LOTTA SHAKING GOING ON
30 July 2008
There was an earthquake in Southern California today. You may have heard. It was first reported to be 5.6, and later downgraded to 5.4.
Earthquake reporting is really kind of funny. Especially if you live in earthquake country. 5.4 is no small quake, to be sure, but it's no huge quake either. It's enough to "shake you up," literally and figuratively, but it's not comparable to the 1991 Northridge quake, for example, which was a 6.7.
On the Richter scale a 1 degree separation, like 5.4 and 6.4, for example is a magnitude of 10 times the intensity. A 6.4 quake is ten times stronger than a 5.4 quake. 5.4 is considered "moderate."
There was a 5.3 quake in San Francisco in 1957. I remember clearly that I was in Sister Benedicta's algebra class just before lunch when the quake hit. It was definitely a strong jolt, and it did do some minor damage throughout the city -- some fires and some broken windows, for example.
The nuns dismissed school and told us all to go home. I opted to stay and help out but they eventually insisted that I had to leave the building.
That night, my mother and I were at St. Dominic's church, attending a novena. It's a big gothic church, cavernous and beautiful inside.
We were in the middle of the novena prayers when an aftershock hit. Imagine being inside a gothic cathedral when the ground the earth moves and those tall brick towers began to crackle. We were all frozen in our seats, as the priest reassured us that we were "in the right place" if the building was going to collapse.
Somehow I was not comforted by the thought! I don't know that I've been back to St. Dominic's since!
When a strong jolt hits, the media goes crazy. During the Loma Prieta quake (magnitude 7.0) for instance, where there really was a lot of damage the media people had a field day. "San Francisco in Ruins" some early headlines blared. "Bay Bridge falls down" others said.
Well...no. Not quite. Most of the damage in the quake, at least in San Francisco, was confined to the Marina, which was originally part of San Francisco Bay , but was filled in for the 1915 Panama Pacific Exposition. At the conclusion of the year-long exposition, the buildings were torn down and housing erected. But because it is fill land, when there is an earthquake, it is not solid and is subject to liquefaction (for a full explanation of liquefaction, check this web site) Basically, the ground turns to jello and that increase the amount of shaking.
The newspapers love to run photos like this
But in reality very few homes were actually destroyed in the earthquake and the reason they were is easily shown here
The building is on the corner of the street and there are garage doors on both sides of the building. Thus, it doesn't have a strong, steady support, so when the earthquake hits, the garage doors buckle and there's nothing strong enough to hold up the building and you get major damage.
It amused me this morning watching reporters struggling to find something
catastrophic to show, but despite the "breaking news" and the continuous
reporting (which I finally turned off), people in Los Angeles were going about their
normal day, a little nervously, perhaps, but we're used to earthquakes out here and
realize that (a) they last only a matter of seconds, and (b) with rare exceptions damage
is minor. It's rarely as awful as it is portrayed in the media and
generally all the photography is taken in one spot, while the rest of the city is just
fine and all busy putting their cans back on shelves and getting on with life.
PHOTO OF THE DAY
Some papers, after Loma Prieta, reported that
the Bay Bridge
MILES TO NOWHERE: 61 miles