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Earthquakes trigger tsunami warnings -

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Earthquakes trigger tsunami warnings

Jennifer Macey reported this story on Tuesday, August 11, 2009 12:44:00

ELEANOR HALL: Early this morning people two earthquakes triggered panic in South East Asia about
another tsunami.

A massive 7.6-magnitude quake struck off the Andaman Islands between India and Burma and six
countries were put on tsunami alert.

Ten minutes later a second earthquake registering 6.6 on the Richter scale hit central Japan.

As it turned out, the earthquakes generated only a small tsunami but they did expose potentially
big problems with the tsunami warning systems, as Jennifer Macey reports.

JENNIFER MACEY: Early this morning a strong earthquake jolted the Japanese capital Tokyo, throwing
produce from the shelves of shops and causing injuries to more than 40 people.

The earthquake also forced the suspension of train services and the shutdown of two nuclear
reactors.

The Japanese Cabinet Secretary Takeo Kawamura says the epicentre was about 170 kilometres southwest
of Tokyo.

TAKEO KAWAMURA (translated): At 5:07am this morning an earthquake with a 6.6 magnitude and centring
on the bay of Suruga hit the region.

JENNIFER MACEY: Only 10 minutes earlier a much larger quake registering 7.6 on the Richter scale
struck off the coast of the Andaman Islands between India and Burma.

This area was badly affected by the 2004 tsunami. The Pacific Tsunami Warning Center in Hawaii
immediately issued an alert for India, Burma, Thailand, Indonesia and Bangladesh.

Gerard Fryer is a geophysicist at the centre.

GERARD FRYER: There was an earthquake in the northern Andaman Islands in the Bay of Bengal in the
Indian Ocean. We issued a tsunami watch. We issued our message nine minutes after the earthquake.

We are now endeavouring to find out if a tsunami was actually generated. Unfortunately our seafloor
gauge is off to the side, it doesn't get a good view of that tsunami. So far we've seen nothing on
that gauge.

JENNIFER MACEY: And he says that wasn't the only problem the centre dealt with this morning.

GERARD FRYER: It would already have reached Burma, unfortunately the tide gauges there are not
functioning, which is unfortunate.

JENNIFER MACEY: So you've got a problem with equipment basically?

GERARD FRYER: Yes, there's a shortage of equipment. But if there was any tsunami generated we're
pretty confident that it would only have affected the Andaman Islands. Via New Delhi I've got
information from the Andamans that people there felt very severe shaking and they spontaneously
evacuated from the coastlines, which is a good thing.

But we don't know for certain yet whether a tsunami was actually generated.

JENNIFER MACEY: The tsunami alert for the Indian Ocean was cancelled about four hours after the
earthquake struck off the Andaman Islands.

Dr Ray Canterford is the head of the weather and tsunami services at the Bureau of Meteorology. He
says there's a number of systems to detect tsunami's and one misplaced seafloor gauge isn't a cause
for concern.

RAY CANTERFORD: There's the sea level gauge, the tidal gauges are located on islands and coastal
areas. Then there's a small number of these deep ocean buoys and then there's the seasonal gauge
has to actually pick up an accurate location and depth of the earthquake.

So the strength of the earthquake and its depth are fed into an open ocean model, independent of
the sea level gauges just to determine whether or not a tsunami may be generated.

JENNIFER MACEY: In Japan where earthquakes are common, tidal gauges recorded a 50-centimetre surge
from the second earthquake.

This is a similar size to the tsunami that hit Australia's coastline last month where a
30-centimetre surge was recorded at Port Kembla south of Sydney.

Dr Canterford says if the tsunami had struck during the day in summer with a lot of people in the
water, it could have been more dangerous.

RAY CANTERFORD: The threat can be important because people can get washed out to sea or get caught
up in a rip if you're swimming.

JENNIFER MACEY: But he says tsunamis are rare events, and alerts and warnings are issued by the
Joint Australian Tsunami Warning Centre about every two years.

ELEANOR HALL: Jennifer Macey reporting.