Earthquakes

Southern California has high seismic activity. We are located at the intersecting point of two massive tectonic plates: the Pacific Plate (extends to Japan) and North American Plate (extends to Iceland). The Pacific Plate is moving northwest, grinding along the North American Plate at a rate of 2 inches a year.

The San Andreas Fault is the largest and most well known fault in California

Los Angeles county is crisscrossed by many smaller active faults. Because of all of these faults, the fact is a Los Angeles earthquake can happen pretty much anywhere.

Los Angeles Faults

 

The most famous earthquake in California was the San Francisco earthquake in 1906. Most of the structures in San Francisco at that time were unreinforced masonry brick buildings- that completely collapsed during the violent shaking of the 7.8 magnitude quake. At the time, seismology was an emerging research field, and this quake was one of the first quakes to be studied using scientific techniques and measuring instruments.

The long beach earthquake in 1933, though much less deadly than the San Fransico quake three decades earlier, narrowly avoided a complete disaster. It occurred at 5:54pm, after school. The quake caved in several school buildings, and if it would have happened earlier in the day… you can imagine what a tragedy that would have been.

As a result of this earthquake, California instated seimic buiding codes to ensure that no public school was unsafe in California. This slowly carried over into residential building during the following 10 years.

In the past one hundred years, there have been four major earthquakes in Los Angeles: Long Beach 1933, San Fernando 1971, Whittier Narrows 1987, and the Northridge Quake in 1994. Earthquake Natural Hazard comes with the territory.

Los Angeles is a sedimentary basin- the soil condition is especially prone to shaking during an earthquake, as oppose to other areas that have bedrock. The magnitude of a quake is not a good indicator of the destruction it can cause. How deep underneath the earth’s surface did the rupture take place, soil conditions, and how close to a densely populated urban area was the epicenter, determine an earthquake’s destructive force. Small tremors can be felt with regular frequency- as Los Angeles is an active seismic zone. Sometimes when I am lying in bed at night I will feel the faintest rocking, which is a gentle reminder that the ground underneath our feet is moving.

Complete California Earthquake History