Earthquake Dialog

The earthquake definition dialog is vertically divided into two identical frames, one for each earthquake. The features of each of these two will be described in what follows:

1. General record information can be entered in three input text boxes: Name, Filename, and Description.
2. A "View" button, which generates a dialog with three plots showing the acceleration, velocity and displacement records of the current ground motion. The plots reflect the "modified" quantities as will be described next.
3. A "Read" button starts the "Read Earthquake" dialog which allows the user to pick a ground motion file to be read, and will be discussed later.
4. Two editable quantities: Amplification and Timescale. Amplification is the amount by which the original record is multiplied before being used. The unchanged and changed records will be referred to as "Original" and "Modified" respectively. The "timescale" is defined as:

dt_modified = dt_original / timescale, which leads to

duration_modified = duration_original / timescale, assuming all the data points are used

5. Two lists of properties, one for the original and another for the modified record. The properties are summarized in the following table, which shows whether that quantity can be edited or not:

The modified PGA, PGV and PGD can be specified resulting in the program choosing an appropriate "amplification" for the original record. It is not possible to specify more than one of PGA, PGV and PGD at the same time. More control can be exercised by modifying dt_modified which will affect PGV and PGD but not PGA. Another is filtering of the ground motion, a function that performs that will be added in the near future.

Figure 2: Earthquake dialog

Earthquake File Selection Dialog

This dialog is called from the Earthquake dialog. The windows Open File dialog will be automatically called if the user doesn't specify a filename in the Earthquake dialog. The user then uses the familiar Windows file picking dialog to choose the right input motion file. It's also possible to type in the file name in a specified box on the dialog. A name without a path description is assumed to be in the same directory as the executable file of BiSpec.

After the file selection, the user should specify the format of the file. Currently only two formats are supported: The SAC format which applies to the SAC motions, and a User format, which is more general and can be defined. If the SAC format is chosen, the user can read the record and exit the dialog, the program will give an error message if the record is not read correctly. However the user should check the number of points read which the program reports to make sure the file was actually read. That's especially the case when the User option is picked.

With the User option, three parameters have to be supplied: Lines to skip, Number of points N, timestep dt, and Units. The first parameter is just the number of lines that should be skipped at the beginning of the file which could contain text description about the record, or other less relevant data. That's meant to avoid the inconvenience of having to delete those lines. The second parameter is the number of points to be read. The program will keep reading values from the file until this number is reached or the end of file reached whichever happens first. This can be used if the user is unsure of the number of points in the record. If the user specifies a larger number than the actual number of values in the file, this number will be replaced by the actual number of points read. Unreasonably high values of N should not be specified since the memory allocated is proportional to the number of points. Timestep dt, is the assumed sampling rate of the record. The units are the assumed units of the read values, which could be ft/sec², in/sec², mm/sec², cm/sec², m/sec² or g.

The user could press on the "Read File" button that reads the file, then check that the file is read correctly and return to the previous dialog by press the "Return" button, or combine both steps by pressing "Read File and Return".

Figure 2: Earthquake File Selection dialog

Earthquake Plot Dialog

Each selected record can be plotted by pressing on the "View" button. This will produce a plot of the acceleration, velocity and displacement histories.

Figure 3: Earthquake Plot