Mar 26, 2006, 12:19 PM
Post #9 of 12
Thanks for the link Rolly. I found it to be very informative. I was born and raised in California, which is the second most seismically active state in The US, and I moved to Alaska, which is the most seismically active state. The pacific plate is sliding under the North American plate at the Alaska coast. In Anchorage, earthquakes are usually at least a weekly occurrence.
I looked up the 1964 Good Friday earthquake in Alaska, and the 1960 earthquake in Concepción, Chile. I knew that the most severe earthquake ever recorded was somewhere in Chile, but I didn’t know where, or when. The second most severe earthquake ever recorded was the 1964 Alaska earthquake, I did know that.
I knew that the tsunami from the Chile quake traveled across the Pacific Ocean and killed people in Japan. The tsunami from the Alaska quake traveled across The Gulf of Alaska and down the western side of The North American continent. It killed people in Canada and as far south as The State of California in The US.
Because of the small population, the loss of life from the Alaska quake was small. Less than a hundred deaths were recorded. It did do a lot of structural damage in Anchorage; there is a type of clay that underlies much of Anchorage that liquefies when it is vibrated at a certain number of cycles per minute. Much of the quake damage in 1964 was because buildings literally sank.
No commercial building may be built in downtown Anchorage now until core samples of the earth at the building site are taken and analyzed to determine that none of that type of clay is present. The tallest building in Anchorage today is 22 stories. The second tallest is 20 stories. I worked on both of them; they were built in the 1980s.
It completely destroyed the town of Valdez. The crest of the tsunami was 67 feet high when it hit Valdez. The highest loss of life from that quake was in Valdez. Valdez was rebuilt and relocated about 7 miles from its original location. Nothing in present day Valdez is more than 42 years old.
Every number on the Richter scale indicates a quake twice as severe as the number before it. So if there is a 4.0 earthquake, and then there is a 4.1 quake, it is twice as severe as the 4.0 quake. If there is a 4.2 quake, it is twice as severe as a 4.1 quake and four times as severe as a 4.0 quake, etc. The 1964 Alaska earthquake was 9.2 on the Richter scale.
I was in Mexico City a few months after the devastating 1985 earthquake. My mother in laws house was destroyed then. Several other relative’s homes were either destroyed or severely damaged too. There were many collapsed high-rise hotels and other buildings with bodies still inside them at that time too.
Much of the damage, in my opinion, was due to the construction methods used here in Mexico. Of course many of the older buildings that were destroyed had no reinforcement at all, just brick construction, etc. The rigidly constructed building, no matter how strong, is the most likely to fail in an earthquake.
The flexible building is the most likely to survive, with little or no damage. Wood or steel framed, or properly engineered concrete, with pre-stressed concrete beams are the most likely to survive an earthquake with little or no damage. Properly engineered concrete, especially pre-stressed concrete beams will flex, without fracturing.
In the meantime, we live with what we’ve got in Mexico. It is too bad that they don’t have any enforced building codes here.
"The supreme happiness of life is the conviction that we are loved" - Victor Hugo