Cascadia’s Fault by Jerry Thompson: America’s Earthquake and Tsunami

The Pacific Ring of Fire of earthquakes, eruptions, and tsunamis from New Zealand, through Asia, to the Americas furnishes 15 of the 16 mega-earthquakes since 1900.

The Ring generates cluster earthquakes, with the Pacific plate’s southeast, southwest, and northwest corners rupturing on February 27, 2010, February 22, 2011, and March 11, 2011. In the above-mentioned cases, the Peru-Chile Trench, the Izu Ogasawara, Japan, and Ryukyu Trenches, and the Kermadec Trench respectively huddle off Chile, New Zealand, and Japan. The trenches off these three countries and off Alaska, Indonesia, Mexico, New Guinea, Philippines, Siberia, and Tonga identify zones where sea plates move under land plates.

From the Pacific plate’s northeast corner, Cascadia’s subduction zone joins the trench warfare. 

Cascadia’s fault line from Cape Mendocino in northern California, through Oregon and Washington, to Vancouver Island off British Columbia in western Canada keeps low geo-historical profiles.

Cascadia’s 19 full margin ruptures of magnitude 9 and 22 partial margin ruptures of magnitude 8 in 10,000 years lead seismologists to rethink California’s upcoming mega-quake. Cascadia’s northern end from mid-Oregon to mid-Vancouver Island and southern end from Cape Mendocino to Newport, Oregon, manifest respectively recurrent intervals of 480 and 240 years. Dr. Kenji Satake of the Geological Survey of Japan and co-authors Kunihiko Shimazaki, Yoshinobi Tsuji, and Kazue Ueda note January 26, 1700, for Cascadia’s last mega-earthquake.

They offer 21:00 local time based upon 10-hour tsunami travel times to Japan. 

Japan proves to be among the world’s most earthquake- and tsunami-prone countries because of offshore trenches and proximity to the Marianas, Philippine, and Siberian (Kuril) Trenches.

Generations of earthquake and tsunami data-gatherers in Japan always question a natural disaster’s origins, particularly regarding orphan and phantom tsunamis independent of earthquakes in the archipelago. Entries from January 27 and 28, 1700, reveal 16-foot (4.88-meter) orphan tsunamis devastating 560-mile (901.23-kilometer) stretches from Kuwagasaki to Tsugaruishi, Kubota Crossing, Nakaminato, Miho, and Tanabe. Japan’s records serve to reinforce Huu-ay-aht, Makah, and Yurok oral histories from Pachena Bay and Columbia River, Copalis River, Grays Harbor, and Willapa Bay ghost-forest dendrochronology.

Cascadia’s Fault takes readers on culturally enriching, educationally entertaining, and geo-historically enthralling adventures. 

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

The Cascadia Subduction Zone lies within the Pacific Ring of Fire. The Pacific Ring refers to volcanic arcs and oceanic trenches that partly encircle the Pacific. The Ring of Fire is a zone of frequent earthquakes and volcanic eruptions.
Trenches are shown in blue-green. The volcanic island arcs, although not labelled, are parallel to, and always landward of, the trenches. Illustration by Jane B. Russell.
W. Jacquelyne Kious and Robert I. Tilling, "Understanding plate motions," This Dynamic Earth (February 1996): US Geological Survey, Public Domain, via USGS Geomaps @ https://pubs.usgs.gov/gip/dynamic/understanding.html

Cascadia earthquake sources: subduction zone, deep Juan de Fuca plate, crustal faults
Pacific Northwest geologic mapping and urban hazards: US Geological Survey, Public Domain, via USGS Geomaps @ http://geomaps.wr.usgs.gov/pacnw/pacnweq/index.html

Cascadia earthquake sources: map of Juan de Fuca plate
Pacific Northwest geologic mapping and urban hazards: US Geological Survey, Public Domain, via USGS Geomaps @ http://geomaps.wr.usgs.gov/pacnw/pacnweq/index.html

"Tsunami Forecast Model Animation: Cascadia 1700" (1:20)
Uploaded January 26, 2015, by PacificTWC (Pacific Tsunami Warning Center) to YouTube ~ URL: https://www.youtube.com/watch?v=4W2iUl0VB8c

The Earth's layer on which we live is broken into a dozen or so rigid slabs (called tectonic plates by geologists) that move relative to one another.
illustration of the world's tectonic plates by Jane B. Russell
W. Jacquelyne Kious and Robert I. Tilling, "Historical perspective," This Dynamic Earth (February 1996): US Geological Survey, Public Domain, via USGS Publications Warehouse @ https://pubs.usgs.gov/gip/dynamic/historical.html#anchor9449934

Part of the Pacific Ring of Fire, the Cascade Volcanic Arc extends for a distance of over 700 miles (1,100 kilometers) from southwestern British Columbia through Washington and Oregon to Northern California.
Subduction along Cascadia Subduction Zone is responsible for the arc's formation.
NASA WorldWind image; Black Tusk graphics: NASA World Wind, Public Domain, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:Cascade_Volcanic_Arc.jpg

Thompson, Jerry. 2011. Cascadia’ Fault: The Earthquake and Tsunami That Could Devastate North America. Berkeley, CA: Counterpoint Press.