All posts by kvan637

information, Uncategorized

How to get involved with Ru

If your institution wants to get involved in the Ru network, there are a couple of things to consider. In terms of hardware, you will need a public place (library, or foyer) with easy access to:

  1. power,  and
  2. a wired internet connection

The hardware you need consists of:

  1. the TC1 seismometer,
  2. a dedicated computer,
  3. a case to protect the device from bumps.

Maybe most importantly, you need a Station Manager.  A teacher would be the most logical choice, but it could be  a parent. The station manager does not need to be a seismologist, but  someone who can field basic questions from students,  solve small problems with the station, and relay bigger ones to us for troubleshooting.

To give you an idea on how your class project may go, you can watch this video.

In the early days, support from the Foundation of the Society of Exploration Geophysicists, allowed us to sponsor scholarships available for the most suited institutions. The current model is for schools to self-fund the hardware. If you want to know more, please write us.

 

SchoolSeismometerSetup
Rangi1: The setup at Rangi Ruru
20140725_123055
AUCK: the station at the University of Auckland

 

information, Uncategorized

SeiSNZ is now Ru!

We are very proud to announce that our team now includes Dan Hikuroa from Nga Pae o te Maramatanga, New Zealand’s Indigenous Centre of Research Excellence. There are several projects around the globe that do seismology in schools, but to celebrate New Zealand’s unique cultural heritage and its natural expressions such as earthquakes and volcanoes, we decided to name our network “Ru”, short for Ruaumoko, The Maori God of Earthquakes and Volcanoes.

information, Uncategorized

You see a blip on the screen. Now what?

More often than not, the screen of your seismic stations may look something like this:

latest

Overall, the wiggles are small. The few spikes in this case are probably due to some electronic interference in the area where station AUCK is housed.

BUT: If you see something on your seismometer screen that stands out from the rest of your recordings, like this:

kermadecscreen

Then, there are a number of things you can check to see if you recorded an earthquake (or if this was some noise generated by bumping into the sensor, for example).

Geonet

Geonet is “the official source of geological hazard information for New Zealand,” according to the site.  They run a large network of seismometers in New Zealand, whose data is the source of information about all recorded earthquakes in New Zealand. Can you find an earthquake that would arrive at your school at the time of your signal?

USGS

The United States Geological Survey runs a world-wide version of Geonet. Its list of recent earthquakes can be found here.

If you want to get updates via email, text message or twitter, you can sign up for alerts from Geonet and from the USGS.

Your sister institutions

You can also directly compare the wiggles on your screen with either the wiggles from the other schools in the network, or with the closest “live” signals that geonet provides.  In this last link is a map on the right where you can find the station that is closest to your school.

earthquakes, Uncategorized

M6.3 earthquake, 15 km east of Eketahuna

greatcircle

 
In the Science Centre of the City Campus of the University of Auckland we record seismic waves with the TC1 seismometer. Routinely, our station AUCK records seismic waves from earthquakes in New Zealand and beyond. On January 20th, 2014, an earthquake occurred on the South side of the North Island, 15 km east of Ekatahuna. Here is a map of the epicentre, our station location, and the great-circle path between them.

 

 

2014-01-20-02-52-44

On the left you can see 10 minutes of recordings, starting at the origin time of this earthquake. The green marker annotated with a Pn is the predicted arrival of the first wave traveling 4 degrees from the epicentre, 15 km east of Eketahuna, to Auckland. This prediction is based on a spherically symmetric model of the Earth, by Brian Kennett, and certainly seems to mark the start of minutes of vibrations in Auckland from this earthquake. In fact, if you look carefully you see that the wiggles after 10 minutes are still larger than before the first wave from this earthquake arrived. Larger earthquakes can make the Earth “ring” for many hours.

2014-01-20-02-52-44_zoom
In the image on the right, we zoomed in on the first-arriving wave, almost exactly one minute after the earthquake originated. Now, you can see that the prediction is actually a few seconds before the arrival. This means the lithosphere under the North Island of New Zealand is a bit slower (~3% on this path) than the average on Earth. In general, a hotter lithosphere is slower than a cold one. This makes seismic waves traversing old, cold, continents relatively fast, and those sampling younger lithosphere like ours in New Zealand, relatively slow.

In general, it is these small travel time differences that provide images of the (deep) earth through a process called seismic tomography.

earthquakes, Uncategorized

A deep earthquake on the eastern margin of the Australian plate

Recently, we recorded seismic waves on our station AUCK from an Earthquake roughly 11 degrees to our North. This event is characterized by a strong P- and S-wave arrival as you can see in this figure:

fiji65_AUCKdata

Given the usual limitations of our (vertical) sensor when it comes to S-wave recordings, this is indicative of a very deep earthquake. The USGS estimates that this earthquake happened at a depth of 460 km. Now, under most places on Earth the rocks at those depths are too ductile to support the brittle breaking necessary for an earthquake, but in this case, the earthquake happened in — or on the boundary of — the brittle Pacific Plate subducted under the Australian Plate. Note that the epicentre of this event is about 500 km from the surface expression of the boundary between these plates. From the depth of the event and the offset to the plate boundary at the surface, we can estimate the angle of subduction may be around 45 degrees.

FIJI65_2014epicentre

The P- and S-wave markers are based on the average wave speed in the earth. In this case, they are a bit earlier than expected, because the subsurface between earthquake and the AUCK recording station is slower than average. As discussed previously, this is indicative of a young, warmer (and thus slower) lithosphere.

Furthermore, such deep earthquakes cause relatively little surface wave energy. The signal after the S-waves is likely a guided wave in the Pacific plate called a “leaky mode.” If you want to learn more about leaky modes in the Kermadecs, you should read this paper.

information, Uncategorized

How to turn off ‘app nap’

On a mac, there is this clever tool to turn off (parts of) applications that the computer thinks you are not using. This tool is called ‘app nap’.

For jamaseis, this has to be turned off. The following video shows how:

18707CAD2AF14F81B7051DAC378E0CFA_2

 

 

(Note: The initial part of the video shows how you can access the relevant settings by right clicking. You may need to hold down the control key on the keyboard while clicking to get to the contextual menus).

 

information, Uncategorized

Correct magnet positions

There are three magnets suspended from the slinky in the TC1. The first two are centred in the coil. Motion of these magnets from earthquakes are responsible for the induced current in the coil. The third magnet is suspended in the copper tube,  and dampens the system via Lenz’s Law.

TC1_zoom.JPG
Correct magnet positions. Click on the image for a closer-up view.

The pair of magnets in the coil, and the single magnet in the copper pipe should not touch the coil and tube, respectively, and their tops should be flush with the coil/tube, as shown in the picture.

If the magnets are not in the right vertical position, you can adjust the magnets by threading the screw on the lid up or down. If you need even more vertical adjustment, you can bunch or release rungs clamped in the lid of TC1.

If the magnets are not in the right horizontal position, adjust the knobs on the legs.