What are the three main types of earthquakes?
The Pacific Northwest is host to three kinds of earthquakes revealed in this Flash rollover. Subduction zone great earthquakes, shallow crustal quakes, and earthquakes within the subducting plate. Scroll over the colored spots for date, magnitude, and location for the smaller earthquakes and additional details for the larger.
VIEW the interactive in a separate tab, by clicking on "Open Resource" then scroll over named features. (Note some browsers lack the plugins for rollovers.)
IRIS may be discontinuing these interactive animations in 2020. This file is an HTML5 file that uses a browser to view.
Scroll over the bathymetric relief map to learn about the geographic provinces of the Pacific Northwest.
Learn about the volcanoes of the Pacific Northwest Cascade Range mountains by scrolling over individual volcanoes on this interactive map.
Learn how the Pacific Northwest tectonic setting and megathrust earthquake of January 1700 is similar to the catastrophic earthquake in Japan in 2011 by touching icons on this interactive map.
Subduction zones show that there are 3 distinct areas of movement in the overlying plate:
GPS can record the movement of the leading edge of the overlying continental plate in a subduction zone. The plates are locked and the overlying plate is forced back. When friction is overcome and strain is released, the GPS receiver will snap back toward its original position.
Subduction-zone megathrust earthquakes, the most powerful earthquakes in the world, can produce tsunamis through a variety of structures that are missed by simple models including: fault boundary rupture, deformation of overlying plate, splay faults and landslides. From a hazards viewpoint, it is critical to remember that tsunamis are multiple waves that often arrive on shore for many hours after the initial wave.
This animation by UNAVCO shows us how an earthquake warning system uses existing seismic networks to detect moderate to large earthquakes. Computers, communications technology, and alarms are devised to notify the public while an earthquake is in progress.
This UNAVCO animation compares Japan's subduction zone at the location of the 2011 earthquake with a mirror-image subduction zone in the Pacific Northwest. There are many similarities.