Japan just had a 7.4 quake off the coast. Tsunami warning issued.

Jesus Christ.

That's all I know right now. It is breaking news.

 

ETA: This was in the same area as the big one. The tsunami alert has been issued for Japan only.

That's all I know right now. It is breaking news.

 

ETA: This was in the same area as the big one. The tsunami alert has been issued for Japan only.

7.4 is pretty massive, though no 8.9. Anyone know how bad this tsunami will be?

7.4 is pretty massive, though no 8.9. Anyone know how bad this tsunami will be?

 

From what I gathered, the tsunami "warning" was really an "alert". So, I don't think they have any clue yet.

It's pretty clear now that the Earth hates Japan.

7.4 is pretty massive, though no 8.9. Anyone know how bad this tsunami will be?

 

It all depends on how much land displacement took place.

Now the USGS is saying they had TWO 7.4 quakes.

Now the USGS is saying they had TWO 7.4 quakes.

 

Wow. Hopefully everyone is OK, but this is scary. Its crazy to think in this case, these are probably aftershocks.

Now they are calling it a 7.1 mag quake and the tsunami warning has been lifted.

7.4 is pretty massive, though no 8.9. Anyone know how bad this tsunami will be?

Very likely not large, although there could be local effects.

 

7.4 on a Subduction zone is not huge in terms of total displacement. These are aftershocks.

Very likely not large, although there could be local effects.

 

7.4 on a Subduction zone is not huge in terms of total displacement. These are aftershocks.

I'm done teaching class now, so I can elaborate.

 

In a subduction zone earthquake, the area of the fault that breaks is directly proportional to the energy released. A magnitude 9 event releases about 100x as much energy as a magnitude 7 event. It doesn't scale perfectly linearly, but you can safely assume that a magnitude 7.4 event was more than a factor of 10 smaller displacement than the large event.

 

These 2 were also centered closer to the islands than the original event. They were therefore probably deeper, which would also mean less oceanic displacement.

 

You can still have something crazy happen. If the magnitude 7 event set off a large landslide, that alone could create a local or regional tsunami, so the tsunami warning center will be overly cautious. They will give a tsunami warning after a quake too small to directly trigger a large tsunami until they know for a fact that there isn't one, for that reason.

Aren't earthquakes more likely after having that massive 9.0 a few weeks ago? That this is basically normal (although it's like seriously Earth leave Japan alone)?

Aren't earthquakes more likely after having that massive 9.0 a few weeks ago? That this is basically normal (although it's like seriously Earth leave Japan alone)?

 

Yes. This is all aftershocks. IIRC, after the Boxing Day Tsunami, they said aftershocks would technically happen for years afterwards.

Aren't earthquakes more likely after having that massive 9.0 a few weeks ago? That this is basically normal (although it's like seriously Earth leave Japan alone)?

These are entirely expected.

 

When you get a magnitude 9 event, you can't be surprised if you get a few magnitude 8 aftershocks, a dozen magnitude 7 aftershocks, a hundred magnitude 6 events, etc.

Yes. This is all aftershocks. IIRC, after the Boxing Day Tsunami, they said aftershocks would technically happen for years afterwards.

Someone was nice enough to make a graph.

 

Someone was nice enough to make a graph.

 

 

I thought I remembered reading that the magnitude of the quake also dictated now long shocks would be happening for after the main event.

Haiti and Japan are results of a new weapon being developed.

Haiti and Japan are results of a new weapon being developed.

 

HAARP!