SYDNEY: A tsunami that hit Indonesia’s Java island on Monday people remained localised because the earthquake that caused it was dramatically smaller than the 2004 quake that generated an Indian Ocean-wide tsunami.
Seismologists also said the earthquake’s physical area was significantly smaller and caused only a small change in the ocean floor, limiting the size of the tsunami that hit Java on Monday.
The two quakes were not linked, except that they occured on the Eurasian fault line which runs along the Indonesian archipelago and is part of the “Pacific Ring of Fire”, they said.
The U.S.-based Pacific Tsunami Warning Center put the latest earthquake’s magnitude at 7.2, while the U.S. Geological Survey estimated it at 7.7. Indonesia’s state meteorology and geophysics agency said the quake’s strength was 6.8 on the Richter Scale.
“The possibility of a 7.2 magnitude earthquake producing an ocean crossing tsunami is very dim, quite negligible. That is why it was more localised,” geophysicist Victor Sardina at the Pacific Tsunami Warning Center in Hawaii, told Reuters.
“In terms of tsunami generating potential it is not even close to the worst case scenario,” Sardina said on Tuesday.
Australia’s Seismology Research Centre said a quake would need to be at least 8.5 to generate an oceanwide tsunami.
The 2004 quake off Indonesia’s Sumatra was 9.3 on the Richter scale, releasing far more energy, and sending a tsunami across the Indian Ocean that left 230,000 people dead or missing.
The Java tsunami only hit 300kms of coast around Pangandaran beach near the town of Ciamis on the southern shore.
“The current magnitude estimate of 7.7 makes the total energy released (by the Java quake) something of the order 1,000 times less than the big earthquake,” said Gary Gibson, senior seismologist at Australia’s Seismology Research Centre.
“The rupture on this one would only be about 70 km (43 miles) long, whereas the length of the rupture of the Sumatra earthquake was about 1,200kms,” Gibson said.
“More importantly, the (ocean floor) displacement on the big one was about 10 to 20 metres in parts, whereas in this one it would be no more than a few metres.”
The Java quake produced smaller waves than the 2004 tsuanmi.—Reuters
