Find the starting point

1 · Say what was forecast

Beginner

What did the team name in advance, in 2019?

The date of the next large earthquake The place the next rupture would start from The magnitude of the next large earthquake

2 · Count the small earthquakes

Gutenberg–Richter law: log₁₀N = a − bM, where N is the number of earthquakes of magnitude M or larger. With b = 1, there are 100 earthquakes of magnitude 2 or more for every one of magnitude 4 or more.

Intermediate

In the loaded zone, where b = 0.7, how many of magnitude 2 or more for each one of magnitude 4 or more?

About 25 About 70 About 140

3 · Explain the offset epicentre

On the map, the epicentre of the magnitude 7.1 earthquake lies outside the 2019 rectangle, 2.9 km from its northern edge.

Expert

Why do the authors still say the rupture started inside the low-b zone?

The rectangle was redrawn after the earthquake Its starting point, 16 km deep, lies inside it The epicentre was later corrected to fall inside

4 · Name the next candidate

Expert

Where do the authors now place the most likely next starting point?

At the fault bend, where b has stayed low since 2000 Around the 2026 hypocentre, still under strain Under the Yatsushiro Sea, where b is lowest

Starting point found

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