Moderate earthquake close to Cobb Mountain and The Geysers geothermal project, Northern California

Update 18:20 UTC : We have pulled the following "I Have Felt It" report out of the many we received as it came from the epicenter area itself :

March 14, 2013 I awoke to the worst shaking and rumbling I have felt in the 8 and half  years that I have been living in Cobb California.  I am used to the shaking but this was different.  For the first time I wondered if I should get out of the house. There was a second shaking 5 to 10 seconds later and rumbling in the distance for 30 seconds more.

Update 11:41 UTC : It looks like this earthquake has some links with the geothermal project at the nearby The Geysers. The extremely shallow location of the hypocenter (2 km) is another indication of this theory.
Read carefully the text of The Geysers below as we might have set a record today.

The Geysers
The Geysers is a complex of 22 geothermal power plants, drawing steam from more than 350 wells, located in the Mayacamas Mountains 72 mi (116 km) north of San Francisco, California. The largest in the world, the Geysers has 1517 MW[1] of active installed capacity with an average production factor of 63% (955 MW).Calpine Corporation operates and owns 19 of the 22 active plants in the Geysers and is currently the United States' largest producer of geothermal energy. Two other plants are owned jointly by the Northern California Power Agency and the City of Santa Clara's municipal Electric Utility(now called Silicon Valley Power). The Bottle Rock Power plant owned by the US Renewables Group was expected to be reopened in 2007. Another plant is under development by Ram Power Corp, formerly Western Geopower, with operation set to begin in 2010. Since the activities of one geothermal plant affects those nearby, the consolidation of plant ownership at The Geysers has been beneficial because the plants operate cooperatively instead of in their own short-term interest.

Seismicity at The Geysers
Current studies of The Geysers Geothermal Field seismicity have reached the conclusion that deep-well injection in the field produces mostly microseismic events between magnitude 0.5-3.0 on the Richter Scale (M).
Worldwide, the largest induced seismic event to date linked to Enhanced Geothermal System (EGS) activity was M3.7 in the Cooper Basin of Australia. However, research based on maximum fault lengths indicates that a M5.0 is the largest possible (but not probable) event in the Geysers.
A concern to the residents is not only the amount of seismicity but the magnitude of the largest seismic event likely to occur. Although no one can accurately predict earthquakes, the magnitude of an earthquake is dependent on the surface area that can slip — the length times the depth or width of the fault. Therefore, a large earthquake can occur only on a large fault. There are no mapped faults of large length in The Geysers, so it is extremely unlikely that induced seismicity caused by activities in The Geysers will lead to a large earthquake.

The Geysers electrical plant reached peak production in 1987, at that time serving 1.8 million people. Since then, the steam field has been in gradual decline as its underground water source decreases. Currently, the Geysers produce enough electricity for 1.1 million people.
Techniques developed from Enhanced Geothermal Systems research will increase the production of the region in the future. By reinjecting greywater from the nearby city of Santa Rosa, existing wells will be recharged. This water will be naturally heated in the geothermal reservoir, and be captured by the existing power plants as steam. The project should increase electrical output by 85 MW, enough for about 85,000 homes. (source Wikipedia)

One of The Geysers geothermal plants - Image courtesy Wikipedia

One of The Geysers geothermal plants - Image courtesy Wikipedia

Update 09:36 UTC : Contrary to what we wrote below, this quake may have been felt a little stronger than expected as we received a readers experience from Santa Rosa, stating : "i was watching tv and i felt everything slightly moving. It was a surprise for me"

Preliminary Magnitude M4.6 at a shallow depth of 2 km.
The epicenter area is mainly a wilderness area, with only some isolated houses.
We do not expect any damage because of the relatively big distance to the nearest villages (considering the Magnitude).
This area has no historic record (since 1900) of a major earthquake.
Cobb (2000 inhabitants) is expected to have experienced a light shaking and Cloverdale (9000 inhabitants) a weak shaking. Other locations in the area a very weak shaking, probably only felt by a very limited number of people.
Santa Rosa : a (theoretically) "not to be felt" shaking

Northern California earthquake March 14 2013

5km (3mi) WSW of Cobb, California
21km (13mi) SW of Clearlake, California
23km (14mi) NNE of Healdsburg, California
29km (18mi) N of Windsor, California
115km (71mi) WNW of Sacramento, California

Most important Earthquake Data:

Magnitude : 4.2

Local Time (conversion only below land) : 2013-03-14 02:09:00

GMT/UTC Time : 2013-03-14 09:09:00

Depth (Hypocenter)  : 4 km

Depth and Magnitude updates in the list below.

