5.1 Quake off the Californian Coast

No injuries have so far been reported after a 5.1 earthquake hit the Northern Californian coast 70 miles west of Ferndale. According to the United States Geological Survey website, the quake struck at 0416 this morning Pacific time.

The largest earthquake to hit California was a 7.9 in 1887. According to the USGS:

This earthquake occurred on the San Andreas fault, which ruptured from near Parkfield (in the Cholame Valley) almost to Wrightwood (a distance of about 300 kilometers); horizontal displacement of as much as 9 meters was observed on the Carrizo Plain. It caused one fatality. A comparison of this shock to the San Francisco earthquake, which occurred on the San Andreas fault on April 18, 1906, shows that the fault break in 1906 was longer but that the maximum and average displacements in 1857 were larger.

California sits in an area that is geologically very active. Plate margins grind against each other causing the tremors. The San Andreas Fault is a huge gash in the landscape that runs from Cape Mendocino down to the Mexican border. It’s a transform or slide fault. The leading edge of the North American Plate and the Pacific Plate slide past each other.

They move in small fits and starts, but on occasion get stuck. The pressure builds and builds, until whatever prominence of rock holding them in position gives way, and the plates move causing an earthquake.

Those living on the West Coast know that at some point the ‘big one’ will hit. This could be a quake caused by the San Andreas or one of the other major fault lines such as the Puente Hills fault rupturing, but many scientists think the worst case scenario would be a subduction earthquake caused by the rupture of the Cascadia fault of the coast of California.

The Cascadia Fault is a subduction zone, an area where one of the tectonic plates is forced underneath the plate it collides into.

In the case of Cascadia, the Juan de Fuca Plate is moving under the North American Plate. These plates have been locked together since 1700(313 years). A particular feature of the Cascadia Fault is that it doesn’t produce small quakes.It remains still and silent until the pressure gets too much and one of the plates slips, giving rise to a mega-thrust earthquake of massive force. These quakes can be compared to the Indonesian quake of 2004 and the Japanese quake of 2011.

The Cascadia fault is long, very long, just over 800 miles (1300km) in length. Based on the findings of the scientists, the tsunami caused by the 1700 event moved inland for more than 60 miles, wiping out everything in its path. Of course in 1700 Seattle wasn’t there, neither was Vancouver, San Francisco, Portland or any of the other cities and metropolitan areas currently occupied by millions of people.

The Cascadia, courtesy of its length, will give rise to a long quake if the whole fault ‘unzips’ at the same time, as it’s believed to have done in 1700. The first P waves will travel the length of the fracture in a minute or two. The S waves that follow, the ones that cause the real damage, are slower and will cause shaking and movement for about five minutes though their speed can vary depending on the rock they are traveling through. (source)

Although there was no tsunami alert issued with this latest quake, that won’t be the case if the Cascadia ruptures. Totally silent for 315 years, it’s not a case of if the Cascadia will slip but when.

There has been no detected slippage, no detected small quakes. This is a feature of the Cascadia, it is silent until there is a sudden and massive release of energy. There will be no warning whatever. No foreshocks, nothing.

On a dark winters night in January 1700 a tsunami struck Japan. It flooded fields, swept away villages for miles inland and cost many lives. Even as far back as 1700 the Japanese had made the connection between earthquakes and Tsunami, but this time there was no earthquake, no warning to allow the people time to evacuate to higher ground. The tsunami was called the ‘orphan tsunami’ because it had no ‘parent’ earthquake. For more than 300 years the origin of the orphan tsunami remained a mystery.

In 1987 Brian Atwater studied soil samples far inland across the length of the fault and discovered that the United States had also suffered a tsunami at the same time as the Japanese. He concluded that Kanamori and Heaton were correct, a massive earthquake had sent a tsunami out from the source of the quake inundating the coasts on both sides of the Pacific.

Recent studies by researchers at the University of Pennsylvania has concurred on the findings of previous studies. (source)

In any disaster, it’s not only the original event that causes problems. The aftermath of a major calamity can cause as many injuries and deaths as the original event. Most of the population are not prepared, they are not able to look after their family in a crisis. Many will sit and wait for the government to ‘rescue’ them, others will be on the prowl looking to supplement their meagre resources by stealing from those who had the foresight to prepare.

At the start of a new year, there is no better time to assess where you are on your preparedness journey. Find the holes in your preps and your plans and plug them while you still have time to do so.

Resources:

The Prepper’s Blueprint: The Step-By-Step Guide To Help You Through Any Disaster

Mr. Heater F215100 MH4B Little Buddy 3800-BTU Indoor-Safe Propane Heater

The Pantry Primer: How to Build a One Year Food Supply in Three Months

The Prepper’s Cookbook: 300 Recipes to Turn Your Emergency Food into Nutritious, Delicious, Life-Saving Meals

SAS Survival Handbook, Revised Edition: For Any Climate, in Any Situation

The Survival Medicine Handbook: A Guide for When Help is Not on the Way

Elite Large Fully Stocked GI Issue Medic First Aid Kit Bag