Whenever we hear news about an earthquake in any part of the world, the following phrase or word will be about the earthquake's intensity to know what damage it caused. Seismographs are the indicator that helps you know the ground motion during the earthquake and helps you see the earthquake's intensity. A simple seismograph is a sensitive device that detects the shaking of the Earth's crust during the earthquake.
A seismograph is securely mounted onto the Earth's surface so that when the Earth bounces, the entire unit shakes with it except the mass on the spring, which has inertia and remains in place without any shakes. As the seismograph shakes under the mass of the Earth, the recording device on the mass records the relative motion on the rest of the device, hence recording the ground motion as well. In practice, these mechanisms are no longer manual but instead work by measuring electronic changes produced by the movement of the ground concerning the mass.
When an earthquake happens, one of the first interrogations is, "where and when was it?" The place may tell us what fault it was on and where damage most likely occurred.
Unfortunately, Earth is not transparent, and it is impossible to just see with our naked eyes or picture the earthquake disturbance like meteorologists can photograph clouds. When a quake occurs, it causes an increasing wavefront from the quake hypocenter at a speed of several miles per second.
We notice earthquakes with a network of seismometers on the Earth's surface. The ground motion at each seismometer is amplified and recorded electronically at the recording site. As the wavefront expands from the earthquake, it reaches distant seismic stations. When an earthquake occurs, we observe the times at which the wavefront passes each station. You should find the unknown earthquake source knowing these wave arrival times.
A seismographic network records earthquakes. Each seismic station in the network determines the motion at that site. The slip of one rock over another in an earthquake releases energy that makes the ground bounce. This vibration pushes the piece of ground and makes it vibrate. The energy proceeds out from the earthquake hypocenter in a waveform.
There are many ways to measure various factors of an earthquake:
Magnitude is the common measure of an earthquake's dimension. It is an estimate of the size of the quake source. It is the same number, no matter where you are or what the shaking feels like. The Richter scale is an old-school method for measuring magnitude that is no longer used for large, teleseismic quakes. The Richter scale determines the largest wiggle (amplitude) on the recording, but other magnitude scales calculate different bits of the earthquake.
Intensity is a measure of the shaking (bounce) and damage caused by the earthquake; this value changes from location to location.
Though there are so many new digital instruments arrives, seismographs have their own merits,
It is the first reliable and straightforward, which geologists and other seismologists can easily understand.
low running cost,
Well accepted equipment worldwide in terms of calibration and data reliability has given in-depth knowledge about the boundaries of earthquakes, their occurrence frequencies, and subsequent advancements.