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Seismology & Hydro-Meteorology (Atmospheric Sciences) Solved Questions & Notes (2026) - Apex Rankers

Meteorology & Atmospheric Sciences > Atmospheric Sciences > Seismology & Hydro-Meteorology

35 Total Solved Questions
~53 mins Estimated Reading Time
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Seismology & Hydro-Meteorology

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Q. 1 Atmospheric Sciences
Difficulty: Easy (1 Mark)
In seismology, what are the two primary types of 'Body Waves' that travel through the interior of the Earth?
A
Primary (P) waves and Secondary (S) waves
✓ Correct
B
Love waves and Rayleigh waves
C
Tsunami waves and Storm surges
D
Radio waves and Microwaves
💡 Step-by-Step Explanation & Concept Rationale
Body waves propagate through Earth's interior: P-waves (compressional/longitudinal) and S-waves (shear/transverse).
Q. 2 Atmospheric Sciences
Difficulty: Easy (1 Mark)
Which seismic wave travels the fastest and arrives first at a seismograph recording station?
A
Primary (P) Wave
✓ Correct
B
Secondary (S) Wave
C
Love Wave
D
Rayleigh Wave
💡 Step-by-Step Explanation & Concept Rationale
P-waves (Primary waves) are compressional waves that travel fastest through rock (approx 5 to 8 km/s in the crust), arriving first at seismic stations.
Q. 3 Atmospheric Sciences
Difficulty: Medium (1 Mark)
Why can Secondary (S) waves NOT propagate through liquids (such as Earth's outer liquid iron core)?
A
Liquids have zero shear modulus (no resistance to shear stress / shape distortion)
✓ Correct
B
Liquids have infinite density
C
Liquids absorb all sound waves
D
Liquids have negative pressure
💡 Step-by-Step Explanation & Concept Rationale
S-waves are transverse shear waves. Because liquids and gases cannot support shear stress (shear modulus mu = 0), S-wave velocity Vs = sqrt(mu / rho) = 0, proving Earth's outer core is liquid.
Q. 4 Atmospheric Sciences
Difficulty: Hard (1 Mark)
What type of seismic surface wave causes particles to move in a retrograde elliptical orbit in a vertical plane along the direction of propagation?
A
Rayleigh Wave
✓ Correct
B
Love Wave
C
P-wave
D
S-wave
💡 Step-by-Step Explanation & Concept Rationale
Lord Rayleigh mathematically predicted Rayleigh waves: surface waves involving coupled longitudinal and transverse motion producing retrograde elliptical rolling, responsible for substantial earthquake ground shaking.
Q. 5 Atmospheric Sciences
Difficulty: Hard (1 Mark)
What type of seismic surface wave consists purely of horizontal transverse particle motion perpendicular to the direction of propagation?
A
Love Wave
✓ Correct
B
Rayleigh Wave
C
P-wave
D
Sound wave
💡 Step-by-Step Explanation & Concept Rationale
A.E.H. Love described Love waves: guided surface shear waves where particle displacement is purely horizontal and transverse to wave propagation.
Q. 6 Atmospheric Sciences
Difficulty: Easy (1 Mark)
What is the 'Epicenter' of an earthquake?
A
The exact underground location (hypocenter/focus) where the seismic fault rupture initiates
B
The point on the Earth's surface vertically directly above the hypocenter (focus)
✓ Correct
C
The instrument that records ground shaking
D
The magnitude of the shock
💡 Step-by-Step Explanation & Concept Rationale
The hypocenter (or focus) is the actual subterranean point of rupture initiation; the epicenter is the geographic point on Earth's surface directly overhead.
Q. 7 Atmospheric Sciences
Difficulty: Easy (1 Mark)
How many independent seismic recording stations are required at a minimum to determine the geographic epicenter of an earthquake using the triangulation method (P-S arrival time differences)?
