[Island Chris]

Hi Tony and all,

I thought it best to restart your thread. Your first and last posts are below. This is pretty interesting; you may want to mention this to Jim Boles; I may or may not forward this (I'll "cc" you if I do). Brian, if you feel like it, put Tony's oil seep and these quakes on a map. I'll go ahead and put the quake into the SCEC Community fault model and will post in a bit.

The focal mechanism of the M4.2 is a bit odd:

It is a thrust/reverse mechanism, but the P axis is in the northwest, which means NW-SE shortening. You expect N-S shortening near a NW-SE right-lateral fault (the San Andreas). There are know to be thrust faults that strike parallel to the San Andreas at these latitudes: the P axis would be for NNE-SSW shortening for a quake like that.

Parallel-striking strike-slip and thrust faults are examples of what is known as slip partitioning. This quake strikes at high angle to San Andreas so is something different.

A nearby M3.1 on Dec 31 gas the same focal mechanism as the 4.2

Chris


http://earthquake.usgs.gov/earthquakes/e...scientific



Hi,

For what it's worth, I'm always out hiking the canyons here in Santa Clarita. I have never seen water accumulate absent precipitation. When it does rain, and there is pooling, flow, etc., the duration is in accord with the usual factors of temperature, etc.

In any event, it will be interesting to see what the respective thoughts are on this.

Tony

Just as a follow up, there have been three quakes about seven miles due north of these observations; a 3.1 on December 30, 2014, a 3.1 on January 3, 2015, followed by a 4.5 about 15 minutes later. It appears that the quakes occurred on a fault running immediately adjacent to the San Andreas.

Tony

[zinnanti]

Thanks for reposting. Please feel free to forward to Jim Boles. I was going to start a new thread, but I felt it better for you to organize the information. Much appreciated.

I might have mentioned this somewhere along the way, but I noticed what also appeared to be increased water flow in the creek at the back of Lake Castaic. What was odd is that the creek had been bone dry for a year. My reason for going back there was quail opener (Oct. 18).

I was surprised to see that, prior to any of this season's rain, the creek was flowing and water was pooling. I don't know if the storms of earlier 2014 could have been responsible for that.

That creek comes down through Ruby Canyon, which runs from the NE to the SW into the back of Lake Castaic. So, a Google maps shot should give a pretty clear indication of its location.

Anyway, thanks for the thread. It will be interesting to see what happens. I nudge people to be prepared. We live in California after all. It's coming sooner or later.

Tony

[Skywise]

(01-04-2015, 12:15 PM)Island Chris Wrote: Brian, if you feel like it, put Tony's oil seep and these quakes on a map.

Turns out the quakes are pretty far from Towsley Canyon - nearly 30km. And there's the San Gabriel Fault Zone between them.

Ruby Canyon, on the other hand, *IS* the Clearwater fault, which is to the east of the quakes by about 8km, and the quakes are on the Clearwater fault. However, the aftershock sequence and focal mechanism seems to indicate it was on a perpendicular cross fault. There does appear to be indications of such on the map at the location of the main shock. This may explains Chris's description of "NNE-SSW shortening".

Map below.

Brian

[zinnanti]

Cool map.

The creek I'm talking about is that which feeds right behind that upper, right finger of Castaic Lake - which comes out of Ruby Canyon.

As far as distance, I didn't think Towsley and the back of Castaic were that far. Interesting.

Thanks for the follow up on things. If you need me to go out and do more photos/vid, just let me know.

Tony

[Island Chris]

I mentioned the quakes to earth scientist, sometimes seismologist Leonardo "Nano" Seeber last night when we were discussing block rotation models for onshore Santa Maria basin. I mentioned the NW-SE shortening of reverse-slip earthquakes for the focal mechanisms, and he said it sounded like what you might get with rotations (vertical axis). Brian's graphic shows the quakes to be on a cross fault (NE-SW), and cross faults can be signs that an area is rotating.

I'll forward the link and my email to Nano.

Chris

[zinnanti]

Hi All,

I took my morning Towsley Canyon hike and ran into some Mountain Conservancy people; volunteers and employees. I mentioned the water in the canyon. One of the employees - who looked like a professional old timer - said that he noticed the same thing.

He did offer, however, that some of the seepage could be coming from a creek at the "back side" of "the narrows." Apparently, if you go over the mountains immediately to the northwest of the narrows, the land is vast and there is a full time running creek back there. He mentioned that, sometimes, it takes a long while for water to "percolate" through to the narrows. (I'm just relating what he stated. I have no idea how this works.) On the other hand, he did notice a considerable increase in the water in the canyon (as depicted in the photos I posted).

Then he offered something very interesting. He stated that, just prior to the Clearwater (?) Fault 4.2 quake of the other day, he had noticed pooling of water in the Santa Clara riverbed. He mentioned that the riverbed was bone dry prior to that. On my way back, I passed over the Golden Valley overpass (right by the intersection of Golden Valley and Soledad Canyon in Santa Clarita) and there was a clear view of water pooling on the sand in the riverbed.

I believe that the valley aquifers are below the riverbed. I know this from the ammonium perchlorate contamination from years ago when the rocket fuel companies would shoot open barrels of ammonium perchlorate and just let it sink into the ground. I understand that some of the aquifers are around 1,500 to 1,700 feet below ground.

He had no idea about the Ruby Canyon water situation.

Anyway, just passing it along . . . .

Tony

[Skywise]

(01-08-2015, 03:33 AM)zinnanti Wrote: He did offer, however, that some of the seepage could be coming from a
creek at the "back side" of "the narrows." Apparently, if you go over the
mountains immediately to the northwest of the narrows, the land is vast
and there is a full time running creek back there. He mentioned that,
sometimes, it takes a long while for water to "percolate" through to the
narrows.

Made a watershed map for Townsley. Used the terrain map from Google
Maps and drew it by hand in about an hour. Had time to kill since I'm
waiting on the computer anyway, rendering some CGI stuff.

Brian