Thursday, March 4, 2021

Lots of earthquakes around New Zealand

 Although they did quite well with Covid, we are reminded that they enjoy the rugged scenery of a huge subduction zone.

The earthquakes are around M7 to 8 and are popping off on this zone.  Each earthquake has a fault length of about the size (on the map) of the Google pin.

This is a fantastic, smooth, clean subduction zone.  In order to maintain such a clean cut, such zones must have an M9 every 300 years (give or take a few hundred).  That type of earthquake only gives a 20 cm/s pgv to New Zealand, but one heck of a tsunami.

These earthquakes give a small shave to the big 300-sided die that rolls every year.  NZ has a heck of a lot worse places for an earthquake.  The big nuclear Japan earthquake gave some warning with m7's, but the odds of these earthquakes meaning anything is still about 1 in 100.

The limit to the Magnitude of earthquakes is about M9.  That translates to thousands of kilometres of fault rupture, and these smooth zones are also limited to this length.  An M9.2 is twice as long.

So, looking at this zone, it's going to radiate one monster tsunami to the coast of South America.  It's mere existence means that those guys better spruce up their tsunami warning systems.

ps.  just had an M8, popping off along the whole length.  I would give this higher odds to rupture.


Harold Asmis said...

This is officially an 'episode'. There are no meaningful criteria to rank a foreshock sequence. Same odds as before.

Brent said...

Are you sure you didn't get it wrong about the cold.

Harold Asmis said...

this is a very scrawny cold prong. It shouldn't last long. I'm not even writing about it.