Tuesday, April 7, 2015

That Earthquake Felt Bigger

... is something we often hear at the office.

Now while an earthquakes magnitude is the true size of that particular quake and the energy it released at the source, it does not describe how that energy was directed,  and how the quake was felt on the surface.

So you can have two magnitude 5 quakes in different towns, with very different results:
~ one causes no damage and not all people felt it,  while the other caused damage in most houses,was felt my most people, and many were shaken and scared.
So why the difference? Read on to see

This is where Intensity comes in

You can see each quakes intensity on our website - its based on a number scale but we have added in words and colours to make it easier/quicker to see. You can see in the table below, the scale ranges from MM1 - unnoticeable (which may be felt by some people)  to Severe - which covers damaging up to worse case scenario MM12.

The two Christchurch quakes this Easter Weekend, both M3.8, were both MM5/Moderate - which if you read below in the table, were not small quakes!

So next time you look at an earthquake, check out its intensity - it will give you a better idea of the effects the quake had on people/buildings etc. on the surface.  If you look at your regions quakes you will see two intensities given, so how the earthquake was felt at its location, and how the earthquake was felt at your location. The Auckland page is a good example of this, as they don't frequently get quakes in the Auckland region, so you can see the quakes listed are all of a larger intensity, but only felt 'weak' in Auckland.


Full page here

So those two Magnitude 5 quakes...
~ The first had an intensity of MM4/ light  and the second was MM6/Strong
So you cannot take a quake at its magnitude/face value, you really need to know the MMI level to truly know how the people on the surface felt it.


Some Intensity examples of our quakes: 

The 2014 Eketahuna quake was MM8

The 2013 Lake Grassmere quake was MM9  and the Cook Strait quake was MM8

Both the 2010 Darfield earthquake, and the 2011 Christchurch earthquake were MM9

The 1855 Wairarapa, and 1931 Hawkes Bay earthquakes both had an intensity of MM10!

Check out the boss' blog with more on felt intensity.


Tuesday, March 31, 2015

A Tardis Trip Down Memory Lane ...

The Beginning - Red and Green


The website geonet.org.nz that we all know and love, first appeared on the internet on May 20 2002.  


Home


As you can see it was pretty basic, with just the latest quakes and volcano cameras and volcanic alert levels.
Recent Quakes

It was nice and bright (and festive) and featured our lovely red and yellow stars for the earthquakes locations.






In April 2004 we added in 'Felt it' to the quakes, so you could tell us how and where you felt an earthquake.

Fun Fact: To date, the most felt reports we have ever received for an earthquake was 13,900+ for a M3.9 Auckland Quake





April 2007 - 5 shades of Gray  



In 2007 we had a big update, as well as a fresh new look we added in a lot more information on our volcanoes, quakes, landslide and tsunami. We also added in information on our network, data and maps and our latest news.


 

 

 

 

 2010 - Canterbury

Now when the Sept 4 Darfield earthquake occurred, the website looked pretty similar, though it had the cool 'Shake Map' which lit up when an earthquake occurred. (why did this go?)


It was this time that GeoNet became a household name, if you check out the 'Google Trends' graph below you will see we were flying under the radar for a bit!  Luckily we had an awesome team of geeks and our website stood up to this heavy traffic! 

 

 

 

Fun fact: we had more web traffic in the week following the Sept 4 quake than the whole previous year!

  Back in 2010 we had our duty officers locating the earthquakes and this took up to 20min so it was around this time we were getting the "Hurry up GeoNet, how big was it" comments! 




 And due to the large amount of aftershocks we were locating, we were limiting the quakes posted on the website, to the larger, more widely felt events. So then we had lots of “I felt it, why isn’t it on the website” comments!   So we knew we needed to fix this!

 

The Fix 



Comparing the two systems EQ posting time


So instead of a person logging on to their computer after they were alerted of an event, SeisComP3 automatically went to work as soon as the data started coming in! 


 

And in 2012 we launched the 'GeoNet Rapid' Beta website and then in September it went live. This was the biggest change to the website yet, and it took people a while to get used to the new way but the speed was definitely appreciated.  You can read more on how it works here

And this brings us to the website we have now, it may not be obvious but we are always working behind the scenes on geonet.org.nz to keep it awesome, and continue to make it better!




Monday, December 22, 2014

2014 - So this was our year ...

Another year almost over!  I thought i would keep it simple and just show you how our year was (its interactive so you can hover over the graphs and see the numbers)

I hope you all have a fantastic holiday break, though many of you, like us, will be working throughout!  And we look forward to another great year in 2015!
And yeah, i am aware that by posting this, the jinx factor is now pretty high .......

Friday, November 14, 2014

Climbing a volcano : the Tongariro Alpine Crossing


On November the 8th I did the Tongariro Alpine Crossing with my partner and two friends, it was a beautiful day and the mountains looked amazing with a fresh topping of snow!

