An example with the 2015 M7.8 Nepal earthquake

Here I will walk you step by step through running the Nepal earthquake. This is one of the pre-canned examples which you can find in the MUD/examples folder. Note this is using only the high-rate GPS stations. If you want to reproduce the full results that we calculated in the Galetzka et al., 2015 paper in Science, that's more complicated because there we used InSAR. That's for another time. The model you will obtain here is different (this is inversion after all!) from the one in the paper but this is a useful end-to-end exercise.

Step 1: Create a folder for your parameter files in and copy the example .inv file

Parameter files used for inversion have a .inv extension. This is not required I just do it so I have an easy way of identifying what is what. I have a folder separate from everything else where I keep my parameter (.inv) files. So create a folder where you will save all your parameter files and then copy the file nepal_version_2.inv.py from $MUD/examples/nepal_inverse\ into that folder. In my case all my inversion files are in /Users/dmelgar/Slip_inv/run/ this is what that folder looks like for me after copying the relevant file:

Step 2: Edit the parameter file and run it with init = 0

Open the nepal_version_2.inv.py file and change the variables that define where the inversion results and auxiliary files will be. This is a different folder than where you save your parameter files, like so:

home='/Users/dmelgar/Slip_inv/'
project_name='Nepal_example'
run_name='example'

home is where all the different inversions will live. project_name will be the folder name for this inversion project, and run_name will be the name of the inversion output files. After this is done set the flags to only initalize the folder structure by doing:

init=1 #Initalize project
make_green=0 #Compute GFs
make_synthetics=0 #Compute synthetics for a given model at given stations
G_from_file=0# =0 read GFs and create a new G, =1 load G from file
invert=0  # =1 runs inversion, =0 does nothing

Nothing else matters for now. Next step is to run it. Go to the terminal and run the script by typing:

  python /Users/dmelgar/code/MudPy/examples/nepal_inverse/nepal_version2.inv.py

You should now see the entire inversion project folder structure. On my system it looks like this:

Step 3: Copy the relevant auxiliary files into the new folder structure

You need 3 auxiliary files to run the inversion (i) a fault geometry file (ii) a layered Earth structure file and (iii) a Green's function list file (GFlist) that specifies the station locations and types of data. MudPy requires the auxiliary files to be in specific locations so from $MUD/examples/nepal_inverse/ copy the following files:

(i) nepal_10.fault is the fault geometry and should be placed in home/project_name/data/model_info/

(ii) avouac.mod is the Earth structure model and should be placed in home/project_name/structure/

(iii) nepal_simple_v2.gflist is the GFlist file and should go in home/project_name/data/station_info/

Step 4: Copy the waveform data

Now you need data to invert! I've provided 5Hz GPS waveforms in $MUD/examples/nepal_inverse/data/. There is data for 5 sites and three components of motion. These are provided as SAC files. Copy all the data into home/project_name/data/waveforms

Step 5: Edit the GFlist file

You need to edit the file by hand. The GFlist file should reflect the type of data that each waveform corresponds to (displacement, velocity, tsunami, etc.) and where the data is. The GFlist file for my system looks like:

#station lon lat "static,disp,vel,tsun,insar" "Static file, displacement file, velocity file,tsunami file,insar file" "static sigmas(n,e,u),displacement sigmas(n,e,u),velocity sigmas(n,e,u),tsunami sigma,tsunami sigma" KKN4 85.2788 27.8008 0 1 0 0 0 /foo/bar /Users/dmelgar/Slip_inv/Nepal_example/data/waveforms/KKN4.disp /foo/bar /foo/bar /foo/bar 1 1 1 1.0 1.0 1.0 1 1 1 0 0 0 0 1 0 NAST 85.3277 27.6567 0 1 0 0 0 /foo/bar /Users/dmelgar/Slip_inv/Nepal_example/data/waveforms/NAST.disp /foo/bar /foo/bar /foo/bar 1 1 1 1.0 1.0 1.0 1 1 1 0 0 0 0 1 0 RMTE 86.5971 26.991 0 1 0 0 0 /foo/bar /Users/dmelgar/Slip_inv/Nepal_example/data/waveforms/RMTE.disp /foo/bar /foo/bar /foo/bar 1 1 1 1.0 1.0 1.0 1 1 1 0 0 0 0 1 0 SNDL 85.7989 27.3849 0 1 0 0 0 /foo/bar /Users/dmelgar/Slip_inv/Nepal_example/data/waveforms/SNDL.disp /foo/bar /foo/bar /foo/bar 1 1 1 1.0 1.0 1.0 1 1 1 0 0 0 0 1 0 SYBC 86.7124 27.8143 0 1 0 0 0 /foo/bar /Users/dmelgar/Slip_inv/Nepal_example/data/waveforms/SYBC.disp /foo/bar /foo/bar /foo/bar 1 1 1 1.0 1.0 1.0 1 1 1 0 0 0 0 1 0 CHLM 85.3141 28.2072 0 1 0 0 0 /foo/bar /Users/dmelgar/Slip_inv/Nepal_example/data/waveforms/CHLM.disp /foo/bar /foo/bar /foo/bar 1 1 1 1.0 1.0 1.0 1 1 1 0 0 0 0 1 0