Localization user guide

The following files are necessary in order to perform the source location, as shown in Figure 1:

1. Seed Waveform: The User selects a Seed file from the Episode database, or after applying the ‘Signal Download Tool’ (see “Data Handling Applications” chapter).
2. Catalog: The User selects a Seismic Catalog from the Episode database (See "AH Episodes" chapter)
3. Seismic Event: The User select a seismic event which has been downloaded after applying the ‘Signal Download Tool’ (see “Data Handling Applications” chapter).
4. Seismogram picks: P-wave first arrival picks, selected by the User from the waveforms (described below)
5. Velocity Model: Velocity model uploaded from the Geological data of the selected Episode (see "AH Episodes" chapter).

Now, all data needed is available for the 'TRMLOC' application.

Figure 1. Input files selection

The TRMLOC application can be selected from catalog or from the seed file as shown in Figure 1b:

Figure 1b. Selection of the application from the waveform data uploaded in the workspace

Once all these files are selected, a map appears on the screen showing the epicenter of the selected event (red circle) and the locations of the seismic stations comprising the regional network (green triangles), as demonstrated in Figure 2. Information on the event and the stations appears on the screen, after clicking on the circle or the triangles, respectively. Moreover, the waveforms are also shown in the screen and are available for elaboration (see also "Waveform viewer guide" in "Visualization" chapter). As depicted in Figure 2, only the vertical channels are shown by default, since the methodology applied in this application uses only P-waves. Nevertheless, the User can make all the channels appear on the window, by ticking the "E" and "N" components, next to the 'Show channels' field, just below the map in Figure 2.

Figure 2. Picking p-wave arrival times on the waveforms

In this application the User has to pick a single point in each waveform (Figure 2), instead of a phase (i.e. two points, starting and ending). For the waveform processing details see also "FOCI” and “Spectral Analysis” chapters.

Parameters selected for the source localization:

The additional input parameters required to execute the application are shown in Figure 3. Some of those parameters take numerical arguments, printed by the User, others take values selected from a list. In any case default values are provided. Advanced options are also available, however the application runs properly even if they are discarded. For detailed description of all application parameters please see at the TRMLOC manual at the document repository.

Figure 3. Input parameters for the application

Once the point picking in the waveforms and the parameter selection is over, the User shall click on 'RUN' (green button) to initiate the Source Localization process.

The results obtained after the process terminates include a variety of output values, files and figures. Numerical outputs are the hypocenter coordinates obtained by different methods, their uncertainties and the original coordinates from the catalog, for comparison (Figure 4, top). These values are also plotted in charts, one showing the epicentral location (longitude-latitude) of the original and obtained solutions together with the stations positions (Figure 4, bottom), and one more showing the vertical (depth) distribution of the aforementioned solutions. Four ascii files are also created ('log.txt', 'res.txt', 'xcp.txt', and 'out.txt'), which contained detailed and specialized information on the process, the results and their uncertainties. These files can be either displayed in the screen or downloaded by the User.

Figure 4. Some of the applications outputs

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