Rob_Porritt's blog

My summer is coming to a wrap so I thought I'd have a pseudo-closer. I'll start by summarizing my summer starting with the orientation:
1. Awesome trip  back to Socorro

2. Fieldwork - uninstalled 32 stations in ~ 2 weeks.

3. Some work on mylithospheric scale model

4. Gained faith in my analysis of the new sensors - starting analysis of horiztonal channels in addition to vertical channels

5. Went to a USArray data processing workshop at Northwestern and got a plethora of ideas on how to improve my data processing

6. Moved into a new place

7. Went camping at Giant Sequoia National Forest

So now I'm at a point were its time to write up a paper on our findings. But first I have to answer some questions about the robustness of our key observations. I'm seeing a low velocity zone which would we not expect and so I'm going to go reanalyze the raw data to see if the data does imply a low velocity zone or if its possible there was a "cycle skip" in the depth inversion which pushed the whole function to lower velocities for an isolated segment.

I also have some work to do on the new sensor testing. We made a new baseplate to put the sensor on and a first test is to see if the new baseplate is good or not. So I have the data available now to do the test to analyze the baseplate. 

Finally some of you may remember my shiny new white shoes I bought in Socorro. Well, they went on fieldwork and then camping this summer and they are far from shiny and new. I'll have to take a picture and put it up sometime.

I've spent this morning reviewing all the blogs and updating a few things on the forums and I've got to say I'm impressed with the amount of progress so far most have had - even if you think you're just starting and the summer's about to end.  Of course I have to add the caveat that this is my first time tracking intern progress that wasn't my own, so I have no yard stick to measure with. Anyway I'm looking forward to hearing about moe progress and seeing results (in whatever form they may be).

As I've commented on figures and captions I thought I should put up a couple of my own. The first one is the result of the Frequecny Time Analysis (FTAN) on the symmetric component correllation between stations ME42 and ME65. These are fairly close stations so only short periods are resolved. You can see the group and phase velocities as well as the prediction used to help find the velocities. The values are basically calculated by a grid search of power vs. slowness at each frequency and tracing the max power through. However, for space I've left the option which outputs that file off so we can't check it.

 The second image is a map of the western US group velocities at 25 seconds period. The dashed lines are the physiographic boundaries such as the Snake River Plain, Colorado Plateau, etc...

I have two projects. The primary one is imaging with our Flexible Arrays currently with ambient noise tomography (ANT). My second project is assessing the performance of the Metrozet replacement STS1 VBB sensor.

The big goal of the flexible arrays is to understand how the Mendocino Triple Junction evolves and to understand why or how there is a segmentation in the episodic tremor and slip recurrence intervals. We are using ambient noise for imaging because the best correlation with recurrence interval so far is topography and ANT is  best at imaging shallow structures. Therefore we should be able to make a shear wave velocity model of the region with ambient noise and try mapping variation in tremor recurrence interval to variation in lithology. Now while we're waiting for our data acquisition phases to finish we're going to start making preliminary investigations into the segmentation. Also we can look at other ways to improve the resolution of the imaging and make other advances to the process. Right now I am mostly working on plotting scripts and final correction programs. These final corrections programs are for simple things like calculating a 1-D model or correcting for topography. I've already made these in shell scripts, but they're slow, so I'm trying to rewrite them in c which makes them fast. I'm also improving my plotting scripts so I can choose what to plot. For instance if i want a cross section with an estimate of the moho, I just add a couple options to the general "plot_cross_section" script.