The Final Countdown

July 29th, 2010

This past week I finished making measurements on all my station data.  Simon came back from his trip on Monday to check up on our progress and look at the results we had gotten so far.  We decided that the rotation-correlation method I had been looking at primarily to make the measurements was suspect because all of the fast-axis directions fell along a line 45 degrees off of the null direction.  We decided to switch over to using the Minimum Energy method, instead, which determines the splitting parameters by finding those that minimize the energy on the transverse wave upon correction.  For me, this meant going through the splits I had already done and finding the ones that had a good ME result as well as RC result and using only those.  This significantly reduced the amount of data I had to work with.  

After I had refined the data for my 5 stations, we started to compare it to results obtained by other people in the region.  In particular we compared it to a paper published by West, Fouch et. al (2009) that used data from the same stations (plus more) but only came up with a 1 layer anisotropic model.  I plotted up their results quickly and made a rough conglomeration of my stations using Illustrator (Splitlab does not allow you to plot and model multiple stations) to compare the two.  Our results appear to be similar, however their results look more like our Rotation-Correlation results than our Minimum Energy results.  Simon asked me to prepare some figures and a short explanation to send to one of his former students, Kris Walker, who is apparently the expert on shear wave splitting.  We want to get his opinion on whether our data is high enough quality to justify fitting a 2 layer model (fingers crossed he says yes).  

In the meantime, Mairi has finished preparing the data from her stations (the ones we recently deployed in NV) and says that somewhere between 6-8 earthquakes occurred during the short time frame she has.  We are working on getting the files in the right format so that I can perform splitting measurements to add to our data collection.

I can't believe it but I only have about a week left here.  I don't know where the summer went but I am definitely feeling the pressure to produce a complete project.

-Kelsey

Example of one possible fit for just one station (ELK).  We are not sure yet if this model will fit the combined data from all the stations.