A Mystery Signal?

Is there anyone out there who can identify this for me? I have not seen this kind on the VLF band before. The left-hand peak is on 14.97870kHz (-81.37dB). This is in the region of the Very Low Frequency (VLF) band, in which you would occasionally find the Russian ‘Alpha’ navigation system time signals. There seems to be a regular pulse, but could it be that this is just interference from somewhere? I am still new to VLF monitoring, and I do not normally go below 20kHz, so this stood out on my screen. I used a simple USB tuning-wheel off eBay to enlarge the screenshot. Used BAZ VLF ferrite bar aerial, 192kHz USB sound card, and the Spectrum Lab software suite.

http://www.vlf.it/alphatrond/alpha.htm