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The bay area is located on the west coast of North America and includes San Francisco, Oakland, San Jose, Silicon Valley, and the surrounding cities. It is densely populated with some 7 million people. The bay area is home to many businesses, airports, parks, and an extensive transportation network. Historically, the bay area is well known for being earthquake country. In 1868, an earthquake with an estimated magnitude of 6.8 occurred on the Hayward fault in the eastern bay area. This earthquake struck with great force and caused extensive damage that is well documented in numerous photos and newspaper reports. Almost 40 years later in 1906, the San Francisco earthquake struck with a magnitude of 7.9. The surface rupture from this earthquake extended for about some 300 miles or 480 km. There was a tremendous amount of damage, huge fires, and a significant loss of life. This earthquake occurred as a result of faulting along the San Andreas Fault, located on the west side of the bay area. The magnitude 6.9 Loma Prieta earthquake of 1989 caused about 6 billion dollars in damage and 63 fatalities. This earthquake exposed the strengths and weaknesses of modern building technology. Although it was a significant earthquake, the 1989 Loma Prieta earthquake did not relieve stress on the Hayward Fault. The Hayward earthquake of 1868 has already passed its 140th year anniversary. Today the Hayward Fault is of great concern, because detailed geological studies show that earthquake occur on this fault approximately every 140 to 160 years.
It looks like maybe in the next 30 years we’d have about a 2 in 3 chance of a magnitude 6.7 earthquake or larger in the bay area based on the historical record that we have and geologists have trenched across the faults and looked at offset geologic layers which give us some idea of how fast the faults are moving and how often they’ve ruptured.
Earthquakes create numerous hazards. Among them are strong ground shaking, landslides, and soil failure. These can lead to building collapse, fire, and major disruptions to transportation systems.
In the bay area, the legal requirements for building homes and structures for earthquakes involve the building code that’s adopted by each of the local communities. The building code requires buildings to be built a certain way. If they’re small buildings, we call those prescriptive requirements and for major buildings, it sets out the design guidelines that engineers need to use to make the buildings seismically safe. The building codes used in the bay area are really quite effective. They are based on national standards that are adopted by the state of California and by each city within the bay area. They need to be enforced. They need to be properly applied. They need to have inspection to make sure that they’ve been done correctly.
Today engineers are using tools such as computer modeling and analysis tools to actually visualize what will a building do in an earthquake so they can look at all of the impacts of a building and watch it move, and find out what the weak points are of the building and then build it stronger to withstand earthquakes.
Safety also has to do with the safety of our communities and that’s something that we’re getting very concerned about is how much damage will the buildings experience and what does that mean to the recovery of a community? Buildings that were built 40 or 50 years ago, in many cases, are going to experience a level of damage that will cause them to be closed until they can be repaired. Sometimes it takes 2 or 3 years to repair a building. If you have a large number of buildings in the community that are going to be closed for 2 or 3 years, it’s going to be very difficult for that community to survive.
Because the San Andreas and Hayward faults run through such highly populated regions, the need to be prepared is quite evident. The US Geological Survey has put together a plan called the seven steps to earthquake safety. Here are some of the ways in which you can prepare yourself and your family for an earthquake. Step one, earthquake proof the interior of your house. This includes securing bookshelves and other top-heavy furniture to the wall. Strapping down large electronics, securing your hot water heater, and knowing how to shut off your home’s natural gas line. Step two, preselect a meeting place for your family, as communication by telephone may be limited or impossible after an earthquake. Step three, make a disaster preparedness kit and store it in an accessible location. Information on what to include can be found on the Red Cross website. Step four, identify your home’s potential weaknesses and fix them.
In an older home that has a cripple wall, this part will be the weakest part and as an illustration, this picture here shows what happens to a house that has a cripple wall that is not braced.
One thing that an older house that has cripple walls, it’s a very cost effective retrofit, to just put some plywood on those walls, get the good bolts into the foundation, and you’ve made that house pretty much as good as new.
Step five, plan how to protect yourself during an earthquake wherever you are. The next earthquake could strike at anytime. Step six, after an earthquake check for injuries and damage.
What we’re demonstrating today is how to shut off your gas in the event of a major earthquake or any incident that involves natural gas. If you go home after an earthquake or any incident and you notice that any of those four are moving, that indicates a large quantity of gas is leaking somewhere and it’s a reason to turn it off. Find the pipe, which is coming up out of the ground to your meter and it’s going to have a valve on it that looks just like this. Straight up and down means that the gas is flowing, because it’s going upwards out of the ground. Take your wrench, move it a quarter turn so that that is now perpendicular to the pipe that indicates that the gas flow is shut off, you’re good to go.
Step seven, when safe, continue to follow your disaster preparedness plan.
The USGS website is quite a popular site. We have a lot of earthquake information there. earthquake.usgs.gov is an entry point for information about earthquakes that have just occurred. If there’s an earthquake anywhere in the US within very few minutes, there’s a lot of information posted on the website.
The San Francisco bay area is a really great place to live, but it’s also earthquake country and we know that there’s a 2 out of 3 chance that there’s going to be a large damaging earthquake in the next 30 years. Fortunately there are a lot of things that you can do to protect yourself and your family. Now is a really good time to prepare for the next big earthquake.
Title: San Francisco, California Bay Area Earthquake Hazards and Preparedness
This video presents information on historical and recent earthquake activity in the Bay Area of California. Experts discuss scientific and engineering issues, as well as personal safety and community well-being. The 7 Steps to Safety are neatly outlined, showing families how to be prepared before, during, and after an earthquake.
Location: , Bay Area of California. Consists of San Francisco, San Jose, Oakland, and the nearby cities., USA
Date Taken: 1/1/2010
Video Producer: Walter D. Mooney , Earthquake Hazards Program
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