The 1933 Long Beach Earthquake
Earthquakes are an extremely dangerous natural disaster and have been known to create intense damage when their magnitude is strong enough. The aftermath of the Long Beach earthquake left a lasting impression on the city. The earthquake was an eye opener and definitely taught engineers a lesson about how to construct an earthquake resistant building.

How Earthquakes are formed:
Earthquakes are formed when rocks break away from the big plates and quickly slide past each other along large fault lines. When the plates slide past each other at incredibly fast speeds it causes the ground to shake, which is what we call an earthquake. This sliding action happens about forty miles below the earth’s surface, another name for this is the focus, (this is where the earthquake originates from). From an earthquake there are three types of surface waves that can occur after the initial quake happens. Compression waves are the primary waves that can take anywhere from ten to twenty minutes to reach their destination. Then the transverse wave are the second to show, and they are much slower than the compression waves and take twice as long to reach the same exact place the first wave ended. The waves are influenced by the kind of plate that the quake happens on.
Image 1.
Below is an image of California and the damage that the Long beach earthquake caused to the area around it. The center portion that is red is where the most damage happened and as it went out the intensity started to get weaker.


When and where did the earthquake occur and what were its consequences?

The Long Beach earthquake was Southern California’s deadliest seismic natural disaster recorded in history at that point and affected people in many different ways. It occurred on March 10, 1933 at 5:54 p.m. with an estimated magnitude 6.4. The Long Beach earthquake occurred on the 46-mile-long Newport-Inglewood right-lateral fault which is located off Newport Beach. The disaster was the first noteworthy earthquake and aftershock sequence to be studied in detail by the Seismological Laboratory at the California Institute of Technology in Pasadena. According to the seismic records, there was a slip along the fault of about 1 meter, which resulted in a total rupture length of about 15 kilometers. The rupture only lasted 5 seconds, but the shaking continued for about 10 seconds. It was reported that the earthquake was felt in almost every southern county of California and even reached far enough in the Coast Range, the Sierra Nevada, the San Joaquin Valley, and the Owens Valley. After the Long Beach earthquake occurred, it was noted that there was a foreshock that ruptured near Huntington Beach on March 9, and many aftershocks occurred for a couple days after. The figure below depicts the intensity of the earthquake, where the shaking was felt, along with the Mercalli Scale. It is easy to identify where the mainshock and the foreshock occurred by studying the figure.

Figure 1: The Intensity Shaking Map of the earthquake.

The Long Beach earthquake occurred during the time California was flourishing and people were flocking to the beach areas. Many were just getting settled in Long Beach and were definitely not expecting nor were they ready for a natural disaster to occur such as this earthquake. It was the first earthquake in the area with destructive results and a lot of people were shook up by the instance.

Even though the magnitude of the earthquake was relatively moderate, there was still serious damage done to weakly built buildings ranging from Los Angeles to Laguna Beach. Properly engineered buildings and reinforced concrete buildings suffered very little if not any structural damage. However, brick buildings with unreinforced walls, including school buildings in Long Beach, were damaged immensely. As a result of the Long Beach earthquake, there was about $45 million in damage, which is about $730 million in today’s dollars, and 115 people died largely because of collapsed houses and buildings or falling debris. The cities of Long Beach, Huntington Park, and Compton endured the most pain from the earthquake. Long Beach experienced an unfortunate total of 127 water breaks and the Seal Beach area had no water for several days after. After the mainshock, there were very powerful aftershocks that caused major damage. Roofs were torn apart and chimneys fell right off to the ground. More than one half of the deaths that were reported happened when people ran outside and were hit by falling objects such as bricks and building pieces.

If the earthquake would have occurred just a few hours earlier in the day, the amount of deaths that were reported would have been much worse because school would have still been in session. As seen in the picture below, the Newport-Inglewood fault exists right under Lincoln High School. The school was poorly built and did not have reinforced buildings to withstand an earthquake, hence the reason why the school suffered so much damage.
Figure 2: Location of the fault under Lincoln High School.

