Statistical Analysis of Point Data
Let's analyze earthquake distributions in Oregon! We'll look at patterns
in both time and space...
We'll also see if there is any correlation with the pattern of
faults in Oregon.
We'll also see how our choice of grid size for analysis can lead to
different results, known as the MAUP.
1. Download the earthquake database from http://nwdata.geol.pdx.edu/NW-Quake/
2. Load it into ArcView (this will require saving it in a format that can
be added as an Event Theme, a task that should be familiar by now). Play with it. Do you
see any patterns? Try different ways of looking at it with graduated symbols, based on the
different fields. Get a feel for what your data set is like!
3. Put in some context... Add the States from the ESRI data (another
familiar task by now). Is everything plotting correctly? :-) Is Percy tricking you again?
I'll show you in class a quick way to deal with this!
4. Download the Faults Shapefile from the State Gis place http://www.sscgis.state.or.us/data/themes.html
5. Use the projection tool to convert this from that goofy state
projection to DD. I'll show you how to do this.
6. Clip the eathquakes theme so that you only have the Oregon set.
7. Use the GridMaker tool (ESRI/AVGIS_30/Arcview/samples/scripts) to
overlay a grid. You're going to try a few different sizes.
8. Count how many points there are in each grid, using the Field->
Summarize feature in the Theme Table screen.
9. Do a quadrat analysis.
10. Try at least 3 different grid sizes, like 10 x 10 and 20 x 20, and
50x50. What differences do you see?
11. Now try different subsets of data, divided out by time and intensity.
Are the spatial patterns the same?
There is a lot going on in this assignment! We're going to take our time
and savor it...