Jake's blog

Abstract

Submitted by Jake on Thu, 2007-08-30 04:51.

Cao, Masson, & Romanowicz in 2006 studied an earthquake doublet which enabled them to determine the existence of short wavelength topography on the Inner-Core Boundary.  Our project focuses on this topography to better understand their distribution.  We have confirmed that the Inner Core Boundary is characterized by globally distributed short wavelength topography.  If the PKIKP/PKiKP amplitude ratio was > 2, then short wavelength topography in which to scatter PKiKP could be inferred.  We used a band-pass filter of 1.0 – 2.0 Hz in order to clearly see PKIKP and PKiKP arrival times.  A ratio of PKIKP/PKiKP < 1 means that no topography is present and indeed these signals were also globally distributed on the ICB.  The ratio of no topography to short wavelength topography on the ICB is ~ 2, further clarifying the overall topography of the ICB.  Short wavelength topography of the ICB may influence fluid motion in the Earth’s Core and ultimately the geodynamo. 

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finish line

Submitted by Jake on Tue, 2007-08-28 19:41.

Looking at the longer frequency range has given us a clear picture of the travel-time differences between the eastern and western inner core hemispheres. The shorter frequency created too much scattering. The big question is why is there a hemispherical difference? Well the composition of the inner core must not be homogenous to create the differing velocities, for one. But why this is I do not know. This question wasn't the main focus for this research however. Finding the bumpy topography was the goal and the goal was completed.

I looked back to see what my goals for the summer were and I'm not disappointed. I've learned how to use C-shell Linux, or is it Unix, I get those confused. I have been learning about how waves propogate through the Earth and how seismologists can interpret them (at least the PKIKP-PKiKP). I have convincingly used this knowledge to detect topography of the Inner Core Boundary. My last goal was to figure out whether Cal would be a good choice for me for graduate school. I know most of the choice is up to the department to accept me, but I have a strong feeling that I could continue research with the seismological lab even if my undergrad performance isn't up to par. However I'm not so sure I want to continue down this path. I'm not so sure that this type of research can keep my interest.  But I love being at Cal and I can definitely see myself continuing my studies here no matter what that may be.  I have much asking and searching to do.

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Tedium

Submitted by Jake on Thu, 2007-08-16 21:21.
Barbara the director came back from France and was "impressed" with the work that has been done. However she suggested that we look at the data AGAIN but with a longer frequency of .7 to 2 Hz. I had only looked at the data from 1 to 2 Hz. The longer frequency might enable us to see larger scale bumps. Larger scale bumps would not show up on the shorter frequencies. I can't wait to go through the thousands of seismograms I already spent weeks looking at...Undecided
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Progress

Submitted by Jake on Sat, 2007-07-28 07:37.
I am done analyzing most of the data for my project this summer. It was quite tedious but I got through it quickly and have learned how to use unix. My results were deemed successful and I will start writing the abstract for AGU later on in the summer. After processing tons of data, we have found a global distribution of seismic stations recording "bumps" at the ICB. This is good news. We now know that the entire ICB is covered with these bumps which form from lower density material in the inner core bouyantly rising (I think). I am disappointed that our research won't be pursued any further to understand what the actual significance of these bumps are. I guess that will be somebody else's job. Here's a generated image from the data I've been working with. Dark blue dots and covered up red and aqua dots represent the distribution of seismographs which detected a clear "bump" at the ICB. The green dots show areas of the ICB which are normal (no bumps). It is expected that there are more normal detections because the bumps are relatively small. The lines represent the paths that the PKIKP-PKiKP waves took from the earthquake to the station. One must note that due to the lack of seismic stations in the oceans there is a sizable gap in our data. This project is inevitably biased towards areas with more seismic stations than others, but hope is not lost as we can still see a global distribution.


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cal

Submitted by Jake on Fri, 2007-07-13 19:37.
I've finally settled in at Berkeley. I've already seen Andrew and Dave from IRIS at the lab. I'm done sorting through thousands of seismograms that we downloaded from IRIS. The next step is to measure the amplitudes of the PKIKP vs PKiKP waves to see if there is any scattering of the PKiKP at the ICB. If the PKiKP is about twice as weak as PKIKP then there must be a bump at the ICB. Knowing the extent of these bumps can help us understand Outercore convection and ultimately the geodynamo and the magnetic field. exciting stuff.

So far I've learned the basics to C-shell Unix and have been using the Seismic Analysis Code (SAC) to look at the seismograms. I also have a better understanding on how seismic waves tell us what is underground. I think I have a good start toward my goals so far. Here are a couple relevant graphics made by the Post-Doc (Aimin Cao) I'm working under (note on the second image he only looked at doublets to see how the inner core rotates over time. For the same location on the ICB there is no bump in A and there is a bump in B, meaning the inner core must have rotated):
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Summer/Goals

Submitted by Jake on Mon, 2007-06-04 07:56.
My mind is completely wide open for this summer, considering I am not too sure of what my daily tasks will be. I know that I will be basically processing seismic data from stations all over the world and using the data to understand how the inner core/outer core boundary looks like. I believe that this information could help us understand the dynamo effect of our planet. It's pretty exciting work, considering that this hasn't been studied in depth before.

Goals:
-Better understand seismic waves and how they function
-Learn how to use one or more computer programs for data processing, looking at seismic waves, and/or creating models
-Figure out what the ICB (Inner Core Boundary) looks like
-Figure out if I want to go to Cal for grad school, and if I want to continue to study seismology
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