Can seismic waves from the other side of the globe be recorded?
As earthquake waves travel along the surface of the Earth, they cause the ground to move. The ground motions can be captured and displayed as a movie, providing a visual demonstration of these often indiscernible movements. The visualizations, using actual data, show how the ground moves as seismic waves sweep across about 400 earthquake recording stations in EarthScope’s Transportable Array (USArray, www.usarray.org/)). These innovative visualizations have been created for selected large earthquakes that have taken place in the US and around the world.
The visualizations illustrate how seismic waves travel away from an earthquake. Because the array’s seismometers are closely spaced in a grid pattern with unprecedented density, the recorded wave amplitudes at each seismometer clearly show through time how wave after wave progresses along the great circle path from the earthquake’s epicenter.
Two types of GMVs are produced:
- Vertical-component GMV:
Produced for US events of magnitude 5.5 or larger and global events of magnitude 6 or larger. The symbol colors represent the amplitude of the vertical ground motion, as detected by the station's seismometer.
- 3-Component GMV:
Produced only for events with magnitude 7 and larger use 'tailed' symbols to show direction and amplitude of the normalized horizontal motion. Symbol colors also represent the amplitude of the vertical ground motion, as detected by the station's seismometer.
- Seismic waves leave an earthquake in all directions.
- P, S, and Surface waves travel in predicable patterns.