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Moderate mag. 4.0 earthquake - 3km SW of Anderson Springs, CA, on 19 Apr 11:50 am (GMT -7)

Moderate mag. 4.0 earthquake - 3km SW of Anderson Springs, CA, on 19 Apr 11:50 am (GMT -7) Moderate mag. 4.0 earthquake - 3km SW of Anderson Springs, CA, on 19 Apr 11:50 am (GMT -7)

Moderate magnitude 4.0 earthquake at 3 km depth

20 Apr 00:56 UTC: First to report: VolcanoDiscovery after 6 hours.
19 Apr 18:54: Magnitude recalculated from 4.2 to 4.1. Hypocenter depth recalculated from 9.0 to 2.8 km (from 5.6 to 1.7 mi). Epicenter location corrected by 4 km (2.5 mi) towards NNE.
19 Apr 18:58: Magnitude recalculated from 4.1 to 4.2.
19 Apr 21:38: Hypocenter depth recalculated from 10.0 to 2.9 km (from 6.2 to 1.8 mi).
Update Mon, 19 Apr 2021, 18:57

Moderate magnitude 4.1 quake hits 22 miles north of Santa Rosa, California, United States in the morning

4.1 quake 19 Apr 11:50 am (GMT -7)
4.1 quake 19 Apr 11:50 am (GMT -7)
A magnitude 4.1 earthquake near Santa Rosa, Sonoma County, California, USA, was reported only 6 minutes ago by the United States Geological Survey, considered the key international and national agency that monitors seismic activity in the US. The earthquake occurred at a very shallow depth of 1.7 miles beneath the epicenter in the morning on Monday 19 April 2021 at 11:50 am local time. The exact magnitude, epicenter, and depth of the quake might be revised within the next few hours or minutes as seismologists review data and refine their calculations, or as other agencies issue their report.
A second report was later issued by the European-Mediterranean Seismological Centre (EMSC), which listed it as a magnitude 4.1 earthquake as well.
Based on the preliminary seismic data, the quake was probably felt by many people in the area of the epicenter. It should not have caused significant damage, other than objects falling from shelves, broken windows, etc.
In Cobb (pop. 1,800) located 5 miles from the epicenter, the quake should have been felt as light shaking.
Weak shaking might have been felt in Healdsburg (pop. 11,700) located 13 miles from the epicenter, Clearlake (pop. 15,200) 15 miles away, Windsor (pop. 27,500) 15 miles away, and Santa Rosa (pop. 175,000) 22 miles away.
Other towns or cities near the epicenter where the quake might have been felt as very weak shaking include Rohnert Park (pop. 42,400) located 29 miles from the epicenter, Petaluma (pop. 60,400) 36 miles away, and Napa (pop. 80,400) 39 miles away.

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Earthquake details

Date & timeApr 19, 2021 18:50:58 UTC
Local time at epicenter19 Apr 11:50 am (GMT -7)
StatusConfirmed
Magnitude4
Depth2.9 km
Epicenter latitude / longitude38.757°N / 122.72283°W (Sonoma, California, United States)
Antipode38.757°S / 57.277°E
Shaking intensityLight shaking
Felt113 reports
Primary data sourceUSGS (United States Geological Survey)
Nearest volcanoClear Lake (28 km / 17 mi)
Nearby towns and cities7 km (5 mi) S of Cobb (pop: 1,780) | Show on map | Quakes nearby
21 km (13 mi) NE of Russian River (Sonoma County) (pop: 11,700) | Show on map | Quakes nearby
21 km (13 mi) NE of Russian River (pop: 11,700) | Show on map | Quakes nearby
24 km (15 mi) SSW of Clearlake (Lake County) (pop: 15,200) | Show on map | Quakes nearby
25 km (15 mi) NNE of Windsor (Sonoma County) (pop: 27,500) | Show on map | Quakes nearby
35 km (22 mi) N of Santa Rosa (pop: 175,000) | Show on map | Quakes nearby
46 km (29 mi) N of Rohnert Park (pop: 42,400) | Show on map | Quakes nearby
59 km (37 mi) N of Petaluma (pop: 60,400) | Show on map | Quakes nearby
64 km (40 mi) NW of Napa (pop: 80,400) | Show on map | Quakes nearby
108 km (67 mi) W of Sacramento (pop: 490,700) | Show on map | Quakes nearby
Estimated seismic energy released6.3 x 1010 joules (17.5 megawatt hours, equivalent to 15.1 tons of TNT) | about seismic energy
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Data for the same earthquake reported by different agencies

