Fast forward to this month, and I'm trying to get a preliminary version of a fault map done for my study area to go with a draft of my research proposal for my committee. I'm having a hard time committing to my interpretations (something I've struggled with since undergrad, when I always said I needed more data for my subsurface geology labs).
Seismic is an amazing tool, but I love being a geologist because it is so tactile. I decided I needed clay. It arrived today. This just might replace colouring as one of my favourite things about being a geologist (although nothing will ever replace being in the field at the very top of the list).
|A new package of modeling clay!|
Using 2D imaging to look at a 3D world is a problem in geology, not only when you're looking at seismic, but often when you're looking at the face of an outcrop. It's easy to misunderstand what you're seeing because you're not seeing the whole picture. Something that looks like this from one angle:
|One side of a smooshed ball of clay|
|The other side of the same smooshed ball of clay.|
Before I got to the point where I had the colourful smooshed ball pictured above, I started out making some layers. My first goal was to create a horst so I could look at what the structures looked like when sliced through at different angles. I used small blocks of clay, about 1" "square" so there will be lots of fresh colours left for me to work with another day.
|The green block is going to be the basement block of the horst|
|My first clay horst|
|A perpendicular cut through the horst.|
|An oblique cut through the horst.|
|An overhead view of the oblique cut through my horst.|
A lot of times, when I'm looking at a highly faulted section in my seismic, I feel like I'm trying to figure out the evolution of something like this:
|Interpreting structural evolution on seismic sometimes feels like trying to interpret this.|
I wasn't thinking about it as an apparent dip problem at that point, but while I was cleaning up my clay, I realized that's exactly what it was. Apparent dip is about more than just the dip angle. When you're looking at seismic, the same fault will have different apparent dips on different seismic lines, especially with a 2D seismic dataset. This is really, really important to keep in mind when I'm correlating faults across 2D lines (and across different vintages of seismic).
The other result of my brief foray into modeling today was that I made some new colours to use for next time (because there will be a next time).
|Some of the pieces of my fault block as new colours for next time.|