The Northridge Earthquake
Emma K. Prince
Nancy Pazmino
GEOG 333: Natural Disasters
Friday, April 25th
The Northridge community, located about 30 kilometers northwest of Los Angeles,
California, is located in the heavily-urbanized San Fernando Valley region and is home to over
84,000 people with a per capita income of $23,308 (11). The San Fernando Valley supports half
of the city of Los Angeles’ population where 48% of the population are homeowners in the
middle class (9). Northridge is known for hosting a branch campus of the California State
University, being home to the New England Patriot’s quarterback Matt Cassel, and having the
Ronald Reagan freeway pass through its northern region (5).
Los Angeles is a very socially and culturally diverse city. It is home to: whites,
Hispanics, African-Americans, and Asian-Pacific Islanders. Also, a considerable portion of the
population consists of immigrants of Latinos, Southeast Asians, Koreans, and others from Pacific
Rim nations and countries of Central America (3).
Being so close to the Pacific Ocean, Los Angeles and all of west coast North America are
included in an area of frequent earthquakes. This area, known as the Pacific Ring of Fire, is a
result of the movement and collision of the Earth’s crustal plates. The instability created by the
activity of these plates, produces faults that in turn produce earthquakes. “The Pacific Ring of
Fire produces ninety percent of the world’s earthquakes and eighty percent of the world’s largest
earthquakes” (6).
On January 17, 1994, at 4:31am, Northridge and surrounding communities experienced a
6.9 Richter magnitude earthquake (8). Examinations of surface faults in the area did not reveal
any disturbances, and even though LA is close to the famous San Andreas Fault, it was obvious
that this specific earthquake was a result of a different fault line. Because there was no visible
evidence of fault movement on the surface, geologists determined the earthquake was therefore a
result of a “blind” or “hidden” thrust fault. To find the thrust fault, geologists had to examine the
location of the epicenter, aftershocks, ground shaking intensity maps, ground motion maps, and
the depth of the focus (2). Thousands of aftershocks occurred after the main earthquake,
including a magnitude 5.9 that occurred one minute after the main shock, and a magnitude 5.6
aftershock 11 hours later. Aftershocks are a concern because they can trigger the collapse of
structures that have been weakened by the initial shock (8).
From geological research, we now know that the fault responsible for the Northridge
earthquake is the Pico thrust fault. The earthquake lasted about 10 to 20 seconds, with the fault
first moving at 10 kilometers deep; this created an offset that stretched just 5 kilometers beneath
the ground, therefore it was hidden under the surface (5). Despite the fault being “hidden”, its
movement caused Northridge to rise 20 centimeters or 8 inches, in addition to causing the Santa
Susana Mountains just north of the San Fernando Valley 40 centimeters or 16 inches (7).
According to the Mercalli intensity scale, damages caused by the earthquake reached an
intensity of 9 near the epicenter. One hundred and twenty kilometers away, Mercalli intensity 5
effects were noted, and ground motions were felt as far as 300 kilometers away from the
epicenter in some places (7). Damages from the earthquake included 57 deaths, and injured
almost 10,000 people (5).
The earthquake occurred on a Monday, ending a three day weekend which celebrated the
national holiday in honor of Dr. Martin Luther King. As a result, many people were out of town
which saved lives. Traffic was light due to both the early morning hour and the holiday.
Although the death toll was moderate, property damage was enormous (10).
Damages to houses and businesses from the earthquake far exceeded damages from
other major disasters such as Hurricane Hugo and Hurricane Andrew. Up to January 1994, the
Northridge earthquake was classified as the most costly natural disaster in United States history
(12). This Northridge disaster was also the worst earthquake to hit Los Angeles since the 6.7
magnitude San Fernando earthquake in 1971 (8).
The level of damage to buildings in the area depended on many factors: distance from the
epicenter, stability of the ground beneath foundations’, and the design of the building. Over
3,000 buildings were closed from entry, and an additional 7,000 were banned from occupation
(7). However, there were variations in damages observed due to different orientations of the
rocks deep in the ground. Folds in deep rock layers affected how much ground motion and
damage occurred at the surface. This resulted in focused waves of energy in some areas, and
diffusion of this energy in others. For example: while one apartment building had no apparent
damages, other buildings were split in half and completely displaced from their original
foundations (7).
The Northridge earthquake caused extensive damage to parking structures and freeway
overpasses. Segments of California’s Interstate 5 collapsed while under construction in the 1971
San Fernando Valley earthquake. It was rebuilt with the same specifications, not retrofitted, and
collapsed again during Northridge’s 1994 earthquake. The steel reinforcement bars within the
concrete shattered as they were not supported and buckled from the quake. Such failure could
have been prevented if the concrete had been tightly wrapped with steel. However, carefully
designed, newer parking garages in the region, also thought to withstand a strong earthquake,
had failed. Thankfully, due to the early morning hour, most of the buildings and parking garages
that collapsed were essentially unoccupied (7). Also, a section of the Antelope Valley Freeway
collapsed onto the Golden State Freeway and similarly, a section of the Santa Monica Freeway in
West Los Angeles collapsed. In addition, Northridge’s branch of Cal State’s 2,500 car parking
garage, located only 3 kilometers away from the epicenter also collapsed (8).
