Major earthquakes can cause severe damage
Earthquakes are classified by depth: shallow (0-70 km), intermediate (70-300 km), and deep (300-700 km). This event occurred at a shallow depth of 33.0 kilometers.
| Coordinates | 51.5870°N, 177.6680°W |
| Depth | 33.0 km |
| Magnitude Type | mwc |
| USGS Status | Reviewed by a seismologist |
| Reports from the Public | No reports |
| Tsunami Risk | No significant tsunami risk flagged |
Epicenter location of the Magnitude 6.9 earthquake, 78 km WSW of Adak, Alaska
A magnitude 6.9 earthquake occurred near 78 km WSW of Adak, Alaska on March 20, 1999 at 10:47 AM UTC. This shallow earthquake originated at a depth of 33.0 kilometers below the Earth's surface. The earthquake was recorded by multiple seismic monitoring stations operated by the United States Geological Survey (USGS). The mwc magnitude measurement indicates this was a magnitude event, which is the standard measurement method for earthquakes of this size. Earthquakes of magnitude 6.0 and above are classified as strong earthquakes by the USGS. This event provides valuable data for seismologists studying earthquake patterns and tectonic activity in the region.
No felt reports available for this event.
Did you feel the shaking? Your story matters—share it with the USGS to help map this quake's impact!
During an earthquake, remember to Drop, Cover, and Hold On. Stay indoors and take cover under a sturdy table or desk, protecting your head and neck. If you're outside, move to an open area away from buildings, trees, and power lines. After the shaking stops, check for injuries and damage, and be prepared for aftershocks. Residents in the affected area should be aware of potential secondary hazards that are common in your region. Prepare an emergency kit with essential supplies including water, non-perishable food, first aid supplies, flashlight, and batteries. Stay informed by following updates from local authorities and emergency services. Consider submitting a felt report to help seismologists better understand this event's impact.