Running Shakyground

You have now completed the editing of your input sheets. Click now the “Space Shuttle” icon on the tool bar. SHAKYGROUND asks for your patience and after some time of processing displays the standard output screen (see Fig. 14). The graphics show three response spectra, i. e., the average obtained over all simulations, the spectrum corresponding to the average plus one standard deviation (often referred to as “84%-spectra”) and the peak-hold spectra, which represent the highest values encountered during the whole number of simulations. Note that due to the stochastic source model there always be a statistical fluctuation of the response spectra even if the model parameters were not subjected to a random fluctuation.

Together with this graphics a table is presented reporting the most important signal parameters as maximum and RMS-values of ground acceleration, velocity and displacement. The strong motion duration is defined in terms of a HUSID plot, and corresponds to the time window where

of the total signal power, and a(t) is the acceleration time series (see Fig. 15).
Finally two magnitude values are given. MS is the surface wave magnitude deduced from the seismic moment after Geller (1976). MWA is the WOOD-ANDERSON magnitude and corresponds roughly to Ml as obtained on common short period recordings. MWA is estimated on the base of the synthetic traces, MS on the other hand on the base of an input parameter, i. e., the seismic moment. Similar to the response spectra the average of these signal parameters is given together with the values of average +one standard deviation and the peak hold values. For the reason explained earlier there will be always a statistical fluctuation of these values (besides MS) even if no random fluctuation was applied to the input parameters of the model.
On the right hand side of your screen you note two buttons labeled “Save Results” and “View Results”. Clicking “Save Results” the contents of the screen are saved to the model data base, for examples “Simul.mdb”. You can also choose to “Save [the]Results in ASCII”. SHAKYGROUND writes the spectra and the contents of the table with the signal parameters to a textfile in your current working directory. This which can be edited with any editor and easily imported to other programs like EXCEL for further processing. Choosing this option SHAKYGROUND asks you to specify the filename; if it alraedy exists you may either overwrite it or append your actually produced results to former ones.
Selecting “View Results” you have the possibility to scroll through the actually created time series and response spectra. Your screen should look like Fig. 16. Note the list-box with the arrow on its right. Use the arrow to get a list of available traces. SHAKYGROUND shows the numbers and you may click one of them in order visualize the corresponding traces.

Fig. 14. SHAKYGROUND’s standard output screen.

Then select the type of traces you wish to see clicking the flip-flop boxes. You may also select the length of the time window you want to see. SHAKYGROUND suggests a default value which should permit you to see all significant parts of the signal. You may choose to see the a longer or shorter window by specifying a corresponding number of points in the box labeled with “Time window”. You can choose the part of the visualized response spectra in a similar way specifying the number of points in the box labeled “RS Window”.

Now click the field with the traces or the response spectrum shown on your screen. The graphic routines used in SHAKYGROUND permit to select the field and to adjust its size. You also may click the strings like “Acceleration (m/s^2)”, “Displacement (m)” and so on and move them around on the field. If you desire to export some graphics to an other application, (e. g., MS Word where you are processing a document) select the area of interest, then press the “Print” key on your keyboard. Doing so you copy the graph to the clipboard of your computer. Now move to your application and point the mouse to the place where you wish to paste the graph.

Fig. 15. Visualizing Synthetic traces (acceleration, speed, displacement)

If there are no created traces or response spectra SHAKYGROUND prompts you a message. Return to the previous screen clicking the little X in the upper right corner of the screen (attention: use the X on the same row as the Strings “Input” and “Output”, otherwise you terminate the SHAKYGROUND session).