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Mag. 5.1 earthquake - 24 mi east of Port Alsworth, Lake and Peninsula, Alaska, USA, on Wednesday, Nov 21, 2018, at 09:21 am (Anchorage time)

A strong magnitude 5.1 earthquake hit 39 km (24 mi) away from Port Alsworth, Alaska,  United States, in the morning of Wednesday, Nov 21, 2018 at 9.21 am local time (America/Anchorage GMT -9). The quake had a moderate depth of 127 km (79 mi) and was felt over a large region.

Mag. 5.1 earthquake - 24 mi east of Port Alsworth, Lake and Peninsula, Alaska, USA, on Wednesday, Nov 21, 2018, at 09:21 am (Anchorage time) Mag. 5.1 earthquake - 24 mi east of Port Alsworth, Lake and Peninsula, Alaska, USA, on Wednesday, Nov 21, 2018, at 09:21 am (Anchorage time)

Moderate magnitude 5.1 earthquake at 127 km depth

21 Nov 18:25 UTC: First to report: EMSC after 3 minutes.
Nov 21 18:27: Magnitude recalculated from 5.4 to 5.7.
Hypocenter depth recalculated from 151.0 to 132.0 km.
Hypocenter depth recalculated from 132.0 to 127.0 km.
Nov 21 18:31: Magnitude recalculated from 5.7 to 5.2.
Hypocenter depth recalculated from 127.0 to 110.0 km.
Nov 21 18:32: Magnitude recalculated from 5.2 to 5.1.
Hypocenter depth recalculated from 110.0 to 127.0 km.

Earthquake details

Date & timeNov 21, 2018 18:21:42 UTC
Local time at epicenterWednesday, Nov 21, 2018, at 09:21 am (America/Anchorage GMT -9)
StatusPreliminary (automatic detection)
Magnitude5.1
Depth127.0 km
Epicenter latitude / longitude60.14°N / 153.63°W Lake and Peninsula, Alaska, United States
Seismic antipode60.14°S / 26.37°E
Shaking intensityWeak shaking near epicenter
Felt74 reports
Primary data sourceEMSC (European-Mediterranean Seismological Centre)
Nearest volcanoIliamna (32 km / 20 mi)
Estimated seismic energy released2.8 x 1012 joules (783 megawatt hours, equivalent to 674 tons of TNT) | about seismic energy
Interactive map
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Nearby places

The closest larger town where the quake might have been felt is Port Alsworth, a town with 159 inhabitants in the United States, in 39 km (24 mi) distance west of the epicenter. People likely experienced weak shaking there.
The following table shows some of the places that might have been affected (or not) by the shaking.
Distance Place Max. shaking intensity(*) Region Country
39 km (24 mi)
W of epicenter
Port Alsworth
(pop: 159)
III: Weak
Lake and Peninsula, Alaska
129 km (80 mi)
SE of epicenter
Gomer
(pop: 5,520)
III: Weak
Kenai Peninsula, Alaska
133 km (82 mi)
E of epicenter
Kalifornsky
(pop: 7,850)
III: Weak
Kenai Peninsula, Alaska
138 km (86 mi)
E of epicenter
Kenai
(pop: 7,660)
III: Weak
Alaska
142 km (88 mi)
NE of epicenter
Nikiski
(pop: 4,490)
III: Weak
Kenai Peninsula, Alaska
147 km (91 mi)
E of epicenter
Soldotna
(pop: 4,540)
III: Weak
Kenai Peninsula, Alaska
164 km (102 mi)
E of epicenter
Sterling
(pop: 5,620)
III: Weak
Kenai Peninsula, Alaska
236 km (147 mi)
NE of epicenter
Anchorage
(pop: 291,200)
II: Very weak
Alaska
257 km (160 mi)
NE of epicenter
Eagle River
(pop: 24,800)
II: Very weak
Anchorage, Alaska
257 km (160 mi)
NE of epicenter
Eagle River
(pop: 24,800)
II: Very weak
Anchorage Municipality, Alaska
Notes:
(*) Shaking intensity according to the Modified Mercalli Intensity Scale (MMI) and estimated using seismic models.

User-reports for this quake (81)

