Final answer:
The statement that modern seismometers record ground motions using electronic motion detectors is true. They use this technology to measure the precise arrival times of S-waves and P-waves from seismic events, which is crucial for determining the distance to an earthquake's epicenter and the detection of underground nuclear tests.
Step-by-step explanation:
Modern seismometers do indeed record ground motions using electronic motion detectors, making the statement True. These advanced instruments can measure the arrival times of seismic waves with remarkable precision. In practice, seismographs can record the arrival times of earthquakes with a precision of 0.100 seconds. To determine the distance to the earthquake's epicenter, seismologists compare the arrival times of S-waves and P-waves, which travel at different speeds through the Earth's crust.
If we take S-waves traveling at 4.00 km/s and P-waves at 7.20 km/s in a given region, we can calculate the precision with which the distance to the source of the earthquake can be determined. Any uncertainty in these measurements, such as the precision of arrival times or the propagation speeds of the S- and P-waves, could impose limits on accurately locating the source of the seismic event, including those from underground detonations of nuclear bombs.
The use of modern seismometers equipped with geophones improves the accuracy and reliability of seismic readings by converting ground movement into voltage that can be recorded and analyzed to understand the Earth's structure. High-precision seismometer equipment, like those housed in secure facilities such as the one in the Santa Catalina Mountains, are capable of detecting seismic events from great distances. It is important to note that other factors, including the sensitivity of the detection devices and environmental noise, may limit the accuracy of seismic measurements.