M4.0 Earthquake 30km SSW of Smith Valley, NV — September 18, 2021
2021-09-18 19:20:31 UTC (2021-09-18) · approx. 11:20 AM UTC-8 local
Felt by 105 people across surrounding communities. Maximum shaking intensity MMI 4.3 (moderate).
On September 18, 2021 at 19:20 UTC, a magnitude 4.0 shallow crustal earthquake struck 30km SSW of Smith Valley, NV, at a depth of 6.8 km and coordinates 38.5468°, -119.4987°. The earthquake was reported felt by 105 peopleacross surrounding communities, with a maximum shaking intensity of Modified Mercalli Intensity (MMI) 4.3 (moderate). This earthquake was detected by 30 seismic stations with excellent location accuracy and was assigned a USGS significance rating of 293, placing it among routine seismic activity.
Physical scale: An earthquake of magnitude 4.0 releases seismic energy equivalent to roughly 14 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 331 m — a useful intuition for the size of the slip patch on the fault.
The epicenter is located in Nevada, a region characterized by Basin and Range extensional tectonics, where normal faulting accommodates east-west crustal stretching at approximately 10 mm per year. The nearest mapped fault system is the Walker Lane fault zone. View all earthquakes in Nevada.
Learn more: Magnitude scale · Aftershock sequences
What the Shaking Felt Like
At MMI 4.3 (moderate), people in the most strongly affected areas would have experienced: Mild shaking, similar to a passing truck. Hanging objects swing. Glasses and dishes may rattle. Not commonly felt outdoors.
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 105 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
Earthquake Details
-119.4987°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 4.0 earthquake near Smith Valley, NV?
The magnitude 4.0 earthquake that struck 30km SSW of Smith Valley, NV on September 18, 2021 at 19:20 UTC had a depth of 6.8 km. It was felt by 105 people with maximum shaking intensity of MMI 4.3 (moderate). For context, this was a minor earthquake typically detected only by instruments.
Where did the earthquake occur?
The earthquake epicenter was located at 38.5468°, -119.4987°, which is 30km SSW of Smith Valley, NV. View all earthquakes in Nevada.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 4.0 earthquakes can continue for several days and gradually diminish over time.
Has Nevada had earthquakes this big before?
The largest recorded earthquake in Nevada was the M7.3 Pleasant Valley earthquake of October 2, 1915. Today's magnitude 4.0 event is significantly smaller than that historical record.
Actions
Authoritative source: USGS event page (event ID: nc73626516). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2021, September 18, 2021). M4.0 Earthquake 30km SSW of Smith Valley, NV — September 18, 2021. Retrieved December 3, 2021 from https://www.earthquaketracker.org/earthquakes/event/nc73626516/