Info: The more agencies report about the same quake and post similar data, the more confidence you can have in the data. It takes normally up to a few hours until earthquake parameters are calculated with near-optimum precision.
Mag.DepthLocationSource
4.02.9 km3km SW of Anderson Springs, CAUSGS
4.03 kmNORTHERN CALIFORNIA, USAEMSC

Seismograms

Seismic station: Marconi Conference Center, Marshall, CA, USA (MCCM/BK network) | Distance from quake: 69 km / 43 mi | Show on map | Station Info
Seismic station Marconi Conference Center, Marshall, CA, USA: vertical movement plot around time of quake (source: IRIS/BUD)
Seismogram (vertical component) around time of quake. Thin dotted red line indicates time of quake. Seismic waves arrive some time later, depending on distance. Bandpass filter applied: 0.2-10.0 Hz. Source: IRIS Buffer of Uniform Data (BUD) webtool
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User reports for this quake (120)

User reports estimate the perceived ground shaking intensity according to the MMI (Modified Mercalli Intensity) scale.
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Cobb, Ca / Light shaking (MMI IV) / rattling, vibrating / 2-5 s : That was wild | 5 users found this interesting.  
Santa Rosa California (30.8 km S of epicenter) [Map] / Light shaking (MMI IV) / 2-5 s : Sitting in my truck. It felt light someone was lightly pushing my truck side to side. | 2 users found this interesting.  
Windsor, ca (23.1 km SSW of epicenter) [Map] / Weak shaking (MMI III) / single vertical bump : Felt a sudden jump and distant sounding “bang.” Dog barked right before. Hi | 2 users found this interesting.  
Santa Rosa, CA (27.7 km S of epicenter) [Map] / Weak shaking (MMI III) / 1-2 s : shaking smoothly side to side | 2 users found this interesting.  
Calistoga / Light shaking (MMI IV) / horizontal (sideways) swinging / 5-10 s : Thought it was a truck going by, but didn't stop for several seconds. Close to about 10 seconds of side to side shaking. | One user found this interesting.  
Windsor (23.2 km SSW of epicenter) [Map] / Very weak shaking (MMI II) / 1-2 s : Heard trinkets in my room shake, that’s the only way I knew, it only went for a second but I definitely felt it. Thought someone hit my house  
Boggs Mtn, lake county, near geothermal fields (29.2 km ESE of epicenter) [Map] / Light shaking (MMI IV) / rattling, vibrating / 5-10 s : It was a shaky rattling. I was on a concrete slab of enclosed patio. Noticed the sound just as it started  
Ross, CA (89.1 km S of epicenter) [Map] / Weak shaking (MMI III) / rattling, vibrating / 1-2 s : My bed and objects around the room rattled. I thought it cou  
Healdsburg, Ca (20.5 km SW of epicenter) [Map] / Weak shaking (MMI III) / horizontal (sideways) swinging / 2-5 s : I was sitting at a table and felt a low vibration but also one gentle but very noticable swaying from left to right. The kitchen window also rattled during this  
Windsor (23.2 km SSW of epicenter) [Map] / Very weak shaking (MMI II) / 1-2 s : Heard trinkets in my room shake, that’s the only way I knew, it only went for a second but I definitely felt it. Thought someone hit my house  
Santa Rosa, CA / Light shaking (MMI IV) / very short : Felt a decent jolt followed by brief shaking of my 4 story apartment building. | 2 users found this interesting.  
Calistoga (23.9 km SE of epicenter) [Map] / Light shaking (MMI IV) / vibration and rolling / 2-5 s : I felt my bed vibrating and shaking . | One user found this interesting.  