A
At least 1
B
At least 2
C
At least 3
✓ Correct
D
At least 50
💡 Step-by-Step Explanation & Concept Rationale
A minimum of three seismograph stations are required to triangulate the intersection of three distance circles to pinpoint an earthquake epicenter.
Q. 8 Atmospheric Sciences
Difficulty: Medium (1 Mark)
What is the primary scientific scale used by seismologists today to measure the total physical energy released by moderate to great earthquakes?
A
Richter Local Magnitude (ML)
B
Moment Magnitude Scale (Mw)
✓ Correct
C
Modified Mercalli Intensity Scale (MMI)
D
Beaufort Scale
💡 Step-by-Step Explanation & Concept Rationale
Moment Magnitude (Mw = (2/3) * log10(M0) - 10.7) is based on the seismic moment M0 = mu * A * D (shear modulus x fault rupture area x average displacement). Unlike Richter ML, it does not saturate for large earthquakes.
Q. 9 Atmospheric Sciences
Difficulty: Easy (1 Mark)
What does the 'Modified Mercalli Intensity' (MMI) scale measure?
A
The physical energy released at the focus
B
The observed qualitative effects, shaking severity, and structural damage produced by an earthquake at a specific location, rated from Roman numerals I (not felt) to XII (total destruction)
✓ Correct
C
The depth of the fault in kilometers
D
The duration of seismic shaking in seconds
💡 Step-by-Step Explanation & Concept Rationale
The MMI scale is an intensity scale measuring the local severity of ground shaking and structural damage experienced at a specific site, ranging from I to XII.
Q. 10 Atmospheric Sciences
Difficulty: Medium (1 Mark)
On October 8, 2005, a devastating Mw 7.6 earthquake struck Azad Jammu & Kashmir and Khyber Pakhtunkhwa, Pakistan. Which active fault system ruptured in this event?
A
Chaman Fault
B
Balakot-Bagh Fault (associated with the Main Boundary Thrust - MBT system)
✓ Correct
C
San Andreas Fault
D
Makran Subduction Zone
💡 Step-by-Step Explanation & Concept Rationale
The catastrophic October 8, 2005 Kashmir earthquake ruptured the Balakot-Bagh fault, part of the Himalayan collision zone where the Indian Plate underthrusts the Eurasian Plate.
Q. 11 Atmospheric Sciences
Difficulty: Medium (1 Mark)
What major left-lateral strike-slip transform fault system traverses western Pakistan through Balochistan, connecting the Makran subduction zone to the Himalayas?
A
Chaman Fault System
✓ Correct
B
Anatolian Fault
C
Dead Sea Transform
D
Alpine Fault
💡 Step-by-Step Explanation & Concept Rationale
The Chaman Fault is a major active left-lateral transform boundary (~900 km long) accommodating relative motion between the Indian and Eurasian plates across western Pakistan and Afghanistan.
Q. 12 Atmospheric Sciences
Difficulty: Medium (1 Mark)
What tectonic boundary off the southern coast of Balochistan and Sindh is capable of producing undersea megathrust earthquakes and tsunamis in the Arabian Sea?
A
Makran Subduction Zone (where the Arabian Plate subducts beneath the Eurasian Plate)
✓ Correct
B
Mid-Atlantic Ridge
C
Mariana Trench
D
Carlsberg Ridge
💡 Step-by-Step Explanation & Concept Rationale
The Makran Subduction Zone off the coast of Pakistan/Iran is an active subduction zone where the Arabian oceanic plate subducts northward beneath Eurasia, source of the Mw 8.1 1945 Makran earthquake and tsunami.
Q. 13 Atmospheric Sciences
Difficulty: Medium (1 Mark)
On November 28, 1945, a catastrophic tsunami struck the coast of Pasni, Ormara, and Karachi, Pakistan. What was the trigger?
