precursory

"There are some cases where there are dramatic and very distinctive precursory seismic signals that precede a catastrophic landslide, sometimes by as much as days," Highman noted.

“It doesn’t give you a precursory, predictive ability because it’s a statement of how you’ve summed it rather than what’s going on at a particular earthquake,” she adds.

These observations suggest perhaps there really are precursory signals for at least some huge quakes.

But researchers said there are few large-scale earthquakes to study in California and that makes it difficult to indicate whether precursory signals at one fault would apply to others.

Not only does immobile magma stay silent, but the molten mass was already so close to the surface that should the flank have broken apart, it would have immediately erupted without the usual precursory clamor.