Seismologists catch every underground tremor the way a doctor listens to a heart. But small earthquakes have weak and fuzzy signals: it's hard to tell exactly where the rock shifted. Usually, scientists look at the first wave motions: compression or dilation. But if the tremor starts gently, without a sharp snap, the picture gets blurred.

The new method FocMecDR does things differently. Instead of analyzing each tremor in isolation, it compares two neighboring earthquakes whose wave paths are nearly identical. One serves as a 'reference' with a known slip mechanism. The second is adjusted to match it, like a translator checking a tricky phrase against an already translated one. This way, the precise rupture direction can be extracted even from a weak signal.

This approach opens the door to assessing a fault's 'readiness' for a large earthquake. When stress in the crust becomes homogeneous, like a taut string, it's a warning sign. Perhaps one day seismologists will be able to warn of major tremors not just seconds in advance, but days.