Earthquakes

Yes, we have earthquakes here in New Zealand.  According to Learnz.org.nz

Earthquakes happen every day in New Zealand. Approximately 14-15,000 occur in and around the country each year. Most earthquakes are too small to be noticed, but between 150 and 200 are large enough to be felt.  …

The most powerful New Zealand earthquake in recent history occurred in the Wairarapa in 1855. During this magnitude 8.2 earthquake, land moved along at least 140km of the Wairarapa Fault. Where the movement was greatest, the land shifted across more than 18 metres along the fault. Part of the nearby Rimutaka Range rose more than 6 metres. This is the biggest known movement by a single earthquake to have been recorded anywhere in the world.  [A meter is a little over three feet.  So the land shifted about 60 feet and the mountain rose about 20.]

So take that California.  You got nothin’ on New Zealand.  There is an app called GEONET which tracks New Zealand quakes, locations, magnitude and impact, letting app users rate what the quake felt like.  A quick perusal of the earthquake list shows that there is not a week that goes by that there is not some kind of earthquake somewhere in the country and there are some places in New Zealand that have earthquakes regularly, perhaps once a week. I make mental notes of the location because I would not want to live in those places. I would not say they happen often where we live, but they happen enough.

The quakes you can really feel start at about three magnitude.  Whether you feel them depends on the depth.  The shallower the quake, the more likely you are to feel it, the more likely it is to cause damage.

So what is it like?  Here is how it goes: first you sense a bit of a shake and hear a rumble.  It snaps you out of whatever you are doing and makes you a little more alert.  I often suddenly feel anxious.  Your brain starts trying to figure out what just happened.  Was that a quake?  Sometimes that is it and we all go, huh.  That was a quake.  But more often in the next second or two later, the floor feels like a rolling sea and the house vibrates from the motion of the earth beneath it, causing everything in the house to rattle and shake, the whole house seeming ready to crack from the movement.  This lasts only a few seconds.  If it lasts longer than a few seconds and is more severe, we have to get out because that might mean a tsunami and we are in a tsunami evacuation zone. We are instructed that if you are near the coast and feel a strong earthquake where it is hard to stand up or you seel a weak rolling earthquake that lasts a minute or more move to high ground or as far inland as you can, out of tsunami evacuation zones.  The rule is “Long or Strong, Get Gone.”    Are we ready?  Yep. We have go bags prepared. 

We just had a 4.1 here not long ago.  It occurred fairly close to us but because of its depth, there was only light shaking.  Think of a large truck rumbling by.  The house shook but the dishes did not really rattle.  Matt was in Wellington and did not even notice.  As I said to him afterward, it scared the hell out of me.  They always do.  Unlike a weather event, earthquakes come with no warning as to when, how strong, or for how long.  You are living in the moment and what will happen is a complete unknown.  I don’t think I will ever get used to them.  

If the quake is strong enough, heading to magnitude five and above, the dishes clatter on the shelves and the pictures on the walls are jostled.  We have never experienced one that was more than that level of impact.  At the next level, things crash and fall.  We have not been there, thank God.  During an earthquake the ground can move horizontally and vertically.  In a severe earthquake there is something called liquifaction where strong shaking causes soil that is wet, sandy, and silty to act more like a liquid than a solid.  Think about how sand moves when you step on it.  It is water saturated and it does not take much to move it.  Now imagine a building on top of sand that is shaking.  That building has a good chance of being damaged or knocked down.  

Probably the most famous recent quake was a magnitude 6.1 that hit the city of Christchurch in 2011 which resulted in 185 deaths and caused extensive damage to structures which are still being dealt with.  Numerous office buildings, churches and hotels were on the verge of or totally collapsed.  Homes were destroyed and even the sports stadium had to be torn down and rebuilt.  But that is only one in a long list of earthquakes that have impacted communities throughout New Zealand.  This country is located on numerous fault lines so it is not surprising but still it is unnerving.