Toxcina King
The citizens of the San Fernando Valley were rudely awakened at 4:31 a.m. on the historical day of Jan. 17, 1994. The loud rumbling that broke the predawn silence lasted more than 30 seconds, with a magnitude measuring 6.7 on the Richter scale.
It was dubbed the Northridge earthquake because the epicenter was just three miles from the Pierce Weather Station.
The force of the earthquake damaged expensive equipment housed at the whether station, including wind velocity-recording equipment and altimeters.
Though this equipment was lost, important data on temperature, precipitation and evaporation remained in tact.
According to the United States Geological Survey (USGS), this was the worst natural disaster in the Los Angeles basin since the 1971 San Fernando earthquake, which had the same magnitude of 6.7.
The Northridge earthquake caused extensive damage all over the Los Angeles area.
For example, a 2,500-car parking structure at Cal State Northridge collapsed.
A section of the Antelope Valley Freeway collapsed onto the Golden State Freeway south of Newhall, and a section of the Santa Monica Freeway in West Los Angeles collapsed.
What’s most concerning about the 1994 Northridge disaster is that the earthquake occurred along what is called a “blind” thrust fault.
Because of the lack of surface evidence, blind thrust faults are difficult to detect until they rupture.
In other words, the earthquake was caused by a previously-undiscovered buried thrust fault.
John Zayac, assistant professor of Geology at Pierce, has been studying and teaching geology for more than 10 years.
He has a Bachelor of Science in Environmental Geology and obtained his master’s degree at U.S. Santa Barbara last year.
“The 1994 earthquake was generated by slip on a fault named the Pico Thrust (sometimes referred to as the Northridge Thrust),” Zayac said.
“These types of faults are very common in this area and are responsible for building most of the mountains in the greater Los Angeles – Pasadena – San Bernardino region. Blind faults are faults that do not intersect the surface, and are thus extremely difficult to detect until they generate an earthquake,” he said.
Scientists and researchers at USGS have concluded that are 60 different surface fault lines in the Los Angeles area.
Yet, because of the Blind fault, they have been unable to determine the exact surface fault line that actually caused the Northridge earthquake.
“The Pico Thrust was not known until the morning the fault slipped. It is hard to estimate how many more of these blind faults may exist, but there are many known faults of this type through the region, including the Santa Susana Fault and the Chatsworth fault, to name a few,” Zayac said.
A need for rapid and inexpensive assessment of earthquake hazards has led to the development of several geophysical testing methods, to determine whether the geological changes in the landscape find some faults moving faster than previously estimated.
“The interesting thing about faults is that they generally do not move until there is an earthquake. That is why there is so much energy released in an earthquake, and that liberated energy translates into the ground motion, and ultimate damage, that humans associate with earthquakes,” Zayac said.
“There are many investigations occurring around Southern California right now to determine the amount of stress that the rocks are under. The truth is that Southern California has not truly experienced a ‘big one’-type of earthquake since 1857, when a segment of the San Andreas from northeast of San Luis Obispo to San Bernardino County ruptured,” he said.
Earthquake preparation starts long before an earthquake hits. While old buildings may be vulnerable to severe damage, newer buildings have design code standards to withstand major earthquakes.
There are many ways students can protect themselves in the event of such an emergency.
“One of the most important things to remember during an earthquake is to remain calm,” said Zayac.
Be aware of your surroundings at all times, so that in the inevitable event that the ground moves again, you can keep yourself from harm.”
Be sure that there are not heavy items that can fall on you. During an earthquake, drop and cover yourself.
Following an earthquake, follow the directions given to you by your instructor or public safety official.
“If you are outside, get away from poles or trees that could fall on you. Most importantly, do not use your telephone following an earthquake emergency unless it is to report life-threatening injuries. The phone lines will be very important to the disaster response teams,” he said.