Share your earthquake experience (I Have Felt It) with our readers.
Click on the "I Felt It" button behind the corresponding earthquake. Your earthquake experience is not only important for science, but also for people in the area as well as our global readership.

Refresh this list
SRC Location UTC Date/time M D INFO
USGS Northern California Mar 14 18:18 2.6 0 MAP
USGS Northern California Mar 14 09:12 2.7 1 MAP
USGS Northern California Mar 14 09:10 3.4 4 MAP I Felt It INFO
USGS Northern California Mar 14 09:10 3.9 3 MAP I Felt It INFO
EMSC Northern California Mar 14 09:09 4.6 10 MAP
  • Deer Park, ca - Up reading when felt the floor seem to twist slightly and the curtains move.
  • 3350 Calistoga Rd. Santa Rosa, CA - Was awoken from sleep by the shaking. Did not look at the clock.
  • USGS Northern California Mar 14 09:09 4.5 2 MAP
    WCATWC 75 Miles W Of Sacramento California Mar 14 09:09 4.2 4 MAP I Felt It INFO
  • Santa Rosa, CA - I was watching TV and i felt everything slightly moving it was a surprise for me.
  • San Francisco, CA - Working at my desk at home -- felt the ground moving, my desk shaking, and watched my floor lamp swaying. Lasted only approximately 5-8 seconds.
  • Cloverdale - I live in a 2 story house so there was light shaking and I could hear the shower doors rattle. I had woken up a few minutes prior because my infant was starting to wake up.
  • San Francisco - was awake in San Francisco sitting in a chair when the whole apartment building started to sway. Seemed to last a while.
  • 95409 - Woke from sleep to short light shaking - dog barking
  • Healdsburg, ca - felt apartment rumble
  • San Francisco - I felt light shaking and my dog sat up off of the couch. After the shaking, I heard a clap that seemed to come from outside. About 30 seconds later I felt more shaking. Each lasted only a few seconds.
  • Santa Rosa - Doors rattled too.
  • Summit Blvd, Cobb, CA - March 14, 2013 I awoke to the worst shaking and rumbling I have felt in the 8 and half years that I have been living in Cobb California. I am used to the shaking but this was different. For the first time I wondered if I should get out of the house. There was a second shaking 5 to 10 seconds later and rumbling in the distance for 30 seconds more.
  • Napa - Bed made noise like a jolt and crystals continued swinging for a couple minutes afterwards probably in reaction to the aftershocks.
  • Santa Rosa, CA - I was in bed wondering if my husband was just restlessly moving. He thought the same of me. Light swaying back and forth for about 5 seconds. We were sure it was an earthquake.



    Other earlier earthquakes in the greater epicenter area (since 2012)

    Strongest earthquakes Magnitude 3.5 or more within a 150 km radius from this earthquake (max. 60)