A
An asteroid impact in the Arabian Sea
B
An Mw 8.1 undersea earthquake and associated submarine landslide in the Makran Subduction Zone
✓ Correct
C
A tropical cyclone storm surge
D
A collapsed volcanic caldera
💡 Step-by-Step Explanation & Concept Rationale
The 1945 Makran tsunami generated waves up to 12-15 meters along the Balochistan coast, claiming over 4,000 lives across Pakistan and India.
Q. 14 Atmospheric Sciences
Difficulty: Hard (1 Mark)
What mathematical formula governs the theoretical phase speed (c) of a shallow-water tsunami wave in the open ocean?
A
c = sqrt(g * d), where g is gravitational acceleration and d is ocean depth
✓ Correct
B
c = g / d
C
c = 2 * pi * d
D
c = sqrt(2 * g)
💡 Step-by-Step Explanation & Concept Rationale
Because tsunami wavelengths (100-500 km) are much greater than ocean depth (approx 4 km), they behave as shallow-water waves with velocity c = sqrt(g * d) (~800 km/h in deep ocean).
Q. 15 Atmospheric Sciences
Difficulty: Easy (1 Mark)
What specialized early warning center does the Pakistan Meteorological Department (PMD) operate to protect coastal communities along Sindh and Balochistan?
A
National Tsunami Early Warning Centre (NTEWC) Karachi / Islamabad
✓ Correct
B
Volcano Watch Office Quetta
C
Desert Locust Control Cell
D
Antarctic Expedition Desk
💡 Step-by-Step Explanation & Concept Rationale
PMD operates the National Tsunami Early Warning Centre (NTEWC) linked with the Indian Ocean Tsunami Warning and Mitigation System (IOTWMS) to issue tsunami alerts for Pakistan's coast.
Q. 16 Atmospheric Sciences
Difficulty: Medium (1 Mark)
What is 'Soil Liquefaction' during a major earthquake?
A
Saturated, loosely packed sandy soils temporarily lose shear strength and stiffness in response to cyclic seismic shaking, behaving like a liquid
✓ Correct
B
Lava erupting through soil
C
The evaporation of soil moisture
D
Soil freezing into solid ice
💡 Step-by-Step Explanation & Concept Rationale
Soil liquefaction occurs when earthquake ground shaking causes pore water pressure in saturated loose granular soils to rise rapidly, causing buildings and infrastructure to tilt or sink.
Q. 17 Atmospheric Sciences
Difficulty: Medium (1 Mark)
What is the historical 'Quetta Earthquake' of May 31, 1935 (Mw ~7.7) renowned for in civil engineering and building codes?
A
It led to the development of the Quetta Building Code, one of the earliest modern earthquake-resistant seismic construction codes in South Asia
✓ Correct
B
It was the first earthquake recorded by a smartphone
C
It occurred during a solar eclipse
D
It caused a tsunami in the Indus River
💡 Step-by-Step Explanation & Concept Rationale
The 1935 Quetta earthquake flattened the city, killing over 30,000 people. In its aftermath, the famous 'Quetta Building Code' of reinforced brick masonry was established.
Q. 18 Atmospheric Sciences
Difficulty: Hard (1 Mark)
What is the 'Main Boundary Thrust' (MBT) in Himalayan tectonics?
A
A major active thrust fault fault system separating the Lesser Himalayas from the Sub-Himalayan Siwalik range across northern Pakistan and India
✓ Correct
B
The boundary of the Indian Ocean
C
The boundary of the Karakoram highway
D
The edge of the Thar desert
💡 Step-by-Step Explanation & Concept Rationale
The MBT is one of the principal regional thrust faults accommodating the continental collision of India into Eurasia, extending across northern Pakistan.
Q. 19 Atmospheric Sciences
Difficulty: Medium (1 Mark)
What seismic instrument records both the horizontal and vertical three-component ground acceleration during strong earthquake shaking?
A
Strong-motion Accelerograph
✓ Correct
B
Mercury barometer
C
Cup anemometer
D
Piezometer
💡 Step-by-Step Explanation & Concept Rationale
Strong-motion accelerographs record ground acceleration (in g or m/s²) during strong shaking without going off-scale, critical for structural and seismic hazard engineering.