The Northridge earthquake triggered landslides that damaged homes, blocked roads, and
damaged water and gas lines. Gas lines damaged from the earthquake created fires intensifying
the damages and making response efforts more difficult (7). Fortunately, the nearby Olive View
Hospital withstood the earthquake. Like Interstate 5, this hospital had been destroyed by the
1971 San Fernando earthquake. However, after the hospital’s collapse, it was rebuilt with higher
standard building codes unlike Interstate 5 (8).
Direct losses from the earthquake amounted to $25 billion, and together with related
losses amounted to $40 billion (12). Here, we use the term “related losses” as indirect losses or
losses resulting from the consequences of physical destruction. Related losses are things such as:
losses in sales, wages, and profits due to loss of function or business interruption, input/output
losses, operational problems as a result of physical damages or infrastructure failure, including
slowdowns and shutdowns (14).
Eighteen months following the Northridge disaster, a survey was performed investigating
the direct impacts and losses businesses suffered in the area. Owners reported business
interruptions making it difficult to provide goods and services. The outcome of the survey
revealed interesting results. It was found that 57% of the businesses surveyed endured some sort
of damage; some damages were structural, some non-structural, and about 13% suffered damage
severe enough to be red- or yellow-tagged. Red-tags warned of an unsafe structure while yellow
restricting all entry (13).
Lifeline disruptions experienced by businesses was extensive and included electricity
loss, telephone service loss, water, natural gas, and/or sewer disruptions. Some sustained only
one of these loses, others sustained them all. Of all businesses surveyed, 47% said that the
damages suffered, mainly the loss of electricity and telephones was quite disruptive to their
companies (13).
In addition to these service losses, many business employees and owners were unable to
get to work following the quake due to the large freeway collapses. Many had to focus on
damages to their own homes before they could even think about their businesses. If these lifeline
losses were not enough already, almost 40% of the surveyed businesses reported few or no
customers following the earthquake; some even experienced trouble delivering goods and
services. In general, smaller businesses tended to suffer more not only because of electricity
loss, but because the small amount of financial backing and manpower to clean up and repair
damages. These small businesses often leased their space instead of owning it, and had less say
on the structural integrity of the property and how prepared it was for disaster (13).
Emergency management in Northridge was completely competent in responding to
problems created by the earthquake. Disasters can aggravate existing social problems, and the
San Fernando Valley was experiencing problems similar to those experienced by metropolitan
areas, including: pockets of high poverty, joblessness, a shortage of affordable housing, and a
growing gap between the rich and the poor. The response and recovery efforts following the
quake were molded by the region’s demographic diversity and its existing social and economic
problems (1).
Despite widespread damage throughout LA, local governments and organization had
planned and exercised any and all emergency services that would be needed in the face of
disaster. These plans and exercises were developed by the state of California and based on
disaster scenarios. Emergency managers and disaster responders do not consider the Northridge
earthquake a major disaster, as it did not overwhelm local emergency and response services.
However, because the earthquake caused over $25 billion of losses it is in fact considered a
disaster (4). Northridge has been a classic example of the economic disruption that can take place
following an earthquake when they occur in highly urbanized areas (3).
This disaster is known as the “Northridge earthquake” because it was initially thought
that the earthquake’s epicenter was in Los Angeles’ Northridge community. However, the actual
epicenter of the earthquake was in the neighboring community of Reseda (5). Locals were
angered at the distorted media coverage Northridge received despite the earthquake’s true
beginnings in the Reseda community. Even more so, other communities in the area received no
media coverage at all including a community that experienced the greatest lost of residential and
commercial structures. Given this, it was pointed out that media reports tended to emphasize
more upscale areas in natural disasters. The naming of the Reseda-epicentered earthquake as the
“Northridge” earthquake to some people revealed possible demographic biases on the media’s
part. Northridge is a more upscale community than Reseda which is in majority a blue-collar
community. As we mentioned before, Northridge’s per capita income is $23,308 compared to
Reseda’s $15,177 per capita income. Such disparities between epicenters and media naming can
have significant consequences for a community. If such disparities as biased media reporting are
proven consistent, it is possible that better off, less affected communities may receive a larger
portion of disaster funds, than more negatively impacted, lower income communities (11).
