Shaking it up: Comparing the 1906 and 1989 Earthquakes

Did you know today is the 25th anniversary of the Loma Prieta earthquake? I doubt folks in the Bay area are celebrating with balloons and cake, but I’ve already seen many of my friends posting the “Where were you when this happened?” type of questions on the internet.

Having spent years researching the 1906 San Francisco earthquake for my novel, Out of the Ruins, I was curious–how did the 1989 Loma Prieta earthquake compare to the 1906 quake?

Of course, the USGS had the answers. [I’ll break them down for you here, but keep in mind–I’m no geologist. I apologize if I use the terms/science incorrectly. I’ll give you the links as well, so if you’d like to learn more, you’ll have the info at your fingertips.]

Thanks to a seismograph in Gottingen, Germany, we have estimates for both quakes. In 1989, the quake registered ~7.0M. How about the 1906? Approximately 7.8M. That might not sound like much of a difference, but with how the scale is designed, that’s about 16 times the energy of the 1989 event. Also, strong shaking occurred for about 15 seconds in the Loma Prieta quake, as opposed to 45-60 seconds or more in the 1906. You can see the seismogram at the USGS website.

Seismic magnitude ranks earthquake according to the energy released. Another scale–intensity–compares people’s observances of the shaking and the damage caused. You can read more about the intensity scales (Modified Mercalli) in this lesson plan designed for teachers. The intensity scale varies according to your location in comparison to the epicenter. This image shows the difference in the two quakes, according to the intensity scale. Learn more about these images at the USGS. Learn more about these images at the USGS.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Can you see the difference? I live in Oregon, and scientists keep warning us that our fault off the coast is capable of magnitude 9 subduction quakes. Having seen the photos of these magnitude 7 quakes, I can’t imagine the level of destruction rendered by a 9M.

In my research of the 1906 quake, it quickly became obvious that most of the destruction occurred after the event. Some buildings crumbled in the initial shaking and during the aftershocks, but many more lives were lost in the three days of fire that followed. That’s the path I followed in my book, Out of the Ruins. If you haven’t had the chance to read it, I hope you will. I was greatly moved by the many personal accounts of the disaster, and I took great care in relating the events in a fictional format. I hope I captured the chaos and the anxious moments in a manner respectful of those who lived through the event.

To read more about the 1989 Loma Prieta earthquake, check out these articles:

• Loma Prieta earthquake: 25 years later, neighborhoods reborn
• Loma Prieta: The Earthquake that stopped the world series
• 25 years later, Loma Prieta survivor recalls terrifying drive

Have you ever experienced an earthquake or another natural disaster? Share your experience in the comments below! And in these times, when the world seems so unstable and frightening, I hope you’ll remember these verses:

Yes, my soul, find rest in God;
    my hope comes from him.
Truly he is my rock and my salvation;
    he is my fortress, I will not be shaken.
My salvation and my honor depend on God;
    he is my mighty rock, my refuge.

(Psalm 62:5-7). 

Blessings!