Ooga Booga: Great Shakes

Occasionally, someone comes out with an "ooga booga" story or book about the Big One (earthquake) that is to come on the Cascadia Subduction Fault Zone.

I'm not saying that we shouldn't be scared.

The Cascadia Subduction Zone had its last major slip and earthquake at 9 p.m. local time on January 26, 1700. How do we know this so precisely? I’m going to put it down to nosy scientists, God bless them.

When such a quake happens again, we can expect coastal towns to be wiped out by tsunamis, along with destruction caused by the quake itself, and tsunamis will spread up and down the West Coast and across the Pacific Ocean.

It will affect the Salish Sea/Puget Sound to a lesser degree, we hope. We'll feel it.  A computer projection of tsunamis caused by the Cascadia Zone Subduction Fault showed tsunami waves traveling up the Sound, bouncing off of Tacoma, and rebounding to smack into the south ends of Vashon and Maury Islands. Something to think about.

The March 2011 Tohoku Earthquake in Japan was a subduction zone quake. Perhaps you remember the havoc and death caused by that quake and ensuing tsunamis.

The 2004 Boxing Day Quake in Sumatra wiped out many places and people in Indonesia and all along and within the Indian Ocean.

The 1960 Chile/Valdivia Earthquake is estimated to have been a 9.4 – 9.6 in magnitude, the largest recorded earthquake in the 20^th Century.

The second largest, the 1964 Alaska Earthquake, was a magnitude 9.2. Most deaths were caused by the tsunamis created in that quake.

These were all Great Quakes. I have never experienced a Great Quake. I am not looking forward to it.

The 1994 Northridge Earthquake was rated as a 6.7, but it caused a degree of death and destruction in the San Fernando Valley and greater Los Angeles area that was unprecedented and led to many changes in building codes and earthquake precautions.

It doesn’t have to be a Great Quake to be a disaster.

Tectonic plate theory arose during the 1960s - before that there was a whole different geological narrative about how the earth moved and quaked.

The Cascadia Subduction Fault Zone is formed by the Juan de Fuca tectonic plate sliding under the North American plate. Such a little piece of tectonic plate causes so much havoc. There are earthquakes along the fault zone frequently, but we don’t feel them here because they are too far out at sea.

When subducted material gets deep enough, it heats up and becomes magma, and produces the chains of volcanoes we have on the West Coasts of the American continents, and around the Pacific Ring of Fire.

I am reminded in my reading that Mt. Rainier is an active volcano. Sigh. Noted.

I grew up in coastal Central California in the San Andreas Fault zone, where minor earthquakes are common, and I considered them kind of fun. Whee! We’re shaking!

That was before I was in the 6.6 Sylmar Earthquake in Los Angeles in February 1971. It was centered on a fault out in the Simi Valley - not the San Andreas Fault, which is supposed to unleash a Big One, so I was told all my life. That 6.6 Richter Scale quake was plenty strong enough for me - portions of freeways collapsed, gas and water mains broke, there were fires, a brand new hospital in the San Fernando Valley pancaked and killed around 40 people. Part of the Tehachapi Mountains was raised four feet.

Where I was, on a hilltop in Silverlake near downtown LA, it felt like a truck was ramming the house repeatedly. It was scary - I'd never been in an earthquake that big before. It happened at 6 in the morning. I went upstairs and watched the TV news with my landlady. It took a while for all the reporters and news agencies to wake up and get organized. Reporters in the San Fernando Valley were reporting as they ran out of their houses.

I went to work around 8, because this is America, you know, and we don’t skip work for a major earthquake. I worked for an insurance agency on Beverly Boulevard. On the way there I saw landslides on hillside roads, and the building I worked in had cracks in the stairwell. I know that because the elevator was out of service.

There were aftershocks all day, and those continued for months. I got so I knew the Richter rating of each aftershock by feel.

