Example MaraRosa
Preliminary steps
Save content of example_mararosa folder of the present ISOLA distribution for later comparison
with your own experiments with this example.
The following text is a guide how you can obtain the same content of the folders and files as that
in the ISOLA distribution.
Create your example_mararosa folder with content identical to example_mararosa_start folder of
the present ISOLA distribution.
It should include folders :
focmec
and the following files:
novotny.cru
network.stn
event.isl
duration.isl
[Creation of poles and zero files, called 'pzfiles', is not described here. For this task, the user is
referred to file how_poles_zeros.doc in folder pzfiles.]
Open Matlab and use example_corinth as the current working folder.
Check Matlab paths [see readme files in isola_GUI_2013]
Run isola (i.e. write the word isola after the prompt).
It creates new folders:
data, gmtfiles, green, invert, output, polarity, synth
[Most of them are empty and later fill-in automatically during the steps described below; finally
you will be able to compare the folder content with the saved content of the ISOLA distribution.]
CONVERTING FROM SAC to ISOLA ASCII FILES, INSPECTING DATA
In ISOLA main window select
Import Data
Choose AutoSAC import
Read NS component of ANX station from data_SAC folder (will need option Big Endian)
All 3 components will appear automatically
[AutoSAC is rarely usable, it needs special filenames. More often each component has to be
entered separately by means of SAC import.]
Stations SERG and TRIZ will use acceleration records (because tehh braod-band records were
clipped).
Choose Save ISOLA ascii; save ANXunc.dat into folder data. Do not exit window. Repeat for all
stations. If button Common start time appears, press it.
Then Exit.
In ISOLA main window select
Try Filters
Load ANXunc.dat from folder data.
Select a few predefined filters or use My filter and Integrate.
E.g., My filter 0.04-0.08 Hz shows a relatively good signal-to-noise ratio in the low-frequency
range. Repeat for all stations, consulting paper sokos&zahradnik_srl2013.pdf.
Try also My filter 0.0-10 Hz and Integrate for all stations.
Station EFP shows a significant low-frequency artifact in all three components (i.e. distortion, or
'mouse' effect; see zahradnik_plesinger_bssa2010.pdf in folder papers). Another very convenient
tool to quickly discover the “mice” is SeisGram (A. Lomax) – see directly SAC file without
filtration, make “remove mean” and “integrate”.
This is why EFP will be excluded from inversion although formally its low-frequency S/N ratio is
high (see later with the tool Calculate SNR). Similar effect is present also in DRO-EW, less
obviously also at PVO-NS and PVO-EW.
Exit
Remark: If the *unc.dat file is acceleration, it is incorrectly called ‘velocity’ in this tool. This is a
small bug to be corrected in a future version. User can make use of Try filters also with *raw.dat
(see below). This is less convenient because *raw.dat files have less space between 0 and P
arrival, but any *raw.dat file is always velocity.
In ISOLA main window select
Calculate SNR
Load *unc.dat files and compare the amplitude spectra calculated from the part of record with
signal (after P onset) and with pure noise prior P onset, using the same lengths in the two
windows. This analysis needs enough part of record before P arrival! Save the SNR ratios.
At some stations (e.g. EFP in this example) the signal spectrum is ‘too much’ above the noise
spectrum, the SNR ratio is ‘too much optimistic’. Avoid saving SNR for such a station because it
would bias the global SNR estimate for your event.
In ISOLA main window select
Data Preparation
Load ANXunc.dat from folder data.
Plot Response to check the used pzfile.
Run Instrumental correction (with default parameters).
Make Origin Align with the automatically provided values of Origin Time and Start Time.
[The start times are saved in *stime.dat files automatically created during conversiuon from SAC
into ISOLA ascii files.]
Save data as ANXraw.dat in folder invert.
Repeat for all 10 stations.
Exit
PREPARING FOR GREEN FUNCTIONS and ELEMENTARY SEISMOGRAMS
In ISOLA main window select
Define Crustal Model
Load novotny.cru file (from the root of working folder), plot, save and exit.
In ISOLA main window select
Station Selection
Browse to network.stn (in the root of working folder).
Make map and select all 10 stations following the available help.
[You will need to adjust the ‘snap’ value to 0.01 to avoid simultaneous selection of two stations.]
