Figure 14.26
Seismographs.Seismographs are anchored to the ground and record Earth movement on paper. The paper record is called a seismogram. (A) Traditional seismographs consist of a box attached to bedrock. Inside the box is a heavy pendulum with an ink pen attached to it. When the ground shakes, the pendulum remains stationary, recording the movement on a seismogram. (B) Modern electronic seismographs use a stationary magnet and a wire coil to generate an electronic signal. Greater Earth movement creates a stronger voltage that moves the needle more.(B. © Zephyr/Science Source)