Cascadian Tsunami

Cascadian Tsunami "Barely had they set foot in the city in mourning the death of their benefactor, they feel the earth shake beneath their feet, the sea rises bubbling in the harbor, and breaks the vessels that are to anchor. Swirls of flames and ashes covered the streets and public places; houses collapsed, roofs are reversed on the foundations, and foundations disperse, and thirty thousand inhabitants of all ages and sexes were crushed under the ruins, said the sailor, whistling and swearing: ʽ There will be something to win here. - What can be the sufficient reason of this phenomenon? said Pangloss. - Here is the last day of the world!’ Cried Candide” (Voltaire, 1759 translated by Google translate) Some of the first descriptions of tsunamis are grim at best this excerpt came from Voltaire’s Candide a French satire published during Europe’s Age of Enlightenment. This gives a chilling view of Lisbon on All Saint’s Day (November first) in 1755. What had occurred is a 200 km offshore 8.5-9.0 magnitude earthquake that resulted in a large-scale tsunami and rampaging fires, effectively killing thousands of people. This is one of the deadliest tsunamis recorded in history, but how do tsunamis function and what do we know about their inner workings. Tsunamis since the early 1600s have been synonymous with some form recording of “shaking of the earth”. Very rarely do you see other forms of tectonic activity such as volcanic eruptions or glacier calving that can create a tsunami. The integral part to the large-scale tsunamis that we see is plate tectonics. The plates converge, diverge, or transform to create a displacement in the sea floor that corresponds to the sea level.

In Figure 1 we see the tectonic components that lead to a sequence that is similar to the 1700 Cascadian Tsunami. Part one shows a subducting oceanic crust; as the plate is subducting under the continental

Cited: Brian Atwater, The Orphan Tsunami of 1700, 2005. Pdf compilation book by Atwater, Brian. Accessed February 27, 2014 Cascadia Region Earthquake Workgroup, Cascadia Subduction Zone Earthquakes: A Magnitude 9.0 Earthquake Scenario, 2005. http://www.crew.org/sites/default/files/CREWCascadiaFinal.pdf. Accessed February 22, 2014 Pacific Northwest Seismic Network, Cascadia Subduction Zone, 2013. http://www.pnsn.org/outreach/earthquakesources/csz. Accessed February 20, 2014 National Oceanic and Atmospheric Administration, Tsunami, 1998. http://www.tsunami.noaa.gov/tsunami_story.html. Accessed February 20, 2014 Voltaire, Candide, 1759. Selected Quote and translated with Google Translate. Accessed February 22, 2014