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What is it? San Andreas Fault, geological fault zone in California
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tarix | 21.06.2018 | ölçüsü | 461 b. | | #50486 |
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What is it? San Andreas Fault, geological fault zone in California 800mi long and approx. 10mi deep Right lateral strike-slip fault Imperial Valley to Point Arena Marks the boundary between N.American and Pacific plates Movement of the plates cause earthquakes
A linear trough reveals the presence of the fault The fault zone is marked by distinctive landforms These include long straight escarpments, narrow ridges, and small un-drained ponds Stream channels characteristically jog sharply to the right where they cross the fault
Brief History The San Andreas Fault has been dated at 29 million years old The greatest recorded movement at one time was 5 meters in the great San Francisco Earthquake of 1906 This measured an 8.25 on the Richter Scale
Major Earthquakes Along the Fault 1906, San Francisco Began at 5:12 am, lasted 20-25 seconds and the aftershocks lasted 45-60 seconds It measured 8.25 on the Richter Scale
The number of deaths resulting from the quake and the fire following the quake was 3,000 The total number of injuries was 225,000 The property damage that occurred was estimated at $400million in 1906 dollars.
1952 Kern County Quake Occurred on July 21, at 5 am The quake measured 7.5 on the Richter Scale The quake was felt from Reno, Nevada to San Diego, California
1952 Quake The quake was responsible for: - 12 deaths
- 18 injuries
- $50 million in property damage
1989 Loma Prieta Quake Occurred October 17th, at 5 pm The magnitude was estimated 7.1 on the Richter Scale The quake did not come as a surprise to geologists
1989 Quake The 1989 earthquake caused: - $7 billion in damage
- 12,000 displaced people
- 3,757 injuries and 67 deaths
New Designs and Construction of Buildings in Earthquake Prone Areas Buildings, homes, bridges and overpasses will be built to withstand strong shaking Some cities have programs to tear down unstable buildings or homes
Places not to build homes or buildings: - Ground failure areas of liquefaction
- Landslide prone areas
Accurate Prediction of Earthquakes (A Work In Progress) China has been the only country who has predicted an earthquake nine hours before, in which they saved lives - However, the next quake they had came unexpected
In Tokyo, Japan they are hard away at work trying to learn how to successfully predict earthquakes Other geologists around the world are also working to find an answer to predict the quakes
Earthquake Probability Research conducted since the 1989 quake helped USGS and other scientists conclude: - 70% probability of at least one magnitude 6.7 or greater quake
- 21% probability of that 70% is on the San Andreas Fault
- The quake might strike the San Francisco Bay region before 2030
- Major quakes may occur in any part of this region
- Communities in the Bay Area region continue to prepare for earthquakes
Earthquake Odds Rates of large earthquakes in the San Francisco have dropped after the Great 1906 Earthquake. San Andreas Fault slipped so much over such a great length in that quake that the strain was reduced on most faults throughout the region. Strain has been slowly building up again. However, level of seismic activity has not yet reached that of the late 1800's.
In Conclusion, we’ve learned: The geography of the San Andreas Fault A few of the major quakes on the fault What everyone can do to help reduce the risk of disaster when a quake hits Probability of the next big earthquake
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