIT

Seminar Description coming soon.

Feb. 13, 2014
4 p.m. - 5 p.m.
Geology 3656

Presented By:

• Josh Colwell - University of Central Florida

The Cassini spacecraft entered Saturn orbit on June 30, 2004. Now in its ninth year orbiting Saturn, Cassini has completed more than 180 orbits of the ringed planet. Although Saturn’s rings are one of the most prominent and dramatic features of the solar system, their origin and age remain uncertain. Clues to the evolution of the rings exist in the complex structure and interactions of the ring particles. The Ultraviolet Imaging Spectrograph (UVIS) on Cassini has observed more than 100 stellar occultations of the rings. These measurements provide the highest spatial resolution data of the structure of the rings, but each occultation is only a one-dimensional cut across the rings. However, the multitude of observations at different times and different viewing geometries enables us to reconstruct the three-dimensional structure of the rings by treating the occultations like a medical Computed Tomography (CT) scan. This has revealed details about the clumping of the ring particles into so-called self-gravity wakes which are the result of the competing forces of Saturn’s tides which inhibit accretion and the gravitational attraction between the ring particles. In addition, occultations have revealed transient or localized structures that are mere meters across. Some of these may be the signature of accretion taking place within Saturn’s rings. I will provide an overview of the ring system and the observations of Saturn’s rings made with UVIS and discuss their implications for understanding the evolution of the ring system.

Feb. 20, 2014
4 p.m. - 5 p.m.
Geology 3656

Presented By:

• Ed Stone - Caltech

Seminar Description coming soon.

Feb. 27, 2014
4 p.m. - 5 p.m.
Geology 3656

Presented By:

• TBA-Geobiology -

Seminar Description coming soon.

March 6, 2014
4 p.m. - 5 p.m.
Geology 3656

Presented By:

• Kate Huntington - University of Washington

Seminar Description coming soon.

March 13, 2014
4 p.m. - 5 p.m.
Geology 3656

Presented By:

• Mike Lamb - Caltech

Seminar Description coming soon.