New broadband seismometers to record Tonga earthquakes [1]
Wednesday, July 8, 2009 - 12:22. Updated on Thursday, July 30, 2015 - 17:01.
The Tonga Seismic Network is now better equipped to accurately measure and record big earthquakes of up to 7 magnitude after being upgraded with new broadband seismometers in the Tongatapu, Vava'u and Ha'apai stations.
Dr Hiroshi Inoue, a seismologist from Japan, who is in Tonga to set up the new instrument said the capability of a broadband seismometer is that it can record underground motions in a faster and longer period of up to two minutes.
This compared to the normal short period seismometer they replaced which was limited to recording earthquake motion up to only a second or less like a quick vibration, hence the data acquired for determining quake size and location was not always accurate, he said.
Dr Inoue said that the replacement seismometers were set up the by Japan's International Cooperation Agency, JICA, in 2003 but they were not always operating, so the main purpose of his visit, from June 20 to July 11 is to make the network operate properly.
Broadband
He said the advantage of broadband is that it is able to relay more accurate and precise information about the earthquake's size, its epicentre and location because of the longer period it records the motion. Its other main advantage is that it can automatically trigger a local tsunami alert.
He explained that broadband connects all island stations via satellite and information is automatically transmitted via its tower to the Tonga Geology main recording office at Vaololoa.
The data automatically generated is provided in real time and is more accurate in measuring and recording an earthquake's magnitude or location than that of a normal one. Geologists could then analyse to see whether a tsunami warning should be issued.
He said that geologists still needed to analyse the data and not solely rely on the data itself to issue out an alert, because sometimes it can be wrong.
Dr Inoue said that the next stage of the project will be the implementing of the broadband tsunami alert system when another system will be set up to enable geologists to properly estimate tsunami arrival time, height, location and size.
Dr Inoue was in Tonga with Dr Daisuke Suetsugu and they were brought to Tonga by JICA under its Technical Cooperation Project of "Operation of Earthquake Observation Network" in response to a request from Government of Tonga.