Tongariro is actually a complex of multiple volcanic cones that was constructed over a period of 275,000 years, the active vents include Te Māri, Emerald Lakes, North Crater and Red Crater. Erosion during the last Ice Age has worn away what was once a large mountain into the amazing hiking destination that it is today. The crossing is 19.4km long and is often called one of the worlds best day walks, the down side of this 'best' status is that the walk is very popular and hundreds of people complete it daily.

The beginning!
We started out at 8:30am with the shuttle dropping us off at Mangatepopo car park, the first hour or so is a nice, mostly flat walk where you can enjoy the scenery.

South Crater
After lulling us into a false sense of security the trail took us to the second stage, the aptly named 'Devils Staircase'.  This is where you climb over 300m up across old lava flows, from eruptions in 1870, and other volcanic deposits (pyroclastic flows in 1975).

This was my least favorite part of the walk, and why there are no photos, however the view from this was impressive and we could even see Mt Taranaki in the distance.  The snow started to come into play on this section, with lots of portions of the track very slippery and covered in snow, I was very grateful for my hiking pole!

We then had a nice flat stroll in the snow across South Crater (which is actually a basin not an actual crater) toward our next climb up to Red Crater, this section had lots of snow and even a chain to clamber up!


On the edge of Red Crater looking towards Ngauruhoe 
The view from Red Crater rim is amazing, although there was lots of snow you could still see where it gets its name from. The red colour is caused by the oxidation of iron in the rock. 


It was then onto (my second least favorite part) the steep scree path down to the Emerald Lakes.


The Emerald Lakes







The Emerald Lakes are actually explosion craters filled with water, they get their neat colouring from minerals that have leached from the thermal area around them.








Beautiful Blue Lake




After walking across central crater (another faker, it's not a true volcanic crater) the next stop was Blue lake, it is an old lava vent and also gets its colour from the minerals that have dissolved into it.






Central Crater










In 2012 we had 2 eruptions in Tongariro, the first activity there since 1897. The volcano is still in a state of unrest and you can see steam and gas plumes from the Te Maari craters most days. 

Looking down to Lake Rotoaira and Lake Taupo in the distance

Te Maari steaming away




The track runs parallel to the craters so you get a great view of the activity on your way down, as well as amazing views across to Lake Taupo.









An impact crater from the Te Maari eruption in 2012


Flying rocks from the 2012 eruption damaged tracks and the Ketetahi hut. You can also see a few impact craters caused by these flying rocks on the way down, they show just how destructive these rocks can be.

The end of the crossing was a long gradual descent, with lots of steps, to the Ketetahi carpark and our awaiting shuttle!

It was an amazing 7.5 hours and I definitely recommend adding it to your 'cool things to do in NZ' list.






My Crossing Recommendations:
*Proper hiking boots. The trail can be rough and in our case, snowy!
*Layer your clothing, merino is good for warm and cool temperatures
*Hiking pole(s) are good, especially if you are as uncoordinated as myself.
*Sunscreen (don't forget your hands, i did learn that the hard way!)
*Pack for the changeable weather, don't get caught out!
*Take plenty of food and water.
*Knees - the 1200m decent is mostly steps, if you have knee issues think twice or take strapping/braces etc! The long hike out is very painful with a sore knee.
*And remember you are walking on an active volcano, pay close attention to the information warning signs

Friday, October 3, 2014

Earthquakes - Where the biggest is not the best ...

I was asked the other day if i knew the worlds largest earthquake, it turned out i didn't as i thought it was the 1964 Alaska quake (i wasn't far off though). So i thought i would take a look at the largest quakes in the world, i settled for the top five. And to compare, the top 5 quakes in NZ.

The top five quakes in the world (since 1900)

1 - 1960, Chile. The largest recorded earthquake in the world, a magnitude 9.5 with thousands of people killed, injured and millions left homeless. Large tsunamis were generated and reached up to 10m in Hawaii.

2 -1964, Alaska. The 'Great Alaska Quake' was a magnitude 9.2 and generated a tsunami with a maximum wave height of 67 meters in the shallow Valdez Inlet. The tsunami caused 122 of the 131 deaths of the quake.

The location of the top 5 quakes in the world
3 - 2004, Northern Sumatra. The Banda-Aceh earthquake was magnitude 9.1 this and the 'Boxing Day Tsunami' caused the deaths of over 200,000 people and displaced millions over 14 countries

4 - 2011, Japan. The magnitude 9.0 Tohoku Earthquake and subsequent tsunami killed thousands of people. The tsunami waves traveled 10km inland and reached heights of 39m.

5 - 1952, Kamchatka, Russia. The magnitude 9.0 earthquake also caused a tsunami, with wave heights of up to 15m causing considerable loss of life and damage.

The Top Five in New Zealand

Although magnitude is our common gauge of earthquake size, intensity is a better indicator of how the quake was felt on the surface. The Modified Mercalli Intensity Scale, or MM, ranges from MM1 (unnoticeable) right up to MM12 (completely devastating). To make it easier we have these intensities on the earthquakes posted on GeoNet as words: weak, light, moderate, strong, severe. 


