Ocean Observing Systems (OOS) have many sensor to detect earthquakes and tsunamis.
Japan’s most powerful earthquake since records began has struck the north-east coast, triggering a massive tsunami. A massive 8.9 magnitude earthquake hit the Pacific Ocean nearby Northeastern Japan at around 2:46pm on March 11 (JST) causing damage with blackouts, fire and tsunami.
Cars, ships and buildings were swept away by a wall of water after the 8.9-magnitude tremor, which struck about 400km (250 miles) north-east of Tokyo.
A state of emergency has been declared at a nuclear power plant, where pressure has exceeded normal levels.
The following videos provide good information.