Avoid double click on the same station. It will select such a station twice. Check the number of
the selected stations.
Exit
In ISOLA main window select
Seismic Source Definition
Choose Sources below epicenter
Select starting depth 1 km, depth step 1 km, number of sources 20
Calculate, see the plots of the trial source positions.
Exit
In ISOLA main window select
Green Function Computation
In fact, code will calculate not only Green functions, but elementary seismograms (see paper
krizova_etal_bssa2013.pdf), which means that a basic moment-rate time function should be also
chosen. It would be possible to change it later in the inversion window, without need to recalculate Green functions, just making convolution of the Green functions with a new time
function.
Choose Time function: Delta.
Choose Maximum frequency: 0.5 Hz, and Run.
Avoid pressing Yes in the Continue operation window until the run (in black window) is
finished!
Wait for message that the resulting files (elementary seismograms elemse*.dat files were copied
into invert folder; here * denotes the trial source number).
Exit
FIRST INVERSION (Case 1 of sokos&zahradnik_srl2013.pdf)
In ISOLA main window select
Inversion
Check the box denoted Filter common to all stations,
and choose the filter values (in Hz): 0.04 0.05 0.15 0.16
[This is the Case 1 of Fig. 3 in sokos&zahradnik_srl2013.pdf]
Time Window Search: choose the range: start -100 dt, step 5 dt, end 100 dt
[This is a window centered at the origin time. The dt is time step, in this example equal 0.03s,
with which all records were automatically re-sampled according to the choice of duration of the
time window in Event Info, 245.76 s = 8192 * dt.]
Choosing the temporal search by menas of multiples of dt is obsolete feature and will be later
removed from the GUI.
Choose Type of Inversion: deviatoric
Choose Number of subevents: 1
Select Stations/Freq. Band: choose stations and components as in cases 1 and 2 of
sokos&zahradnik_srl2013.pdf
[It means this: deselect EFP using column 1; deselect ANX EW and Z in columns 3 and 4;
deselect PVO NS in column 2; deselect DRO EW in column 3].
Remark: Deselecting of ANX-NS and ANX-EW was due to malfunction of the seismograph,
detectable only during a more sophisticated data quality control - PQLX software.
Update and Exit the Select Stations window.
Run the inversion in the non-interactive mode (i.e., in the 'black window' where the code is
running, you should answer n).
Plot the space-time correlation diagram [be patient it takes some time; if not working, watch
messages in Matlab window; most often the failure is due to missing system path to GMT and/or
missing Matlab path to gsview].
Exit the inversion window.
In ISOLA main window select
Plot Results
Check inv files if you are an advanced user (mainly inv1.dat, inv2.dat, you can also find them in
invert folder). Beginners should see results in a plot produced by the button Plot moment tensor.
Plot waveforms, see Remark below. Most often (except cases of big mistakes in instrumental
gains) it is recommendable to plot non-normalized waveforms.
Plot correlation vs. Source (find *inv1.ps file in invert folder; here * denotes the event
identification).
Plot moment tensor (Find *best.ps file, and find also the mtsol.txt file in invert folder)
If you like mtsol.txt file and want to use such an ISOLA output in your network, edit manually
the files footer.txt and header.txt (but please keep the acknowledgment to ISOLA).
Plot FM_STVAR index – a tool described in paper sokos&zahradnik_srl2013.pdf.
[For comparison with the ISOLA distribution, save these output files from FM_STVAR in
subfolder invert\SRL_case1]
Exit
Remark: Plotting waveforms
It is possible to make figure in different formats, use the Export Figure menu at the top of the
waveform plot. If choosing PNG format, the plot will appear in the output folder.
If choosing Prepare a GMT script, the script plobs_syn.bat will appear in the invert folder, then
you can run it manually and obtain post-script file 120425_10_34_11.59_wave.ps in the invert
folder.
In ISOLA main window select
Uncertainty Estimate
The estimate is relative, based on size of the data variance; it is a difficult parameter
(zahradnik_custodio_bssa2012).
Most recommended is to let the code helping you by choosing Estimate Data Variance
Select C=1
Choose the Source number (the sequential number of the trial source position, most likely the
position found in the inversion, i.e. the first column of inv2.dat, i.e. source number 8 for case 1
of sokos&zahradnik_srl2013.pdf)
Check (or edit) other parameters which are copied from the current inversion result.
