Northridge

= = Revised by Salvador Ceja GSC-350 on 12-01-2007 = = = = =__1994 Northridge Earthquake__=

__Background__
It was 4:30 A.M. on January 17th, 1994 when the Northridge earthquake struck southern California. I actually did not live far from the epicenter having been just a few miles away in the Santa Clarita Valley. For me it was pretty intense having never been in an earthquake before. All I can remember is getting out of my bed to the voice of my mom and running into my wall just left of my door and franticly trying to get out of the house. I was only nine years old at the time and it was definitely a new experience. The Northridge earthquake hit with a magnitude 6.7 that lasted somewhere around 15 seconds and was followed by a number of aftershocks.(Fig.1 shows the area of Northridge, Ca. and the area around it) Some of the after shocks were quite large there was one aftershock measuring a 5.9 magnitude just minutes after the main shock and another one 11 hours later that measure 5.6 on the Richter scale. The major problem with aftershocks is that they will cause weakened buildings from the main shock to collapse so it is important that if there is another earthquake of this size that people be very careful in the time they wait to return to there houses or businesses. We learned in class that the safest thing to do in the event of an earthquake is to try and get under a sturdy desk and then once it is safe get out of the building and find a safe place away from other buildings so that if a aftershock does occur no debris will fall on you from other buildings. What was the also significant about the Northridge earthquake was the fact that the ground acceleration was the highest ever recorded in an urban area within North America. As we learned in class the L.A. basin and Mojave Desert area create longer lasting ground motion so for the ground acceleration to be the greatest ever it would have been intense in those areas. With this being known Santa Monica had a lot of structural damage not only caused by the resonance of the earthquake but because a lot of the apartment buildings and other buildings were built with wood frames with weak first floors as there base. The hypocenter was located 20 miles northwest of Los Angeles under the San Fernando Valley at about 17km deep, which was essentially Northridge, California. The Northridge earthquake was one of the costliest natural disasters in United States history. __**Monetary Effects**__ There was an estimated 44 billion dollars in damage caused by the earthquake. Money collected by insurance claims was estimated somewhere in the range of 30 billion dollars. The Northridge earthquake claimed the lives of 57 people and left around 15,000 people injured. The devastation of the earthquake made President Clinton labeled it a federal disaster and FEMA was used to help elevate the pressure and stress caused by the earthquake. Hundreds of workers from FEMA were brought in to help the victims of the earthquake and also used millions of dollars in there efforts. There were more than 600,000 people who applied for state and federal disaster assistance. Even tough there was loss of life, injuries and a lot of damage finically if California had not created such strict building codes there could have been even more damage and greater loss of life. As we saw in class places where building codes were non-existent the damage and the loss of life was increased drastically.
 * __Personal injury and loss__**

__**Earthquake Damage**__


 * It is relevant to note that most of the damaged caused during this earthquake was due to the frequency of the earthquake "S" waves and the combination of soils found in the area. The area most damaged by the earthquake was not near the epicenter, however the soil conditions were one of the the reasons for the damage. The partial liquefaction of the soil allowed for greater shaking and massive damage. During the earthquake multiple shaking directions were experienced. Not only did the ground shake in the horizontal direction but also in the vertical. The increased stress brought on by the multiple shaking caused structures to weaken sooner.

It is also important to note that the frequency of the waves were not necessarily the only thing to blame for the freeway overpass collapse, instead the blame can be directly placed on the the poor construction and engineering of the support columns holding up the overpasses.

The construction method used for tying the rebar found inside the concrete columns was inadequate for sudden horizontal movements. The rebar (steel mesh and support found inside concrete) was not tied or wrapped appropriately. The concrete was shaken and crumbled leaving slim steel bars to support the bridges and overpasses leading to total and partial collapse. The other problem was the poorly engineered connections between the overpass bridges and their end supports. The connection relied primarily on gravity to hold the bridges down. Instead the bridge should have been tied to the ground and end supports with rated steel. The earthquake did create a massive re-evaluation of existing bridges, roadways and overpasses all throughout the southern California area. Because of the lessons learned during that quake Cal trans has been working on updating Souther California's transportation infrastructure. Over the last thirteen years Cal-Trans has renovated and upgraded roadways and bridges to withstand earthquakes similar if not greater than the North ridge Earthquake.** (revision by Salvador Ceja)

