M1.8 earthquake 9 km SSE of Copperopolis, California
A magnitude 1.8 earthquake struck 9 km SSE of Copperopolis, California on Mon, Apr 13, 1987, 2:36 PM PDT (21:36 UTC), 6 km (4 mi) below the surface.
A larger quake followed: M2.5 1 km S of Mokelumne Hill, California. This one was a foreshock.
Map
Where this earthquake was located, with the others nearby. Select one for its page.
The earthquake
- Magnitude
- 1.8 (Md, duration), micro
- Magnitude from
- Northern California Seismic System
- Local time
- UTC
- 1987-04-13 21:36:09 UTC
- Depth
- 6.2 km (3.9 mi), shallow
- Epicenter
- 37.911° N, 120.589° W
- Region
- California
- Tsunami flag
- No
- Status
- Reviewed by a seismologist
Did you feel it?
No one has reported feeling this quake to the USGS.
How well it is located
Reviewed by a seismologist.
- Location uncertainty
- About 5.1 km horizontally, 5.4 km in depth
- Magnitude uncertainty
- ±0.01
- Depth from
- From location
- Station coverage gap
- 212°, poorly surrounded by stations
- Stations used
- 5
Nearest places
Distance and direction from each place to the epicenter, with its forecast.
Nearby
Within 100 km, magnitude 1.5 and up: 6 in the 60 days after this one and 4 in the 30 days before it.
After
- 1.95 km SW of Mokelumne Hill, California · 14411 days ago · 0 km deep · 41 km away
- 1.84 km SSW of Mokelumne Hill, California · 14405 days ago · 1 km deep · 41 km away
- 2.012 km SSW of Bootjack, California · 14392 days ago · 5 km deep · 83 km away
- 2.51 km S of Mokelumne Hill, California · 14387 days ago · 0 km deep · 43 km away
- 1.812 km SW of Chinese Camp, California · 14384 days ago · 5 km deep · 15 km away
- 2.07 km WNW of Coarsegold, California · 14355 days ago · 3 km deep · 99 km away
Before
- 2.013 km SSW of Bootjack, California · 14422 days ago · 36 km deep · 85 km away
- 2.07 km SW of Mountain House, California · 14425 days ago · 15 km deep · 91 km away
- 1.714 km SE of Catheys Valley, California · 14427 days ago · 5 km deep · 83 km away
- 2.616 km SSE of Catheys Valley, California · 14429 days ago · 13 km deep · 85 km away
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Sources
From the USGS Earthquake Hazards Program and its partner networks, event nc10083666. Read Thu, Oct 1, 2026, 3:58 AM UTC.