NOAA's West Coast and Alaska Tsunami Warning Center , in Anchorage, Alaska, said the earthquake did not pose a threat for a tsunami . Before the Center issues a tsunami warning, an earthquake threshold has to exceed 7.0 on the Richter Scale and occur near coastal areas, Sokolowski said. Sokolowski said within two minutes after the earthquake occurred, the Center notified state emergency officials in the Pacific Northwest. We told them that there was no chance of a coastal tsunami. A tsunami is a series of traveling ocean waves of extremely long length generated by disturbances associated primarily with earthquakes occurring below, or near, the ocean floor.
Earthquake magnitude is measured based on calculations from ground motion recorded on seismographs.
An increase in one full number means the earthquake's wave amplitude actually is 10 times greater. NOAA's National Weather Service has tsunami warning centers in Alaska and Hawaii, which monitor all earthquake activity in the Pacific region. Through a program combining education and research, NOAA and its partners have increased public awareness of the risks of tsunamis as well as increased the scientific understanding on how these events behave. Computer simulations of potential and historical events give better pictures of areas that could be affected by tsunamis. Large earthquakes produce about 90 percent of the tsunamis.