2 shallow earthquakes strike near Berkeley, San Fransisco + aftershock October 27

Last update: October 27, 2011 at 7:22 pm by By

Earthquake overview : At 02:41 PM a moderate magnitude 4.0 earthquake with epicenter near Berkeley shook the San Fransisco Bay area. 6 hours later a similar earthquake  this time measuring 3.8 hit the same Berkeley area. Both quakes were felt far away from San Fransisco.
“I have Felt it” Reports –> see below + Let us know “how you have felt this earthquake”
To read the full story as it happened, we advise our readers to start at the lower part of the page (earthquake data).

Epicenter San Fransisco October 20 2011 earthquake

Aftershock October 27 2011,
M 3.6      2011/10/27 12:36     Depth 9.7 km     SAN FRANCISCO BAY AREA, CALIFORNIA
05:36:44 AM at epicenter
A serious aftershock which woke up a lot of people occurred in the same fault area close to the UCLA Berkeley
This fault zone is very active since a number of days
2 km (1 miles) E (87°) from Berkeley, CA and 9 km (6 miles) NNW (347°) from Oakland, CA
Satellite map of the greater epicenter area

For the I Have Felt It reports related to this aftershock, see below

Aftershock October 22  00:10
M 2.8      2011/10/22 07:06     Depth 8.0 km     SAN FRANCISCO BAY AREA, CALIFORNIA
3 km (2 miles) ESE (122°) from Berkeley, CA
Harmless but unnerving aftershock
I Have Felt It reports : see bottom of page

Mainshocks October 20
We have the pleasure to report that after checking our many sources, NO damage or injuries have been reported for this  earthquake.

Update : The earthquakes were felt as far as Portland, Oregon to the north, Sacramento to the east and San Diego to the south.

Update : The police has received many house and car alarms activated by the quake.

Important Update 03:45 UTC : At 08:16 PM another earthquake hit the same Berkeley area.  The Hayward fault line was also here the main responsible. The 08:16 quake has to be regarded as an aftershock of the earlier 02:41 earthquake.

Most important Earthquake Data (second earthquake):
Magnitude : 3.8
UTC Time :  Friday, October 21, 2011 at 03:16:05 UTC
Local time at epicenter : Thursday, October 20, 2011 at 08:16:05 PM at epicenter
Depth (Hypocenter) : 9.6 km
Geo-location(s) :
2 km (1 miles) E (100°) from Berkeley, CA
5 km (3 miles) ESE (123°) from Albany, CA
5 km (3 miles) NE (41°) from Emeryville, CA
8 km (5 miles) NNW (346°) from Oakland, CA

Update : USGS has revised the strength of the earthquake to Mw 4.0

Update : Earlier in the day, millions of Californians participated in a statewide earthquake preparedness drill that was sponsored by state and federal emergency response agencies, the American Red Cross and others.

Update: In the  Oakland City Hall employees dived under their desks. The nine-story police department building, an aging structure built in the 1960s, was evacuated as a precaution immediately after the temblor. Employees have returned to their offices soon thereafter.

Update : All BART trains were halted or slowed due to the earthquake and trains are stopped or are traveling slowly as train operators conduct track inspections.

Update : Earthquake-Report.com thanks the people from the Bay Area in sending their I Have Felt It reports. MMI numbers are good but the description of what people exactly felt is always more informative. (see below for the I Have Felt It reports)

Update:  We have no reports of any serious damage or injuries and we do not expect to find them neither. Falling objects and moments of fear are the main disturbances of this earthquake.

Update:  We just received a report from Portland, Oregon, that somebody felt this earthquake as a very weak shaking.

Update:  As most of the people in this part of California know, weak aftershocks can occur after such a mainshock.

UpdateWe congratulate USGS for their very good theoretical intensity strength calculation. As they have expected, only the direct epicenter area reports a max. MMI V intensity (moderate shaking).

Update:  Most of our readers are reporting 2 strong jolts from a couple of seconds

Update: The earthquake occurred almost below a known Hayward Fault line. The earthquake was the largest one in this fault line since several years.

Shaking map of the San Fransisco October 20, 2011 earthquake

UpdateEarthquake-Report.com does not expect damage or injuries based on the depth and the magnitude of this earthquake.

Update: As can be seen in the I Have Felt It report (more to come) a lot of people were frightened from the jolts

Update : USGS expects that 88,000 people will have experienced a Moderate MMI V shaking. 901,000 people will have felt a light shaking.


