Question

d. Earthquake Waves: What are the two types of Seismic Waves? Draw and describe each.

P-Waves (Primary Waves) S-Waves (Secondary Waves)







e. Click “Next”. Describe a Tsunami.
f. Click “Next”. Describe how we can prepare for an earthquake.

Answer 1

d. Earthquake waves — two main types of seismic (body) waves

1) P‑Waves (Primary waves)
- Type: Compressional (longitudinal) body wave.
- Particle motion: Particles move back and forth in the same direction the wave is traveling (parallel).
- Properties:
- Fastest seismic wave → arrives first at seismic stations.
- Travels through solids, liquids, and gases.
- Generally smaller amplitude than S‑waves, but higher frequency.
- Typical speeds in Earth’s crust ≈ 5–8 km/s (varies with material).
- Simple diagram (side view, particles along direction of propagation):
- o —> o —> o —> o
- Compression: o oOOo (particles temporarily closer)
- Rarefaction: o o o (particles temporarily farther apart)

2) S‑Waves (Secondary waves)
- Type: Shear (transverse) body wave.
- Particle motion: Particles move perpendicular to the direction of wave travel (up/down or side/side).
- Properties:
- Slower than P‑waves → arrives second.
- Only travels through solids (cannot pass through liquids) — this helps reveal liquid outer core.
- Generally larger ground shaking (more destructive) than P‑waves.
- Typical speeds in crust ≈ 3–4.5 km/s.
- Simple diagram (direction of wave is →, particle motion is up/down):
- wave travel: ——————>
- particles: ^ v ^ v ^

e. Describe a tsunami
- A tsunami is a series of very long ocean waves caused by a sudden displacement of a large volume of water — most commonly from an undersea earthquake, but also from underwater landslides, volcanic eruptions, or meteor impacts.
- Characteristics:
- Very long wavelengths (tens to hundreds of kilometers) and long periods (minutes to an hour).
- In deep water the wave height is small and often unnoticeable, but wave speed is very high (roughly sqrt(g·h); e.g., several hundred km/h in deep ocean).
- As the wave approaches shallow coastal water (shoaling), its speed decreases and wave height (and destructive energy) increases — can flood far inland.
- Tsunamis typically come as a series of waves; the first may not be the largest.
- Simple cross-section idea:
- Deep ocean: long, low swell → shore: taller, steep wave and inundation inland

f. How to prepare for an earthquake
Before
- Secure your space: anchor heavy furniture, bookcases, water heaters; strap appliances; use latches on cabinets.
- Retrofit/inspect: fix weak foundations, bolt house to foundation, reinforce cripple walls, follow local seismic building codes.
- Make a plan: family communication, meeting place, know utility shutoff locations (gas, water, electricity).
- Assemble an emergency kit (72+ hours): water (1 gal/person/day), nonperishable food, flashlight, batteries, radio, first aid kit, wrench to turn off utilities, medications, copies of important documents, cash, sturdy shoes, warm clothing, whistle.
- Know safe spots: under sturdy tables, against interior walls, away from windows, bookshelves, tall fixtures.
- Practice drills: drop‑cover‑hold on; rehearse evacuation routes and tsunami evacuation routes if coastal.

During (if an earthquake happens)
- Indoors: Drop, Cover, Hold On — drop to floor, take cover under sturdy furniture, hold on until shaking stops. Stay away from windows and heavy objects that could fall.
- Outdoors: Move to an open area away from buildings, streetlights, utility wires.
- In a vehicle: Stop safely, stay in vehicle until shaking stops; avoid bridges/overpasses if possible.
- If near the coast and shaking is strong or lasts a long time, move inland or to higher ground immediately (tsunami risk).

After
- Expect aftershocks; they can be dangerous.
- Check for injuries and hazards (gas smell, chemical spills, electrical damage). If you smell gas, turn off gas only if trained and evacuate.
- Provide first aid; don’t move seriously injured unless in danger.
- Listen to emergency broadcasts for instructions and evacuation orders.
- Use phones only for emergencies to keep lines open.
- Inspect your home for structural damage before reentering; avoid downed power lines and debris.
- Help neighbors, especially elderly or disabled people.

Quick emergency kit checklist (brief)
- Water, food, flashlight, batteries, radio, first aid kit, whistle, multi‑tool, copies of documents, cash, medications, basic toiletries, sturdy shoes, warm blanket.

If you want, I can make a printable one‑page earthquake/tsunami checklist or draw clearer ASCII diagrams for classroom use.