When considering the human dimensions following the quake in this area, it is important
to examine all aspects of vulnerability on a local level; vulnerability of households, and the
problems that existed before the quake occurred. These include social class, gender, ethnicity,
migration and residency, language/literacy, and age/life cycle (1).
Social class tops most lists when considering vulnerability. In the case of Northridge,
access to resources and affordable housing before the quake were limited, only exacerbating
residents’ abilities to cope with property loss afterward. The communities that were affected
were already faced with severe overcrowding, especially farm workers who could not afford to
buy their own homes. These farmers and their families resorted to living with multiple other
families in ‘single-family’ dwellings because of limited rental availability. It had already been
recognized that there was a need for low-income housing in the area; however this was
repeatedly ignored, and several higher-income facilities were constructed. Also, even more
housing problems occurred; while it is often the case that low-income families are not home
owners, such families in Northridge’s damaged areas did in fact own homes. However, their
homes were mobile homes therefore making them more vulnerable. Depending on assistance
following the disaster, the question of who is better off between homeowners and renters varies.
Homeowners were unable to obtain resources to repair the damages because they lacked
insurance, financial reserves and the ability to qualify for loans. The Northridge earthquake
caused damage to nearly 5,000 homes and destroyed 184 (1).
Another aspect of vulnerability is gender. While many may not consider this a major
issue, such things caused problems after the quake, particularly for female farm workers. This
category, while it relates to class factors, is considered a separate vulnerability. Already farm
workers were considered low on the totem pole, but households lead by females were affected,
more specifically than households with children under the age of 5. These households, according
to the social service agencies were considered more at risk because of increased living expenses
following the quake (1).
Depending on whom you ask, ethnicity may also be a factor to consider when
determining vulnerability caused by the Northridge earthquake. This is because, as with gender
there are people who are more at risk than others. Specifically in the Northridge quake, Spanish
and Mexican immigrants were at risk. This group of people displayed differences in their ability
to acquire resources and recover losses (1). For example, a Central American woman (a recent
immigrant of LA), had been working as a live-in nanny with a family in the San Fernando
Valley. She was working in exchange for room and board and a small amount of money. The
family with whom she lived and was employed, left their damaged home to move in with
relatives after the earthquake; there was no room for her. She found herself homeless and jobless
and unable obtain aid because she had no proof of having lost a home or employment as a result
of the earthquake (11). However, in two counties of the damaged area, vulnerabilities among
Latinos were unexpected. The majority of Latinos were middle to higher income, and did not
share similar vulnerabilities to other Latino populations in the area (1).
Some households are vulnerable in terms of political issues surrounding migration and
residency. Illegal immigrants from Mexico, tend to stay with other families in single family
houses or garages at night, only leaving to work in the field during the day. Immigrant workers
do this in order to reduce their housing expenses. These people and houses are sometimes
considered “invisible” as they have no legal identity here in the states. Thus, populations of
illegal immigrants are less able to cope with losses resulting from disasters (1).
After any disaster, English literacy for immigrants and residents is vitally important when
applying for emergency services or government assistance. Emergency information in the U.S.
is more readily available in English than any other language in the wake of disasters. This was
the case in the Northridge area. Lower-income, poorly educated, non-English speaking residents
had difficulty obtaining public and private resources after the earthquake due to such language
barriers (1).
Vulnerability is also influenced by victims’ age, or life cycle, which is a constantly
changing variable. Typically, the most vulnerable in any circumstance include children and the
elderly. Children obviously are dependent on their care-givers provisions and ability to recover,
but they are also vulnerable to emotional stress following disasters, especially those in larger
households. The elderly, specifically those forced to reside in mobile homes due to fixed
incomes, found it particularly difficult to bounce back after the quake struck their communities.
At the time of the quake, the average fixed income for those over 65 was under $10,000.
Because of rising inflation of house values in California, the cost required to repair a home may
have exceeded ten times the original purchase price. Affording the reconstruction costs for these
individuals was financially impossible (1).
Overall, 60% of houses in the area were red-tagged. Of those, very few were middleincome neighborhoods. Many people abandoned their houses making way for looters, squatters
and street gangs. One reason why residents chose to leave their homes is that while living in an
earthquake prone area, earthquake insurance is extremely expensive. Not only that, if you have
earthquake coverage in your insurance plan, it would only cover the replacement of your house
and not the land itself. This is a huge issue especially in California where real estate is expensive
to begin with.
The presence of looters, squatters and street gangs once residents abandoned their homes,
lead to degradation of the society and economically hurt remaining housing, businesses and
neighborhoods. While assistance was targeted in these areas, it was hard to reconstruct housing
in an already weak housing market. As a consequence there was very little low income housing
in LA. Because larger structures were not repaired, fixing small things like parking garages and
other conveniences were even more out of the question. All of this together led to a decline and
negative effect on property value (9).
