Earthquakes

সারসংক্ষেপ

An earthquake is the sudden release of elastic strain energy along a fault, producing seismic waves.

মূল ধারণা

ব্যবস্থাটি বুঝুন

An earthquake is the sudden release of elastic strain energy along a fault, producing seismic waves.

কেন ও কীভাবে ঘটে

কারণ ও প্রেক্ষাপট

Earthquakes occur when tectonic stress overcomes frictional resistance on a fault. Elastic strain accumulates during locked motion, rupture releases that strain suddenly, and the resulting seismic waves transmit energy through the crust and across the surface.

কীভাবে কাজ করে

First, stress deforms rocks around a locked or slipping fault. When resistance is exceeded, rupture starts at the focus and propagates. P, S and surface waves then travel outward; shaking, rupture, liquefaction and secondary hazards vary with distance and ground conditions.

মূল তথ্য

• Focus is the underground origin; epicentre is its surface projection.
• P-waves are fastest; S-waves cannot pass through liquids.
• Magnitude measures released energy, whereas intensity describes observed effects at a place.

গুরুত্বপূর্ণ পরিভাষা

• focus
• epicentre
• fault
• magnitude
• intensity

উদাহরণ ও কেস স্টাডি

• The 2015 Nepal earthquake illustrates how Himalayan convergence creates seismic risk.

কারণ ও উপাদান

• Elastic strain accumulates as fault-block motion is temporarily locked by friction.
• Rupture begins when shear stress exceeds fault resistance.
• Tectonic loading, volcanic activity, collapse or human activity can trigger seismic events.

প্রভাব ও গুরুত্ব

• Seismic shaking damages buildings, roads, bridges and lifelines.
• Surface rupture, liquefaction, landslides and fires create secondary losses.
• Undersea displacement can generate a tsunami.

ভূগোলের সাথে সংযোগ

The 2015 Nepal earthquake illustrates how Himalayan convergence creates seismic risk. This illustrates how earthquakes varies by location, scale or environmental context.

বাংলাদেশের সাথে সংযোগ

Bangladesh faces earthquake risk from the Dauki Fault, Madhupur Fault and active tectonic systems toward the Indo-Burma ranges.

BCS প্রিলিমিনারির তথ্য

• Focus is the underground origin; epicentre is its surface projection.
• P-waves are fastest; S-waves cannot pass through liquids.
• Magnitude measures released energy, whereas intensity describes observed effects at a place.

BCS লিখিত বিশ্লেষণ

একটি বিশ্লেষণধর্মী উত্তর তৈরি করুন

• Explain elastic rebound from stress accumulation to fault rupture and wave propagation.
• Distinguish magnitude as source energy from intensity as observed effect at a site.
• Discuss Bangladesh preparedness through seismic codes, land-use planning, public awareness and resilient lifelines.

প্রচলিত ভুল ধারণা

• Magnitude and intensity are not interchangeable.
• The epicentre is not the underground point where rupture begins.

দ্রুত রিভিশন

• Earthquakes
• Focus is the underground origin; epicentre is its surface projection.
• P-waves are fastest; S-waves cannot pass through liquids.
• focus / epicentre
• Definition → process → spatial example