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Old 2019-07-05, 21:25   #408
ewmayer
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Here is a good description of yesterday's series of Mojave quakes from a local.
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Old 2019-07-06, 14:06   #409
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Quote:
Originally Posted by ewmayer View Post
Here is a good description of yesterday's series of Mojave quakes from a local.
Quote:
* Earthquakes are more disconcerting than those who haven’t experienced them think they are.
In the early 1980's, I experienced a minor bit of trembling from the July 27, 1980 magnitude 5.1 earthquake near Sharpsburg, KY, which was several hundred miles away from where I was, in my office, on the third floor.

At first, it seemed like a bit of vibration. I thought a truck was going by. The vibration continued, and I looked outside on the street. No truck.

The vibration progressed to a kind of rocking and shaking. A large wooden book case in my office, full of books and with glassed panels in front to keep out dust, began to wobble back and forth. I knew it must be an earthquake. I didn't feel panicky, but I remember freezing in place, desperately trying to decide whether to go over to the book case and steady it, or get out of its path should it fall. After a couple of more wobbles, I decided I had time to go over and steady it, and did so.

When the book case stopped trying to rock back and forth, I went out to check on what else might have happened. A guy in another office said his door had been ajar when the quake started, and started swinging jerkily on its hinges.

I later heard from someone who'd happened to have clothes drying in the back yard. They were doing a "line dance" during the quake.

Curiously, some years later I experienced an extremely minor quake, as subsequently reported on the news. (I can't remember the magnitude, but I think it was between 3 and 4.)

I felt a vague "unsteadiness" but no real shaking. Nonetheless, the sensation threw me into a panic. I tried to fight off the sense of terror at impending doom by thinking, "this must be an earthquake, but a really minor one." It did help, but, despite the vagueness of the physical sensation, it is no exaggeration to say that it left me shaken.

Last fiddled with by Dr Sardonicus on 2019-07-06 at 14:13
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Old 2019-07-06, 18:51   #410
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So, Thursday's 6.4 tunred got demoted to foreplayshock status yesterday evening, when a shallower M7 hit in the same general area. We now hope the M7 doesn't end up getting similarly relegated.

Last fiddled with by ewmayer on 2019-07-06 at 18:52
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Old 2019-07-07, 09:14   #411
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I [expletive] Love the USGS!
The immensely long link, below, leads to a live updating map. It is currently set for a very tight view of the active area for the quakes being discussed. The screenshot shows the settings: 7 days, 4.5+. This view is only showing 28 of the 122 quakes in the map area in the time period. Set it for 2.5+ and it gets a lot busier. Setting it for All Magnitudes produces the Caution pop-up. "We recommend at most 2000 earthquakes for your device."
EDIT: I was looking at the live page when I wrote the number '122'. I see now that a quake had been added since I took had taken the screenshot.

https://earthquake.usgs.gov/earthqua...t%22%3Anull%7D
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Old 2019-07-24, 01:18   #412
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Some photos of the effect of the recent 7.1 quake in california
https://www.latimes.com/california/s...-broken-ground
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Old 2019-08-02, 16:23   #413
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Jakarta? No she went on foot.

As is well known, I happen to think the old ones are the best.
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Old 2019-08-02, 20:28   #414
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Quote:
Originally Posted by xilman View Post
Jakarta? No she went on foot.

As is well known, I happen to think the old ones are the best.
My favorite variant of that is, when someone asks "What brings you here?", to reply "I came [by car|on foot|etc]".

Another good one is in reply to the common suspense-drama line "can I ask you just one question?", to counter with "I think you just did."
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Old 2019-08-03, 14:31   #415
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Long ago, the BC comic strip had a scene with two snakes. One says, "Grandpa! What brings you here?" Grandpa answers, "Horny plates."
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Old 2019-10-15, 06:19   #416
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4.5 near Walnut Creek, CA -- I'm in Novato (NW Bay Area, quake was in NE Bay Area), first set of p-waves felt like upstairs neighbor had dropped something heavy on the floor (my ceiling), but 2-3 sec later (best guesstimate) the second set of s-waves, much stronger, hit, at which point I realized it was a quake. No more "swimming pool slosh meter" like I had at my previous address in the S Bay (Cupertino), but based on past experience I guessed M4-5; the local news said first-look data was M2.5, which I knew was way too low.
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Old 2019-10-15, 12:51   #417
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Quote:
Originally Posted by ewmayer View Post
but based on past experience I guessed M4-5
A true Californian. Did you try to guess direction and distance too?

Last fiddled with by Uncwilly on 2019-10-15 at 12:52
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Old 2019-10-15, 18:29   #418
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Quote:
Originally Posted by Uncwilly View Post
A true Californian. Did you try to guess direction and distance too?
Per Wikipedia, "On average, the kilometer distance to the earthquake is the number of seconds between the P and S wave times 8." So if my 2-3 sec difference guesstimate was about right, figure ~16-24 km. I'll let you look up th distance between Novato and Walnut Creek and tell me if that's within a factor 2.

Direction ... that seems rather more difficult. One could build a cheap home version of that famous ancient Chinese quake-o-meter, which used a ring of delicately balanced bronze balls, supposedly the pattern of balls which drop allows one to infer direction. Probably amounts to a way of gauging the transverse-motion component of the S-waves.

Last fiddled with by ewmayer on 2019-10-15 at 18:37
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