(Orals passed through Autumn '15)
Download the Dissertation Topic List in pdf format.
Presented below are the research topics that Ph.D students in the Department of Earth and Environmental Sciences at Columbia University are currently engaged in.
Date Orals Passed: 4/13
Advisory Committee: Hemming, Christie-Blick, Broecker
Date Orals Passed: 4/15
Advisory Committee: Linsley, deMenocal, B. Anderson
Date Orals Passed: 4/15
margins from multi-beam sonarand multi-channel seismic reflection data.
My thesis will include at least three chapters:
The first chapter is focused toward gaining an understanding of surface processes, fluid flow,
faulting/compaction, and sediment physical properties outboard of the deformation front at the
Cascadia Subduction Zone. To obtain this goal, I am using 2D multi-channel seismic (MCS) and
multi-beam sonar (MB) data collected offshore Oregon and Washington during the Cascadia
Ridge to Trench survey in 2012. I first performed detailed p-wave velocity analysis to achieve
sub-surface perspective on seafloor surface related fluid flow features (e.g. pockmarks). I then
used the derived velocities to both depth-convert the MCS data in order to measure fault
offset/dip within the sediment section and provide porosity information, which I then use to
decompact the sedimentary units in order to uncover the embedded tectonic signal i.e. intra-plate
faulting. As an additional project, I mapped large-scale scour marks on the distal Astoria Fan and
then inverted for the source process azimuth. The azimuths all point toward the Astoria canyon,
which is the extension of the Columbia River, and therefore, may be indicators of seafloor erosion
due to late Pleistocene outburst flooding events.
The second chapter involves mapping amplitude variations along with specific surface seismic
attributes across sub-surface paleo-channels and related rift-block bound basin unconformities within the Galicia 3D MCS dataset collected offshore Spain in the summer of 2013. The 3D volume is ~20km x 67km and has been processed to pre-stack time migration. I am then relating the amplitude variations/surface seismic attributes to current seafloor reflectivity derived from the MB backscatter data in order to better constrain channel morphology and abyssal plain sand distribution as it relates to tectonic and climatic forcing processes from the Miocene to present. Furthermore, I plan to use the drilling results/check-shots to generate synthetics in order to better constrain the time-depth relationship indicated by the reflectivity series.
The third chapter will involve 2D MCS and MB data collected offshore the US East coast during
both the ENAM & USGS/NOAA surveys in 2013-2015. I will develop a 1D inversion algorithm to
constrain the p-wave velocities and use them to study the physical properties of discrete Holocene submarine slope failures. Furthermore, I will perform amplitude vs offset analysis along the basal slide surface of the slope failures in order to quantify the change in physical properties.
One of the primary goals of my research is to understand the processes of shelf-slope exchange along the WAP margins. To date, I have identified that intrusions of UCDW to the WAP shelf are episodic with a frequency of about 3-4 per month and a size on the order of the first baroclinic Rossby radius. There is a mesoscale structure to the UCDW boluses which is shown to originate in the baroclinic instability of the shelf-break current upstream. The advective component of the intruding current is coherent with the along-slope wind stress in the weather-band and intrusion sites are tied to bathymetry at the shelf break (both cross-cutting canyons and seaward-veering isobaths). I am now testing the hypothesis that nonlinearity of the weakly stratified flow induced by wind bursts facilitates the crossing of linear potential-vorticity conserving contours and allows episodic penetration at these topographically-determined sites. The hope is to isolate essential dynamics so as to extend these findings to regions of similar shelf-break and current configuration around the Antarctic continent. Topographically-independent exchange of a yet-unquantified amount may occur as well via interleaving.
A parallel goal of my research is to quantify the modification (by vertical and lateral mixing) of the intruding water mass. Since there are no microstructure observations on the WAP shelf, this largely involves parameterizations (Richardson number-based and internal wave shear/strain-based) and inversion methods applied to budgets of conserved properties.
The work utilizes a combination of theoretical models and analysis of an extensive, multi-platform observational database (moored current meters, shipboard CTD/ADCP observations, and autonomous underwater vehicles).
Advisory Committee:Class, Shillington, Hemming
Magmatism at the southern end of the East African Rift System - origin and role during early stage rifting.