What are the different operating modes of the tsunameters?
The DART® technology has several operating modes and the data modes are: Standard Mode and Event Mode.
- Standard or Normal Mode: This is the mode when no other data mode is in operation. The system makes measurements every 15 seconds. Every 15 minutes the system subsamples the 15-s data and once an hour forwards the 4 measurements to the surface buoy in a single message. The surface buoy collects these one-hour messages and transmits them in a six-hour collective. Standard mode indicates that the system is working satisfactorily and the data are used for tidal analysis. An important part of the tsunami assessment is to determine the amplitude of the tsunami by removing the tidal signal.
- Event or Tsunami Mode: The Bottom Pressure Recorder (BPR) has a Tsunami Detection Algorithm on board that places the tsunameter in Event Mode. Event Mode provides data more frequently - an initial 4 minutes of 15-second with one-minute averaged data for the hour before and the three hours after going into Event Mode. Not every Event is a tsunami. In some cases, it can go into Event Mode because of electronic problems, or during the recovery of a BPR. The tsunami warning centers can initiate an Event to have the tsunameter report more frequently in anticipation of tsunami. Events are usually initiated by the seismic signal from an earthquake, and the actual tsunami, if there is on, will pass the tsunameter later. It requires expert analysis to determine a tsunami from the tsunameter data.