In a study of global body wave coda, it could be shown that PREM-seismograms (shaded) can model global envelopes (full colors) for several hours down to periods of 2 seconds. The results have been part of a study just published in Geophysical Research Letters and would not have been possible without AxiSEM and much less convenient without Instaseis.
http://onlinelibrary.wiley.com/doi/10.1002/2015GL065108/full
![broken image](http://user-images.strikinglycdn.com/res/hrscywv4p/image/upload/c_limit,f_auto,h_2000,q_90,w_1200/177765/envelope_synth_comparison_2d_vfihe6.png)