Tsunameters in the Pacific Ocean
 

Tsunamis are large water waves created by seismic activity, land slides, volcanic activity or by any vertical disturbance of water.  Historically, tsunamis have killed tens of thousands of people and have caused significant damage to coastal areas of the world.  The word "tsunami" comes from the Japanese and means "harbor wave".

Tsunamis differ from regular wind-generated waves in that wind-generated waves have shorter period and wavelength. A tsunami can have a wavelength in excess of 100 km over  a period of hours. 

Tsunamis can travel at hundred of miles per hour for great distances.  As tsunamis get closer to shore and water depth becomes shallower, a tsunami slows down.  As a tsunami slows, its height increases. Once ashore, tsunami height may reach up to 30 meters.  A tsunami continues inland until it loses its energy.  While proceeding inland, it causes flooding, death and destruction.  

Figure 1. NOAA Tsunameter Stations

To reduce loss of life and property in coastal communities, NOAA Pacific Marine Environmental Laboratory built a Deep Ocean Assessment and Reporting of Tsunamis (DART) network (Figure 1) to implement the capability of early detection and real-time reporting of tsunamis in open ocean.  DART consists of a seafloor bottom pressure recorder (at 6000 meters) capable of detecting tsunamis as small as 1 cm, and a surface buoy for real-time communications as in Figure 2.

Figure 2. DART Station

The bottom pressure recorder uses a Digiquartz® Pressure Transducer manufactured by Paroscientific, Inc.  Digiquartz® Instruments were selected for this application due to their high accuracy, excellent resolution and long-term stability.  Digiquartz® Technology provides a resolution of 0.0001% of full scale, enabling NOAA PMEL to measure very small waves (1 cm) on the surface from 6000 meters (21,000 ft) depth.  Pressure readings from the bottom pressure recorder are acoustically transmitted to the surface buoy. The data are then relayed via a GOES satellite link to ground stations, which demodulate the signals for immediate dissemination to NOAA's Tsunami Warning Centers and PMEL.

Digiquartz® Pressure Products make the detection of a tsunami possible from great ocean depths with the highest resolution, lowest noise, and most accurate instruments available today. The transducers are based on the inherently digital, highly stable, vibrating quartz crystal technology developed by Paroscientific over the last three decades. They are designed and tested to deliver outstanding performance even under difficult field conditions.

Although many applications require both high resolution and accuracy, short-term measurements generally benefit more from our high pressure sensitivity,  while longer term measurements need our accuracy, stability, and insensitivity to environmental errors.

With a sensor of inadequate resolution, real signals can be obscured by noise, or sensor noise can be misinterpreted as real signals. Paroscientific transducer mechanisms, oscillator circuits, and digital interfaces are carefully designed for high resolution. Typical delivered resolution of our transducers is better than one part per million, and under stabilized laboratory conditions, resolution can approach 1 part per billion.

For further information on this application and Digiquartz® Products, contact our applications engineers.