What are tsunamis and what causes them

What are tsunamis and what causes them?
What are tsunamis and what causes them?

     What is the difference between surface seismic waves and body seismic waves?

The Correct Answer and Explanation is :

Tsunamis are large ocean waves generated by the sudden displacement of a substantial volume of water. Unlike typical wind-generated waves, tsunamis are often caused by significant geological events such as underwater earthquakes, volcanic eruptions, or landslides. The term “tsunami” is derived from the Japanese words “tsu” (harbor) and “nami” (wave), reflecting the devastating impact these waves can have on coastal communities.

Causes of Tsunamis:

1. Underwater Earthquakes: The most common cause of tsunamis is the sudden vertical displacement of the ocean floor during an earthquake. When tectonic plates shift abruptly, they can lift or drop the seabed, displacing the overlying water and generating waves that propagate across the ocean.
2. Volcanic Eruptions: Submarine volcanic eruptions can displace water through the force of the eruption itself or by causing the collapse of the volcanic structure into the sea, leading to tsunami formation.
3. Underwater Landslides: Massive landslides occurring beneath the ocean can displace large amounts of water, generating waves that travel across the ocean.
4. Meteorite Impacts: Although rare, the impact of a large meteorite in the ocean can displace water and generate a tsunami.

Surface Seismic Waves vs. Body Seismic Waves:

Seismic waves are energy waves that travel through the Earth’s interior and along its surface, generated by events such as earthquakes. They are categorized into two primary types: body waves and surface waves.

1. Body Waves:

• Primary Waves (P-waves): These are compressional waves that move through the Earth’s interior, traveling through solids, liquids, and gases. They are the fastest seismic waves and are typically the first to be detected by seismographs.
• Secondary Waves (S-waves): These are shear waves that move through the Earth’s interior but can only travel through solids. They are slower than P-waves and arrive after them.

1. Surface Waves:

• Love Waves: These waves cause horizontal shearing of the ground and are the fastest surface waves.
• Rayleigh Waves: These waves produce an elliptical rolling motion, similar to ocean waves, causing both vertical and horizontal ground movement.

Key Differences:

• Propagation Medium: Body waves travel through the Earth’s interior, while surface waves move along the Earth’s exterior.
• Speed: Body waves are faster than surface waves.
• Detection: Surface waves typically cause more ground displacement and are often more destructive than body waves.
• Motion: P-waves compress and expand the material they move through, S-waves shear the material, and surface waves cause complex ground motion.

Understanding these seismic wave types is crucial for earthquake analysis and for designing structures that can withstand seismic events.