“I Have Felt It” reports as received by Earthquake-Report.com
Alameda: I felt 2 jolts about 3-4 seconds apart.
Alameda: Very short — the building kind of thumped loudly, and some shaking.
Concord:  I thought there was someone on the roof at first and then the ground was shaking too. It was pretty big
San Fransisco: 2 seconds of shaking enough to shake the house.  Scary.
San Fransisco: The room shook for 2 seconds. The dog went crazy.
San Fransisco: Just felt it a few minutes ago.
Oakland: shelf items knocked off of shelves and refrigerator.  lasted less than 2 seconds but it was strong.
Alameda: sounded like a boom was outside heard the house move a bit
94595: Two medium “wobbles”, not shock or up and down (wave) motion.
Alameda: Loud rumbles. Shook a 5 story apartment decent to hear sounds, blinds moving, floor motion, short duration. I am 8 miles from supposed center in Berkeley.
Alameda County: Alameda CountyVery short — the building kind of thumped loudly, and some shaking.
???: The as a whole shook…no rolling. Some sound, almost like crackling. Quite brief.
Oakland: Two very strong jolts!
Pacifica: Two shakes thud like -moderate – seemed around a 4 in Pacifica.
Hayward: I was just sitting in my bed. And I felt the bed shake for about 3 seconds and also heard the lamp on my night table made that clink-clank noise
Concord: I work in concord, california and let me tell you it felt like a big rock hitting the building then the rolling sensation.  Sure woke me up.
Oakland: building shook and made ‘shaking building’ noises.  Rattled door and dishes. Took a quick break and gave a last couple of quick shakes.
Walnut Creek : light shaking indicated
Portland, Oregon: I was on my computer and there were a few shakes that were not normal and I thought that it might be an earthquake. Low and behold my friends from the Bay Area said there was one the same time I had thought I felt something. Probably not the same one or I just had a feeling about the one in CAR
San Fransisco, Richmond: I live on the top floor of a 4-story brick building. Felt the trembling coming and pass under the chair I was sitting on for at least 4 seconds, if not longer. Possibly the construction of the house changes the impression of the quake’s strength.
San Fransisco: im in a tall building near city hall, the entire building swayed for a while. it was pretty scary
Fairfax: I was in my house on the computer when the whole house shook.  Went outside to see if anyone else felt it, but nobody did.  Nothing like the “89 quake though!
Oakland: Strong, quick shakes in Oakland, CA. Several small items fell off the shelves and shattered on the floor, medicine cabinet items tumbled out.
Concord: First earthquake! I’m on the 7th floor of a building and we swayed left and right for a few seconds.
Pleasanton: On 5th floor of office building. Building shook for about 10 seconds
San Francisco, 1/2 block south of Silver 4 blocks east of Mission: Strongest earthquake I have felt in years. Started with a rumbling noise followed a split second later by a very distinct jolt with shaking about a quarter second, quieted down, about a half second later a weaker shaking lasting about a second gradually fading away total lasting 2.5 to 3 seconds.
San Fransisco: Northern part of San Francisco.  Picture frame fell off mantelpiece, broke the glass in the frame.
San Fransisco: The room shook for a couple seconds. My mom was is another room and didn’t feel it. I was laying down.
Oakland: I was on the phone with someone in Mexico when it occurred.  There was a small jolt, a pause, and then strong shaking for less than 2 seconds.

