Earthquakes 101

"My head hurt, my ear was cut, I was flung off the seat, couldn't hear anything and everything was quiet. That's when things started falling from the auditorium from above me, big clags of cement, dust, dirt."

This is the situation Elaine Stamford found herself in on Thursday, 28 December 1989.

Her workplace was crumbling around her, as the town of Newcastle suffered through the most deadly geological hazard ever to strike Australia: a 5.6 magnitude earthquake.

In the Newcastle Earthquake, thirteen people died, many of the city's historical buildings were destroyed along with 35,000 homes, 1000 people were displaced, and the town was left with a $4 billion damage bill.

In Australia, there are an average of 80 earthquakes of magnitude 3.0 or more each year, according to Geoscience Australia – but earthquakes as devastating as this one 28 years ago are extremely rare.

But what causes an earthquake? Why do some countries have more? Can we predict them? And what should you do if you get caught in one?

The answers lie in understanding tectonic plates; giant slabs of solid rock that cover the outer shell of the earth.

The majority of the world's earthquakes happen at plate boundaries, where the tectonic plates push against one another. These interactions between plates are called tectonic activity.

Australia lies in the centre of the Indo-Australian tectonic plate. Our plate is colliding with the Eurasian, Philippine and Pacific plates, causing stress to build up in the 25km-thick upper crust. 

So, whilst the likelihood of a severe earthquake in Australia is very rare, our plate is actually causing a lot of earthquakes in the region, particularly for countries like Indonesia, New Zealand and Japan.

Plate Tectonics Explained. Video: Minute Earth

Professor Phil Cummins, a Professor of Natural Hazards in the ANU Research School of Earth Sciences is undertaking research to understand the way the ground moves. This can tell us about stresses building up in the interior of the earth, which might lead to earthquakes.

Essentially – he’s trying to understand how likely it is for an earthquake to occur at any given place, and how strong the seismic waves will be if one does occur.

One instrument he relies on is called a seismometer, which detects any small movement in the Earth and converts it into an electrical signal that is sent to an earthquake monitoring system.  

“With an extensive network of seismometers and sophisticated communications systems it’s possible to measure the first arriving seismic wave of an earthquake and try to provide people with a few tens of seconds warning before the more damaging seismic waves arrive.

“A few tens of seconds warning might not sound like much, but in an earthquake, a few tens of seconds warning can be significant.

“Unfortunately, in many countries, there is no access to such sophisticated seismograph networks and communications systems, so there is no warning at all.”

When you’ve only got a few tens of seconds warning, there’s a couple of things the SES suggest you do in an earthquake, which could mean the difference between life and death.

  • If you’re already inside, drop to the ground, take cover under a sturdy table or other piece of furniture; and hold on until the shaking stops. Stay inside until the shaking stops and it is safe to go outside.
  • Research has shown that most injuries occur when people inside buildings attempt to move to a different location inside the building or try to leave.
  • If you’re already outside, move away from buildings, streetlights, and utility wires. Once in the open, stay there until the shaking stops.
  • And if you get trapped under rubble? Tap on a pipe or wall so rescuers can locate you, and shout only as a last resort. Shouting can cause you to inhale dangerous amounts of dust.

While earthquakes usually only last for 10 to 30 seconds, the impacts can be devastating, and rebuilding cities and communities can take many years, says Professor Cummins.  

“Earthquakes disrupt water and electricity supply, and hospitals may have collapsed, meaning people don’t have access to key services that are so critical at these times, like healthcare, food and water, and shelter.

“This is a major problem, especially for developing countries, that have difficulty in being able to quickly provide those services.”

There is only one way to prevent large-scale destruction and fatalities in an earthquake, and that is by ensuring countries are properly prepared and buildings are earthquake resistant.

After the Newcastle Earthquake, Australian building standards were amended to require some resilience to earthquake shaking, as 12 of the 13 lives lost were a direct result of crumbling structures.

The only effective means for reducing earthquake fatalities is to build better buildings that are more resilient and will not have a high chance of collapsing in an earthquake,” he says.

 “To do that in a cost effective way, we need to know what kind of ground motion might happen if there was an earthquake, and build appropriately.”

Find out the when and where the most recent earthquakes have been happening around the world on the Geoscience Australia website.

Image: Haiti Earthquake 2010 courtesy of European Commission DG ECHO, flickr