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Predictions for Earthquakes in California: Analyzing Past Seismic Activity

  • 27 August, 2018

Seismic activity, which is the activity relating to earthquakes, is monitored very closely in the state of California. Although it is difficult to make an earthquake prediction for California, scientists can make rough estimations based on California's earthquake history. Throughout the years, earthquakes have caused great damage to infrastructure as well as a number of injuries and deaths in California. For instance, in 1994, a 6.4 magnitude earthquake struck Northridge, California. This earthquake caused 57 deaths, approximately 9,000 injuries, and about $40 billion in property damage.

A new study published in the AGU 100 Journal, a journal which focuses on advancing earth and space science, evaluates common trends in earthquake occurrences. Geologist researchers, Roger Bilham and Rebecca Bendick, noticed a common trend when looking at earthquakes that happened as early as 1900. They noticed that periodically there are spikes in the rate of earthquakes with a magnitude of 7 or higher. "While in most years there is an average of just 15 such major shake-ups - already more than enough - there have been evenly spaced intervals in the past 117 years in which the annual total jumped to between 25 and 30," an analysis of the study by TIME journalist, Jeffrey Kluger, reported.

Why is there periodically a spike in the total number of earthquakes in a year? Bilham and Bendick think it is due to an occasional slowing of the earth's axial spinning. And by slowing down, the earth is only slowing down by a millisecond. "The last such time the planet slowed was in 2011, and recent events suggest a troubling pattern again playing out: the magnitude 7.1 quake that struck Mexico City on Sept. 19; the 7.3 event on the Iran-Iraq border on Nov. 12; and the 7.0 off New Caledonia on Nov. 19," the TIME article stated, referring to earthquakes in 2017.i

Because of the structure of the earth, the slowing rotation does not immediately cause earthquakes. When the earth slows, it takes approximately six years for the energy from the core of the planet to radiate to the platelets. So, when scientists detect a slowing of rotation, they can estimate that a surge of earthquakes will follow within the next decade.

When earthquakes occur, it is extremely important to be prepared. Buildings and various other types of infrastructure are typically the victims of earthquakes, but damaged infrastructure can have detrimental safety effects. This is where seismic engineers come in. Seismic engineers analyze how infrastructure interacts with the ground and the effects shifting ground has on the infrastructure. According to Wantman Group, Inc., a national infrastructure consulting company, states, "One of the primary aims of seismic engineering is proper designing and construction of buildings, in line with existing building codes, so as to reduce the damage due to earthquakes." ii

Seismic engineers are needed statewide in California to develop new infrastructure plans and to evaluate current infrastructure to ensure that it can withstand earthquakes. In California, those who are aiming to become seismic engineers must take the PE Civil exam along with the CA Seismic and Surveying exams.

To assist California PE Civil applicants in preparing for their exams, School of PE offers both CA Seismic and CA Surveying exam review courses. The CA Seismic exam review course offers 15 hours of comprehensive review lectures and practice sessions, which cover topics such as seismic forces, seismic analysis procedures, and seismic detailing.


i. Kluger, J. Scientists Predict 2018 Will Be a Bad Year for Earthquakes. Here's Why. Retrieved from

ii. Seismic Engineering. Retrieved from

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