[Skywise]

Dunno why I only just now noticed this, but there has been a swarm of small quake occurring about 7-8 km west of Anza, CA. Anza is no stranger to quakes being close to the San Jacinto Fault Zone, but this cluster is well away from there.

This swarm appears to have started on the 3rd, but has really picked up in the last week.

I'd be tempted to say we could expect something bigger, but I wouldn't go so far as to make a prediction. I just wouldn't be surprised. Yet, this is away from any know faults, not that that stops quakes form happening.

I'm about to go to bed, but tomorrow I'm going to take a closer look at this area and it's history. I expect the Hauksson relocated data set should show something interesting.

Here's a link to a zoom on the USGS map. Gosh, I wish their links weren't so nasty looking, so I made a tinyurl of it.

http://tinyurl.com/mzrarag

Brian

[Island Chris]

Brian,
I had not noticed that; I usually check the quakes via USGS with just M2.5 and larger (I know I can set all quakes, but it defaults next time to 2.5). I know that there are papers by Seeber et al and Nicholson et al from the mid and late 80s about cross faults (left-lateral NE-SW faults) between the San Jacinto system and the San Andreas proper: Ellmore Ranch M6.2 is on one of these, and it triggered the M6 1/2 Superstition Hills right lateral quake within a day. (1987 I think).

I don't know whether these faults are in the area of your swarm, between San Jacinto and Elsinore.

I'm interested in the distribution of faults, as I am working on a manuscript about some of the small, distributed offshore faults, including the Newport-Inglewood.

I'll email you off-list.

Chris

[Skywise]

I've generated a map comparing current activity since the beginning of the month (April 2014) against the Hauksson relocated catalog.

The area has had quakes in the past, and it's obvious from the distribution that there are small branches or filaments of faults in the area.
They run generally parallel to the San Jacinto Fault Zone with runs SE to NW as seen on the right of this image.

Obviously the current USGS locations are rough but the distribution almost appears to make this current activity on a cross fault.
However, I suspect relocation would put things 'straight'.

Brian

[Island Chris]

Hmm,

interesting. I'll send the links to Craig Nicholson and ask if he has any comments, and whether I can post them.
Chris