Learn the signs that a tsunami is coming in this PHIVOLCS video

The Philippine Institute of Volcanology and Seismology on Tuesday observed World Tsunami Awareness Day with an informative video about the natural phenomenon and the signs that one of these potentially deadly waves is coming towards you.

In "Tsunami 101," PHIVOLCS showed images of tsunamis causing destruction in several parts of the world, including the tsunami created by the magnitude-8.1 Moro Gulf earthquake on August 17, 1976. Reaching a height of nine meters, the big wave devastated the southwestern coast of Mindanao and killed almost 8,000 people.

The Philippines is located on the Pacific Ring of Fire, where many active tectonic plates lie. The plates' movement can result in offshore earthquakes.

If one of these underwater earthquakes is shallow enough to displace parts of the seabed and disturb the mass of water over it, it can create tsunami waves "that can travel great distances with immense strength," the video said.

Other phenomena can also produce tsunamis, such as underwater landslides or underwater volcanic eruptions or the very rare occurrence of a large meteorite impact, but these do not cause tsunamis as frequently as earthquakes do.

According to the video, tsunami waves are so strong and fast that they can cross the entire length of the Pacific Ocean—and do so in less than a day, traveling almost as fast as a jet at 800 kph.

Tsunami warning signs

The United Nations declared November 5 as World Tsunami Awareness in honor of a true story from Japan, "Inamura-no-hi" which means the burning of the rice sheaves.

During an 1854 earthquake, a farmer saw the tide receding—a sign of a looming tsunami. He set fire to his harvested rice to warn the villagers, who immediately fled to high ground.

PHIVOLCS lists the warning signs that coastal populations must be alert for:

1. An earthquake is felt, especially in coastal areas. The ground shaking is usually strong enough that a person can hardly stand.

2. This is followed by an unusual sea level change—either a rise in seawater, or a sudden drop in seawater that exposes corals, underwater rocks, and marine life.

3. The third sign is an unusual sound produced by the approaching wave. According to the video, most tsunami survivors describe the sound as a loud "jet-like" roar or rumbling, or a strong rain sound.

PHIVOLCS Director Undersecretary Renato Solidum urged the development of tsunami-prepared communities, which includes establishing community-based early warning systems as well as pre-determined routes and evacuation areas and conducting drills.

Planting trees such as mangroves along the coast and preserving coral reefs can also help, he said. — Joviland Rita/BM, GMA News