LONG BEFORE news of the Sendai earthquake was first broadcast, scientists in Dublin already knew about the powerful quake and were measuring its strength.
It took just 12 minutes for shock waves from the quake to travel through the earth and reach the sensitive seismic recording equipment operated by the Dublin Institute for Advanced Studies.
“I have to say I have not seen anything as bad since 2004,” said Tom Blake, director of the institute’s system and an experimental officer.
“They are quite powerful and more so because of the number of aftershocks there have been.”
The institute has four monitoring stations, in Dublin, Kerry, Donegal and Galway, with a fifth station due to open in about a month in Wexford.
The shock waves readily travel through the earth, but they also produce ripples that move along the earth’s surface like the waves caused by dropping a pebble in a pool.
“The arrival time [in Ireland] was at about six o’clock, 12 minutes to get from Japan to here,” he said. The seismic equipment takes recordings that measure the waves and from this it is possible to measure the strength of the quake. “We can always measure the magnitude no matter how far away we are,” he said.
Efforts to measure the Sendai earthquake will go on for some time, he said.
This is because major seismic events also tend to send out many smaller aftershocks.
These occur as the rock surfaces at fault lines go through the process of “resettling”, he said. “Now we have this resettling period as the rocks get back into equilibrium.”
The aftershocks can also be quite substantial and just like the main shock, these later movements could also trigger tsunamis that will add to the danger in the coming days.
Visit dias.ie to read more about the quake and to see recordings made by the monitoring system.
