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New tool to accurately map earthquake risk

Padang earthquake Indonesia

The new technique could help better understand seismic activity in places like Indonesia (Source: Crack Palinggi/Reuters)


The findings were presented today at the Australian Earth Sciences Convention in Canberra.

"What we're talking about here is mapping the earthquake faults in the Earth," says seismologist David Robinson, of the Australian National University in Canberra.

Conventional monitoring triangulates the location of an earthquake using the travel time of seismic waves to a number of different earthquake recording stations, says Robinson, also of Geoscience Australia.

The speed of seismic waves vary greatly along with the variability of the Earth, and this method can provide a high level of accuracy in areas that have a high number of recording stations.

But in places other than Japan and California, says Robinson, this method can only pinpoint the location of an earthquake to within 5 or 10 kilometres.

While this level of accuracy is good enough for alerting emergency services about the general location of an earthquake it is not enough to provide scientists with information they need to better understand earthquake risk.

Greater accuracy

Robinson, and colleagues from Colorado School of Mines, have developed new computer programs that can use measurements from just one monitoring station to locate earthquakes to within an accuracy of 200 metres.

This could be useful in countries like Indonesia, Haiti and Australia.

While traditional monitoring uses the first second or so of seismic signals, the new technique uses the entire seismic wave, which can go on for 30 seconds.

"By using more of this information from a single station we can actually get away from the need to have multiple stations," says Robinson.

Traditionally the focus has been on locating the main earthquake, but the new technique images all of the minor quakes and aftershocks associated with it.

It maps what is happening underground using similarities in the frequency of seismic waves from different quakes to work out how close they are together.

This tells seismologists the distribution of quakes in a particular area, and potentially gives them a better picture of where the next quake is likely to be.

"You might be able to identify where there's a gap in the activity, for example. That might indicate a region of the fault which has not had an earthquake yet," says Robinson.

Proof of concept

Australia experiences about two magnitude 5 earthquakes each year and a magnitude 6 quake every five years.

Robinson says current maps of Australia's earthquake hazard, based on conventional techniques, show hotspots to the north east of Perth, the Flinders Ranges and around Newcastle.

He says his technique is still at the proof-of-concept stage. But he hopes one day it can be used to narrow down these hotspots, providing useful information for building codes and insurance pricing.

As for scientists being able to predict an earthquake of a particular size on a particular day, Robinson is doubtful.

"It's probably unlikely that we'll ever get there," he says. "But what we hope to do is to be able to identify certain regions that are more active than others."

Tags: earthquake, computers-and-technology