While the other earthquakes have been basically slow steady rumbles, this one felt more intense and in the middle of it had a real kick that jarred everything. It knocked my computer monitor out of place!
This magnitude 4.1 earthquake was also located in Hawthorne, CA, 4.88 miles from the house--very close to the last epicenter. The depth was 7.5 miles. Maybe that's why it had such a kick to it.
I wonder if they feel worse right on top of the epicenter or out a ways. Interestingly, the deep rumbling sound appeared to be coming from south of here, and Hawthorne is north. Is that because there are mountains just south of me?
The waveform is above. The USGS had the information up on their site when I checked it within a minute of the earthquake. I wonder if it is completely automated? [Update: after reading some on the site, yes. The process is automated. Cool!]
[Again, after reading more, the sheer, or S-wave travels more slowly and is ultimately what is used to measure the magnitude of the quake. I wonder if the jolt I felt today was the S-wave passing through this area? The S-wave is colored green on the waveform to the right, which represents 120 seconds.]
This one, with its jarring jolt was more frightening than any of the others have been. I've got my seismometer running on my iPhone in case we have any aftershocks.
[Update: Apparently we had another earthquake, 2.1 magnitude, 9.9 miles deep, about 1.5 miles from where I'm sitting. The epicenter was across the street from where I had dinner last Sunday. Worse than that: it was only .82 of a mile from one of those huge Chevron gas tanks! But, I didn't feel a thing or thought it was part of the previous earthquake, which seemed to rumble for quite some time.]
By the way, I just love Google Earth and the way the USGS site integrates with it. I can click a link which downloads a KLM file. Double click it and see exactly where the epicenter is. Then I select the measure tool and draw a line from the epicenter to any spot to see how far it is away.
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