UPDATE: The USGS has, as you probably already know, downgraded this morning’s (apparently damage free, according to reports) quake to a 4.3. According to their NoCal Chief of Earthquake Effects Investigations, Jack Boatwright, “the small, unmapped fault that appears to have produced the earthquake is believed to be a ‘splay fault’ off the Calaveras Fault, which is itself a branch off the San Andreas Fault.” Since the fault lies beneath a difficult-to-map area east of SJ.

Since the new fault is not considered a major fault, experts at the USGS do not believe this morning’s tremor is a precursor to a larger quake. Hey, guess that is kind of comforting.

UPDATE: BART keep it coming, with “Attention Passengers! Earlier, an earth tremor had been felt within the area serviced by Bart. Trains were running at reduced speeds completing track inspections. Expect residual delays of 10 to 15 minutes throughout the BART system. Thank you.”

Oh, this is fun: CBS5 has video of a seismograph reacting to the quake.

UPDATE: Bart says “There is a 5-10 minute delay system wide due to a earthquake within the BART service area, trains will be delayed to determine if there is damage to any BART facilities. Expect delays while this procedure is completed.”

Newsflash: Twitter people tweeted.

And here’s a nifty little Google Map illustrating the quake area.

A 4.4 earthquake centered in an area just outside Morgan Hill just shook the Bay Area — we felt it here in the Outer Sunset, how about you?

Here’s what the usgs says:

Magnitude: 4.6
Date-Time: Monday, March 30, 2009 at 10:40:29 AM at epicenter
Location: 37.285N, 121.620W
Depth: 6.2 km (3.9 miles)
Distances: 18 km (11 miles) N (7) from Morgan Hill, CA, 25 km (16 miles) ESE (104) from San Jose City Hall, CA

Here’s the cisn shake map

the author

Eve Batey is the editor and publisher of the San Francisco Appeal. She used to be the San Francisco Chronicle's Deputy Managing Editor for Online, and started at the Chronicle as their blogging and interactive editor. Before that, she was a co-founding writer and the lead editor of SFist. She's been in the city since 1997, presently living in the Outer Sunset with her husband, cat, and dog. You can reach Eve at eve@sfappeal.com.

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  • Erik

    The Northridge earthquake happened on a previously unknown fault also. If you want to see fewer earthquake on unknown fault then write to your congressperson and tell them to give the USGS more money for exploration.

  • Erik

    The Northridge earthquake happened on a previously unknown fault also. If you want to see fewer earthquake on unknown fault then write to your congressperson and tell them to give the USGS more money for exploration.