Station Locations
Two of the stations are located as close as possible to the Vanuatu subduction zone, ie LIFNC and MARNC at Wahanam, Lifou, and La Roche, Mare, respectively. The Lifou Station has been operating since April 2010 and the Mare station is due to be set up in the first quarter of 2011.
On the southern mainland, YATNC is located at Yate and ONTNC in Noumea with the latter station operating since 2010. OUENC station on Ouen Island is scheduled for the first quarter of 2011, as is PINNC on the Isle of Pines.
KOUNC at Koumac has been up and running since March 2011.
Operating principle: a seismic station is made up of several sensors (in this case a broadband seismometer and accelerometer) connected to a digitiser. The latter converts analogue signals from the sensors into digital signals. It records them and constantly transmits them to IRD’s Noumea centre that processes all signals from all the stations simultaneously. Monitoring is, therefore, on-going for all the stations spread across New Caledonia.
Equipment
 |
 |
 |
| Agecodagis digitiser Kephren-BB |
Broadband seismometer 120 PA Nanometrics Trillium |
ES-T Episensor accelerometer |
Software
Each sensor provides the digitiser with an analogue signal that is digitised and retransmitted to IRD in real time. The software that processes the data in real time is SeisComp3. In a nutshell, its role is to :- analyse each signal or “trace” in real time, thereby detecting any seismic signals
- correlate incoming signals from all stations. If a minimum number of stations detect signals in a meaningful timeframe that accounts for the distances to the various stations, a new quake is deemed to have been detected and its main characteristics, ie focus co-ordinates, magnitude, number of stations detecting it, etc, are determined
- using Seiscomp3, all the region’s stations and their status can also be visualised, including those in the New Caledonian network. An “alert screen” immediately displays the stations that detect the arrival of a seismic wave, with the stations’ symbols flashing, and when an earthquake has actually been detected, it displays its characteristics in real time
Example of Real-Time Earthquake Detection
Signals from stations are detected. The closer the station is to the earthquake, the earlier the signal arrives. The illustration clearly shows all the stations that detected the earthquake, ranging from the nearest to the focus to the furthest :
At the same time on the control panel, the stations that detected the earthquake are shown by a flashing symbol :
The earthquake characteristics are then determined in near real time, depending on when the data arrive. In this case it is in approximately 12 minutes. For an earthquake occurring in the region, the time is 4 to 5 minutes :
