M4.3 Earthquake 22 km S of Naalehu, Hawaii — October 10, 2021
2021-10-10 21:53:08 UTC (2021-10-10) · approx. 11:53 AM UTC-10 local
Felt by 19 people across nearby locations.
On October 10, 2021 at 21:53 UTC, a magnitude 4.3 shallow crustal earthquake struck 22 km S of Naalehu, Hawaii, at a depth of 36.0 km and coordinates 18.8680°, -155.5420°. The earthquake was reported felt by 19 peopleacross nearby locations, with a maximum shaking intensity of Modified Mercalli Intensity (MMI) 3.8 (light). The USGS PAGER system issued a green alert level for this event, indicating no significant casualties or damage expected. This earthquake was detected by 48 seismic stations with moderate location accuracy and was assigned a USGS significance rating of 287, placing it among routine seismic activity. The nearest populated place is Hawaiian Ocean View (population 4,437).
Physical scale: An earthquake of magnitude 4.3 releases seismic energy equivalent to roughly 37 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 524 m — a useful intuition for the size of the slip patch on the fault.
The epicenter is located in Hawaii, a region characterized by intraplate volcanic activity over the Hawaiian mantle plume hotspot, with seismicity driven by magma intrusion and flank instability. View all earthquakes in Hawaii.
Learn more: Magnitude scale · Aftershock sequences
Nearest Populated Places
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 19 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 | 6,922 |
| MMI 4 | light | 10 |
Earthquake Details
-155.5420°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 4.3 earthquake near Naalehu, Hawaii?
The magnitude 4.3 earthquake that struck 22 km S of Naalehu, Hawaii on October 10, 2021 at 21:53 UTC had a depth of 36.0 km. It was felt by 19 people with maximum shaking intensity of MMI 3.8 (light). For context, this was a light earthquake commonly felt near the epicenter.
Where did the earthquake occur?
The earthquake epicenter was located at 18.8680°, -155.5420°, which is 22 km S of Naalehu, Hawaii. The nearest populated place is Hawaiian Ocean View (population 4,437). View all earthquakes in Hawaii.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 4.3 earthquakes can continue for several days and gradually diminish over time.
Has Hawaii had earthquakes this big before?
The largest recorded earthquake in Hawaii was the M7.9 Ka'u District earthquake of April 2, 1868. Today's magnitude 4.3 event is significantly smaller than that historical record.
Authoritative source: USGS event page (event ID: hv72748787). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2021, October 10, 2021). M4.3 Earthquake 22 km S of Naalehu, Hawaii — October 10, 2021. Retrieved December 18, 2021 from https://www.earthquaketracker.org/earthquakes/event/hv72748787/