I have learned that that skill does not travel. We had a 6.8 quake here on February 28, 2001, the Nisqually Ash Wednesday Quake. It was centered near Olympia. I was working at a local hardware store at the time, and I thought it was a 5-something quake.  It was long, almost a minute the record says, and it started, and paused, then started again and shook harder. There was surprisingly little damage at the hardware store. We lost some glass lamp chimneys and that was about it. People ran outside, of course, because that’s what people do. You aren’t supposed to run outside. My father’s Uncle Ralph died in an earthquake in Santa Barbara, California, in 1925, when he ran outside and was buried in bricks falling from the building. This is why you are not supposed to run outside.

This is also why I wouldn’t live in a brick house.

But never mind – no bricks hit anyone on Vashon, as far as I know. Some of the older brick buildings around the area did suffer damage, and cars were damaged by falling bricks.

The original Richter Scale has been upgraded for more accurate earthquake measurement, because it was originally designed for earthquakes in Southern California. It was supposed to be an objective measurement, but earthquakes are subjective experiences.

Let's just say that anything over a 6 is getting into major earthquake territory, and you will not enjoy it.  

The 1906 San Francisco earthquake, which had its epicenter in Tomales Bay, north of San Francisco, was traditionally rated as an 8.3 on the Richter scale. In recent years it has been downgraded to a 7.7-7.9 magnitude. A lot of the damage in San Francisco was caused more by the fires after the quake than the quake itself, except, of course, on fill land, which liquified when the quake hit. 

I'm not trying to make it sound nicer than it was by saying its numbers have been lowered. It was as bad as we have heard.

The October 1989 Loma Prieta quake was rated a 6.9, and perhaps you are old enough to remember the damage that caused - a section of the Bay Bridge collapsed, and the double-decker Nimitz Freeway in Oakland pancaked, killing people in their cars. Lots of buildings in San Francisco that had been built on fill land collapsed or sank, and there was fire in the Marina District. 

Santa Cruz and Watsonville were devastated by the quake. Many buildings collapsed or had to be bulldozed and both downtowns had to be rebuilt.

Again, the Loma Prieta Quake was not a San Andreas Fault quake. It was generated by a lesser fault in the San Andreas Zone. The epicenter was in the Nisene Marks Forest, east of Aptos. 

So the 1971 San Fernando Quake (6.6) and the 1989 Loma Prieta Quake (6.9) were big and did a lot of damage and killed people. But they were not Great Quakes. Neither was the Big One.

The 2011 Japan Tohoku Quake was rated a 9.0 to 9.1, the 2004 Aceh Banda Quake a 9.1, and the last Cascadia Subduction Zone Quake in 1700 - well, there was no Richter Scale in 1700, but those were all Great Quakes.  

(see: https://www.king5.com/article/weather/earthquakes/copalis-beach-ghost-forest-cascadia-subduction-zone-earthquake/281-045a5189-de8b-4e25-be36-8271bd4bbfa2)

So, yes, there will be Big Ones, from the Cascadia Subduction Zone and from the San Andreas Fault, and elsewhere, and those quakes will be scary and destructive and deadly.

So someone occasionally says, “Yoo hoo, big earthquake coming. Get prepared.” They are correct.

Big quakes are rare enough that we are lulled into complacency. Be ready. Stock up on drinking water and foods that don’t need to be cooked.

Have I done this preparation?

Oh, heck no. But writing this essay is motivating me to do so. As my mother used to tell us, do as I say, not as I do.

Anecdotes:

In the 1971 Sylmar quake, Dr. Richter, who devised the Richter Scale in 1934, and lived out in the vicinity of Cal Tech in Pasadena, said that his dishes rattled.

In the 1906 San Francisco Quake, springs dried up in Santa Cruz County. My father was born in 1912 and he heard stories from the old timers in Watsonville.

Also in the 1906 Quake – Malvina Reynolds was born in 1900 and her family lived in the Mission District in San Francisco. She told me that the chimney collapsed in their building, and her baby brother, in his crib, disappeared down the hole. Major panic! They found him, sitting on his mattress on a pile of rubble, safe and sound. If he’d been able to talk, he might have said, “Again!”