Karin Sigloch
Graduate
Student - Geosciences
Department
of Geosciences
312 Guyot Hall
Princeton University
Princeton, NJ 08544
Phone:
(609) 258-1504
E-Mail: sigloch
at princeton dot edu
Advisor: Guust Nolet, Tony Dahlen
Research
My Ph.D. research is in global seismic tomography, the science and art of making three-dimensional maps of the Earth's deep interior - essentially mapping temperature variations. Thermally driven motions shape the face of our planet and ultimately enable life on Earth. Understanding this "convection machine" is therefore of fundamental interest, and seismic imaging is the most immediate leverage point on the problem. Ultimately, we want to answer geodynamical questions such as these: How large are the heat fluxes of mantle plumes? Why do some plumes and subducting slabs seem to be stalling at the 670-km discontinuity? Is the lower mantle layered? What is the structure of the inner core?
Our group at Princeton has developed powerful theoretical and computational tools to capture the essential characteristics of seismic wave propagation on a global scale. In order to take full advantage of these modeling techniques, data needs to be measured in a much more sophisticated way than the traditional "picking" of a wave's arrival time. The subject of my Ph.D. research is to develop these new measurement techniques and to generate the first data sets tailored to the theory. I am also the first to systematically estimate anomalies of wave amplitudes, which is a much more delicate measurement than travel times but delivers complementary information. The central goal is to measure travel times and amplitudes in arbitrary frequency bands instead of just one. Wavelength discriminates between objects of different sizes; short waves are distorted by large and small anomalies, whereas long waves hardly sense small objects.
My dissertation summary (pdf file, written March 2006)
GJI (2006) paper describing the new measurement methods (pdf)
Homepages of my Ph.D. advisors: Guust Nolet, Tony Dahlen
Non-geophysical work
I first came to the U.S. as a student in Electrical Engineering to do research for my master's thesis at Bell Labs. Then as now, I was interested in the application of cutting-edge signal processing techniques to challenging physics problems, especially those involving waves. I used time-frequency methods to estimate radio wave propagation more efficiently.
The limited and thus precious resource in communications is the product of time and bandwidth. In order to successfully recover transmitted information, the receiver must always know how waves were distorted by the "channel", i.e. on the way from the sender to him. Estimating the channel's properties means sacrificing some of the overall resources because that time and bandwidth is lost to the transmission of actual information. When transmitters and receivers move rapidly in space, such as cell phones used in cars, the channel estimate must be updated very frequently. I worked on the first channel estimation method that explicitly took into account channel distortions (both over time and spectrum) that occur during the transmission of a single bit. Capturing the channel in this more realistic way means that we do not need to re-estimate it as often as before. People get to talk more on the phone for less money, and calls don't get dropped as often.
IEEE (2005) paper (pdf)
Updated 10/16/01