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Low Level Services Data Handling Applications are distinguished from High Level Services Data Processing Applications because they perform relatively simple data transformations, resulting to data as well. On the contrary, High Level Services Data Processing Applications perform specific analyses and methods, utilizing data in order ti produce more sophisticated results, not just simple data elaboration/transformation. The Low Level Services The Data Handling Applications available in the IS-EPOS web platform, are described in this section:

• SEED to SAC Converter
• Ground Motion Parameters Tool
• Seismogram picking tool
• Catalog Filter
• Magnitude Conversion
• Signal download tool 
• Waveform Download tool
• Time-Series Builder
• Catalog Export
• GDF Export
  
  
  Description of Low-Level ServicesData Handling Applications:

•  SEED to SAC Converter

This application uses seed files (uploaded from the episode data or imported from the episode catalog available in the workspace) as input, to convert the signal into SAC format. The User may select from 'Actions', 'Use in Application' and then 'SEED to SAC converter' (Figure 1). Then the screen shown in Figure 2 appears and the User just clicks on the button /RUN' to execute the conversion.  

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Seismogram picking tool takes as input seed files. The service application interface is shown in Figure 4. Here the User can pick phases or points from the given waveforms (also see Waveform "Viewer guide" section in "Visualizations" chapter). Once the picks have been chosen, the User may proceed to further analysis by clicking the green "Run: button (blue button, Figure 4.). The number of picked phases are counted by the system. The User can now recall the output file (picks.xml), for any Waveform-based application (i.e. Moment Tensor Inversion, Earthquake Spectra, Source Location). Optionally, the user can select the seismic events (second input, top of Figure 4) from the seismic catalog, or postpone this action for after selection of the application to perform. 

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Figure 4.

•  Catalog Filter

This is a service an application for filtering seismic catalogs. The product is a new catalog filtered upon the User's parameters setting. The input file is a seismic catalog that can be uploaded from "Change Input" tab (shown in the yellow frame of Figure 5). Next, the User may perform various filtering according to the values of the attributes assigned in the catalog. The User may choose one of these attributes (as ID, ML, Lat etc, displayed in Figure 5) and provide the values he/she wishes, selecting among 'Select all values' (e.g ID field, Figure 5), 'Select Range' (from the calendar - Field 1, Figure 5, or by typing values range - Field 1, Figure 5) and 'Select list of values' (Field 3 Figure 5).

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As soon as the filtering criteria have been defined, the User shall click on the "Run" button (green button at the bottom of Figure 5) to apply the those criteria. The User may also select the "Preview Selection on map" tab (indicated by the green frame, at the bottom of Figure 5) in order to view an illustration of the events from the original catalog (red circles) and the events included in the filtered catalog (green circles). A new catalog (catalog.mat) has been created and it is available for any further processing. In addition the system provides all the information and services applications that are valid for the original catalogs (see "AH Episodes" Chapter, for details).

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•  Magnitude Conversion

Magnitude Conversion is a service a application used for establishing linear relationships between different magnitude scales, which can be later used for conversion of magnitudes from one scale to another. The input file is the seismic catalog that can be uploaded from "Change Input" tab (shown on right side of Figure 7). The Service The application can be performed only in datasets in which more than one magnitude scale (or, alternatively, Energy or Seismic Moment can be introduced as inputs as well) is assigned for the seismic events (e.g. ML and Mw). The parameters that the user has to set/choose are also shown in Figure 7:

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• Choose first vector to compare: The user may choose among the different magnitude scales available in the catalog.
• Choose second vector to compare: The user may choose among the different magnitude scales available in the catalog.
• Regression Method: Three different regression methods can be used - General Orthogonal Regression, Standard Least Squares and Inverted Least Squares.
• Error Variance Ratio: A float number should be assigned here (default is 1). Note that this option is only valid when General Orthogonal Regression method, is chosen.

The outputs that the service the application produces are:

•  A report with the parameters (slope and intercept) of the regression process and some associated statistical parameters (Figure 7)
• Vectors of the first, second magnitude selected, together with the vector of the new (converted) magnitudes obtained by the application of the regression equation.
• A figure with one magnitude scale plotted versus the other one (scatter plot) and the linear regression curve (Figure 8). Zooming option is enabled for this Figure.

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•  Signal download tool

This services applications extracts seed files and event files from a selected catalog into the User workspace. These extracted files can be used later on at any service any application dealing with waveform processing, including Spectral Analysis, Source Location, Moment Tensor Inversion and Seed response calculation. This is an alternative way of exporting seed files instead of searching into the episode database. The User needs first to select a catalog from the workspace and click subsequently on ACTIONS, USE IN SERVICE APPLICATION and Signal download tool tabs, as indicated by the red boxes in Figure 9.

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After this step, the list of events appears in the screen as shown in Figure 10 and the User is requested to select  an event for extracting event information and seed file. The User may also chose downloading between Seed Signal, Accelerogram Seed Signal, or All, by ticking on the respective box shown at the bottom left corner of Figure 10.Then, the output files are extracted after clicking on the RUN button (green button, bottom Figure 10). Those files are stored in a Signal Download folder, into the User's workspace and can be further used as input in several services applications as mentioned above.

Figure 10.

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This application allows for ordering parts of continuous waveforms for specific dates and stations as processed by Seiscomp. The User needs to upload the application from the low-level services applications repository to the personal workspace. The preparation of the waveform is executed by Arclink-fetch. The User has to select the respective episode and time period of interest, as shown in Figure 11). For selection of the the time period the User may either set values to the 'Start' and 'End' point, or specify the 'Start' point and the duration (length) of the periods he/she wishes to study. After this the User selects among the channels and the stations available for each episodes and clicKs on "RUN" button. A *.seed file is soon to be created, and it can be furthered processed within other applications, such as, FOCI, Waveform Analysis or Seismogram picking tool.

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