M5.5 Earthquake near Lake Almanor Earthquake — May 11, 2023
2023-05-11 23:19:41 UTC (2023-05-11) · approx. 3:19 PM UTC-8 local
Felt by 7,030 people across a wide area. Maximum shaking intensity MMI 6.4 (very strong).
On May 11, 2023 at 23:19 UTC, a magnitude 5.5 shallow crustal earthquake struck near Lake Almanor Earthquake, at a depth of 5.8 km and coordinates 40.2042°, -121.1095°. The earthquake was reported felt by 7,030 peopleacross a wide area, with a maximum shaking intensity of Modified Mercalli Intensity (MMI) 6.4 (very strong). The USGS PAGER system issued a green alert level for this event, indicating no significant casualties or damage expected. This earthquake was detected by 54 seismic stations with excellent location accuracy and was assigned a USGS significance rating of 1072, making it one of the most significant global earthquakes in recent days. The nearest populated place is Greenville (population 1,129).
Physical scale: An earthquake of magnitude 5.5 releases seismic energy equivalent to roughly 3 kilotons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 3.6 km — a useful intuition for the size of the slip patch on the fault.
Nearest Populated Places
What the Shaking Felt Like
At MMI 6.4 (very strong), people in the most strongly affected areas would have experienced: Strong shaking felt by everyone. Heavy furniture may move. Books fall from shelves. Plaster and chimneys may crack. Damage is generally slight in well-built structures.
ShakeMap — predicted shaking intensity
Modeled ground-motion intensity contoured on the Modified Mercalli scale (MMI). Computed by the USGS from the moment-tensor solution and regional ground-motion prediction equations.
Source: U.S. Geological Survey ShakeMap. View interactive ShakeMap on USGS
Did You Feel It? — community-reported shaking
Aggregated felt-report intensity from 7,030 citizen responses to the USGS Did You Feel It? system. Each colored zone represents the average MMI from reports in that area.
Source: U.S. Geological Survey Did You Feel It?. View on USGS · submit your own report
Population exposure (USGS PAGER)
Estimated population that experienced each level of shaking. Based on the USGS PAGER rapid impact assessment, which combines ShakeMap output with global population grids.
| Shaking intensity (MMI) | Description | Population exposed |
|---|---|---|
| MMI 3 | weak | 3,146,688 |
| MMI 4 | light | 88,882 |
| MMI 5 | moderate | 8,368 |
| MMI 6 | strong | 1,237 |
Earthquake Details
-121.1095°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 5.5 earthquake near Lake Almanor Earthquake?
The magnitude 5.5 earthquake that struck near Lake Almanor Earthquake on May 11, 2023 at 23:19 UTC had a depth of 5.8 km. It was felt by 7,030 people with maximum shaking intensity of MMI 6.4 (very strong). For context, this was a moderate earthquake that could be widely felt.
Where did the earthquake occur?
The earthquake epicenter was located at 40.2042°, -121.1095°, which is near Lake Almanor Earthquake. The nearest populated place is Greenville (population 1,129).
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 5.5 earthquakes can continue for days to weeks and gradually diminish over time.
Actions
Authoritative source: USGS event page (event ID: nc73886731). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2023, May 11, 2023). M5.5 Earthquake near Lake Almanor Earthquake — May 11, 2023. Retrieved April 26, 2025 from https://www.earthquaketracker.org/earthquakes/event/nc73886731/