M5.5 Earthquake 61 km NE of Masjed Soleym?n, Iran — October 4, 2021
2021-10-04 02:39:28 UTC (2021-10-04) · approx. 5:39 AM UTC+3 local
Felt by 25 people across nearby locations. Maximum shaking intensity MMI 6.3 (very strong).
On October 4, 2021 at 02:39 UTC, a magnitude 5.5 shallow crustal earthquake struck 61 km NE of Masjed Soleym?n, Iran, at a depth of 13.0 km and coordinates 32.3350°, 49.7618°. The earthquake was reported felt by 25 peopleacross nearby locations, with a maximum shaking intensity of Modified Mercalli Intensity (MMI) 6.3 (very strong). The USGS PAGER system issued a green alert level for this event, indicating no significant casualties or damage expected. The nearest populated place is Qal`eh-ye Khvajeh (population 0).
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 3.8 km — a useful intuition for the size of the slip patch on the fault.
The epicenter is located in Iran, a region characterized by the Zagros fold-and-thrust belt, where the Arabian Plate collides with Eurasia at 20-25 mm per year. The nearest mapped fault system is the Zagros Fault. View all earthquakes in Iran.
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 25 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 | 12,762,387 |
| MMI 4 | light | 1,363,957 |
| MMI 5 | moderate | 7,415 |
| MMI 6 | strong | 1,455 |
Earthquake Details
49.7618°E
Technical Information
Common Questions
How strong was the magnitude 5.5 earthquake near Masjed Soleym?n, Iran?
The magnitude 5.5 earthquake that struck 61 km NE of Masjed Soleym?n, Iran on October 4, 2021 at 02:39 UTC had a depth of 13.0 km. It was felt by 25 people with maximum shaking intensity of MMI 6.3 (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 32.3350°, 49.7618°, which is 61 km NE of Masjed Soleym?n, Iran. The nearest populated place is Qal`eh-ye Khvajeh (population 0). View all earthquakes in Iran.
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.
Has Iran had earthquakes this big before?
The largest recorded earthquake in Iran was the M7.8 Tabas earthquake of September 16, 1978. Today's magnitude 5.5 event is significantly smaller than that historical record.
Actions
Location
Authoritative source: USGS event page (event ID: us6000frf2). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2021, October 4, 2021). M5.5 Earthquake 61 km NE of Masjed Soleym?n, Iran — October 4, 2021. Retrieved December 22, 2025 from https://www.earthquaketracker.org/earthquakes/event/us6000frf2/