User Guide: Spectral Analysis

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 phase 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).

Figure 1.

Figure. 2. Waveform data selection from a catalog uploaded in the workspace

The Spectral Analysis application can be selected from the seed file as shown in Figure 2b:

Figure 2b. Selection of the application from the data uploaded in the workspace

Waveform Processing

The options provided by the waveform viewer are described in Figure 2 (see also "Waveform viewer guide" section within "Visualizations" chapter) : When clicking on one waveform, additional options appear.

Figure 2. Demonstration of waveform processing tool

1. The user selects the component(s) that he/she wishes to be displayed on the screen. East-West, North-South, Vertical.
2. Horizontal zooming in-out.
3. Vertical zooming in-out.
4. Undo zooming.
5. Select between phase (start and end point) picking and single point picking.
6. Select between P-wave and S-wave picking.
7. .Undo picking.
8. Horizontal zooming tool. The User may alternatively zoom in-out the waveform by clicking on this small vertical bar and move the mouse left-right.
9. Collapse the details of the waveform.

Picking Phase for Waveform Analysis:

The User has to select 'Phase' and 'P' options from the fields 5 and 6 of Figure 2 for the vertical component of a station (**Z channel) and 'Phase' and 'S' options from the fields 5 and 6 of Figure 2 for one of the Horizontal components of a station (**N or **E channel). Then he/she has to pick the starting and ending point that wishes to use in Spectral Analysis (Figure 3).

Figure 3. Phase picking demonstration for S (upper frame) and P (lower frame) waves

The User may repeat the process for additional vertical or horizontal components of other stations. When the picking is over, the User shall click on the 'RUN' tab (green button) to initiate the waveform analysis. Soon the process will terminate and the Spectral Analysis results are available (Figure 4). Graphs are also generated (Figure 5) and can be downloaded in different formats. Similar results are also obtained for the P-Wave analysis.

Figure 4. Output parameters of the application

Figure 5. An output graph of the application

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