The Cascadia Fault Line: Locked, Loaded And Ready To Fire
Wednesday, June 19, 2013
On a dark winter’s night in January 1700 a tsunami struck Japan. It flooded fields, swept away villages for miles inland and cost many lives. Even as far back as 1700 the Japanese had made the connection between earthquakes and Tsunami, but this time there was no earthquake, no warning to allow the people time to evacuate to higher ground. The tsunami was called the ‘orphan tsunami’ because it had no ‘parent’ earthquake. For more than 300 years the origin of the orphan tsunami remained a mystery.
In the 1980s Hiroo Kanamori and Tom Heaton published a paper that said the 1700 tsunami was caused by a massive rupture of the Cascadia fault line that runs off the west coast of the United States from California to Vancouver. In 1987 Brian Atwater studied soil samples far inland across the length of the fault and discovered that the United States had also suffered a tsunami at the same time as the Japanese. He concluded that Kanamori and Heaton were correct, a massive earthquake had sent a tsunami out from the source of the quake inundating the coasts on both sides of the Pacific.
Recent studies by researchers at the University of Pennsylvania has concurred on the findings of previous studies.
The Cascadia Fault is a subduction zone, an area where one of the tectonic plates is forced underneath the plate it collides into. In the case of Cascadia the Juan de Fuca Plate is moving under the North American Plate. These plates have been locked together since 1700, 313 years. A particular feature of the Cascadia Fault is that it doesn’t produce small quakes, it remains still and silent until the pressure gets too much and one of the plates slips…giving rise to a mega-thrust earthquake of massive force. These quakes can be compared to the Indonesian quake of 2004 and the Japanese quake of 2011.