Hi All. It seems that the “slow, silent earthquakes have been with us for some time.
The following was taken from the June 2001 Gegtimes. Take Care…Don in creepy town

One question that arises from this quake is whether silent earthquakes can be used to predict shallow thrust earthquakes where the movement is fast and ruptures the ground above the fault. In several documented cases — Chile in 1960 and Nankai Trough, Japan in 1944 and 1946 — silent earthquakes preceded giant thrust earthquakes.

But with so many uncertainties about earthquake initiation, “it is very misleading to link silent or slow events directly to ‘earthquake’ prediction,” says geophysicist Hiroo Kanamori of the California Institute of Technology. “Even if slow events represent an important stress accumulation process before a large earthquake, [they] cannot be used directly for prediction.”

Silent earthquakes may not be good predictors of larger thrust quakes, but they can be used to begin to assess stress buildup along fault zones. Until the Pacific Northwest event, it had been generally assumed that deeper slip along the Cascadia subduction zone occurred steadily.

“The discovery that such events do take place indicates that the rate of stress accumulation is not steady but can occur in pulses,” Dragert says. “For the magnitude of the deep slip that we observed, we estimate that it would take somewhere in the neighborhood of 100 such slip events to bring the locked zone to failure.”

Dragert adds that because scientists do not know the current stress level on the fault, they “cannot say whether this last slip event brings the locked zone perilously close to that critical stress level required for rupture.”

• Geotimes