The second stage of the project was a bit harder to get started with. The task itself was fairly straightforward: to pick the arrival point of the p-waves I had selected during the first stage of sorting. However, I needed to continue to build on my understanding of the terminal in order to get the files ready to run with the new picking program.
The first day, Professor Ford met with me and directed me through the process. First, I combined all of the selected files from the first stage saved in the Mark1 files into one file if any had multiple Mark files. I then created three copies of this file and named each 'Mark1r.txt,' 'Mark1t.txt,' and 'Mark1z.txt.' I then opened each in xcode and used the find and replace function to replace all of the '.z.'s in the file names with r or t for the r and t files. I then used the terminal to move all of the selected files from SAC to a new bpband folder. From there, I was ready to make the macro for the new program. Using the terminal window, I generated a new macro list, and then used the terminal to open the program to begin picking arrival points. For each waveform, I would zoom in on a broad area around where I thought the signal arrived, then press T and 1 with the cursor hovering over the arrival point to mark it. Then I would press Q to move on to the next wavelength and repeat until all arrival points had been picked.
Initially, everything seemed to make sense with Professor Ford's guidance, though there were many steps to keep track of. I took what I thought were detailed notes along the way, but as I began to repeat the process myself, I started to find holes in my notes. Because my notes were handwritten, there were places where the terminal code was not correct simply because I hadn't thought to be careful enough in denoting where a space should be, or what a symbol was. For example, I couldn't get my waveform files to move because I was typing “chmod utx move_ranked.csh.” When I asked Professor Ford for help, she said that the 't' in 'utx' was supposed to be a '+,' so I went back to my notes and sure enough it was shorter than I usually write my t's, but I decided to add 'plus' over the symbol to better remind myself in the future. It took me two or three days of getting used to the process, asking Professor Ford for corrections here and there, and modifying my notes to finally get the process to run smoothly. Once it did, though, it was very smooth sailing and I was able to gain a much better understanding of the terminal process and complete picking p-waves relatively quickly.
Picking the p-wave arrival times themselves was fairly straightforward. Most of the files had clearly visible arrival times, so I was able to pick them in just a few seconds and move on. A few, though, were not quite as clear. After a while, though, I found a good rhythm by zooming in on a broader section so I could get a good sense of the pattern before and after the arrival time. In doing so, I could spot exactly when the patterns shifted from one to the next, and picked the arrival time accordingly. This whole process only lasted a couple weeks as opposed to the initial stage, so we were quick to move on to the third stage once all of the seismic station files were completed.