The record obtained by the measurement of earthquake is called a:
- (a)seismic wave
- (b)seismograph
- (c)seismology
- (d)seismogram
Answer
Why
Correct — D. The suffix decides it. -graph names the instrument that writes, -gram names the thing written.
The seismograph is the machine bolted to the ground. The trace it draws — ground motion plotted against time — is the seismogram, and a record obtained by measurement is exactly that trace.
The same pair runs through telegraph and telegram, cardiograph and cardiogram. So the record is a seismogram, option (d).
Why the others are wrong
- (a)seismic wave — A seismic wave is the energy travelling through the Earth. It is the event the instrument detects, not the paper the instrument produces.
- (b)seismograph — The seismograph is the instrument. It makes the record but is not the record, and separating the two is the whole point of the question.
- (c)seismology — Seismology is the branch of science that studies earthquakes and seismic waves. A field of study cannot be a record obtained from one measurement.
Concept
An earthquake is measured by recording how the ground moves over time.
A seismograph carries a mass that stays nearly still while its frame shakes with the ground, and a pen or a sensor writes out that relative motion.
The output is the seismogram: a line that is flat while the ground is quiet and breaks into large oscillations as waves arrive. Reading it gives the arrival times of the P and S waves, and the gap between those arrivals is what lets a station work out how far away the focus lay.
SSC likes -graph and -gram pairs because the difficulty sits entirely in the word, not in the physics. The same suffix rule settles barograph against barogram and cardiograph against cardiogram.
Key facts
- A seismograph is the instrument and a seismogram is the record it produces.
- P waves are the faster primary waves and reach a station before the slower S waves.
- S waves cannot travel through liquids, which is how the Earth's outer core was shown to be liquid.
- The point inside the Earth where an earthquake originates is the focus, and the point on the surface directly above it is the epicentre.
Study next
Common traps
- Choosing seismograph because it is the word candidates hear most often.
- Reading the word record as the act of recording rather than the document produced.
- Confusing the magnitude scale with the recording instrument.
SSC runs a steady physical-geography strand through GA, and word-pair items like this one are decided in the vocabulary rather than the geology.
Fix the -graph and -gram split once and the whole family of instrument-and-record questions goes with it.
Related PYQs
No directly related past PYQ was found.