Earthquake near Loyola, CA

No: USGS classifies this as a quarry blast, not an earthquake. A magnitude 1.8 quarry blast was recorded 3 km (2 mi) S of Loyola, CA, at 2:15 pm PDT on 28 April 2016 (21:15 UTC), less than 1 km deep.

This was on 28 April 2016. The latest near Loyola: M 2.5 on 19 September 2026.

USGS: 3 km S of Loyola, California

25 km (16 mi) W of San Jose, CA · in Cupertino, CA

2:15 pm PDT, Apr 28, 2016 · 2016-04-28 21:15 UTC · -0.3 km deep · released about 13 lb of TNT

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Distance rings around the epicentre, with the nearest towns at their true direction and later quakes as coloured dots. Not a shaking map — see the USGS ShakeMap for that.

When: 2:15 pm PDT on 28 April 2016 (2016-04-28 21:15 UTC)
Where: 3 km (2 mi) S of Loyola, CA · earthquakes near Loyola
Magnitude: M 1.8 (md)
Depth: -0.3 km below the surface
Felt: no reports yet
Nearest: San Mateo County, 26 km WNW
Nearest mapped fault: Monte Vista-Shannon fault, 1 km from its surface trace — near is not the same as on
Status: Reviewed by a seismologist

USGS · last changed by USGS 3532 days ago · we first saw it 3532 days ago

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 13 km (8 mi) from the epicentre. In Loyola, 3 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: Loyola 3 km, intensity II · Cupertino 6 km, intensity II · Los Altos 7 km, intensity II · Mountain View 7 km, intensity II · Sunnyvale 8 km, intensity II · Saratoga 9 km, intensity II · Stanford 13 km, intensity II. Estimated for each town centre; each link is that town's own record.

USGS catalogues this as quarry blast, not an earthquake.

How big was it?

This earthquake released about 13 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.8 would have released about 32 times as much.

Mineral, Virginia 2011 M 5.8 1,200,000× the energy of this one
Magna, Utah 2020 M 5.7 840,000× the energy of this one
Around the size people start to feel M 3.0 75× the energy of this one
This earthquake M 1.8 about 13 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

No earthquake of M4 or more has been recorded within 50 km since our catalogue begins in 2016.

Before 2016, the USGS record lists 19 earthquakes of M5 or more within 50 km; the five largest:

6.9 The 1989 Loma Prieta, California Earthquake · 37 km SSE of this epicentre Oct 18, 1989
6.5 Near Morgan Hill, California · 47 km ESE of this epicentre Jul 1, 1911
6.3 16 km SW of Davenport, California · 49 km SSW of this epicentre Oct 22, 1926
6.2 Near San Jose, California · 27 km E of this epicentre Aug 3, 1903
6.2 The 1984 Morgan Hill, California Earthquake · 37 km E of this epicentre Apr 24, 1984

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

Map loads when it scrolls into view

Nearby places

Place	Distance	Direction from the epicentre
San Mateo County, CA	26 km (16 mi)	WNW	earthquakes near San Mateo County
Santa Cruz County, CA	35 km (22 mi)	SSE	earthquakes near Santa Cruz County
Santa Clara County, CA	38 km (24 mi)	ESE	earthquakes near Santa Clara County
Alameda County, CA	40 km (25 mi)	NNE	earthquakes near Alameda County
Contra Costa County, CA	68 km (42 mi)	N	earthquakes near Contra Costa County
San Francisco County, CA	94 km (58 mi)	WNW	earthquakes near San Francisco County

Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.

Aftershocks so far

40 earthquakes have been recorded within 50 km since this one.

1.8 5 km SSE of Loyola, California 23:19 UTC
1.7 15 km WNW of Davenport, California 14:11 UTC
2.2 9 km NNE of East Foothills, California 09:02 UTC
1.6 6 km ENE of East Foothills, California 20:35 UTC
1.6 3 km S of Loyola, California 17:22 UTC
1.7 8 km SSE of Sunol, California 21:32 UTC
1.6 8 km S of Sunol, California 14:04 UTC
1.6 4 km NNE of Half Moon Bay, California 20:15 UTC
1.6 3 km S of Loyola, California 17:18 UTC
1.8 1 km NE of Pacifica, California 00:26 UTC
1.7 18 km SSE of Livermore, California 09:16 UTC
2.4 6 km E of Milpitas, California 03:06 UTC
1.7 2 km SW of Portola Valley, California 19:05 UTC
1.6 1 km NE of Pacifica, California 18:49 UTC
1.6 14 km E of Seven Trees, California 04:37 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 09:27 UTC. 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.