    I felt the shaking *
    Country where you felt the earthquake *
    City/Village where you felt the earthquake *
    Street or suburb (area) where you felt the earthquake
    Latitude (area) where you felt the earthquake
    Longitude (area) where you felt the earthquake
    Shaking Strength *
    MMI II (Very weak shaking) ?
    People :
    Felt by persons at rest, on upper floors or favorably placed.
    MMI III (Weak shaking) ?
    People :
    Felt indoors; hanging objects may swing, vibration similar to passing of light trucks, duration may be estimated, may not be recognized as an earthquake.
    MMI IV (Light shaking) ?
    People :
    Generally noticed indoors but not outside. Light sleepers may be awakened. Vibration may be likened to the passing of heavy traffic, or to the jolt of a heavy object falling or striking the building.
    Fittings :
    Doors and windows rattle. Glassware and crockery rattle. Liquids in open vessels may be slightly disturbed. Standing motorcars may rock.
    Structures :
    Walls and frames of buildings, and partitions and suspended ceilings in commercial buildings, may be heard to creak.
    MMI V (Moderate shaking) ?
    People :
    Generally felt outside, and by almost everyone indoors. Most sleepers awakened. A few people alarmed.
    Fittings :
    Small unstable objects are displaced or upset. Some glassware and crockery may be broken. Hanging pictures knock against the wall. Open doors may swing. Cupboard doors secured by magnetic catches may open. Pendulum clocks stop, start, or change rate.
    Structures :
    Some large display windows cracked. A few earthenware toilet fixtures cracked.
    MMI VI (Strong shaking) ?
    People Felt by all. People and animals alarmed. Many run outside. Difficulty experienced in walking steadily.
    Fittings :
    Objects fall from shelves. Pictures fall from walls. Some furniture moved on smooth floors, some unsecured free-standing fireplaces moved. Glassware and crockery broken. Very unstable furniture overturned. Small church and school bells ring. Appliances move on bench or table tops. Filing cabinets or "easy glide" drawers may open (or shut).
    Structures :
    Slight damage to buildings with low standard. Some stucco or cement plaster falls. Large display windows broken. Damage to a few weak domestic chimneys, some may fall.
    Environment :
    Trees and bushes shake, or are heard to rustle. Loose material may be dislodged from sloping ground, e.g. existing slides, talus slopes, shingle slides.
    MMI VII (Very strong shaking) ?
    General alarm. Difficulty experienced in standing. Noticed by motorcar drivers who may stop.
    Fittings :
    Large bells ring. Furniture moves on smooth floors, may move on carpeted floors. Substantial damage to fragile contents of buildings.
    Structures :
    Unreinforced stone and brick walls cracked. Low standard buildings cracked with some minor masonry falls. A few instances of damage to buildings of ordinary workmanship. Unbraced parapets, unbraced brick gables, and architectural ornaments fall. Roofing tiles, especially ridge tiles may be dislodged. Many unreinforced domestic chimneys damaged, often falling from roof-line. Water tanks Type I burst. A few instances of damage to brick veneers and plaster or cement-based linings. Unrestrained water cylinders (hot-water cylinders) may move and leak. Some common windows cracked. Suspended ceilings damaged.
    Environment :
    Water made turbid by stirred up mud. Small slides such as falls of sand and gravel banks, and small rock-falls from steep slopes and cuttings. Instances of settlement of unconsolidated or wet, or weak soils. Some fine cracks appear in sloping ground. A few instances of liquefaction (i.e. small water and sand ejections).
    MMI VIII (Severe shaking) ?
    People Alarm may approach panic. Steering of motorcars greatly affected. Structures : Low standard buildings heavily damaged, some collapse. ordinary workmanship buildings damaged, some with partial collapse. Reinforced masonry or concrete buildings damaged in some cases. A few instances of damage to buildings and bridges designed and built to resist earthquakes. Monuments and pre-1976 elevated tanks and factory stacks twisted or brought down. Some pre-1965 infill masonry panels damaged. A few post-1980 brick veneers damaged. Decayed timber piles of houses damaged. Houses not secured to foundations may move. Most unreinforced domestic chimneys damaged, some below roof-line, many brought down. Environment : Cracks appear on steep slopes and in wet ground. Small to moderate slides in roadside cuttings and unsupported excavations. Small water and sand ejections and localized lateral spreading adjacent to streams, canals, lakes, etc.
    MMI IX (Violent shaking) ?
    Structures Many low standard buildings destroyed. Ordinary workmanship buildings heavily damaged, some collapse. Reinforced masonry or concrete buildings damaged, some with partial collapse. Buildings and bridges designed and built to resist earthquakes damaged in some cases, some with flexible frames seriously damaged. Damage or permanent distortion to some buildings and bridges, designed and built to normal use standards. Houses not secured to foundations shifted off. Brick veneers fall and expose frames. Environment : Cracking of ground conspicuous. Landsliding general on steep slopes. Liquefaction effects intensified and more widespread, with large lateral spreading and flow sliding adjacent to streams, canals, lakes, etc.
    Tell us your experience and how many seconds the shaking lasted + let us know if your property has been damaged (even slight damage). (max. 500 characters)
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