If you are among those convinced that talk of a major (potentially 9.0 magnitude) earthquake in Oregon in our lifetime is needlessly alarmist, we urge you to attend a talk Friday afternoon in the Medford City Hall council chambers. (Correction: The location of the presentation has been updated.)
Officials of the Oregon Office of Emergency Management will describe the effects of a quake that large and explain how to be prepared for it and survive it most successfully.
Geologists' understanding of earthquakes and their ability to predict them has come a long way, but science still cannot say with precision when they will occur.
For some time, the consensus has been that the last subduction zone earthquake that large to strike the Pacific Northwest coast occurred in 1700. Historical records indicate the resulting tsunami destroyed fishing villages in Japan.
Earthquakes that large are thought to occur approximately every 400-500 years. Recently, however, new research has led to more alarming predictions.
A study by Oregon State University researchers published last year concluded that quakes centered off the Southern Oregon coast occur approximately every 240 years — and it's already been longer than that since the last major one.
Study co-author Jay Patton said, "By the year 2060, if we have not had an earthquake, we will have exceeded 85 percent of all the known intervals of earthquake recurrence in 10,000 years."
And the one we are likely to have will be big — perhaps 10 times more powerful than the Loma Prieta quake of 1989 in the San Francisco Bay Area.
That would be a 7.9 magnitude quake — still a long way from a 9, which would be an additional 12 times more powerful — but extremely destructive nevertheless.
What makes the Pacific Coast so vulnerable is the subduction zone — where one tectonic plate of the earth's crust is diving beneath another. Pressures build up over time and the resulting movement causes devastating quakes.
Examples of massive subduction zone quakes in recent history include the Alaska earthquake of 1964, magnitude 9.2. The Fukushima quake of 2011, which killed 18,000 people, was a 9.
So, if you're inclined to think all this talk about huge earthquakes here is irresponsible speculation, think again. And think about learning to prepare your home and family to survive one if it happens.