9.  How do scientists find out the intensity and duration of Earthquakes?*1 pointSeismic wavesSeismographSeismogramSeismos

Scientists find out the intensity and duration of earthquakes using a seismograph. Here's the step-by-step process:

1. An earthquake occurs and sends out seismic waves in all directions.

2. These seismic waves reach the seismograph. The seismograph is a device that has a base fixed to the ground and a free hanging weight with a pen attached to it. When the ground shakes, the base of the seismograph shakes with it, but the hanging weight does not move due to inertia.

3. As a result, the pen attached to the hanging weight records a trace on a paper that is fixed to the base of the seismograph. This trace is a record of the ground motion at the seismograph's location and is called a seismogram.

4. Scientists then analyze the seism