7.Tsunami

Tsunami Overview

  • Tsunami: Large series of waves, often caused by underwater earthquakes, landslides, or volcanic eruptions.

  • Mega Tsunami Events:

    • Miyako, Japan (2011)

    • Chile Tsunami (1960)

Hazard Zones and Response

  • Key areas like Miyako, Japan (2011) were heavily impacted.

  • Tsunami Hazard Zones indicate areas at risk; residents should seek high ground or inland if an earthquake occurs.

NOAA and Tsunami Data

  • 2011 Japan Tsunami highlights various risk areas across the Pacific Coast including:

    • Alaska, California, & Oregon

  • Emphasize the need for preparedness in coastal cities.

Tsunami Characteristics

  • Wave Dynamics

    • Waves: Energy in motion.

    • Key terms include:

      • **Wave Crest

      • Wave Trough**

      • Wavelength (L), Wave Height (H), and Wave Period (T).

  • Propagation:

    • Tsunamis are characterized by long wavelengths and high speeds (up to 835 km/hr).

Causes of Tsunami

  • Tsunamis can be generated by:

    • Earthquakes

    • Landslides

    • Volcanic eruptions

Subduction Zones

  • Most tsunamis originate in subduction zones, where tectonic plates interact leading to massive energy release.

    • Example: Cascadia Subduction Zone potentially has M=9 megathrust quakes.

Historical Tsunamis

  • 2004 Sumatra Tsunami impacted numerous areas, causing significant loss of life and damage.

    • Magnitude: 9.2 resulted in significant casualties (230,000 dead), lack of warning system in affected regions like Sri Lanka.

Seismic Activity

  • Detailed assessment of seismicity, tectonic plates, and potential tsunami impacts observed in diagrams.

  • Seismogram records display the intensity, wave types, and aftershock patterns following earthquakes.

Emergency Preparedness

  • Drop, Cover, and Hold On as effective strategies during an earthquake.

  • Utilize technology like the ShakeAlert system for earthquake notifications and preparedness.

Estimated Damage Estimation and Global Impact

  • Tsunami effects spread widely across multiple countries, emphasizing the global impact of seismic events.

    • Example areas: Myanmar, Sri Lanka, Thailand saw enormous death tolls.

Cultural Responses

  • Historical teachings like that in Aneyoshi, Japan emphasize community preparedness and resilience post-tsunami.

Conclusion

  • Awareness of tsunami characteristics, causes, and responses remains crucial in risk areas and for global seismic preparedness.