ABSTRACT

This invention is a self-powered, free-floating, coconut-shape “Floater”, with onboard sensors, GPS receiver, a central processing unit, and a radio transmitter. The unit directly measures the horizontal motion of a tsunami by tracking its position relative to an arbitrary starting point. Tsunamis on the open ocean have a small vertical motion, but large horizontal motion. The vertical motion (only tens of centimeters for a potentially damaging tsunami) is beyond the measurement ability of simple GPS receivers, but the horizontal motion (from a few meters to tens of meters) is measurable. Through on-board bandpass filtering, the unit separates tsunami motion from wind-wave motion and tidal motion, and transmits the resulting signal to a receiving station, via low-orbit-satellite or other constellation. Data from multiple Floaters is interpreted by a remotely located "Floater base". Several dozen Floaters may provide effective tsunami detection coverage for the whole Pacific. A few dozen more may achieve this coverage globally. Applications include sensing of earthquake, landslide, avalanche, volcano, asteroid hit, climate, and ocean event characteristics. Subsequent generations of Floaters will be submersible, remotely programmable, micro or nano scale, and ultimately constitute self-assembling massive arrays. The special feature of this Floater-Base network is the above-described characteristics of the Floaters, plus the network capacity to differentiate between varieties of phenomena that often confuse sensing networks. Other keywords are: environmental sensing, microelectrical mechanical systems, nanotechnology, natural disaster preparedness, disaster prevention, pollution prevention, remote sensing, robotics.

BACKGROUND

The Tsunami Warning System in the Pacific uses a combination of seismometers and coastal tide gauge recorders to evaluate tsunami hazard. Because of difficulties in interpretation (such as determining actual earthquake rupture, or relating coastal tide gauges to open ocean wave height), the system has been supplemented by sea-floor pressure gauges for direct measurement of tsunamis on the open ocean. The sea floor measurement system, known as DART (“Deep-ocean Assessment and Reporting of Tsunamis”) involves a battery-powered bottom package, an acoustic link to a moored surface buoy, and satellite communications to shore. Sea floor packages have to be serviced annually, buoys require maintenance on at least an eighteen-month schedule, and the large (4,000 kg) buoys are subject to vandalism. The DART system is characterized by high capital cost, high deployment cost, high maintenance cost, low redundancy, and most significantly, sparse data coverage. The sparse coverage (as of February 2002 only six systems are deployed) requires that a source be assumed in interpreting the DART data. If the source is an earthquake, a combination of seismic data and DART wave-height in...