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Roger Weller, geology instructor

Northridge Earthquake
Joshua Humphrey

Physical Geology
Spring 2011


4:31 a.m.
 Inside the Northridge Earthquake

       There as several moments within a person’s life that shape who they are as a person, for me one of those events happened on January 17, 1994 and 4:31am. The weekend was supposed to be a holiday weekend with no school on Monday because of Martin Luther King Day. There was no school Monday so I stayed up late that night, and went to bed about 4:00 am. I can remember looking out the window of my bedroom and noticing how quiet it was, I lived in a more rural community called Chatsworth a suburb of Northridge, CA.  At 4:31 A.M. my mom came into my room very franticly to wake me up because there had just been a large earthquake.  I remember remarking “Mom I don’t have to go to school today!”  And then I felt the aftershock that shook my room and I promptly got up and got out.  This was definitely a defining moment in my life as a person and shaped my future to this day.


       Earthquakes occur with the movement of the earth’s tectonic plates, and when two different plates meet the plate with the greater density dives under the plate with the lesser density forming an seduction zone. The area where the two plates meet is a fault zone, as the pressure at the area grows the danger of earthquakes grows as well. When the pressure on the surrounding rocks reaches the slipping point the two plates shift and the pressure is released causing a seismic wave or an earthquake. The area under the ground where the earthquake is at is called the focus and the area directly above the focus is called the epicenter.


       The Northridge earthquake occurred on Monday, January 17, 1994 at 4:31 A.M Pacific Standard Time. The earthquake was a magnitude 6.7 and lasted for 10 to 20 seconds and was felt as far away as Las Vegas, NV.  The Earthquake happened at a depth of 19.0 km (11.8 mi).  The Northridge earthquake casualties are officially listed as: 57 people killed and 1800 people injured.  The Northridge earthquake was a surprise to the residents of the community and caused an estimated $20 Billion dollars in damage. So why was the Northridge earthquake so devastating?  The earthquake struck in the San Fernando Valley about 20 Miles northwest of Los Angeles, the epicenter was located in Reseda at the intersection of Reseda Blvd and Saticoy St.  The earthquake did not happen along the San Andres fault, but rather (an unknown to that point) the Northridge blind thrust fault known as the Pico Thrust Fault.  A Blind Thrust Fault is when the fault plain terminates before it reaches the earth’s surface, and because of the lack of surface evidence they can go unknown until they erupt.  Because of this it ended up taking several days to pin point where the Northridge earthquake actually originated at.  (Wiki)



      The damage to the communities of Northridge and Chatsworth were extensive. For example my school Lawrence Middle School was shut down for 2 months. From my yearbook the event was covered this way: “ The January 17, 1994 quake caused extensive damage throughout the school including parts of the MPR, Library ,Cafeteria, Classrooms, and hallways.” A large section of the main hallway at the school was destroyed by the earthquake and caused the school to build a walkway that extended into the quad so students could get to classes.  As a personal note I remember running fire and earthquake drills in school in southern California. When you run these drills you never think you will ever have to use them.  Damage was not just located at my school; the entire area of the San Fernando Valley was affected. Freeways were heavily damaged including Hospitals and utilities like water and power lines.








Photograph by Robert A. Eplett taken on 01-17-1

     One of the areas of extensive damage was to the local apartment complexes in the area.  Several Apartment complexes collapsed the first floor apartments into the parking garage. My sister a week prior to the earthquake moved back to Michigan, she lived in the bottom floor of an apartment building that collapsed in on its self.

Photo courtesy of NASA Ames Research Center DART



     One of the more interesting things of the Northridge Earthquake was the interruption of the Utilities. The water and power were off for several days, the electricity was off of about 24 hours. When the power came back on it was the evening and we went from darkness to light instantly. The water on the other hand was a different story, and was not suitable for several days following the quake. I can remember being sent on the mission to the swimming pool to retrieve buckets of water to work the toilet and to wash off. My birthday was only a couple of days following the earthquake, and my family and I visited a restraint in the area. When we ordered our meal the waiter told us two things: 1 the water was still contaminated and so there was no Ice and 2. If there were any aftershocks then he would be out the door before us.

     Following the Northridge earthquake there were sweeping changes to the building codes for the area. Advancements in technology, testing systems, seismic modeling, and building design have changed the way structures are built. A large array of building reforms have also changed what is considered to be legal to build in southern California.   An example of this is the “soft story” multifamily apartments. The upper two floors overhand the lower follow and are supported only by simple pipe columns so cars can park underneath.  During the earthquake these lower floor were crushed by the upper floors because the pipe supports were not able to support the structure, because of the damaged caused this structure is no longer legal to be built.

        This earthquake had a profound effect on my life as well as the lives of thousands of others. Our house didn’t really sustain any major structural damage. We had the motor of our brick patio wall all fall our so every time there was an aftershock the walls swayed back and forth. The drywall of our house pulled away from the wood framing. The result of this earthquake was much more for our family just structural damage, the end result for us of the earthquake is following the completion of the 8th grade in California our family packed up and moved back to Arizona.  The 1994 Northridge earthquake was a turning point for many of people of southern California, and showed us that we still have a lot to learn about how the earth works and where the next earthquake will be.


Works Cited