The Loma Prieta Earthquake

The Loma Prieta Earthquake and its impact on San Francisco – a description of the damage caused Although the epicentre of the 1989 Loma Prieta earthquake was nearly a hundred kilometres outside of San Francisco and had a strength of „only“ 6.9 on the Richter scale (the Big One of 1906 having released 97% more energy), consequences could be seen big time whatsoever in and around San Francisco: i.

60 deaths were noted; most occured due to the collapse of the Cypress Freeway, which was previously known not to be conforming to any aseismic building codes (rigid pillars etc.).

ii. 16,000 homes and apartments were so badly damaged that they had to be broken down iii. 142 roads and bridges had to be temporarily closed due to damaged parts. The Bay Bridge for example was built on soft sand and clay. The process of soil liquefaction amplified the initial strength of the earthquake to a much greater level in the Bay Area iv. Monetary losses amounted to about $10 billion

Levels of shaking during the 15 seconds of the Loma Prieta earthquake. Noticeable is the red spot near Oakland, the area in which both the Cypress Structure and the Bay Bridge collapsed due to soil liquefaction.

Why the Cypress Structure collapsed

The benefits of predicting the probability of the next major earthquake The underlying thought of predicting hazards is to safe lives and economic values. Knowledge is the basis for any kind of protection or even prevention. Since attempts to prevent earthquakes have proved unsuccesful, predicting them and warning people is the only effective measure to date. Possible methods are the gap theory which uses 'locked' areas as a criterion (long-time) or measuring foreshocks and observing unusual animal behaviour shortly before an earthquake happens. Safe predictions are probably the first step needed to arouse the attention of the government and its people. Richer countries may modify the event, i.e. build aseismic buildings, or work for the preparedness of its emergency services (i.e. they should be built in an earthquake-safe area, thus be accessible and have specific technology) and population (see below). Poorer countries have at least the opportunity to safe lives through reasonable land-use planing. An alternative to predicting how strong an earthquake will be is to construct a hazard zone map which identifies the most hazardeous areas (those where the impact will be strongest) through taking into account the type of soil, the assumed strength of shaking, the likelihood of landslides and so on. Whatever system is being used: the bottom line is that improved seismic monitoring leads to improved decision-making!

Preperations for the family – What preperations can be made for an earthquake? Will these preperations make a difference? An protection plan could look like this: 1. Identify potential hazards in your home (e.g. loose and heavy objects or rigid gas pipes) and begin to fix them (e.g. buy 'smart meters' which automatically cut off the gas line in an earthquake). 2. Create a disaster-preparedness plan, know exactly what to do during the earthquake. 3. Hold a first-aid kit at home. 4. Protect yourself during earthquake shaking: „Drop, cover and hold on“

5. After the quake, check for injuries and damage. 6. When safe, continue to follow your disaster-preparedness plan.

Such preperations, and test drills, could easily make a difference. Whilst economic losses are rather difficult to reduce, it is essential to know what to do during and after an earthquake and to remain calm in order to safe your own life and the lives of others. Perhaps even more important and more fundamental is that information on how earthquakes are formed and in which area they are most likely to happen are made available to all social classes, races and ages. Only with the sufficient knowledge, maps like the following can be interpreted correctly:

A major earthquake ahead

How prepared is San Francisco for the Big One?

The Big One of 1906 – will it happen again?

“California has a very commendable record of dealing with large natural disasters,” says Richard Andrews, a member of President Bush’s Homeland Security Advisory Council. Fact is that this is simply untrue. Worringly, a massive earthquake will occur in the near future (as said above). And still, nothing is done about it. The ulterior motive is money: Sadly, for the government many human losses appear more attractive than large-scale expenses in order to make buildings and other structures safe. Even public or official buildings, such as schools, hospitals, libraries and town halls were exempt from safety measures like retrofitting, as can be seen in this diagram:

Number of critical facilities that are built on either soft soil or directly above a hazardeous fault line and are therefore likely to collapse during a strong earthquake

It is generally known that California is possibly THE most earthquake-prone region in the world. Now wonder, since the two World's largest tectonic plates grind past one another here beneath the West Coast of the USA. Scientists can also predict with safety that a „big“ earthquake of at least 6.5 on the Richter scale will occur in the next 20 or 30 years. Since 1906, the epicentres where always further away from the city, so, according to the gap theory, it's also very probable that it will be dangerously closer to San Francisco this time, meaning much greater damage to life and property inside the city itself. Most importantly, we even know how to deal with earthquakes, i.e. we COULD know if we only took this more seriously. BUT: 1. Fewer than 50 % of households have emergency kits (water, food, medication) 2. Only about 10 % of households have an emergency plan 3. Fewer than 10 % of households are retrofitted Fires and landslides, which can be directly triggered by earthquakes, are additional hazards which have not been taken into account for protective measures right now.