Hi Tony. Slow quakes do indeed exist. There have been a couple of them not to far from where I live. Take Care…Don in creepy town

“Sequences of near-silent earthquakes were recorded on a network of three borehole strainmeters along 15 km of the San Andreas fault north of San Juan Bautista (SJB), California, in December, 1992 and in April, 1996. Other events were recorded on borehole strainmeters along the Hayward fault in June, 1993, November, 1993, and September, 1994. "Silent" or "Slow" earthquakes resemble ordinary earthquakes in the pattern of strain release but occur over several days with little or no seismic radiation. The SJB events have associated earthquake swarms, an "aftershock" sequence and observable surface rupture (creep) days to weeks later. The first in the SJB sequence started on December 11, 1992, and continued for a week. It eventually ruptured an 8 km long section of the fault to a depth of about 8 km in several sub events, each closely associated with moderate magnitude earthquakes and microseismicity.”

http://erp-web.er.usgs.gov/reports/annsum/vol39/pt/46011590.htm

• Slow Quake