Daily Static Quiz Prelims Practice 2027
The epicentre is the point on the surface directly above the focus, where shaking is usually strongest. The hypocentre is instead another name for the focus, the point inside the Earth where the rupture begins; a shadow zone is the area where seismic waves are not recorded; and a seismic gap is a section of an active fault that has not ruptured for a long time, signalling higher future risk.
- S-waves can travel through the liquid outer core of the Earth.
- P-waves can travel through solids, liquids and gases.
Statement 1 is incorrect — S-waves (secondary or shear waves) are transverse waves and cannot pass through liquids, and their absence beyond a certain distance is the key evidence that the outer core is liquid. Statement 2 is correct, since P-waves (primary waves) are longitudinal and can travel through solids, liquids and gases; they are the fastest seismic waves and arrive first at a seismograph.
Option (c) is incorrect — the Richter scale measures magnitude, the energy released by an earthquake, while intensity, based on observed damage, is measured on the Modified Mercalli scale. Options (a), (b), and (d) are all correct — Alfred Wegener proposed Continental Drift in 1912; the Himalayas formed when the Indian plate collided with the Eurasian plate at a convergent boundary; and at the Mid-Atlantic Ridge plates move apart and new crust forms through sea-floor spreading.
- Assertion (A): An S-wave shadow zone exists on the side of the Earth opposite the earthquake's epicentre.
- Reason (R): S-waves cannot pass through the liquid outer core of the Earth.
Assertion A is correct — S-waves are not recorded beyond about 105° from the epicentre, creating a large shadow zone. Reason R is correct and directly explains A, since the liquid outer core blocks S-waves, which produces the shadow zone described in A, and this observation is the principal evidence for the outer core being liquid.
- Seismic waves are recorded by an instrument called a seismograph.
- The "Ring of Fire" is a belt of volcanoes and earthquakes around the Atlantic Ocean.
- The focus of an earthquake is also called the hypocentre.
Statement 1 is correct — a seismograph records seismic waves. Statement 2 is incorrect — the Ring of Fire surrounds the Pacific Ocean, not the Atlantic, and contains about 75% of the world's active volcanoes and most of its large earthquakes. Statement 3 is correct too, since focus and hypocentre are interchangeable terms for the point of origin inside the Earth.