Remember that the station/component selection is that one chosen in the inversion window.
Press Calculate, be patient, wait and then press Plot and/or Nodal Line Plot.
[The present version does not support GMT plotting of nodal lines, therefore choose no].
Calculations are performed in the invert folder. Copy results manually into
example_corinth\uncertainty\SRL_case1 for comparison with the distribution [mainly the file
statistics.dat, mean Kagan equal 14.3 degrees]; save also plot of nodal lines.
SECOND INVERSION (Case 2 of sokos&zahradnik_srl2013.pdf)
Go back to Inversion window.
Open Select Stations/Freq Band and edit the table according Case 2 of Fig.3 in
sokos&zahradnik_srl2013.pdf [i.e. different frequency band at different stations]
Run inversion
Inspect and plot all results as before
[Save output files in subfolder invert\SRL_case2]
CHECKING THE FIRST-MOTION POLARITIES
Use window Plot results, and the tool Polarities there.
The button Input Polarities will show the station.dat file which was automatically copied from
folder green into folder polarity. Edit the last column to enter the observed polarities. Use either
U, +, or C for compression and D or - for dilatation. A possible symbol is also ? to indicate an
unclear polarity. Save the file after editing. (It will be saved in the polarity folder). [You could
also do it manually by editing station.dat file in the polarity folder.]
Then use Copy - Edit (open, check and close two files without editing) to include the computed
focal mechanism. This feature is obsolete and will be later removed from the GUI.
Optionally, using button Add a mechanism, you may include some other focal mechanism for
comparison (e.g. that from a different seismic agency, e.g. Harvard GMT, if available).
See box Disable crustal.dat editing. If the box is checked, crustal.dat will be copied from
green.dat and used.
If un-checking the box, you can edit crustal.dat in the polarity folder. This allows users to project
station onto focal sphere in different model than that used in the waveform inversion, e.g. when it
is necessary to inspect possible effect of the Moho depth.
The polarity folder contains also source.dat. Its third column is the source depth taken from the
Event Info window. You may edit the source depth manually in the polarity folder. For example,
the source depth can be changed to the (centroid) depth obtained by the waveform inversion in
ISOLA, provided you believe that the centroid position is a better approximation of the
hypocenter position than the one used in Event Info.
Remark: Head waves are considered as possible first arrivals for polarity checking only if they
correspond to the Moho discontinuity. GUI assumes that Moho is the last discontinuity in the
velocity model crustal.dat. If your source is bellow Moho, the head waves will not be considered
in this GUI at all. In that case your velocity model may have some discontinuities even below
Moho, but only above the source. The velocity model crustal.dat in the polarity folder will need
editing: one formal layer (arbitrary thickness) will have to be added at the bottom of the model,
containing exactly the same parameters as in the layer containing the source.
This is the end of the most standard usage of ISOLA for single point sources.
OTHER OPTIONS
For Jacknifing option of the main ISOLA window, see paper sokos&zahradnik_srl2013.pdf.
There are also other options in the main ISOLA window, e.g. the Time Function, or H-C plot,
which are discussed in example_costarica. Option Forward Simulation is useful to create
synthetic tests.
Remark – missing stations, or fictitious stations
It is generally not recommended to select more stations than those which you intend to invert
(=for which you have *raw.dat files). But there are exceptions.
Let us assume that the code of the station is SPEC and that SPECraw.dat
is missing, we do not intend to invert it. If station SPEC has been selected,
Green function and elementary seismograms are calculated for this station, too.
The station appears in the list of the stations (file allstat.dat in invert folder) accessible from
the inversion window (the Select stations button). The station also appears in station.dat
accessible from Polarity plotting window. However, inversion will not run, even if the station
SPEC is deselected in the inversion window because SPECraw.dat is missing. [Formally we can
make inversion running for the other stations by copying any other *raw.dat from invert folder
into SPECraw.dat, but, of course, we should deselect SPEC from the inversion.] On the other
hand, Uncertainty analysis will work, both in the case that SPEC station is selected or deselected
in the inversion window. This is useful when analyzing uncertainty of a larger fictitious
(designed) network. Also Plot polarities will work with SPEC station. This is useful because you
can check polarity in more stations than those included in the waveform inversion.