A small but strong earthquake shook through the Northern California coastline Sunday evening, March 8, at approximately 7:59 p.m.
The National Weather Service has reported the event was a magnitude 5.9 earthquake that began about 70 miles off the coast of Eureka, to the southwest, at a depth of approximately 1.2 miles, in the Mendocino Triple Junction.
The Mendocino Triple Junction is a point where three faults — the Gorda plate, the North American plate and the Pacific plate — meet in the Pacific Ocean near Cape Mendocino in Humboldt County. Seismic activity there is often responsible for the earthquakes felt in our area. There is strong suspicion that this triple junction might be the site of a future Tsunami.
I was sitting in my chair reading a book when the quake struck. No damage at our house.
The first European to record Point Arena was Spaniard Bartolomé Ferrer in 1543, who named it Cabo de Fortunas (Spanish for “cape of fortunes”). The cape was renamed to Punta Delgado (narrow point) in 1775 by lieutenant Juan Francisco de la Bodega y Quadra (commander of the schooner Sonora), part of a royal expedition chartered by the government of Mexico to map the north coast of Alta California. Later the point, and the small harbor town south of it, were called Barra de Arena (i.e. sandbar) and finally Punta Arena (literally “sand point”). The Punta Arena post office opened in 1858, and was renamed Point Arena in 1889. The first store at Point Arena opened in 1859. Point Arena incorporated in 1908. It isn’t very big now and was even smaller when the 1906 earthquake hit.
Virtually all visitors to our layout in Fort Bragg are amazed to find out that the 1906 earthquake was not just about San Francisco but the entire Californian Coast north up to Eureka. I think I have finally found a way to show visually just how close the fault line is to the Mendocino Coast. Look at this topo map which shows Point Arena in the centre. The land features to the right (east) of Point Arena are the same as the features under the sea. The dark blue streak in the water running from the top left corner of the map to about a third of the way across the middle of the bottom is the San Andreas Fault – a mere four miles offshore. Click on the map to see it enlarged.
Topo Map of Point Arena
This picture which I recently received shows the damage to Point Arena Main Street caused by the Quake.
On April 1st 1946, an undersea earthquake off the Alaskan coast triggered a massive tsunami that killed 159 people in Hawaii.
In the middle of the night, 13,000 feet beneath the ocean surface, a 7.4-magnitude tremor was recorded in the North Pacific. (The nearest land was Unimak Island, part of the Aleutian chain.) The quake triggered devastating tidal waves throughout the Pacific, particularly in Hawaii.
Unimak Island was hit by the tsunami shortly after the quake. An enormous wave estimated at nearly 100 feet high crashed onto the shore. A lighthouse located 30 feet above sea level, where five people lived, was smashed to pieces by the wave; all five were killed instantly. Meanwhile, the wave was heading toward the southern Pacific at 500 miles per hour.
Here an abfab computer animation of the tidal wave:
As you can see from the animation Hawaii was slap dab in the middle of the path of the monster.
In Hawaii, 2,400 miles south of the quake’s epicenter, Captain Wickland of the United States Navy was the first to spot the coming wave at about 7 a.m., four-and-a-half hours after the quake. His position on the bridge of a ship, 46 feet above sea level, put him at eye level with a “monster wave” that he described as two miles long.
As the first wave came in and receded, the water in Hawaii’s Hilo Bay seemed to disappear. Boats were left on the sea floor next to flopping fish. Then, the massive tsunami struck. In the city of Hilo, a 32-foot wave devastated the town, completely destroying almost a third of the city. The bridge crossing the Wailuku River was picked up by the wave and pushed 300 feet away. In Hilo, 96 people lost their lives.
Tsunami hitting Hawaii
The picture shows the tidal wave breaking over the Pier No. 1 in Hilo Harbor, Hawaii. The man in the foreground (lower left) became one of the 159 deaths on the islands.
On other parts of the island of Hawaii, waves reached as high as 60 feet. A schoolhouse in Laupahoehoe was crushed by the tsunami, killing the teacher and 25 students inside. The massive wave was seen as far away as Chile, where, 18 hours after the quake near Alaska, unusually large waves crashed ashore. There were no casualties.
This tsunami prompted the U.S. to establish the Seismic SeaWave Warning System two years later. The system, now known as the Pacific Tsunami Warning System, uses undersea buoys throughout the ocean, in combination with seismic-activity detectors, to find possible killer waves. The warning system was used for the first time on November 4, 1952. That day, an evacuation was successfully carried out, but the expected wave never materialized.
Going back to the animation you can see that the tsunami hit everywhere down the American Pacific Coast including Fort Bragg’s Noyo Harbour and the Navarro River. Remarkably there are photos of the event:
In 1946 the entrance to the River Noyo was vastly different from today
Effect of the Tsunami in Noyo Harbour
Noyo Harbour showing fishing fleet in a small area and esily affected by the Tsunami
I’m a natural events freak. I admit it. Ever since the 7.i I have been reading about it.
The Ridgecrest earthquakes of July 4 and 5 occurred north and northeast of the town of Ridgecrest, California and west of Searles Valley, California (approximately 122 miles north-northeast of Los Angeles). There were three main shocks of magnitudes 6.4, 5.4, and 7.1, and many perceptible aftershocks, mainly within the area of the Naval Air Weapons Station China Lake. The first main shock (now deemed to be a foreshock) occurred on July 4 at 10:33 a.m. PDT, approximately 11.2 miles ENE of Ridgecrest, and 8.1 mi WSW of Trona, on a previously unnoticed NE-SW trending fault where it intersects the NW-SE trending Little Lake Fault Zone.
