Tsunami Overview and Generation

Study Notes

Tsunami is a series of sea waves generated by geological processes, often undersea earthquakes
Wave heights can exceed 5 meters
Recent examples in the Philippines include the August 1976 Moro Gulf Earthquake and Tsunami, and the November 1994 Oriental Mindoro Earthquake and Tsunami.

Tsunami, meaning "harbor waves" in Japanese, is generated by earthquakes disrupting the ocean floor.
Strong, shallow-seated earthquakes displace significant water volumes, creating tsunamis.
Storm surge is a rise in sea level associated with strong winds or tropical cyclones.

Tsunamis are commonly generated in subduction zones, where two tectonic plates collide, with one plate moving under the other.
When plates get stuck, the overriding plate is distorted.
The stuck area ruptures, triggering an earthquake that pushes the ocean floor and seawater upwards, initiating the tsunami.
The tsunami then moves in opposite directions.

Local Tsunamis: Contained within 100 kilometers of the source, typically caused by earthquakes and landslides. They reach the shoreline within 2 to 5 minutes.
Far-field/Distant Tsunamis: Can travel 1 to 24 hours before reaching the coast, originating from earthquakes in other countries (e.g., Chile, Alaska, Japan). Monitoring centers like Pacific Tsunami Warning Center (PTWC) and Northwest Pacific Tsunami Advisory Center (NWPTAC) track these and warn nearby countries.

The Philippines is at risk of tsunamis, particularly coastal areas along the Pacific Ocean, West Philippine Sea, Sulu Sea, and Celebes Sea
These are caused by undersea earthquakes or submarine landslides
Tsunamis from other countries can also affect the Philippines

1. Feel an Earthquake: A strong undersea earthquake, often felt in coastal areas, can precede a tsunami. However, if shaking occurs far from the shore, you might not feel it.
2. See Receding Water: Before a tsunami wave arrives, water may recede significantly from the shoreline.
3. Hear an Unusual Roaring Sound: A loud roar or sound like a jet or train suggests an approaching tsunami.

PHIVOLCS issues tsunami warnings to alert the public of potential danger.
GREEN Advisory: No tsunami threat; no evacuation needed. The advisory is for information purposes only.
YELLOW Advisory: Sea level changes are being monitored.
ORANGE Advisory: Minor sea level disturbance; people are warned to stay away from the coast.
TSUNAMI WARNING: Destructive tsunami with potentially life-threatening waves, necessitating immediate evacuation. Evacuation of areas near the coast is advised. Ownership of boats near the coast should be secured away from the coast. People at sea should move away from the shore to deeper waters until further notice.