Laurie Dengler | The best antidote to earthquake vagaries is getting ready for action – Times-Standard

[ad_1]

There is a topic for many conversations these days – we have outgrown earthquakes, winds and rains. The combination of rivers and earthquakes puts everyone on edge. Was that an earthquake or a storm? Air pressure changes as storms come in and out and can cause a house to creak or shiver in an earthquake-like manner.

If it makes you feel better, there is no connection between earthquakes and weather. Storms do not affect what happens many miles below the surface where earthquakes are centered. Variations in surface conditions never reach those depths. Temperatures are only controlled by the heat coming from deep within the Earth.

The last three devastating earthquakes occurred in the middle of winter – the most recent M6.4 and 2021 M6.2 earthquake and the Eureka earthquake on January 9, 2010. Pure coincidence and nothing more unusual than being in a group of 20 and discovering the two share the same birthday. Earthquakes are all-weather, all-season events that occur in icy cold or very hot conditions.

Precipitation also does not play any role. Our earthquakes are much less than the water level and the weight added by a large storm is negligible compared to other forces such as the twice daily tides. But the opposite can be true. A seismic slide changes pressure in the surrounding rocks and affects the water table. There are many documented reports of wells suddenly flowing or running dry after earthquakes.

Fluids and fluid pressure are important in the genesis of an earthquake. It is clear that the injection of drilling waste fluids into deep wells led to increased seismic activity in the Midwest. But we need to forcibly transport these fluids to great depths to have any effect. Discharging this waste into a tank or surface sewer as was common before the 2000s had no effect.

Large reservoirs can also trigger earthquakes. The M5.9 Oroville earthquake of 1975 may have been caused by the rapid fluctuations during the filling of the dam. Large earthquakes in India and China have also been linked to reservoirs. Congress approved the Auburn Dam project in 1965, but the near collapse of the Van Norman Dams in the 1971 San Fernando earthquake and a potential link in Oroville halted construction. In recent years, water problems in California have revived discussions about the Auburn Dam so that the Auburn Dam story may not end.

Last week, only one aftershock of the Ferndale earthquake was recorded. There have been many other felt earthquakes, but this series of aftershocks seems to be losing strength. I hope so, but I wouldn’t bet on it. And on the North Coast, there’s always a chance of something else going wrong.

We have good records of earthquakes since 1970. In that period, the North Coast has earned its place as the most seismically active area of ​​the lower 48 states, achieving nearly 30% of M6s and five of 9 M7s. Since 1900, 39 earthquakes have reached the M6 ​​threshold in our region. If earthquakes were repeated like clockwork, we would have an earthquake approximately every three years. But earthquakes clump, and I can’t give you three years’ notice before the next one. We had a quiet 15-year period in the ’60s and early ’70s. In 1992, we were hit by three strong earthquakes in a 15-hour period.

The best remedy for fear and anxiety about the next earthquake is to take action to make you, your family, and your workplace safer before the inevitable next earthquake. I’ll start with the easy things that require little effort and no expense.

What do you do when the ground shakes? The 2:34 am Ferndale earthquake provides a good lesson. Most of you were asleep. The earthquake woke you up (very rudely) and you stayed where you were. Didn’t have time to answer. As a result, casualties were very low. I was recently on a call with the North Coast Medical Advisory Committee where they mentioned surprisingly only 17 infections and very few hospital visits, even in hard-hit Fortuna.

There have been many studies on the causes of injuries in California earthquakes. The only factor going up to the top is how much people move as the ground shakes. Five feet is the magic number – move further and you start increasing your odds of falling or getting hit by falling objects. And the more you move, the greater your odds.

Had the Ferndale earthquake happened while I was awake, some of you would have had the urge to crash, and like the daytime earthquakes of 1992 and 2010, we would have seen more casualties and more traffic to health centers. Your home is also a safer place to be than most workplaces and public places as there are more things to fall into.

Our motto is “Drop, Cover, and Hold”. It’s good advice for when you’re awake and indoors. The most important part is the Drop because once you’re on the ground it’s hard to let go. Always cover the back of your neck with an arm or pillow, and if there is a table or desk nearby, slide under it.

But some of us aren’t agile enough to drop, and 33% of the time earthquakes strike while we’re asleep, we wouldn’t have time to do it anyway. Here is where more effort is being made. Make your sleeping area as safe as possible. My earliest memories of the earthquake were when I was seven years old and a M6. 4 quake struck 40 miles from our home in Rancho Mirage. All the books fell into the bookcase above the bed above me. I suspect this had much to do with my later choice of job, but it made an impression.

Take a moment today to survey where you sleep and where your children or relatives with restricted mobility spend most of their time. Children’s beds should be installed on wheels and heavy objects that can fall should be removed. Attach a bag to the bed frame to store a flashlight, gloves and goggles. Rolled slippers by the bed are fine but turn them upside down so you don’t collect the broken pieces.

More preparation tips at Living on Shaky Ground (https://rctwg.humboldt.edu/prepare/shaky-ground). Next week I’m going to take some harder steps.

Laurie Dengler is Professor Emeritus of Geology at Cal Poly Humboldt, and an expert on tsunami and earthquake risk. Questions or comments about this column, or want a free copy of Living on Shaky Ground readiness magazine? Leave a message at 707-826-6019 or send an email to [email protected].

[ad_2]