WHEN THE EARTH QUAKES

Rex Burress

Although one of the largest earthquakes to occur in America was in my home state of Missouri, California is more generally thought of as being quake country.

Down around the New Madrid, MO bootheel back in 1811-12, a series of 7.9 and 8.1 earthquakes were so strong they affected the flow of the Mississippi River and destroyed towns! There are still small tremors in that zone, three to 15 miles down, called ''interplate quakes' separate from tectonic plate quaking edges.

Even so, I had never been in an earthquake until I made a home in CA and felt a tremor in Berkeley. Jo and I had an apartment in 1959 when our daughter Rebecca was born, and our bedroom was in a second floor garden-overhang perched on stilts. Bam! It was such a jolt I thought the room would collapse! But it was only a 'three.' For comparison, the recent August 24 Italy quake was 6.2 and killed about 250 people.

I was also in the 1989 “Loma Prieta” Bay Area quake and was really swayed in that 6.9 bit of devastation. It was centered in the Santa Cruz mountains and shook the land all the way to the Bay. I was sitting by the swimming pool at my son's apartment in Palo Alto waiting for him to get home to take me to the airport for a trip to Missouri, when all at once the land rolled and the pool silently sent two feet of water sloshing over my legs! Ben had arrived and was upstairs holding his bookcase up!

Amid some alarming reports that the Bay Bridge and the Oakland freeway had collapsed, I canceled the trip and sped back to see if my home in Oakland had been affected, but it was intact. Chaos was rampant as aftershocks settled in. Since 63 people died and 3,800 were injured amid six billion dollars of damage, I felt extremely fortunate.

Earthquakes could be thought of as the cooling of the land's crust that was once a fiery mess 4.8 billion years ago. The solidifying and quake process involves the sliding around of vast tectonic plates under the soil's surface, colliding and repositioning like ships at sea. Some of those shiftings happen miles underground, although in places like Yellowstone Park, Iceland, and in the Lassen thermal zone, the crust is thinner, allowing hot, semi liquid magma to escape the earth-crust-capping in the form of volcanoes, geysers, and hot springs.

About 1972, my family and I lived at White Sulphur Springs west of St. Helena, CA in the Mayacama Mountains, involved with camp work. Featured was a hot, healthful, sulphur spring pool that had attracted people from the Bay Area for a hundred years. It was rather ominous that steaming water poured constantly out of the mountainside, but there is a thermal region close to the surface all the way to Calistoga where it pops out as an “old faithful” geyser.

I explored those rugged mountains and made a nature trail up and over a steep ridge into a wooded valley. I later realized that it was the crater of an ancient volcano, clothed with an oak-madrone forest featuring a basin of giant ferns. “Fern Springs Trail.”

I discovered a depression on the opposite canyon wall where a large swath of soil had seemingly simply settled a couple hundred feet as if dug by a giant scoop. It was a fault line of some ancient quake. I wondered what else was hidden under those hills. The cut is larger than the trench left by the ruptured San Andreas fault at Point Reyes. The San Francisco 7.8 quake was in 1906, and killed 3,000 residents, reeking havoc to the city.

Oroville has had a few quakes, too. Manmade land disturbances, such as dams and fracking, can alter the balance of pressure on Earth's tectonic plates and cause a seismic event, like the 5.9 quake around Lake Oroville in 1975.

Notes:

The continental crust is about 20-30 miles thick, indeed a thin layer when you consider that the Earth is 7,917.5 miles in diameter.

“We are like ships floating on a sea of molten lava that is 752 F degrees at the mantle boundary.”

Largest modern quake was 9.5 near Valdiva, Chile in 1960.

The deadliest quake in recorded history killed 830,000 people in Shaanki, China in 1556.

There are about 500,000 measurable quakes worldwide each year.

“Those who survived the San Francisco earthquake said, 'Thank God, I'm still alive.' But, of course, those who died, their lives will never be the same again.” --Barbara Boxer