Seismograph Practice Questions
19 free Seismograph practice questions for the General Science. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
What is the primary function of a seismograph?
- A To record ground vibrations from earthquakes
- B To measure variations in atmospheric pressure
- C To measure the height of ocean tides
- D To record wind speed and direction
Correct answer: To record ground vibrations from earthquakes
A seismograph is an instrument designed to detect and record vibrations in the Earth's crust caused by earthquakes. It converts ground motion into a graphical record known as a seismogram.
The recorded output produced by a seismograph is called a:
- A Seismogram
- B Seismograph
- C Seismology
- D Seismic wave
Correct answer: Seismogram
A seismogram is the graphical record produced by a seismograph. It shows the amplitude and timing of seismic waves generated by earthquakes.
Which scientist developed one of the first practical modern seismographs?
- A John Milne
- B Charles Richter
- C Zhang Heng
- D Alfred Wegener
Correct answer: John Milne
John Milne, a British geologist and engineer working in Japan, built one of the first practical seismographs in the 1880s and helped set up a worldwide network of recording stations. Zhang Heng's ancient instrument could hint at an earthquake's direction but produced no written record.
Which type of wave is usually recorded first by a seismograph during an earthquake?
- A Surface waves
- B Secondary waves
- C Primary waves
- D Ocean waves
Correct answer: Primary waves
Primary waves, or P-waves, travel the fastest through the Earth. They are compressional waves and therefore arrive first at seismograph stations.
Which seismic waves move only through solid materials?
- A Secondary waves
- B Primary waves
- C Rayleigh surface waves
- D Sound waves
Correct answer: Secondary waves
Secondary waves, or S-waves, can only travel through solid materials because they involve shear motion. They cannot propagate through liquids or gases.
Which scale is commonly used to measure the magnitude of earthquakes recorded by seismographs?
- A Mercalli scale
- B Richter scale
- C Beaufort scale
- D Mohs scale
Correct answer: Richter scale
The Richter scale measures earthquake magnitude from the amplitude of seismic waves recorded by a seismograph, with each whole unit representing about a tenfold increase in amplitude. The Mercalli scale rates observed shaking intensity rather than magnitude, while the Beaufort and Mohs scales measure wind force and mineral hardness.
Which branch of science studies earthquakes and seismic waves?
- A Meteorology
- B Seismology
- C Oceanography
- D Astronomy
Correct answer: Seismology
Seismology is the scientific study of earthquakes and seismic waves that travel through the Earth. Seismographs are essential instruments used in this field.
What type of motion does a seismograph primarily detect?
- A Air pressure changes
- B Ground vibration
- C Temperature variation
- D Ocean currents
Correct answer: Ground vibration
Seismographs detect ground vibrations caused by seismic waves. These vibrations are recorded and analyzed to understand earthquake characteristics.
Which seismic waves typically cause the most damage during an earthquake?
- A Primary waves
- B Secondary waves
- C Surface waves
- D Sound waves
Correct answer: Surface waves
Surface waves travel along the Earth's surface and often produce large ground movements. These waves usually cause the most structural damage during earthquakes.
Which principle allows a seismograph to record ground motion accurately?
- A Magnetic induction
- B Inertia of mass
- C Refraction
- D Electric conduction
Correct answer: Inertia of mass
Seismographs rely on the inertia of a suspended mass. While the ground and frame move during an earthquake, the mass tends to remain stationary, allowing motion to be recorded.
Which instrument records seismic waves in three perpendicular directions?
- A Tiltmeter
- B Triaxial seismograph
- C Strainmeter
- D Single-component seismograph
Correct answer: Triaxial seismograph
A triaxial seismograph measures ground motion along three perpendicular axes: vertical, north-south, and east-west. A single-component instrument records only one direction, while tiltmeters and strainmeters measure ground tilt and deformation instead of wave motion.
Which term describes the point inside the Earth where an earthquake begins?
- A Epicenter
- B Fault
- C Plate boundary
- D Focus
Correct answer: Focus
The focus, also called the hypocenter, is the point within the Earth where the earthquake originates. Seismic waves spread outward from this point.
What is the point on the Earth's surface directly above the earthquake focus called?
- A Plate margin
- B Fault
- C Seismic zone
- D Epicenter
Correct answer: Epicenter
The epicenter is the point on the Earth's surface directly above the earthquake focus. It is usually where the strongest shaking is felt.
Which instrument is used in modern digital stations to detect and measure ground motion?
- A Seismometer
- B Barometer
- C Hydrometer
- D Thermocouple
Correct answer: Seismometer
A seismometer is the sensor that detects ground motion, and modern digital versions record it electronically with high precision. A barometer measures air pressure, a hydrometer measures liquid density, and a thermocouple measures temperature.
Which natural event is most commonly studied using seismographs?
- A Volcanic eruptions
- B Hurricanes
- C Floods
- D Earthquakes
Correct answer: Earthquakes
Seismographs are primarily used to detect and analyze earthquakes. They measure seismic waves generated by sudden movements in the Earth's crust.
What is the main purpose of analyzing seismograms?
- A To predict the exact date of the next earthquake
- B To measure the temperature of Earth's core
- C To map ocean floor topography
- D To determine earthquake location and magnitude
Correct answer: To determine earthquake location and magnitude
Seismograms record the arrival times and amplitudes of seismic waves at each station. Comparing records from several stations lets scientists work out an earthquake's location, depth, and magnitude, but it does not allow the timing of future earthquakes to be predicted.
Which type of motion do primary waves cause in the ground?
- A Up and down motion
- B Side-to-side shearing motion
- C Compression and expansion
- D Circular motion
Correct answer: Compression and expansion
Primary waves cause particles in the ground to move back and forth in the same direction as the wave travels. This motion is similar to compression and expansion.
What makes it possible to detect and locate earthquakes anywhere on Earth within minutes?
- A Satellite imaging of surface changes
- B Weather radar
- C GPS navigation
- D Seismic monitoring networks
Correct answer: Seismic monitoring networks
Seismic monitoring networks consist of many seismograph stations worldwide. They help scientists detect earthquakes quickly and analyze seismic activity globally.
What is the main reason seismographs are often installed deep underground?
- A To reduce surface noise and vibrations
- B To avoid daily temperature and humidity changes
- C To measure groundwater
- D To prevent corrosion
Correct answer: To reduce surface noise and vibrations
Placing seismographs underground reduces interference from surface vibrations like traffic or wind. This improves the accuracy of seismic measurements.