The ground under Manteigas, Portugal — measured by the GEOFON network (GFZ Potsdam) station GE MTE 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 |
|---|---|---|---|
| M7.7 | 12 km WSW of Pitaloza Arriba, Panama | 1970-01-01 00:00 UTC | 8,043 km |
| M7.0 | 191 km ENE of Nagqu, China | 1970-01-01 00:00 UTC | 8,589 km |
| M6.9 | 76 km NE of Ozernovskiy, Russia | 1970-01-01 00:00 UTC | 9,638 km |
| M6.9 | 197 km WNW of Port-Olry, Vanuatu | 1970-01-01 00:00 UTC | 17,010 km |
| M6.8 | central Mid-Atlantic Ridge | 1970-01-01 00:00 UTC | 4,695 km |
| M6.7 | central Mid-Atlantic Ridge | 1970-01-01 00:00 UTC | 4,644 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.