The ground under Black Hills, United States — measured by the Global Seismographic Network (IRIS/USGS) station IU RSSD and redrawn here every 15 minutes. A thin band means a quiet ground; a tall spike is a passing earthquake, near or on the other side of the planet.
| Mag | Where | When | Distance |
|---|---|---|---|
| M4.2 | 1970-01-01 00:00 UTC | 1,491 km | |
| M4.0 | 1970-01-01 00:00 UTC | 1,385 km | |
| M4.0 | 1970-01-01 00:00 UTC | 1,177 km | |
| M3.8 | 1970-01-01 00:00 UTC | 1,387 km | |
| M3.7 | 1970-01-01 00:00 UTC | 1,382 km | |
| M3.6 | 1970-01-01 00:00 UTC | 1,442 km | |
| M3.6 | 1970-01-01 00:00 UTC | 1,386 km | |
| M3.6 | 1970-01-01 00:00 UTC | 1,306 km | |
| M3.6 | 1970-01-01 00:00 UTC | 1,312 km | |
| M3.5 | 1970-01-01 00:00 UTC | 1,099 km |
| Mag | Where | When | Distance |
|---|---|---|---|
| M7.7 | 12 km WSW of Pitaloza Arriba, Panama | 1970-01-01 00:00 UTC | 4,646 km |
| M7.0 | 191 km ENE of Nagqu, China | 1970-01-01 00:00 UTC | 11,319 km |
| M6.9 | 76 km NE of Ozernovskiy, Russia | 1970-01-01 00:00 UTC | 6,806 km |
| M6.9 | 197 km WNW of Port-Olry, Vanuatu | 1970-01-01 00:00 UTC | 11,123 km |
| M6.8 | central Mid-Atlantic Ridge | 1970-01-01 00:00 UTC | 9,609 km |
| M6.7 | central Mid-Atlantic Ridge | 1970-01-01 00:00 UTC | 9,530 km |
Waves from a large earthquake reach this station minutes later — up to about 20 minutes from the far side of the Earth. Look for a spike in the helicorder at that time.