How to Use The Command Line Tools

OK, work with us here ... we going to go through a pretty simple, potentially meaningless, example of how to use the CLT utilities separately or together. We assume that you have installed SOD and have the CLT commands somewhere in your search path. If this assumption is true, you can sing along with these examples. If not, consider humming. Or, better yet, follow the instructions on the install page to get SOD setup.

Now, let's say you'd like to find all Mb=6.2 and above earthquakes in 2006 within a 10 degree box of the M8-ish Kuril Island event on 13 Jan 2007. The find_events command would be:

find_events -R 149/159/41/51 -b 2006 -e 2006 -m 6.2 -t MB

This command produces a line of output for each event it gathers:

153.1841 46.5550 10 2006_274_09_06_001 6.2MB
153.2660 46.5920 10 2006_319_11_14_013 6.5MB
154.4750 46.3710 10 2006_319_11_29_022 6.2MB
155.3050 46.6520 10 2006_319_11_34_058 6.4MB
154.7260 46.4830 10 2006_319_11_40_055 6.4MB
154.3860 46.1530 16 2006_341_19_10_021 6.3MB

This takes about 32 seconds to execute on a Mac laptop. Not a screamer, but try to get the same info faster elsewhere and it does directly access the IRIS DMC database by default.

Now, many of you will realize that station MAJO is in that part of the world. Those of you who do not know this could use find_stations to discover as much. But, for brevity, lets say you just know it is there, not where it is or if it was operating during the time range of interest. Just type:

find_events -o none -R 149./159/41/51 -b 2006 -e 2006 -m 6.2- -t MB -r |
find_stations -s MAJO

which produces

 138.2073  36.5425 405. MAJO

The output in this case is not particularly useful, but it does let you know that MAJO was operating during the time range of interest because a location is returned. Notice the little "-r" that was added to the find_events command. That just says pipe this request to the next command. Think of it like that annoying -K in GMT! [ASIDE: In reality, what -r does is generate a SOD XML recipe file instead of actually running the command. Using it without piping to another CLT utility is a good way to ease yourself into learning SOD XML recipes.] Also, notice the "-o none" that was added to find_events as well. That just says there is no need to print out the events anymore. Use it when you are satisfied with your request and want to just use it or pipe it elsewhere. OK, a minute or so is required for this. Again, nothing to write home about, but you know a lot more than you did and it beats your other options.

And [DRUM ROLL] ... you are poised to get seismograms! Try this:

find_events -o none -R 149./159/41/51 -b 2006 -e 2006 -m 6.2- -t MB -r | 
find_stations -s MAJO -n IU -o none -r | 

Note, we added "-n IU -o none -r" to find_stations and piped the output to find_seismograms, which gets 'BH*' data for all these events at station MAJO. That's it! When the smoke clears, you will have a subdirectory called "seismograms" that in turn has one directory per event and SAC seismograms for that event at MAJO. By adding "-n IU" to find_stations you tell SOD to restrict its station search to the IU network which greatly speeds up its work. The smoke takes less than 3 minutes to clear and in that time, you have directly accessed the IRIS DMC data archive and delivered seismograms to your machine, ready for analysis. All from a single command line sequence! Cool, eh?