Q. 20 Atmospheric Sciences
Difficulty: Easy (1 Mark)
Which PMD observatory, established historically in 1952 in Balochistan, is a premier national center for geophysical and seismological research in Pakistan?
A
Geophysical Centre Quetta
✓ Correct
B
Coastal Station Gwadar
C
Radar Station Rahim Yar Khan
D
Dera Ghazi Khan Observatory
💡 Step-by-Step Explanation & Concept Rationale
The Geophysical Centre in Quetta, established with UNESCO assistance after independence, is PMD's primary historical institution for seismology and geomagnetic observations.
Q. 21 Atmospheric Sciences
Difficulty: Medium (1 Mark)
What is the 'Penman-Monteith' equation universally recommended by the FAO (FAO-56) used to calculate?
A
Reference Crop Evapotranspiration (ETo)
✓ Correct
B
The speed of ocean currents
C
The magnitude of earthquakes
D
The velocity of tornado winds
💡 Step-by-Step Explanation & Concept Rationale
The FAO-56 Penman-Monteith method combines net radiation, air temperature, wind speed, and vapor pressure deficit to compute reference crop evapotranspiration (ETo).
Q. 22 Atmospheric Sciences
Difficulty: Hard (1 Mark)
What is a 'Unit Hydrograph' (UH) in engineering hydrology?
A
The direct surface runoff hydrograph resulting from one unit (e.g., 1 mm or 1 cm) of effective rainfall falling uniformly over a watershed at a constant rate for a specified duration
✓ Correct
B
A gauge measuring ocean salinity
C
A hydrograph of water in an aquifer
D
A map of river depths
💡 Step-by-Step Explanation & Concept Rationale
Formulated by L.K. Sherman in 1932, the Unit Hydrograph is the direct runoff response to 1 unit depth of excess rainfall distributed uniformly over a catchment.
Q. 23 Atmospheric Sciences
Difficulty: Easy (1 Mark)
What is the primary source of perennial water flow in the upper Indus Basin during the early summer months (April to June) before the onset of monsoon rains?
A
Snow and glacial meltwater from the Karakoram, Hindukush, and Himalayan ranges
✓ Correct
B
Heavy tropical monsoon rain
C
Desalinated Arabian Sea water
D
Underground fossil aquifers only
💡 Step-by-Step Explanation & Concept Rationale
Snowmelt and glacier melt in the high mountains of Gilgit-Baltistan and KP contribute over 70% of early summer streamflow to the Indus River Basin, vital for Tarbela and Mangla reservoirs.
Q. 24 Atmospheric Sciences
Difficulty: Hard (1 Mark)
What anomalous cryospheric phenomenon in northern Pakistan is known internationally as the 'Karakoram Anomaly'?
A
Glaciers in the Karakoram range exhibited stability or slight mass gain in recent decades, contrasting with the rapid global retreat of glaciers elsewhere
✓ Correct
B
Glaciers glowing in the dark
C
Glaciers flowing uphill
D
Complete melting of all ice in 1990
💡 Step-by-Step Explanation & Concept Rationale
The 'Karakoram Anomaly' refers to the observed stability or minor expansion of glaciers in the central Karakoram during the late 20th and early 21st centuries, driven by winter Western Disturbance snow accumulation.
Q. 25 Atmospheric Sciences
Difficulty: Medium (1 Mark)
What hydrological instrument is used to directly measure actual evapotranspiration and percolation from a vegetated soil block?
A
Lysimeter (weighing lysimeter)
✓ Correct
B
Anemometer
C
Barometer
D
Pyranometer
💡 Step-by-Step Explanation & Concept Rationale
A lysimeter is a buried tank containing soil and vegetation; by precisely weighing mass changes (water loss), actual evapotranspiration is directly measured.
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