We received 74 reports for this quake.
User reports estimate the perceived ground shaking intensity according to the MMI (Modified Mercalli Intensity) scale.
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Leave a comment if you find a particular report interesting or want to add to it.
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Anchorage, Keno Hills / Light shaking (MMI IV) : Did not hear it; felt like one quick, strong jolt followed by slight shaking, less than 30 seconds total.  
Eagle River west of the Glenn / Weak shaking (MMI III)
Kenai / Light shaking (MMI IV)
ANCHORAGE / Light shaking (MMI IV)
Anchorage / Weak shaking (MMI III)
South of kenai 3 miles. About 5 seconds. Light sh / Light shaking (MMI IV) : Lasted about6 seconds  
Wasilla / Light shaking (MMI IV) : I woke up to light shaking and some items rattling.  
Valdez / Moderate shaking (MMI V)
Nikiski / Light shaking (MMI IV)
Sterling, AK / Very strong shaking (MMI VII)
Seward, AK / Weak shaking (MMI III)
Soldotna AK / Moderate shaking (MMI V)
7206 Rovenna St, Anchroage, AK 99518 / Weak shaking (MMI III) : It could be felt by those sitting in rolling desk chairs, but not by most people standing. Items that hang from the ceiling were slightly swinging.  
Soldotna, AK / Strong shaking (MMI VI)
JBER Alaska / Light shaking (MMI IV)
Anchorage / Light shaking (MMI IV) : I was sleeping but then was awakened by the hard jerk of the bed and realized the whole floor was moving from  
Eagle River west of the Glenn / Weak shaking (MMI III)
Homer, Tulin Lane / Light shaking (MMI IV)
Anchorage AK / Light shaking (MMI IV) : Things rattled and the house shook a bit.  
Tesoro Refinery Nikiaki Alaska / Moderate shaking (MMI V)
soldotna / Light shaking (MMI IV)
Kasilof / Strong shaking (MMI VI)
Anchorage Oceanview area / Weak shaking (MMI III)
Cabin lake north Kenai / Light shaking (MMI IV)
KENAI / Moderate shaking (MMI V) : Initial jolt then 10sec light roll  
Kenai alaska / Moderate shaking (MMI V)
Chugiak- Eklutna Lake / Moderate shaking (MMI V) : hard jolt felt, pet birds and dog alarmed, wood stove glass broken  
Anchorage / Strong shaking (MMI VI)
Seward ,AK / Light shaking (MMI IV)
Anchorage / Very weak shaking (MMI II)
Palmer / Very weak shaking (MMI II) : I was sitting down, one light jolt and then tapered down. Palmer AK Family walking around didn't feel it.  
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What is Intensity and the Mercalli Intensity Scale?


The amount of shaking that occurs on the surface due to an earthquake is called the intensity. It is commonly measured on the so-called Modified Mercalli Intensity Scale (MMI) ranging from 1 (not felt) to 10 (extreme shaking), and given in Roman numerals as I,II,...IX, X, and often displayed with color codes ranging from light blue to dark red.
Earthquake intensity depends mainly on the magnitude and depth of the quake as well as the distance from the epicenter: The further away, the less shaking intensity occurs.
Read more about the MMI scale!

Compare Quake Data

Data for the same earthquake as reported by different agencies

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 Time GMT
2018-11-21
Epicenter Agency
5.1 127 km
79 mi
18:21:42 SOUTHERN ALASKA EMSC (European-Mediterranean Seismological Centre)
5.8 118 km
73 mi
18:21:44 - Southern Alaska
21 km (13 mi) epicenter difference with EMSC
USGS (United States Geological Survey)
5.5 114 km
71 mi
18:21:42 Southern Alaska
8.3 km (5.1 mi) epicenter difference with EMSC
GFZ (German Research Centre for Geosciences)
5.5 122 km
76 mi
18:21:42 Southern Alaska
18 km (11 mi) epicenter difference with EMSC
GeoAu (Geoscience Australia )

Seismograms

Seismic station: College Outpost, Alaska, USA (COLA/IU network) | Distance from quake: 603 km / 375 mi | Show on map | Station Info
Seismic station College Outpost, Alaska, 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: 0.02-5.0 Hz. Source: IRIS Buffer of Uniform Data (BUD) webtool
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Aftershocks for this quake

No aftershocks have been recorded so far. When aftershocks are detected, we will update this section.

What are aftershocks?


Larger earthquakes (above magnitude 5 or so) such as this one are usually followed by smaller ones known as aftershocks that occur in the same area during the days, weeks, months or even years after the main shock.
[More info]

What about this quake?


Based on its magnitude, the fault that was active during the quake likely ruptured beneath a surface of approx. 13 km2 (=5 sqare miles) as a first-order estimate. The length of the rupture zone thus was probably around 6 km (4 mi).
[More info]


Recorded aftershocks, latest first (0 quake)

Date and Time GMTMag
Depth
DistanceRegionDetails
Nov 21, 2018 09:21 am (Anchorage)
5 years ago - felt
5.1

127 km
0 km - This quake24 mi E of Port Alsworth, Lake and Peninsula, Alaska, USA
Main Shock (this quake)
More

Map of aftershocks

Earthquake statistics

Average number of earthquakes

Based on data from the past 10 years and our earthquake archive back to 1900, there are about 15,000 quakes on average per year in the area near the epicenter of this quake (within 100 km/61 mi):
  • Mag. 6 or higher: 0.06 quakes per year (or 1 quake every 15.6 years)
  • Mag. 5 or higher: 0.78 quakes per year (or 1 quake every 1.3 years)
  • Mag. 4 or higher: 9.3 quakes per year
  • Mag. 3 or higher: 45 quakes per year
  • Mag. 2 or higher: 580 quakes per year (or 48 quakes per month)
  • Mag. 1 or higher: 1,400 quakes per year (or 3.7 quakes per day)
The area where this quake occurred has a high level of seismic activity. It has had at least 8 quakes above magnitude 6 since 1900, which suggests that larger earthquakes of this size occur infrequently, probably on average approximately every 15 to 20 years.

Number of quakes per year

Previous quakes in the same area of this earthquake

Map of earlier quakes in the area of this quake

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Map to embed or share

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