There was also major structural damage caused by the earthquake which hindered people from going about there daily lives. The closest structural damage that was to where I lived in the Santa Clarita Valley was the collapse of the I-5 and 14-freeway interchange.(Fig. 2 shows the collapse of the I-5 and 14 freeway interchange) The collapse of this interchange took the life of a Santa Clarita police officer Clarence W. Dean which to me made me realize at the young age of nine that that an earthquake does not just make the ground shake and that everything is not alright but that there is tragic events that occur. Other major freeway damage the earthquake caused was at the I-10 freeway, Route 118 freeway, and another bridge collapse on the I-5. Freeways were not the only structures that felt the wrath of the earthquake. Other earthquake damage that was widely seen was damage done to homes. 25,000 residential buildings reported damage. Of these government building officials declared these homes as being either red tagged or yellow tagged. Red tagged means that they are too dangerous to inhabit; yellow means that they are moderately damaged and their inhabitability is limited. They declared that 7,000 building were to be red-tagged, and 22,000 buildings were yellow tagged. They also closed down 9 hospitals and 9 parking structures collapsed. These freeways that collapsed also led to a number of problems in Santa Clarita affecting business because the I-5 and 14-freeway are the main entrances point to Santa Clarita but the I-5 freeway is also a major truck route and with the collapsing of the freeway it hindered and delayed shipments. After the earthquake happened it was still affecting people up to 8 weeks after the initial quake with the outbreak of coccidioidomycosis, which is known as valley fever. Coccidioidomycosis is a respiratory diease that is caused by inhaling fungal spores in the air. There were a reported 203 outbreaks and of those 3 were fatal. The fever affected people not only in the Los Angeles county but also reached upto Ventura County. The northridge earthquake was a definitly a wake up call to southern California reassuring people that live here that earthquakes are staple of our lives. People need to be aware about the damage that can be caused by another earthquake here in Southern California. The Insurance commissioner, John Garamendi urges people to make sure they have adequate insurance so if another earthquake hits they will not have to worry about there lively hood after the quake. The earthquake also affected insurance by making legaslative changes because insurance compainies either stopped offering our restricted there coverage for earthquake insurance there was a legaslative change that help create the CEA our California Earthquake Authority that is a publicly offered but privately organization that offers earthquake coverage. There have been a lot of advancements in the science world to help get to victims of earthquakes faster and more effiecently. There is a $6 million dollar super computer at the California Institute of Technology that can analyze the destructive force of an earthquake in less than an hour. It is good to know that there is a lot of investments into learnig about earthquakes and the damage they can cause. Fig. 2 Freeway damage Fig 1. Area intensity map of Northridge, Ca.
 * __Coccidioidomycosis Outbreak__**
 * __Conclusion__**

Sources. “Anniversary of Deadly Northridge Quake.” __ABC.com.__ 17 Jan. 2006. 2 Nov. 2007 http://abclocal.go.com/kabc/story?section=local&id=3819852 “Coccidioidmycosis Outbreak.” USGS. 19 Mar. 1997. 2 Nov. 2007 http://landslides.usgs.gov/recent/archives/1997northridge.php “Northridge Earthquake.” DIS. 2 Nov. 2007  “Northridge Earthquake.” Southern California Earthquake Data Center. 2 Nov. 2007. http://www.data.scec.org/chrono_index/northreq.html Earthquake Images. www.scarborough.k12.me.us/ wis/teachers/dtewhe... Northridge Earthquake. http://en.wikipedia.org/wiki/1994_Northridge_Earthquake DIS. Your Partner in Earthquake Protection. http://www.dis-inc.com/northrid.htm
 * Coritme Peek-Asa, Jess F Kraus, Linda B Bourque, Dushyanthi Vimalachandra, Jenny Yu and Jackie Abrams. “**Fatal and hospitalized injuries resulting from the 1994 Northridge earthquake.” __Oxford Journals__. 16 September 1997. 2 Nov. 2007. http://ije.oxfordjournals.org/cgi/content/abstract/27/3/459

Background of Earthquakes (Written By Joe Oh)
Earthquakes occur when there is a sudden movement of the earth along faults. An Earthquake itself is started by a theory called the Elastic Rebound Theory. Under this theory, elastic strain builds up along a fault as the rocks slowly bend. As the rocks suddenly snap back to relieve the built up stress, strong seismic waves are created which induces the shanking of the ground itself.

Why So Much Damage In Santa Monica? (Written By Joe Oh)
As we have learned in our Natural Disasters class, basins are notorious when it comes to earthquakes. In the tremors of an earthquake, the grounds will continue to shake for a longer duration then it would at other locations. Because Santa Monica is located in the Los Angeles Basin, most of the high-frequency waves of the earthquake was focused in the basin which cause significant damage to building throughout Santa Monica which was unprepared for an earthquake of that magnitude.