Today at 10.31, Italian time, an earthquake of magnitude 7.6 (estimated by the Rome operations room of the National Institute of Geophysics and Volcanology INGV in the first minutes of the event) occurred off the island of Kodiak, 300 km south –east from the coast of Alaska. Following the strong shock, a tsunami warning was issued for the Northern Pacific area, which was subsequently returned after checking the data from the tide gauges which excluded significant phenomena. In the Aleutian Islands and Alaska, earthquakes capable of generating large tsunamis that can spread throughout the Pacific Ocean are not uncommon.
On March 27, 1964, an earthquake of magnitude 9.2 near Anchorage (naval port overlooking Cook Bay), generated a huge tsunami that penetrated inland up to a height of 30 meters above sea level and a peak of over 60 meters in the port of Valdez, causing at least 131 victims and damage from Alaska to California.
The INGV Tsunami Warning Center (CAT) operates 24 hours a day, evaluating in real time the possibility that a specific earthquake, with its epicenter in the sea or in the immediate vicinity, could generate a tsunami, estimating the arrival times and the alert expected along the exposed coasts. The messages issued by the CAT for the Mediterranean are then transmitted to the DPC which has the task of disseminating them to the structures and components of the National Civil Protection Service and reaching the potentially interested population as quickly as possible.
Earthquakes are the main cause of tsunamis (about 80%), although they are not the only one. In any case, earthquake-induced tsunamis are the only ones for which it is possible, with current monitoring networks, to define an alert system on a regional scale. Other causes that generate tsunamis, on which the Institute has begun to work, concern landslides generated by volcanic systems.
The CAT-INGV also makes use, as indicated in the SiAM Directive, of the data of the National Mareographic Network of the Higher Institute for Environmental Protection and Research (ISPRA) and of the other Mediterranean mareographic networks for the verification of a possible tsunami.
In the period between October 2014 and June 2017, the CAT analyzed hundreds of seismic events of magnitude greater than 5.5 in all coastal areas of the world. Five of these earthquakes originated in the Mediterranean, particularly in the Greek islands, in the Gibraltar area off the coast of Morocco, and in Cyprus. For these events, CAT-INGV sent warning messages between 9 and 12 minutes from the time of origin of each earthquake.
There are currently nine countries receiving CAT-INGV messages: Egypt, France, Germany, Greece, Israel, Italy, Lebanon, Portugal, Turkey, and three international organizations: IOC (Intergovernmental Oceanographic Commission of UNESCO), ERCC ( Emergency Response Coordination Center of the European Commission), JRC (Joint Research Center of the European Commission).
Epicenter map of this morning's earthquake off Alaska. The star represents the epicenter of the main earthquake (the one with magnitude 7.6 at 10:31 Italian time), the other symbols are the epicenters of the lower magnitude aftershocks that occurred in the first hours after the strongest event.