Moderate mag. 4.0 earthquake - 16 mi northwest of Ukiah, Mendocino County, California, USA, on Wednesday, Mar 24, 2021 at 8:41 am (GMT -7) -

Moderate magnitude 4.0 earthquake at 8 km depth

24 Mar 15:42 UTC: First to report: USGS after 1 minute.
24 Mar 15:44: Magnitude recalculated from 4.0 to 3.8. Hypocenter depth recalculated from 9.0 to 6.6 km (from 5.6 to 4.1 mi).
... [show all] ...
24 Mar 21:52: Hypocenter depth recalculated from 8.5 to 8.2 km (from 5.3 to 5.1 mi).

Update Wed, 24 Mar 2021, 15:48

Small earthquake of magnitude 3.8 just reported 16 miles northwest of Ukiah, California, United States

3.8 quake 24 Mar 8:41 am (GMT -7)

The United States Geological Survey reported a magnitude 3.8 quake in the United States near Ukiah, Mendocino County, California, only 7 minutes ago. The earthquake hit in the morning on Wednesday 24 March 2021 at 8:41 am local time at a very shallow depth of 4.1 miles. 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.
Our monitoring service identified a second report from the European-Mediterranean Seismological Centre (EMSC) which listed the quake at magnitude 3.8 as well.
Based on the preliminary seismic data, the quake should not have caused any significant damage, but was probably felt by many people as light vibration in the area of the epicenter.
Weak shaking might have been felt in Comptche (pop. 160) located 6 miles from the epicenter, Willits (pop. 4,900) 13 miles away, Redwood Valley (pop. 1,700) 14 miles away, and Brooktrails (pop. 3,200) 15 miles away.
Other towns or cities near the epicenter where the quake might have been felt as very weak shaking include Ukiah (pop. 15,900) located 16 miles from the epicenter, Fort Bragg (pop. 7,300) 23 miles away, and Clearlake (pop. 15,200) 50 miles away.

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Earthquake data

Earthquake details

Date & time	Mar 24, 2021 15:41:13 UTC -
Local time at epicenter	Wednesday, Mar 24, 2021 at 8:41 am (GMT -7)
Status	Confirmed
Magnitude	4
Depth	8.2 km
Epicenter latitude / longitude	39.24483°N / 123.47433°W (Mendocino, California, United States)
Antipode	39.245°S / 56.526°E
Shaking intensity	Light shaking
Felt	9 reports
Primary data source	USGS (United States Geological Survey)
Nearest volcano	Clear Lake (68 km / 42 mi)
Nearby towns and cities	10 km (6 mi) ESE of Comptche (pop: 159) \| Show on map \| Quakes nearby 21 km (13 mi) SSW of Little Lake (pop: 4,860) \| Show on map \| Quakes nearby 23 km (15 mi) W of Redwood Valley (pop: 1,730) \| Show on map \| Quakes nearby 25 km (16 mi) WNW of Ukiah (pop: 15,900) \| Show on map \| Quakes nearby 28 km (17 mi) NNW of Boonville (pop: 1,040) \| Show on map \| Quakes nearby 36 km (22 mi) SE of Fort Bragg (Mendocino County) (pop: 7,290) \| Show on map \| Quakes nearby 80 km (50 mi) WNW of Clearlake (Lake County) (pop: 15,200) \| Show on map \| Quakes nearby 96 km (60 mi) NW of Windsor (Sonoma County) (pop: 27,500) \| Show on map \| Quakes nearby 111 km (69 mi) NW of Santa Rosa (pop: 175,000) \| Show on map \| Quakes nearby 187 km (116 mi) WNW of Sacramento (pop: 490,700) \| Show on map \| Quakes nearby
Weather at epicenter at time of quake	Clear Sky 6.1°C (43 F), humidity: 75%, wind: 2 m/s (3 kts) from N
Estimated seismic energy released	6.3 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.	Depth	Location	Source
4.0	8.2 km	21km SSW of Willits, CA, USA	USGS
4.0	8 km	NORTHERN CALIFORNIA, USA	EMSC

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User reports for this quake (11)

User reports estimate the perceived ground shaking intensity according to the MMI (Modified Mercalli Intensity) scale.

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near Bodega Bay, Sonoma, California (110.5 km SSE of epicenter) [Map] / Strong shaking (MMI VI) / single lateral shake / 1-2 s : I was lying on my temper-pedic mattress on bed, awake, when a very strong vertical shake was felt -- just once. I live between Ukiah and Comptche, off of Orr Springs Rd, (9 miles from Ukiah) on Running Springs Rd.-- 3.65 miles south of Orr Springs Rd. It | 4 users found this interesting.

Redwood Valley, Reeves Canyon Rd 5.5 miles from Hw / not felt : Experienced as redwood duff suddenly falling with a sprinkling sound on the metal roof or our cabin. It was very strange and inexplicable as there was no wind in our canyon this morning. It wasn’t til later that we thought it might have been an earthqua | One user found this interesting.

Willits (17.1 km NE of epicenter) [Map] / Light shaking (MMI IV) / 1-2 s

lower merion PA (4088.9 km ENE of epicenter) [Map] / Weak shaking (MMI III) / rattling, vibrating

Albion (23.2 km WSW of epicenter) [Map] / Light shaking (MMI IV) / single lateral shake / very short

Willits (17.1 km NE of epicenter) [Map] / Light shaking (MMI IV) / 1-2 s

near Redwood Valley, Mendocino, California (13 km ESE of epicenter) [Map] / Moderate shaking (MMI V)

Kelseyville , downtown about 245 am Aug 8 / Weak shaking (MMI III) / 15-20 s : I thought somebody was outside my trailer rocking it back and forth I turn my TV down to stop and then I feel the aftershocks a little bit later

San Rafael, CA / not felt

San Bruno / Very weak shaking (MMI II)

mendocino / Weak shaking (MMI III)

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