What is the Field Act and its relationship to the earthquake?

In 1933, the force resistant designs of public schools and other buildings were based on the estimate of wind loads. In that time, engineers thought that buildings could withstand anything, such as earthquakes, if they could withstand wind forces. The Long Beach Earthquake of 1933 proved that theory wrong when it destroyed 70 schools and another 120 schools suffered major damage. The damage done during the earthquake clearly showed that something needed to be done in order to fix the structural resistance of school buildings to ensure that students are safe during any future earthquake.

As a result of all the destruction, the California State Legislature passed the Field Act only a month after the earthquake struck which enforced building codes. The Field Act demanded that the building designs be based on high-level building standards proposed by the state and that all the plans and intricate details be organized by qualified state designers. All the construction done by the designers had to undergo a thorough inspection to make sure all the laws were followed and they met the state’s expectations. The Field Act was applied strictly to new construction and did not include the schools that withstood the earthquake. After looking at the figure below, one can easily see how the Field Act was put into action. Franklin Junior High School was destroyed during the earthquake, and the picture shows how the school looked before and after the quake. It was extremely obvious that the school was poorly engineered and the enforcements of the Field Act made it a very resistant school building.

Figure 3: Franklin Junior High School before and after the earthquake and what it looks like today.

The Field Act has proven extremely successful since it was passed in 1933. Since then, it has been required that maintenance programs require school districts to mitigate any part of the building that is rotting, repair roof leakage, and pay attention to any other serious maintenance that will help reduce seismic integrity.

Key provisions of the Field Act:

  • A licensed structural engineer must prepare the structural plans.
  • The division of the State Architect (DSA) must approve the structural plans.
  • A DSA approved project inspector obtained by the school district must continuously inspect all the work
  • Construction observation and administration must be performed by project architiect and engineers.
  • DSA oversees the construction process.
  • The projects architect, engineers, inspectors, testing labs and the contractor must file the Final Verified Report.

Since the act was instated, no student or teacher has been injured or killed due to poor engineering of a building. The success of the Field Act has inspired other city engineers to study the resistance of buildings and they too have helped to reduce the amount of deaths that have been recorded after an earthquake erupted.

Hence, the Long Beach earthquake of 1933 is a very significant earthquake in history. The quake was one of the most disastrous of any that occurred in the United States in the beginning of the Twentieth century. It encouraged the Field Act to be instated which required better building of infrastructures and worked to protect people during earthquakes. The earthquake helped engineers realize that weakly built buildings cannot withstand strong earthquakes and must be built using the proper procedure. California is seismically active and has experienced major earthquakes in the past and is expecting one in the future, therefore it was extremely sensible to make corrections to help protect students from the dangers earthquakes can propose.


Figure 4: The Field Act, improving the design and building standards for California Schools

1). Bellet, Dennis. “Design to Maximize Student Safety.” Aug 21, 2008. Online Nov 28, 2009. <>

2). Fiske, Molly Hennessy.. (2008, March 10). '33 quake is still a powerful reminder; Long Beach temblor killed 115 people, spurred legislation. Los Angeles Times,p. B.1. Retrieved November 4, 2009, from Los Angeles Times. (Document ID: 1442782041). <>

3). Lincoln High School Picture. <>

4). Parrish, John. “75th Anniversary of the 1933 Long Beach Earthquake.” Sep 2007. Online Nov 28, 2009.

5). Stover, Carl W. and Jerry L. Coffman. U.S. Geological Survey Professional Paper 1527, United States Government Printing Office, Washington: 1993. Online Nov 4, 2009.

6). Southern California Earthquake Center. "Long Beach Earthquake: 75th Anniversary." April 3, 2009. Online Nov 4, 2009. <>

7). 1933 Long Beach Earthquake Picture(75th Anniversary) <>

8). Division fo the State Architect. April 10, 2008 <>