Source sheet

If you clicked the first icon on the tool bar (the “New model” button), then you really have to see them all. Check if your screen looks like the one shown in Fig. 8. Otherwise click the “Source” sheet which makes your screen reproduce the Fig. 8. At the top of the “Source” sheet there is a listbox (with the downward arrow on its right) labeled “Sources in Catalog”, which can be used to access source parameter sets specified in earlier sessions. Clicking the source listbox you get a list of the available sources in the catalog chosen by you earlier. You may select a source parameter set by clicking the corresponding name. This fills all boxes below with the corresponding entries

for your selected seismic source. You can now edit the source parameters (“Seismic moment”, “Global Stress Drop” etc) in the corresponding boxes. Click the button “Save in Catalog” if you wish to save the source parameters to the catalog. If you are re-editing a previous source model SHAKYGROUND asks you whether to overwrite the entry in the database. On the other hand you can create a new entry in the source catalog specifying a new source name in the textbox “Source Name” and pressing the “Save in Catalog” button on its right. Or, if you dislike the source parameter set at all you can delete it from the catalog clicking the button “Delete Source” on the of the listbox “Sources in Catalog”.

For changing the source parameters simply move the mouse over the item you wish to edit. The column of textboxes on the left hand side contain the average source parameters. SHAKYGROUND prompts you some message like “Insert seismic moment”. Click the item and insert your desired values. Note that SHAKYGROUND performs a rough control on your input in order to prevent problems, for instance, by misspellings. We give the range of parameters permitted by SHAKYGROUND in a separate table in the Appendix.

The meaning of the single parameters is explained in chapter 4.1. You may also make reference to the index and glossary given at the end of this document. Here we restrict ourselves to comment the items “UTMX” and “UTMY”, which are the epicentral coordinates of the source. UTMX and UTMY are referred to a rectangular coordinate system such as as GaubKrüger or Gaub-Boaga given in meters. The epicentral distance is determined by the UTMX/Y of the seismic source and the receiver. In order to get a correct epicentral distance you must check the entries on the “Receiver” sheet, too.

Next to the textboxes to the left you find a column of so-called spinboxes, i. e., white boxes with a horizontal double arrow on their right. These spinboxes are used to specify a random variation the corresponding parameter undergoes during the simulation. As mentioned in the introduction SHAKYGROUND performs a number of simulations, 50 for instance. During each single simulation a random fluctuation is added to the average given in the text box on the left. The bandwidth of the random fluctuation is given in terms of standard deviation specified in % with respect to the mean value of the parameter. For instance, choosing a random fluctuation of 15% of a seismic moment of 1017 Nm means, that the standard deviation of the seismic moments is ±15% or 1.5*1016 Nm, according to a bandwidth of 30%. SHAKYGROUND offers the choice of a random parameter fluctuation according to a uniform or a gaussian distribution. You can do this choice on the “General” sheet. Finally note the third column of boxes, which, however, cannot be edited. SHAKYGROUND reports the absolute values of the random fluctuation which you specified using the spinboxes.