USGS reported that a magnitude 7.3 earthquake struck off-shore Alaska a short time ago and now the National Weather Service’s Tsunami Warning Center is warning that a tsunami is likely to impact portions of the Alaskan coastline. While tsunami is expected in Alaska, there is no threat of tsunami to the rest of the U.S. or Canadian coastline including to the islands of Hawaii.

Right now, a Tsunami Advisory in Effect for South Alaska and the Alaska Peninsula, along the Pacific coasts from Kennedy Entrance, Alaska (40 miles southwest of Homer) to Unimak Pass, Alaska (80 miles northeast of Unalaska). The tsunami is triggered by an earthquake which struck at 12:38 pm local time from a depth of 12 miles 55 miles south of Sand Point, Alaska and 605 miles southwest of Anchorage, Alaska.

“Actions to protect human life and property will vary within tsunami advisory areas,” says the Tsunami Warning Center. “If you are in a tsunami advisory area, move out of the water, off the beach, and away from harbors, marinas, breakwaters, bays and inlets.  Be alert to and follow instructions from your local emergency officials because they may have more detailed or specific information for your location.”

After shocks are possible too.

The Tsunami Warning Center adds, “If you feel a strong earthquake or extended ground rolling take immediate protective actions such as moving inland and/or uphill preferably by foot.”

They have also provided advice for those on the water: “Boat operators, where time and conditions permit, move your boat out to sea to a depth of at least 180 feet. If at sea avoid entering shallow water, harbors, marinas, bays, and inlets to avoid floating and submerged debris and strong currents.”

Officials are urging that people not go to the shore to observe the tsunami. People shouldn’t return to the coast until local emergency officials indicate it is safe to do so.

Those in the Tsunami Advisory area are warned that waves and currents can drown or injure people who are in the water. Currents at beaches and in harbors, marinas, bays, and inlets may be especially dangerous. Some impacts may continue for many hours to days after arrival of the first wave.  The first wave may not be the largest so later waves may be larger. Each wave may last 5 to 45 minutes as a wave encroaches and recedes.

Coasts facing all directions are threatened because the waves can wrap around islands and headlands and into bays.

Strong shaking or rolling of the ground indicates an earthquake has occurred and a tsunami may be imminent. A rapidly receding or receded shoreline, unusual waves and sounds, and strong currents are signs of a tsunami.

The tsunami may appear as water moving rapidly out to sea, a gentle rising tide like flood with no breaking wave, as a series of breaking waves, or a frothy wall of water.

Tsunamis are giant waves caused by earthquakes or volcanic eruptions under the sea. Out in the depths of the ocean, tsunami waves do not dramatically increase in height. But as the waves travel towards land, they build up to higher and higher heights as the depth of the ocean decreases. The speed of tsunami waves depends on ocean depth rather than the distance from the source of the wave. Tsunami waves may travel as fast as jet planes over deep waters, only slowing down when reaching shallow waters. While tsunamis are often referred to as tidal waves, this name is discouraged by oceanographers because tides have little to do with these giant waves.

A tsunami is a series of waves. The time between wave crests can vary from 5 minutes to an hour. The hazard may persist for many hours or longer after the initial wave. Impacts can vary significantly from one section of coast to the next due to local bathymetry and the shape and elevation of the shoreline. Impacts can also vary depending upon the state of the tide at the time of the maximum tsunami waves.