Geodetic Science Snapshots - Ocean

Central America faces tsunami threats along the Pacific and Caribbean coasts and at the shores of large lakes. Large earthquakes caused the most damaging tsunamis, however, landslides or volcanic eruptions can cause tsunamis around large lakes. Warning systems rely on seismic and geodetic observations. The Central American Tsunami Advisory Center (CATAC) will use these observations to help reduce losses.

Long-term records from GPS stations along the Atlantic Coast of North America show long term subsidence due to geologic adjustments and short term subsidence due to human-related groundwater extraction. These measurements are critical for understanding water use, sediment structure and sea level rise.

Most of the ocean floor is unknown. Gravity models generated from satellite radar altimetry provide one of the only ways to map the height of the seafloor beneath all of the oceans. Years of data and thousands of satellite tracks have yielded unprecedented detail of major spreading ridges and thousands of seamounts.

The damaging March 11, 2011 Tohoku earthquake caused significant tsunami waves that were recorded on videos by eyewitnesses. Two survivor videos from building rooftops at Kesennuma Bay were combined after the catastrophe and compared with on site terrestrial laser scans, using ground-based LiDAR.

The forces of the Japanese Tohoku-oki 2011 magnitude 9.0 earthquake, the fifth most powerful in the past century, set off a large tsunami that further devastated the shaken island. The earthquake and tsunami also badly damaged a six-reactor nuclear power plant in Fukushima, located 241 kilometers north of Tokyo.

UNAVCO’s Plate Boundary Observatory (PBO) includes 75 borehole strainmeters installed predominantly throughout the west coast of North America. Strainmeters work by detecting changes in the size of the borehole, and are sensitive enough to detect a 4 picometer change (smaller than the width of a hydrogen atom). Because they are so sensitive, they pick up every thump and shake in their vicinity, including the arrival of a tsunami wave from across the ocean.