After such disasters, many people hope to recover and return to pre-disaster conditions.
They want to achieve the status quo of the socio-economic and built environment prior to the
disaster. While these hopes are understandable, they are almost impossible to achieve. At best,
recovery can take the form of restructuring. While Northridge was provided with generous
federal aid, those affected by the earthquake received only partial compensation for their losses
and were forced to cover the rest on their own. Including the afore mentioned declining housing
market, defense spending was cut, increases were seen in the liabilities of the underemployed,
and insurance deductibles were rather high. The deductibles were high because they were based
off of property value rather than the level of damage (9).
To cover costs not provided by federal aid, many people had to change their spending
patterns, draw from savings accounts and turn to credit for essential rebuilding. Because the
victims overall income was lower, and so much of their money was going to essential rebuilds,
many couldn’t invest as much into their local communities, hurting many small businesses. With
lack of financial aid these businesses and people moved out of the damaged towns never to
return. Almost 60,000 people migrated out of the area with only 20,000 moving in. These 20,000
new residents were young minorities, and poorer than those previously occupying the area. This
new population not only had different retail habits, but a different culture, therefore changing the
social structure of the area. Certain groups, such as this, are less likely to bring the community to
the previous socio-economic and building environment. These groups are the most vulnerable in
society along with immigrants, the unemployed, children and elderly people. Not only are they
less likely to return the area to its previous state, but in the case of another disaster, they have
limited access to resources and their vulnerability only becomes more apparent. Northridge and
its surrounding communities recovered slower than hoped (9).
The earthquake struck a region known to have earthquake preparedness and hazard
reduction at the top of its priority list. Despite this, all disasters offer communities the chance to
learn and further improve their safety measures in some way or another. After the Northridge
earthquake, the area increased its number of geological hazard maps, increased building code
standards, required more seismic retrofitting of older structures, and improved their emergency
preparedness. Many of the problems discovered after the earthquake were determined to be
construction flaws rather than design issues. In 2001, the Federal Emergency Management
Agency (FEMA) responded with new guidelines for steel construction in earthquake prone areas
(7). In addition, response teams have offered disaster training for residents and homeowners, an
emergency network was established, and community organizations were created that would
provide help to vulnerable members of the community whose needs were not met through other
aid services (9).
References
(1) Bolin, Robert, and Lois Stanford. The Northridge Earthquake: Vulnerability and Disaster.
New York: Routledge, 1998.
(2) Greenberg, Steve. "Blind Thrust Fault." Informational Graphics. 21 Mar. 2008
<http://www.greenberg-art.com/graphics.html>.
(3) Hall, John F. "Earthquake Spectra." The Professional Journal of the Earthquake Engineering
Research Institute (1995).
(4) Nigg, Joanne M. "THE SOCIAL IMPACTS OF PHYSICAL PROCESSES." 18 Mar. 2008
<http://www.udel.edu/DRC/preliminary/238.pdf>.
(5) "Northridge Earthquake." Wikipedia. 21 Mar. 2008
<http://en.wikipedia.org/wiki/Northridge_earthquake>.
(6) "Earthquake Hazard Program." USGS. 18 Apr. 2008
<http://earthquake.usgs.gov/learning/faq.php>.
(7) Hyndman, Donald, and David Hyndman. Natural Hazards and Disasters. CA: Thomson,
2006.
(8) "NORTHRIDGE 1994." 18 Apr. 2008
<http://www.vibrationdata.com/earthquakes/northridge.htm>.
(9) Petak, William J., and Shirin Elahi. "The Northridge Earthquake, USA and Its Economic and
Social Impacts." 21 Mar. 2008
<http://www.iiasa.ac.at/Research/RMS/july2000/Papers/Northridge_0401.pdf>.
(10) Place, Susan, and Christine M. Rodrigue. "MEDIA CONSTRUCTION OF THE
"NORTHRIDGE" EARTHQUAKE IN ENGLISH AND SPANISH LANGUAGE
PRINT MEDIA IN LOS ANGELES." Center for Hazards Research. 21 Mar. 2008
<http://www.csulb.edu/~rodrigue/igu1994.html>.
(11) Rovai, Eugenie. "Developing a Conceptual Framework: Media Coverage, Mental Maps and
Response to Disaster."
(12) Tierney, Kathleen J. "Business Impacts of the Northridge Earthquake." Contingencies and
Crisis Management 5 (1997).
(13) Tierney, Kathleen J., and James M. Dahlhamer. "Business Disruption, Preparedness and
Recovery: Lessons From the Northridge Earthquake." Disaster Research Center (1997).
(14) "The Impacts of Natural Disasters: a Framework for Loss Estimation." National Academic
Press (1999). 13 Apr. 2008
<http://www.nap.edu/openbook.php?record_id=6425&page=37>.