Napa (60.6 km SE of epicenter) [Map] / Very weak shaking (MMI II) / vibration and rolling / 5-10 s : Slight small shaking about 10 seconds | One user found this interesting. (reported through our app)  
Middletown, Lake, California (9.5 km E of epicenter) [Map] / Weak shaking (MMI III) / horizontal (sideways) swinging / 2-5 s : It felt like a gust of wind was attempting to lift the building. Plexiglass protectors were shaking. | One user found this interesting.  
Healdsburg (19.1 km SW of epicenter) [Map] / Light shaking (MMI IV) / vibration and rolling / 2-5 s : Heavy rolling shake and vertical felt worse upstairs | One user found this interesting. (reported through our app)  
St. Helena, Napa, California (35.6 km SE of epicenter) [Map] / Weak shaking (MMI III) : East west east movement. 2 seconds. Heard items rattle. | One user found this interesting.  
Sebastopol, CA (41.9 km S of epicenter) [Map] / Very weak shaking (MMI II) / single lateral shake / very short : A hard shift east to west | One user found this interesting.  
Fulton road (31.2 km S of epicenter) [Map] / Very weak shaking (MMI II) / single vertical bump / very short : Window settling and nudge of couch | One user found this interesting.  
Windsor ca (23.1 km SSW of epicenter) [Map] / Very weak shaking (MMI II) / horizontal (sideways) swinging / 2-5 s : House shaking | One user found this interesting.  
Santa Rosa (31.8 km S of epicenter) [Map] / Weak shaking (MMI III) / horizontal (sideways) swinging / 10-15 s : I was on a second story and I just started moving | One user found this interesting.  
Novato, Marin, California (72 km SSE of epicenter) [Map] / Very weak shaking (MMI II) / rattling, vibrating / 1-2 s : Slight vibration that lasted a few seconds. | One user found this interesting.  
San Francisco (112.4 km SSE of epicenter) [Map] / Very weak shaking (MMI II) / 1-2 s : Apartment slightly rocking | One user found this interesting.  
Yuba City / Light shaking (MMI IV) / single lateral shake / 1-2 s : Was fast asleep and felt a large jolt and the house cracked. Felt like a truck hit the house or the front door was 8x15 feet big and someone slammed it. Weird dream?  
Sebastopol, California / Weak shaking (MMI III) / horizontal (sideways) swinging / 1-2 s : Just sitting at my desk and heard the house creaking and then a slight sway. Looked at my lamp chain to see if it was moving, and it was ever so lightly. Thanks.  
Santa Rosa. Rincon Valley / Very weak shaking (MMI II) / single vertical bump / 1-2 s : I was sitting at the computer. Sounds like a boom - like something hit the house. Then small shaking and I got nauseous. That’s my tell tale sign. Others in my household felt nothing.  
Santa Rosa California / Very weak shaking (MMI II) / complex motion difficult to describe / very short : Computer screen shook...small vibration... felt nauseous... | One user found this interesting.  
Guerneville CA / Weak shaking (MMI III) / horizontal (sideways) swinging / 2-5 s : Like gentle shake side to side | One user found this interesting.  
santa rosa / Light shaking (MMI IV) / single vertical bump / 2-5 s : was very fast | One user found this interesting.  
Santa Rosa / Very weak shaking (MMI II) / rattling, vibrating / 1-2 s : My bed shook | One user found this interesting.  
Windsor, caO / Light shaking (MMI IV) : Slight shaking like something hit my house | One user found this interesting.  
Working in Healdsburg, CA / Light shaking (MMI IV) / single vertical bump / 1-2 s : Felt the whole house shake! | One user found this interesting.  
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