M4.0 Earthquake 6 km SSE of Guánica, Puerto Rico — October 6, 2020
2020-10-06 23:03:02 UTC (2020-10-06) · approx. 7:03 PM UTC-4 local
Felt by 32 people across nearby locations. Maximum shaking intensity MMI 4.4 (moderate).
On October 6, 2020 at 23:03 UTC, a magnitude 4.0 shallow crustal earthquake struck 6 km SSE of Guánica, Puerto Rico, at a depth of 6.0 km and coordinates 17.9193°, -66.8908°. The earthquake was reported felt by 32 peopleacross nearby locations, with a maximum shaking intensity of Modified Mercalli Intensity (MMI) 4.4 (moderate). The USGS PAGER system issued a green alert level for this event, indicating no significant casualties or damage expected. This earthquake was detected by 26 seismic stations with moderate location accuracy and was assigned a USGS significance rating of 268, placing it among routine seismic activity. The nearest populated place is Guanica (population 9,224).
Physical scale: An earthquake of magnitude 4.0 releases seismic energy equivalent to roughly 18 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 375 m — a useful intuition for the size of the slip patch on the fault.
The epicenter is located in Puerto Rico, a region characterized by the Puerto Rico Trench oblique subduction zone and the Muertos Trough, with complex Caribbean–North American plate interactions. The nearest mapped fault system is the Puerto Rico Trench. View all earthquakes in Puerto Rico.
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 32 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 | 313,057 |
| MMI 4 | light | 68,709 |
| MMI 5 | moderate | 97 |
Earthquake Details
-66.8908°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 4.0 earthquake near Guánica, Puerto Rico?
The magnitude 4.0 earthquake that struck 6 km SSE of Guánica, Puerto Rico on October 6, 2020 at 23:03 UTC had a depth of 6.0 km. It was felt by 32 people with maximum shaking intensity of MMI 4.4 (moderate). For context, this was a light earthquake commonly felt near the epicenter.
Where did the earthquake occur?
The earthquake epicenter was located at 17.9193°, -66.8908°, which is 6 km SSE of Guánica, Puerto Rico. The nearest populated place is Guanica (population 9,224). View all earthquakes in Puerto Rico.
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 Puerto Rico had earthquakes this big before?
The largest recorded earthquake in Puerto Rico was the M7.3 offshore earthquake of October 11, 1918. Today's magnitude 4.0 event is significantly smaller than that historical record.
Authoritative source: USGS event page (event ID: pr2020280013). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2020, October 6, 2020). M4.0 Earthquake 6 km SSE of Guánica, Puerto Rico — October 6, 2020. Retrieved December 12, 2020 from https://www.earthquaketracker.org/earthquakes/event/pr2020280013/