geoff_morphini wrote: 
are you a seismologist? that is pretty impressive. 

 NoEnzLefttoSplit wrote: 
The seismogenic (deep) part of the fault is in older rocks (likely Tertiary seds or Mesozoic Franciscan Fm.-equivalent).  The people and houses are sitting on younger alluvium/marine seds that are poorly consolidated.  As for the causative fault, it appears, from first motion to be dominantly reverse with a lessor component of right-lateral strike-slip.  There are two choices for the fault plane shown on the beachball.  The likely one, based on past seismicity, is the plane dipping to the northeast.  If it turns out to be the southwest-dipping plane it will be a reverse fault with lessor left-lateral motion (unlikely).

This is all caused by the large left-stepping bend in the right-lateral strike-slip San Andreas fault.  That is why the Transverse Ranges formed and why there are so many blind thrusts in the LA basin (blind meaning, they typically don't rupture to the surface and display a scarp). 

... but the fault itself is not in recent sedimentary deposits is it? (i'll have to rethink all my conceptions first), but in bedrock

and I thought the region was dominated by strike slip movement.. is the vertical moment something we could ignore or is it indicative of a more widespread graben type scenario... no wait a minute, it's a reverse fault, we're looking at compression and slip.. is that right?

 geoff_morphini wrote: 
thanks for that! i did feel it...and i will send in the questionnaire.

 KurtfromLaQuinta wrote: 

Those two were enough to give me a scare in Orange County.  I will never forget the 6.3 Whitier-Narrows quake in 1987.  I was in Long Beach on a water table...sliding back & forth...and it happened to be the first major quake I have experienced!

 KevinM wrote: 
The computer generated intensity maps are always interesting.



This earthquake, while not very large, was shallow, in a sedimentary basin, and, from the first motion solutions, generated by a reverse fault (actually oblique - just for NoEndz).  These three things will contribute to higher accelerations and shaking.

If you are in the area you could do the scientific community a favor and go to: Did you feel it?  It is an anonymous questionnaire that asks for your zip code.  It is a short series of questions about whether you felt the quake, where you were located, what you were doing, etc.  This information is compiled to generate better computer-generated shake maps, like the one above.  The map above was generated almost instantaneously, by computer based on earthquake size, location and style.  Compare it to the one that is being developed as the 46,000+ respondents to the questionnaire respond.  You can see that the ground motion people are starting to get pretty good at estimating the shake from a real event.  Why is this of any use?  First-responders (fire, EMT, police, etc.) can look at the shake map and know where the greatest probability of damage might have occurred, quickly, and start to mobilize there rather than wait for information to trickle in.



Here's the moment tensor solution (beachball):

I hope no one was hurt.

 NoEnzLefttoSplit wrote: 
I lived through some biggers.

Brawley (south of us here) had a couple of healthy ones in the 70's... 6.8's
One knocked down a few buildings there.
We felt them very well here.
They knocked the power out here for a short time.

We had a good sized one in the early 80's centered near Whitewater (10 miles noth of Palm Springs).
It was about a 6.2.
It knocked out our power again, for a short time.

Landers (about 40 miles north of us) in the early 90's was the gnarliest one.
A 7.2 that killed a small girl in Yucca Valley when a fireplace fell on her.
It ripped a scar in the earth up there a few miles long.
My parents thought there was a broken water main in their neighborhood because of all the water roaring down their street.
It was just water sloshing out of all the neighbors pools.
The next day followed  with a 6.7 in Big Bear!
Those were some tense days around here.
Especially with all the aftershocks.

Hector Mine (about 80 miles north of here) in the later 90's was a big one... around 6.8.
It derailed a passenger train outside of Barstow.

With this one in L.A., the media around here will be doing stories for months on the Big One we're going to have any day now.
 

 KurtfromLaQuinta wrote: 
sort of depends where you're sitting at the time.

 NoEnzLefttoSplit wrote: 
Under 6.0.... Pfffffffffft!

right smack in the middle of town by the looks of it, but thankfully sub 5M.. must've been a pretty decent jolt. Any reports of damage? Sometimes local geography can amplify the effect of these things and the LA basin is meant to be one such place.

 dmax wrote: 
after something like this, is she going to come back to stuff fallen down and maybe broken on the floor?  like spilled plants?   and you are worried about structural damage? or can it be just like she left it.

 KevinM wrote: 
All three of them were only a mile or so from my mom's, but she's in Milwaukee right now, so I hope the house is ok....

 KevinM wrote: 
Was manxbird in the area at the time? 'Cause if he was...

 rachlan wrote: 
Yep,

Pretty good jolt but no damage or frayed nerves.

 KevinM wrote: 
did ya feel it?

5.0 in Inglewood (Near Los Angeles)

LINK