What Is Going on?
So many of our lovely friends and family from around the world have reached out to us this week and for this I am grateful. I’ve been trying to write back to everyone and give you some details of what’s happening as time permits, but there’s much to communicate and not enough time.
In my previous post, I wrote a bit about our last few days and ways in which one can help. In this post, I want to provide some links to information on what’s happening in Christchurch and what’s been happening seismically.
First, two sources for the latest information on the rescue and relief efforts:
Second, some very good websites about the seismic activity happening:
Canterbury Quake Live: This site provides seismic data in a variety of interesting formats.
GeoNet: Gives you updates on seismic intensity around New Zealand. As you can see from the main page, there’s lots more activity going on in the North Island. However, the majority of quakes are magnitude 2’s and 3’s which are not often felt. You can also see a list of the latest quakes here. Tonight there have been two ‘4’s’ which we felt out in Wainui. Just quick few second shakes which roar through the earth.
And finally, some words from one of my dear friends who’s a seismologist for GNS Science:
“Here are answers to some common questions that have come up:
– The earthquake was an aftershock of the Sept 2010 magnitude 7.1 earthquake. It is typical for the largest aftershock to be about 1 magnitude unit less than the mainshock, so yesterdays M6.3 event was about the right size for the largest aftershock. The quake was much closer to Christchurch , and shallower than the Sept 2010 quake, which is why it caused so much damage. We know it is an aftershock as it is within the zone of aftershocks from the 2010 quake, and it has happened less than a year after the mainshock ( a year is short in seismology terms). We expect aftershocks to continue for some time yet, but don’t have any numbers on this as yet.
– Anything you hear about the Canterbury quakes being the start of an “earthquake cascade” up and down NZ should be taken with less than a grain of salt. There are no statistically valid findings that show this is going to happen. Any kind of earthquake forecast or prediction methodology has to be thoroughly reviewed and tested many times over before it can be taken seriously. Just remember though, that NZ is an active country in nearly every way, and we should be prepared for anything. Earthquakes, floods, landslides, volcanoes and tsunamis. Find out more about where you live.
– In terms of our earthquake hazard estimates for the country, the strong earthquake ground shaking in this week’s quake was equivalent to what we would expect for CHCH on average about once every 10000 years. Unfortunately this very rare strong shaking happened in our lifetime, and in fact in our civilisation! There is plenty of evidence as to the rarity of this shaking in the CHCH area. Not only the 100-plus year old CHCH Cathedral received the worst damage ever, but features like the old abandoned seacliffs in the Sumner/Redcliffs area have been majorly damaged for the first time since they were formed thousands of years ago.
– The liquefaction mainly happens where sandy/muddy materials have a high water table, and the shaking causes the materials to lose their internal tension and turn into flowing, bubbling liquid. Much of CHCH is on liquefiable materials, particularly in the eastern parts of the city.”
I know this information is of no comfort to those of us here experiencing it all, but it may help others outside of New Zealand understand a bit better about what is going on.