What Causes Earthquakes in Northern California?

The San Andreas fault system is the major geologic boundary between the North American and Pacific tectonic plates and passes through much of the state. It will create the biggest earthquakes—as big as magnitude 8—that will disrupt the whole region. An earthquake is a weak to violent shaking of the ground produced by the sudden movement of rock materials below the earth’s surface. The earthquakes originate in tectonic plate boundary.

San Francisco earthquake of 1989, also called Loma Prieta earthquake, major earthquake that struck the San Francisco Bay Area, California, U.S., on October 17, 1989, and caused 63 deaths, nearly 3,800 injuries, and an estimated $6 billion in property damage.

All areas of Northern California have experienced earthquakes in the past and will do do again in the future. In the past 150 years, nearly 40 earthquakes of magnitude 6 or larger have affected Northern California.

The driving force of earthquakes in California is movement along the San Andreas Fault and the many associated faults within the San Andreas Fault System that form the tectonic boundary between the Pacific and North American tectonic plates.

If available, the safest place is under a strong table or desk. If no sturdy object is available, get next to an interior wall with no windows. Finally, HOLD ON to your shelter if you have one, as the temblor will likely involve great shaking.

California has more earthquakes that cause damage than any other state. Alaska and California have the most earthquakes (not human-induced).

The Seismic Hazards Program delineates areas prone to ground failure and other earthquake-related hazards including soil liquefaction (the failure of water-saturated soil), earthquake-induced landslides, surface fault rupture, and tsunami inundation.

Major Types of Disasters Include Flooding, Fires, and Earthquakes. California is prone to various disasters, most notably those from excessive rain (flooding and other storm damage), fires, and earthquakes.

Despite rumors that a large earthquake will cause California to break off into the ocean, there is no need to worry. This is impossible to occur from an event on the San Andreas fault, due to its fault type.

The ‘Big One’ is a hypothetical earthquake of magnitude ~8 or greater that is expected to happen along the SAF. Such a quake will produce devastation to human civilization within about 50-100 miles of the SAF quake zone, especially in urban areas like Palm Springs, Los Angeles and San Francisco.

Narrator: The quake could kill about 1,800 people and leave 50,000 or more with injuries. While people could die from falling debris and collapsed structures, the highest death toll would be from fires. Vidale: Historically, the biggest hazard from earthquakes has been fire.

There are four different types of earthquakes: tectonic, volcanic, collapse and explosion. A tectonic earthquake is one that occurs when the earth’s crust breaks due to geological forces on rocks and adjoining plates that cause physical and chemical changes.

We cannot prevent natural earthquakes from occurring but we can significantly mitigate their effects by identifying hazards, building safer structures, and providing education on earthquake safety. By preparing for natural earthquakes we can also reduce the risk from human induced earthquakes.

Featured Photo by Jens Aber on Unsplash