# An Interactive System Based on the IASP91 Earth Model for Earthquake Data Processing
## 3 Major Functions
### Seismic Phase Identification  
For the massive amount of broadband seismic observations, download the seismic catalogues for the appropriate time period according to the USGS seismic catalogue search engine ([[https://earthquake.usgs.gov/earthquakes/search/](https://earthquake.usgs.gov/earthquakes/search/)]([https://earthquake.usgs.gov/earthquakes/search/](https://earthquake.usgs.gov/earthquakes/search/)) (accessed on 1 September 2022)) [31] and create the seismic event catalogue file *.evt for this project. The seismic event catalogue file *.evt will be placed under the catalogue for this project for later use; then, the seismic wave phase identification process can begin.  
Search the seismic event catalogue for the time of the possible event and determine the location of the earthquake in the data record, such as date and time, based on the location of the source, magnitude and distance of the observation area from the earthquake source, and the desired length of the imported data record (in minutes), the time system used for the region where the data is to be observed (UTC), etc. Finally, you can start reading the desired import data by executing File\(\rightarrow\)Open and selecting the appropriate data type.  
If the imported data is from a different format and thus may have different sampling intervals, the system will resample all the data to the dTsamp sampling interval in the Settings display to create seismic data with the same sampling rate.  
Once the data has been imported, the parameters are displayed in the Data Information section of the Setting area, including the sampling rate (Rate \(\times\) 1000) and the total number of stations (Ntrace/3), the length of the data in seconds (Xmax), the start time in T0 (yymmddhhmmss), and the total number of stations in Nstat.  
Since earthquakes occur every minute on Earth, the seismic catalogue downloaded from the above website is a large amount of data and reading them all into memory would affect the speed of the system. Generally speaking, the time between the occurrence of an earthquake and the observation of that seismic signal anywhere on Earth is no more than one hour, so this system uses a process to run Processing\(\rightarrow\)Load Events, which reads the event information for a time range of one hour before and one hour after the start time of the imported data into the system, and stores it in the Setting.  
Select the event in the drop-down menu and the parameters of the selected event will be displayed in the Event Selection with the date, time, epicenter location (Lon., Lat.), depth and magnitude (Mag) of the event.  
Once the source parameters have been determined, Processing\(\rightarrow\)Parameterizing Stations is run to calculate the center distance of each station, followed by ray tracing to calculate the theoretical traveltime of the selected phase. Once the ray tracing is complete, the theoretical traveltime curve is displayed on the seismogram and the average epicenter distance from all stations is also displayed in the Event Selection section of the Delt within the Settings display.  
If the ray tracing fails due to the selection of the phase, then the phase can be reselected according to the Delt value in the Event Selection column in the Settings display and the ray tracing can be performed again until successful.  
Once the theoretical traveltime has been calculated, the seismic records can be displayed by selecting Display\(\rightarrow\)Align in the Plotting Frame Parameters section within the Settings.