This quake was preceded by several smaller earthquakes, and was followed by more than 1,400 detected aftershocks. The M 5.4 and M 7.1 quakes struck on July 5 at 4:08 a.m. and 8:19 p.m. PDT approximately 6 miles to the northwest. The latter, now considered the mainshock, was the most powerful earthquake to occur in the state in 20 years. Subsequent aftershocks extended approximately 30 miles along the Little Lake Fault Zone. Relatively minor damage resulted from the initial foreshock, though some building fires were reported in Ridgecrest near the epicenter. The main quake on July 5 cut power to at least 3,000 residents in Ridgecrest. Effects were felt across much of Southern California, parts of Arizona and Nevada, as far north as the San Francisco Bay Area and Sacramento, and as far south as Baja California, Mexico. An estimated 20 million people experienced the foreshock, and approximately 30 million people experienced the main shock. We didn’t feel it here in Fort Bragg in Northern California.
Click on the images to see full size.
Here’s a map showing where this earthquake and other southern California earthquakes were located:
Location of Ridgecrest Earthquake
What areas were affected:
Potential disaster area of the Ridgecrest earthquake
These two ground level pics show the damage caused by the quake:
Crack in the earth opened up by the Ridgecrest quake
Road damage caused by the Ridgecrest quake
This aerial pic REALLY shows the severity of the quake. The road has been displaced several feet:
Road displaced by the Ridgecrest quake
This before and after pic I got from Google Maps. You need to click on the pic to see the animated effect.
Before and after animation of the Ridgecrest quake
Two Saturdays ago I was sitting at my desk when my chair moved, my fob watch swung on its’ chain and a picture on the wall gyrated. Earthquake!! I looked up the USGS site and found that it was a 5,6 quake centred near Fortuna which is to the north of us who live in Fort Bragg. It was a magnitude 5.6 earthquake and was reported at 8:53 p.m. on California’s North Coast. The quake was felt to the north in Eureka and also to the south. There were no reports of damage or injuries and there was no tsunami. The map below shows just how much seismic activity there is in the Fortuna area.
Earthquake activity around Fortuna
And this map shows just how much seismic activity there is in Northern California on an ongoing basis:
Eathquake Activity in Northern California and Nevada
Me being an auditor sat there wondering just how much, how bad, how many big ones there have been along the Mendocino Coast. I remembered that Thad Van Buren’s book, “Belonging to Places” had a table in it showing earthquake events over a long period of time:
We are on the coast so my next question was, “And Tsunamis?” Again Thad Van Buren came to the rescue with this table:
Tsunami Events Table
Having absorbed that I DEFINITELY decided that I was better off here vs the East Coast – Hurricanes, or middle America – Tornadoes.
The lighthouse at this site was constructed in 1870. The brick-and-mortar tower included ornate iron balcony supports and a large keeper residence with enough space to house several families. The April 1906 earthquake struck the light station. The keeper’s residence and lighthouse were damaged so severely they had to be demolished. The United States Lighthouse Service contracted with a San Francisco based company to build a new lighthouse on the site, and specified that it had to be able to withstand any future earthquakes. The company chosen normally built factory smokestacks, which accounts for the final design for the new Point Arena Lighthouse, featuring steel reinforcement rods encased in concrete. This was the first lighthouse built this way.
The new lighthouse began operation in 1908, nearly 18 months after the quake. It stands 115 feet tall, and featured a 1st Order Fresnel Lens, over six feet in diameter and weighing more than six tons. The lens was made up of 666 hand-ground glass prisms all focused toward three sets of double bullseyes. It was these bullseyes that gave the Point Arena Lighthouse its unique “light signature” of two flashes every six seconds. The optics, which held an appraised value of over $3.5 million, was set in solid brass framework, and was built in France.
Prior to the introduction of electricity, the lens was rotated by a clockwork mechanism. The Keepers, or “wickies” as they were called, had to hand crank a 160-pound weight up the center shaft of the lighthouse every 75 minutes to keep the lens turning. Light was produced by a “Funck” hydraulic oil lamp, that needed to be refueled every four hours, and whose wicks would have to be trimmed regularly. Later, two 1,000 watt electric lamps were installed to replace the oil lamp, and a 1⁄8 horsepower electric motor was installed to replace the clockworks.
Below are three recent photos of the Point Arena Lighthouse.
An intriguing question was posed to me today by a visitor who was EXTREMELY surprised to learn that Fort Bragg along with every other town along the Mendocino Coast was severely damaged in the 1906 earthquake. The question was, “Was there any evidence of the earthquake that a person could see absent the damage to structures?”
I told the man about the Earthquake Trail at Point Reyes National Park – he hadn’t heard of it. I also told him that I had one, maybe two pics of the fault rupture on the surface. I told him I would post the pics here if I had them. Well. I do have them and here they are:
A split on the north end of East Street from the earthquake. East St. is now the Embarcadero. San Francisco, California: 1906.
1906 earthquake rupture at ground level
Also in my file were two clips about the 1906 earthquake that were contained in out of state newspapers: