Earthquake · reviewed by a seismologist
M 1.7ml
Earthquake near Portola, CA
No earthquake was likely felt in Portola in the 24 hours to 4:50 am PST (12:50 UTC). The last one was M 2.7, 8 km (5 mi) N, at 8:16 am PST on 10 November 2026, estimated intensity III (weak) in town; 9 felt reports to USGS. Every earthquake near Portola
This page: a magnitude 1.7 earthquake was recorded 9 km (6 mi) south-southeast of Portola, CA, at 7:13 am PST on 17 December 2018 (15:13 UTC), 2.6 km deep.
USGS: 8 km NNE of Calpine, California
53 km (33 mi) WNW of Reno, NV
- When
- 7:13 am PST on 17 December 2018 ()
- Where
- 9 km (6 mi) south-southeast of Portola, CA · earthquakes near Portola
- Magnitude
- M 1.7 (ml)
- Depth
- 2.6 km below the surface
- Felt
- no reports yet
- Nearest
- Sierra County, 20 km SSW
- Nearest mapped fault
- Mohawk Valley fault, 9 km from its surface trace — near is not the same as on
- Status
- Reviewed by a seismologist
USGS · last changed by USGS · we first saw it 2888 days ago
Earthquake alerts for Portola, CA
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Alerts are on for .
Not a warning. An alert comes after USGS publishes a quake, usually minutes after the shaking. For early warning use ShakeAlert, through your phone's Wireless Emergency Alerts or the MyShake app.
This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.
At this magnitude and depth, people at rest would likely notice it out to about 12 km (7 mi) from the epicentre. In Portola, 9 km away, the estimate is intensity II (weak). Estimated from magnitude, depth and distance with the intensity equation USGS Did You Feel It? uses; felt reports, where there are any, are the measurement.
Likely felt in: Portola 9 km, intensity II. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 11 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.7 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 1,400,000× the energy of this one
- Magna, Utah 2020 M 5.7 1,000,000× the energy of this one
- Around the size people start to feel M 3.0 89× the energy of this one
- This earthquake M 1.7 about 11 lb of TNT
Energy from the Gutenberg–Richter relation (log10E = 1.5M + 4.8), rounded to two figures; bar length is magnitude, which is already a logarithm of energy. Magnitudes of past earthquakes from the USGS catalogue.
For this area
The largest earthquake within 50 km since 2016 was M 4.5 on 2016-08-04 — about 15,000 times the energy of this one.
Before 2016, the USGS record lists 9 earthquakes of M5 or more within 50 km; the five largest:
- 6.0 6 km WNW of Verdi, California · 35 km SE of this epicentre
- 5.9 9 km NW of Truckee, California · 40 km SSE of this epicentre
- 5.6 6 km NNE of Doyle, California · 48 km NE of this epicentre
- 5.6 5 km NE of Loyalton, California · 18 km E of this epicentre
- 5.3 11 km N of Soda Springs, California · 34 km S of this epicentre
Since 2016: the QuakeIndex catalogue (US, M1.5+), built from the USGS FDSN event service. Before 2016: USGS ComCat, M5+ from 1900. Distances are between epicentres. This is the record, not a forecast.
Where
Epicentre 39.7379, -120.4119. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Sierra County, CA | 20 km (13 mi) | SSW | earthquakes near Sierra County |
| Plumas County, CA | 45 km (28 mi) | NW | earthquakes near Plumas County |
| Nevada County, CA | 58 km (36 mi) | SSW | earthquakes near Nevada County |
| Placer County, CA | 80 km (50 mi) | SSW | earthquakes near Placer County |
| Storey County, NV | 83 km (52 mi) | ESE | earthquakes near Storey County |
| Carson City, NV | 87 km (54 mi) | SE | earthquakes near Carson City |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
51 earthquakes have been recorded within 50 km since this one.
- 1.5 9 km NNW of Truckee, California
- 1.5 16 km SE of Sierraville, California
- 2.1 19km W of Truckee, CA
- 1.5 6 km SSE of Sierraville, California
- 1.6 7 km SSE of Sierraville, California
- 2.3 10km ESE of Taylorsville, CA
- 1.9 4km SSE of Johnsville, CA
- 2.3 11km NE of Cromberg, CA
- 2.3 2km ESE of Johnsville, CA
- 1.5 14 km SSE of Sierraville, California
- 2.1 19km SSW of Whitehawk, CA
- 1.6 7 km SSE of Sierraville, California
- 1.9 3km SE of Taylorsville, CA
- 2.3 10km NNW of Truckee, CA
- 2.4 4km SE of Taylorsville, CA
Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of . QuakeIndex does not forecast aftershocks. When USGS issues an operational aftershock forecast it appears on the USGS event page.
On USGS
- The official USGS event page — the source of record for every value above
- Did you feel it? Report it to USGS — reports go to USGS, not to us
- ShakeMap for this event, when USGS has produced one
QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.