A Tsunami is a series of sea waves commonly generated by under-the-sea earthquakes and whose heights could be greater than 5 meters. It is erroneously called tidal waves and sometimes mistakenly associated with storm surges. Tsunamis can occur when the earthquake is shallow-seated and strong enough to displace parts of the seabed and disturb the mass of water over it.  

There are two types of tsunami generation: Local tsunami and Far Field or distant tsunami. The coastal areas in the Philippines especially those facing the Pacific Ocean, South China Sea, Sulu Sea and Celebes Sea can be affected by tsunamis that may be generated by local earthquakes. Local tsunamis are confined to coasts within a hundred kilometers of the source usually earthquakes and a landslide or a pyroclastics flow. It can reach the shoreline within 2 to 5 minutes. Far field or distant tsunamis can travel from 1 to 24 hours before reaching the coast of the nearby countries. These tsunamis mainly coming from the countries bordering Pacific Ocean like Chile, Alaska in USA and Japan. The Pacific Tsunami Warning Center (PTWC) and Northwest Pacific Tsunami Advisory Center (NWPTAC) are the responsible agencies that closely monitor Pacific-wide tsunami event and send tsunami warning to the countries around the Pacific Ocean.

The Philippines is frequently visited by tsunamis. On 17 August 1976, a magnitude 8.1 earthquake in Moro Gulf produced up to 9-meter high tsunamis which devastated the southwest coast of Mindanao and left more than 3,000 people dead, with at least 1,000 people missing. Also on 15 November 1994 Mindoro Earthquake also generated tsunamis that left 49 casualties.

Each one of us in the community should learn some important Tsunami Safety and Preparedness Measures such as the following:

1. Do not stay in low-lying coastal areas after a felt earthquake. Move to higher grounds immediately.

2. If unusual sea conditions like rapid lowering of sea level are observed, immediately move towards high grounds.

3. Never go down the beach to watch for a tsunami. When you see the wave, you are too close to escape it.

4. During the retreat of sea level, interesting sights are often revealed. Fishes may be stranded on dry land thereby attracting people to collect them. Also sandbars and coral flats may be exposed. These scenes tempt people to flock to the shoreline thereby increasing the number of people at risk.

A Tsunami is a series of sea waves commonly generated by under-the-sea earthquakes and whose heights could be greater than 5 meters. It is erroneously called tidal waves and sometimes mistakenly associated with storm surges. Tsunamis can occur when the earthquake is shallow-seated and strong enough to displace parts of the seabed and disturb the mass of water over it.  

There are two types of earthquakes: tectonic and volcanic earthquakes. Tectonic earthquakes are produced by sudden movement along faults and plate boundaries. Earthquakes induced by rising lava or magma beneath active volcanoes is called volcanic earthquakes. 

PHIVOLCS operates seismic monitoring stations all over the Philippines. These stations are equipped with seismometers that detect and record earthquakes. Data is sent to the PHIVOLCS Data Receiving Center (DRC) to determine earthquake parameters such as magnitude, depth of focus and epicenter. Together with reported felt intensities in the area (if any), earthquake information is released once these data are determined.