LA is built upon a mass of faults in the Earth’s crust. These include: the Santa Monica fault, the San Fernando fault, the Santa Barbara fault, and of course, the infamous San Andreas fault, which is a conservative plate boundary. The most violent earthquakes seen occur on the San Andreas Fault, although small movements are observed among the other fault lines.
The most recent (of 11 earthquakes in total to have affected LA since 1970) occurred in January 1994, with its focus found in the Northridge area. It registered at a shocking 6.7 on the Richter scale and lasted around 30 seconds. The aftershocks lasted several days. This earthquake killed 60 people, injured many thousand and also caused buildings and sections of freeway to collapse. It caused fires to start due to a gas leak and explosion in the Granada Hills area, and also left half a million homes without power and 200 000 homes without water.
The LA public are somewhat indifferent towards earthquake risks. They understand the dangers, but feel that it won’t happen to them. There currently aren’t any plans to fund complete structural improvements, simply because in order to do this, taxes would have to be raised. This would cause outrage among the people.
The local governments in LA are have an assertive stance concerning the legislation of new buildings and developments. The structures have to be designed to withstand earthquakes (in particular high-rise buildings). In order to take action in the aftermath of a quake, the government is well prepared in terms of action plans. Gas, water, and electricity pipelines and cables have to pass extremely demanding safety measures in order to reduce damage to people and the L.A area in the case of a quake.
Tsunamis are extremely large tidal waves which are triggered by earthquakes under the sea (submarine earthquakes). Tsunamis can travel across and envelope whole oceans at tremendous speeds. The 1964 Alaskan submarine earthquake particularly caused significant damage in several Californian regions. L.A itself is considered to be a very high risk tsunami prone area, due to it’s situation in relation to great expanses of ocean, and the sheer number of plate boundaries it is located above.
Landslides can potentially be very dangerous hazards. They can be caused by earthquakes, heavy rain, flooding, deforestation, urbanisation and forest fires. Sadly, L.A encompasses all of these landslide-causing effects, urbanisation probably being the most prominent. As L.A is a large, major city, many places have been urbanised and covered in concrete etc. This increases the dangers of surface runoff, especially when you consider that most of L.A’s rivers are artificially channelised. Due to the water having nowhere to go, the risk of the ground becoming saturated is even higher, thus increasing landslide risks. Many roads have been cut through the steeper hillsides, and this too increases the risk. Landslides are particularly dangerous as they can destroy homes and developments at frightening speeds, due to the whole hillside collapsing. As they are so sudden and not easy to predict, there is also a danger to the human inhabitants.
Due to the unpredictable nature of landslides, the majority of the responsibility falls on the city government and building companies. In order to prevent landslides, some soil stabilisation measures are taken, such as reinforcing the ground with mesh metal sheets, using pebbles and also metal poles. These methods can be expensive if used in a wide area, however, so for now, the city government has restricted any developments on steep slopes and other risky areas. Risk analysis has also been carried out in some areas.
The extreme winter storms bring unrelenting rain and very strong winds. These are especially severe during an El Nino event. Although most rivers in the L.A vicinity are short and seasonal, they can transport huge volumes of water and material during floods. Deforestation due to brush fires and urbanisation on the steep surrounding hillsides and valleys have increased surface runoff, as has the urbanisation in the city centre. Large dams have been built to try and combat this problem, but even so, the flood risk remains. The heavy rain can also cause problems with landslides. In February 1992, during an El Nino event, eight people died and 200 of cars and caravans were swept out to sea.
Due to such a high average annual temperature, L.A is very susceptible to drought. Almost every year there is a hosepipe ban, most notably in 2007, which was the driest year in over a century. The long dry summers associated with the Mediterranean climate puts extreme amounts of pressure on the already diminishing water supplies. Also, the decision of Arizona to withhold some runoff from the mountains has been devastating, because previously, Southern parts of California had been able to use the surplus from Arizona’s requirements. L.A has one of the highest water consumption per capita rates in America, and this doesn’t help matters. So much water is taken from the Colorado River that it almost dries up before reaching the sea, during the years of drought.
Much of Los Angeles’ ground surface is covered in drought resistant brush vegetation. This has the potential to burn very quickly and easily due to its dryness. L.A’s rainfall per annum is extremely low, as aforementioned, so in the autumn, after six months without rain, this vegetation is exceptionally dry. There is also a hot, dry wind called the Santa Ana which descends from the mountains. This doesn’t help matters! The intense heat and extremely low humidity of the Santa Ana cause discomfort to humans and increase the dryness of the vegetation. Therefore, in these conditions, a small spark or an electrical storm can cause serious fires. In September 1970 a fire which was 56 km wide, travelled from the Santa Monica Mountains to Malibu. 72 000 hectares of brush and around 300 houses were destroyed and three people died. Again in November 1993, over 1000 homes were destroyed once again in another brush fire.
Due to L.A’s situation as a very large city, the hazard of sexually transmitted diseases like HIV, and others such as TB and influenza can be caused due to the high density of population. TB is extremely infectious and is becoming more difficult to treat as is has developed resistance to antibiotics. It can cause thousands of deaths especially in the poorer areas where there is limited medical care. HIV is also more prevalent as it can remain unnoticed for many years, during which time many other people could become infected. There is no cure. Education is the main preventative by the government. Concerning TB, bad living conditions such as damp housing, makes people more susceptible to infection. The approach to the TB problem has been to vaccinate people where possible. For flu, the outlook is to vaccinate only those most at risk such as the young and elderly.
Crime is a huge problem in L.A, never absent from the news. The type of crime does tend to vary according to the affluence of the district. Crime is aggravated by the infamous strong gang culture found in L.A. During 1995 there was a partial truce, but it didn’t include the entire city. In turn, drug related crime rates are high, particularly among the gangs. New approaches to crime have included the introduction of Community Support Officers. When these were introduced to the Anaheim district, they reduced crime by 21%. Some tougher policies against gang crime have had a positive effect, but the problem of funding these schemes is always present.
Fog can occur when the cool air from the offshore Californiadrifts inland where it meets warm air. It forms most afternoons between May and October, as the sea breeze increases.Warm air then becomes trapped under colds. Smog can be caused by the pollutants from LA’s traffic, power stations, and industry when they are released in to the air. When they return to Earth, they cause acid rain. 1,130 tons of polluting gases, such as nitrous oxides, sulphur dioxides and hydrocarbons are released into L.A’s atmosphere each day. New regulations have been recently introduced to reduce pollution. Some policies include to introduce strict emission levels for vehicles, power plants and industry in general. Businesses with over 50 employees have a legal responsibility to organise car pooling programmes. Catalytic convertors are mandatory on all cars, too. Interestingly, on the human side of things, according to a recent study reported in the Los Angeles Times, residents showed lung damage that might be expected of someone who smoked half a pack of cigarettes per day.