21.   Scientists track underground nuclear blasts and earthquakes in the same way, measuring the seismic waves they send out through the earth, often over extremely long distances.

22.   Seconds after the federal building blast, the seismograph detected two seismic waves rippling across the flat Oklahoma countryside.

23.   The cometary impacts may have set in motion the same kind of seismic waves generated by terrestrial earthquakes, waves capable of traveling all the way through a planet.

24.   The catastrophic seismic waves that hit Papua New Guinea last week could be repeated anywhere along the West Coast of the United States, experts say.

25.   The idea is reinforced by seismic analysis indicating the object reflects seismic waves in a more complicated manner than ordinary oceanic crust.

26.   The inner core has a narrow region where seismic waves move unusually fast, perhaps because atoms are aligned in a particular direction.

27.   The researchers suggest that seismic waves from a far-off earthquake could increase the pressure within the chamber enough to make the volcano blow its top prematurely.

28.   The seismic waves cause the frame to move by a few micrometers, and an optical sensor detects the relative motion between frame and plate.

29.   The seismic waves from Landers, Linde says, did just that.

30.   The speed with which seismic waves travel through the Earth varies according to factors such as ground density and composition.