The location of the top 5 NZ quakes
1 - Our largest earthquake was in 1855, the magnitude 8.2-8.3 Wairarapa quake had an intensity of  MM10 and killed 7-9 people. It was also highly destructive in Wellington and generated a tsunami in Cook Strait and Wellington Harbour. It resulted in extensive uplift, including what is now the Hutt Road alongside Wellington Harbour and the Basin Reserve (which was originally part of a waterway that led into the harbour and was proposed as a shipping basin until the quake!)

A damaged road after the Hawkes Bay Quake
2 - 2009, Dusky Sound (Fiordland) magnitude 7.8, MM7.  Due to its isolated location only a few properties were damaged, though it did generate a small tsunami.



3 - 1931, Hawkes Bay,  Also magnitude 7.8, but with an intensity of MM10, this quake is New Zealand's most devastating quake. 256 were killed, thousands injured and it altered the landscape forever. It was followed by uncontrollable fires due to broken water mains, and  is recorded as having caused the largest loss of life in New Zealand’s history.

4 - 1929, Buller. Another MM10, this magnitude 7.8 quake killed 15 people, severely damaged many roads, buildings, and bridges. The massive rumbling of this quake was heard as far away as New Plymouth. It also created thirty-eight new lakes from blocked rivers and waterways. 21 still exist today.  

Ground rupture following the Buller quake
5 - 1934, Horoeka (Pahiatua). Magnitude 7.6. This event caused widespread damage especially in Pahiatua where a number of buildings collapsed.

Although not up there in size, the magnitude 6.3 Christchurch earthquake in 2011 had a MM9, and is our second most devastating quake with 185 deaths. This quake was so damaging due to its shallow (5km) depth and location within 10km of the city.

You can read more information on these, and other historic events here


It is estimated that there are 500,000 detectable earthquakes in the world each year. 100,000 of those can be felt, and 100 of them cause damage (USGS)




Info Sources:

USGS - United States Geological Survey
GA - GeoScience Australia 
GeoNet
Te Ara - The Encyclopedia of New Zealand

Wednesday, August 6, 2014

Earthquakes and Pancakes

I was on the WestCoast last week and decided to check out Punakaiki, which is about 40minutes North of Greymouth. As well as home to some amazing scenery, its famous for The Pancake Rocks!

They were formed around 35 million years ago when tiny bits of dead plant and sea creatures settled on the seabed along with mud and sand. This lovely mixture was then squished by the water pressure and turned into the hard and soft 'pancake' layers of  Limestone and siltstone. 

Then the earthquakes come in, and all of this land was folded and lifted above the seabed, where it was then 'sculpted' (especially the soft layers) by rain, wind and the pounding sea. (this occurred over a long time period!)

The path to the rocks




Stepping off the State Highway you are immediately transported into an amazing lush green sub-tropical forest with Nikau Palms standing above.
Amazing backdrop of misty hills







It wasn't long before i heard the roar of the first blowhole and looked up to see saltwater mist blowing around in the wind.  It was called 'sudden sound' and was very true to its name! (I thought it sounded like a dragon was breathing under the rocks - must watch too many movies)

Mist swirling in 'Putai'





The blowholes work when it is high tide and a rough sea, as the large waves surge into the rocks, seawater is forced under great pressure into the underground passages. The water follows these passages to the surface and then escapes as fine mist above your head. 




Waves crashing into the rocks

You then walk on to more exciting sights! I had stormy weather when i visited so the waves were going really high!


The rock has eroded into some really cool looking shapes and although my pancakes have never looked like that, i can see where it gets its name!





So if you are ever on the West Coast i recommend you stop in and have a look, its worth it. And the cafe next to the visitors centre sells pancakes ....


Beautiful views everywhere!






Tuesday, June 24, 2014

We can't feel your ghost quakes

Recent quakes close to Raoul Island
Today there was a large quake in the Kermadecs. This is thousands of kilometers North-East of New Zealand, not far off the volcano Raoul Island.

Unfortunately this quake, and a few other deeper distant events, cause our system some strife!  Our instruments are very sensitive and have no trouble recording distant quakes.

Now if we start with a wee earthquake 101: Earthquake waves are made up of P-waves and S-waves (amongst others). The P wave arrives first and and then the slower S-wave arrives, you can see this on the photo below.

M7.2 Japan Quake arriving on our stations

 The delay in the arrival of the S wave (as well as a few other depth related factors) causes our automated quake system SeisComP3 to think that there were actually multiple large quakes in New Zealand, as shown on our app below.

 
 
 We have nicknamed these events 'Ghost Quakes'.

Todays event even gave us "Ghost Aftershocks" with numerous mag 3 and 4 events being posted due to the aftershocks from the large Kermadec event.

We are always working on our automated system and are trying to teach the system to stop doing this, it is a tricky task however!  99% of the time our system works amazingly and you get good quake info really quickly.  If you do get alerted to a large quake the best thing to do it check our website and see if it has been reviewed by one of our team.  Another trick is to check the 'felt reports'  if a large quake has none, its a bit suspect!