Tectonic Setting

Alaska has three physiographic divisions: the Rocky Mountain system to the north, the Intermontane Plateau in the interior and the Pacific Mountain system to the south that includes the coastal zone. The Pacific Mountain system includes the Aleutian Island Arc, the Alaska Peninsula and the Alaska Range west of the "Panhandle". The arc system is defined by an oceanic trench (the Aleutian Trench), numerous volcanic islands and an active zone of earthquakes. The arc is divided in to approximately 12 separate tectonic blocks and major earthquakes are related to the boundaries of these blocks. Each block is about 350 to 700 km long and the recurrence interval for large magnitude earthquakes is about 100 to 200+ years. Teletsunamis generated by earthquakes occurring along these tectonic blocks radiate perpendicular to the arc and therefore, tsunamis generated in the western Aleutian Islands are likely to effect Japan and the western Pacific. Those from the central parts will effect Hawaii most strongly and those generated in the eastern end of the arc will effect the coast of western North America.