I Have Felt It reports which were received after the second earthquake
Berkeley: Another one similar to this afternoon but longer! A few things fell off shelves and a plant pot broke.
Santa Cruz
: Just sitting at my desk doing homework and my chair and table wobbled and I felt the ground slightly shake for 6 sec
Santa Clara: Sitting in bed watching tv, bed shook twice.  Much like someone getting out of bed.
Oakland: 2nd quake of the day.  pretty intense.  nothing fell over but there was a lot of shaking
Richmond: While having a deep conversation, the walls in my apt and windows began to shake. At first I thought it was my neighbor upstairs until my other half received a phone call about an earthquake. Second time today.
Berkeley: rond 8.00pm terug beving in Berkeley / California (2de vandaag), enkele lichtere voorwerpen vallen van kast, duidelijke beving van het huis, waarschijnlijk terug rond de 4 op schaal van Richter.
Fremont: A sudden sideways jolt, creak of wood studs and sideways shaking lasting 2-3 seconds.
Alameda: No damage, it lasted about 8 seconds
Berkeley: Short–maybe 2 seconds of shaking.
Castro Valley: Light shaking indicated
San Fransisco: What was that? Nine seconds (counting “One one thousand, two one thousand …) Second time today, and stronger this time. Place, basement, half a block south of Silver, four blocks east of Mission, Excelsior district San Francisco. Initial shock strongest, then stayed fairly even for about seven seconds, then tapered off two more seconds. There was an initial noise, may mostly have been sound of the house flexing, though there seemed to be a faint background rumbling.
Oakland: Felt like a strong jolt, almost like something slammed into our house. Seemed much stronger than the earlier 4.2 (or 3.8) quake earlier. Scared the bejeezuz out of us!
San Fransisco: about 10 seconds of moderate shaking – on the Berkeley Hayward fault around 8:16 PM
Palo Alto: my house os on the third floor we delt the building shaking for 10 seconds.
Concord: I was sitting at my desk when the apartment building started to shake for a few seconds – it felt similar to the one that occurred earlier today in south east Berkeley.
San Fransisco: it felt lyk vibration… (magnitude 5.1?)  It felt lyk something dropped and then the shaking
Berkeley: at zip code 94708, regal rd. berkeley ca.  at 2;40 pm the quake felt like a  strong jolt. at zip code 94708 grizzly peak blvd. berkeley ca. at 8:16 pm quake felt like shaking motion
Scotts Valley: First earthquake I’ve ever felt! I thought someone was pounding on the door extremely hard for a few seconds…
Grass Valley: I was sitting there on the apartment floor and felt the floor doa rumble effect at first I thought it was my neighbors slamming there door but I soon figured out it wasn’t that,pretty weird how we felt this shake here in the mountains…
Downtown Berkeley Near the BART Station: I was eating at ground level restaurant. First heard the heavy shaking sound coming from South, then the ground outside the  restaurant shakes, like if a bomb exploded. Then our table shakes, forcing the plates on the table to produce a shaking sound. That was it.
San Fransisco: I live close to St. Francis Hospital.  Felt both earthquakes. Aggressive type. Had to move to a safer environment, away from any moving or falling objects or furniture.

I Have Felt It reports Aftershock midnight (October 21/22)
Berkeley: More a brief sharp jolt. It felt like an after shock on the same  fault as the two jolting Berkeley quakes of Thursday.
I live in North Berkeley.
Oakland: Putting away dishes before ending the day. Happened around midnight.
Oakland: 12:08 am 10/22/2011. Just a few rattles–husband was asleep and didn’t wake up.
Alameda county : weak shaking indicated
Montclair Hills: Two more hit this evening.  10-22.  Uggg, I can hear them coming like a low rumble.

I Have Felt It reports Aftershock midnight (October 27)
Oakland : My bed was shaking for About 5-7 seconds.
Castro Valley : My bed was shaking for About 5-7 seconds.
Berkeley : Light shaking indicated
Richmond : Earthquake felt around 5:30am in Richmond california
San Leandro : Woke me up out of my sleep at about 5:30am
Berkeley : the house rumbled and my bed shook at around 5:37AM PDT on October 27th 2011 My dog sita was petrified (maybe she felt it before i did)
Martinez : At first I thought someone was walking heavily upstairs, but then the house shook laterally once or twice. Nothing fell.
Oakland : Acaba de temblar como a eso de las 5: 55 de la madrugada , de pronto sentij un golpe y se movio el edificio , esto que empeso el dias 20 creo que ya es mas un aviso que debemos prepararnos…..
Oakland : Woke up to a large jolt while lying down in bed
Benicia : Felt like something had hit the house, from the upper story bed
Santa Cruz : I felt my apartment rumble for about 15 sec.
San Fransisco : I woke up because the bed was shaking. It only lasted 2 or 3 seconds after I was awake.


Most important Earthquake Data (first earthquake):
Magnitude : 3.9  4.0 (preliminary)
UTC Time :  Thursday, October 20, 2011 at 21:41:04 UTC
Local time at epicenter : Thursday, October 20, 2011 at 02:41:04 PM at epicenter
Depth (Hypocenter) : 9.8 km
Geo-location(s) :
2 km (2 miles) ESE (112°) from Berkeley, CA
8 km (5 miles) NNW (346°) from Oakland, CA

Links to important maps
USGS Did You Feel It Map
Google satellite map showing the epicenter and the surrounding area.
Shaking map
Focal mechanism report
Human impact map

QuakeSOS+ and QuakeSOS free are iPhone applications developed by Armand Vervaeck, the founder of Earthquake Report. The Application simplifies immediate group communication to friends and family members (with your exact GPS location) and is feeding the users with Earthquake Report news. The 0.99 US$ QuakeSOS+ version will support the activities of SOS Earthquakes.

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I did feel it – Ik heb het gevoeld – Το έκανα αισθάνεται Yo lo he sentido – 我的确感到了 – 私はそれを感じていました- Ich habe es gefühlt – Bunu hissediyorum yaptı – لم أشعر أنه

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