The ground under Sondre Stromfjord, Greenland — measured by the GEOFON network (GFZ Potsdam) station GE SFJD 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 |
|---|---|---|---|
| M5.5 | Reykjanes Ridge | 1970-01-01 00:00 UTC | 1,359 km |
| M5.3 | Reykjanes Ridge | 1970-01-01 00:00 UTC | 1,417 km |
| M5.2 | Reykjanes Ridge | 1970-01-01 00:00 UTC | 1,360 km |
| M5.0 | Reykjanes Ridge | 1970-01-01 00:00 UTC | 1,398 km |
| M5.0 | Reykjanes Ridge | 1970-01-01 00:00 UTC | 1,410 km |
| M5.0 | Reykjanes Ridge | 1970-01-01 00:00 UTC | 1,333 km |
| M5.0 | Reykjanes Ridge | 1970-01-01 00:00 UTC | 1,342 km |
| M4.8 | Reykjanes Ridge | 1970-01-01 00:00 UTC | 1,401 km |
| M4.7 | Reykjanes Ridge | 1970-01-01 00:00 UTC | 1,370 km |
| M4.3 | 1970-01-01 00:00 UTC | 1,268 km |
| Mag | Where | When | Distance |
|---|---|---|---|
| M7.7 | 12 km WSW of Pitaloza Arriba, Panama | 1970-01-01 00:00 UTC | 6,987 km |
| M7.0 | 191 km ENE of Nagqu, China | 1970-01-01 00:00 UTC | 8,564 km |
| M6.9 | 76 km NE of Ozernovskiy, Russia | 1970-01-01 00:00 UTC | 6,580 km |
| M6.9 | 197 km WNW of Port-Olry, Vanuatu | 1970-01-01 00:00 UTC | 13,564 km |
| M6.8 | central Mid-Atlantic Ridge | 1970-01-01 00:00 UTC | 7,880 km |
| M6.7 | central Mid-Atlantic Ridge | 1970-01-01 00:00 UTC | 7,807 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.