San Francisco is especiallysusceptible to major damage by earthquakes due to massive construction onestablished earthquake hazard zones with poor ground foundation. Beginning inthe Gold Rush of 1848, San Francisco experienced a massive population and landexpansion.
The selling of underwater land, called “water lots,”began in 1846, when the leaders of San Francisco desired to raise money for newgovernment and powerful landowners. To this day, many buildings continue to be builton a foundation of landfill, thus posing the risk of liquefaction upon thetremor. Liquefaction occurs when loose soil becomes saturated with water,losing all fluidity and strength (Travis 1989). In these areas, younger Bay mudcreates a soft and malleable soil foundation. This mud, as compared to olderbottom mud, carries more moisture and becomes weak in the presence of pressure,thus amplifying the motion of the ground (Travis 1989).
Surprisingly, “the earthquake epicenter is NOT thepoint at which most damage occurs…Thick, loose soils tend to amplify andprolong the shaking. The worst such soils in the Bay Area are the loose claysbordering the Bay – theBay mud” (Associationof Bay Area Governments 1998). Additionally, when the “waterlots” were purchased, the governmentcreated a regulated requirement for the lot fill level. Many people did notthink twice before looking to the quickest and least expensive method to fillthem. This lead to modern day cities continuing to be built on a foundation madeof a mixture of sand, debris, and mud. “Evennow, remains of the Yerba Buena Cove vessels from 1851 are found under thefilled foundations of houses (BigThink 2015). Between 1849 and 1965, landfillshad intruded one third into the open area of the Bay (Travis 1989).
Approximately 2,300 acres of baysurface “were being lost each year to landfillsfor housing, ports, industry, airports, real estate, and dumps” (Travis 1989). Now, it has been shown thatinfrastructure built on this land are slowly sinking, wobbling, and tilting dueto prolonged stress on the soft soil. In multiple areas, sand intrusions inbasements and ground floors of buildings have been reported (Seed 1991).
However,the competition for this area among construction industries persists, declaringthat it is the buyer’s responsibility for the upkeep of thewobbly foundation. Much of this desire to continuously expand and build up theoutskirts of San Francisco began in 1906, following the catastrophic 1906earthquake and fire which had caused severe damage to major areas of the city.The hydraulic fill was placed to create new land to host the World Fair, bringingin a large financial value, celebrating the successful rebuilding of the city,and demonstrating to the rest of the world that the San Francisco had beensuccessfully resurrected (Seed et al 1991). It wasn’t until 1965 when California Legislature finally establishedthe BCDC, the first San Francisco Bay Conservation and Development Commission,who was designed to halt the indiscriminate filling of the Bay (Travis 1989). However,this new rule did not apply to the shoreline structures that were not part ofthis “New Bay Fill Project.” Most importantly, shoreline landfill is the mostsusceptible landfill area to damage during an earthquake.
Additionally, norules were passed regarding correcting the previous inaccurate, carelessfilling of these shoreline areas. Thus, these areas remain located in high-riskdanger zones, continuing to wobble on a foundation of loose soil.Not only does this unstable foundationpose a direct risk to citizens, but also raises a concern for adequate transportationin the case of an emergency. Buildings keep going up in landfilled areas, butlittle attention is brought to the difficulty for fire trucks and emergencyvehicles to navigate through damaged streets and piles of rubble. The loose,fine sand has created areas of “sandboils, lateral spreading, settlement, partial bearing failures, structuraldistress, pavement damage, and damage to pipes and other buried utilities” (Seed 1991).
As demonstrated inthe major 1989 Loma Prieta Earthquake, a “number of buildings were destroyed or badlydamaged; much of the area was evacuated and public access was restrictedimmediately following the earthquake’s initial impact” (Seed 1991). A lesson demonstratedby the 1989 Loma Prieta Earthquake showed major damage to major routes oftransportation throughout the city that were built on landfill. This included damageto the East Bayshore Highway (Interstate Hwy 80) and the “parallel coastal frontage road fromsouth Berkeley to the Bay Bridge” (Seed 1991). In other areas alongside majorhighways, sand boils were observed on the sides of roads and cracked roads wereriddled with uprising sand, with fissures up to 300 feet long. This lead to theBay Bridge being completely shut down in the event of liquefaction.
Other areasshowed damage in uneven railroad tracks and damaged pavements, making a numberof cranes unable to get through to certain areas. Additionally, major damageoccurred in San Francisco International Airport, Oakland International Airport,and Alameda Naval Air Station, showing damage to runways, large sand boils, andsand intrusion in certain terminal buildings. During a time of major crisis,such as an earthquake, emergency air transport is a vital component foremergency response teams. This past evidence shows potential damage and likelyloss of service due to their wobbly foundations, in which case would be anabsolute tragedy for the city.Anotherbarrier to earthquake emergency response teams is the increasing cost of realestate in San Francisco, lessening the likelihood of emergency personnel to benearby and available on-demand.
To demonstrate the rapid increase, according toTrulia, market trends indicate an increase of $100,000 (9%) in median home salesin the past year (Trulia 2017). Trends also show the average price per squarefoot rose over $80, in the same time period (Trulia 2017). This skyrocketing greatlyprevents many public emergency personnel from living in the City or even inclose proximity. Many citizens are choosing to move across the bay to areassuch as Emervyille or Oakland where prices are slightly more stable. However,as demonstrated in the last major quake, a powerful tremor could damage or completelyshut down the Bay Bridge, eliminating the quickest method for externalemergency personnel to reach affected areas of the densely populated city.