Hi Randall. A couple of questions if I may. How do you know that the silent quake occurred? My understanding of a silent quake is a quake that isn’t recorded on the seismograph, but is detected only by GPS receivers.

Secondly how are you able to determine that a silent quake is about to occur? I know you mention the association with ULF, but how can that be related to a silent quake and not anything else?

I have read that earthquakes near magnitude 6 give bigger and much longer precursors than magnitude 4 earthquakes, all lying within 150 km of the monitoring station. Just before the Loma Prieta quake ULF was seen by Antony C. Fraser-Smith from the University Stanford, but no silent quake was detected although I don’t know if there were any GPS receivers in the immediate area. There were however two foreshocks to this quake. One was 15 months, the other 2 months prior to the quake. This quake also occurred in a known seismic gap. I don’t think this would fall into the category of being a silent quake. Take Care…Don in creepy town