Tsunami Philippines

Tsunami in the Philippines are extremely rare. 

The last measurable tsunami in the Pilippines affected the northern and the eastern seaboards on March 11, 2011. In that event, tsunami waves of around half a meter, resulting from a relatively shallow and very large 8.9 magnitude earthquake off the coast off Miyagi prefecture, Honshu, Japan, arrived in the early evening and caused a little or no damage, and no loss of life.

Prior to March 2011, the last recorded tsunami in the Philippines, that actually caused loss of life, occurred in the Verde Island Passage (between Batangas & Mindoro Island, affecting Puerto Galera) in the early morning of November 15, 1994, originating from a 7.1 magnitude (Richter) earthquake, 11KM West of the Baco Islands, according to the Philippine Institute of Volcanology and Seismology. The tsunami waves, resulting from the 7.1 magnitude earthquake, were measured at 6 meters in many areas when they reached land, but up to 8.5 meters in a few locations (primarily the Baco Islands) where the bathymetry was favorable; the tsunami waves reached up to 250 meters inland in areas that faced the earthquake epicenter. The death toll was 41 people. 

References: http://www.pgyc.org/tsunami-earthquake.php

1976 Moro Gulf earthquake

The 1976 Moro Gulf earthquake and tsunami took place on August 16, 1976, at 16:11 UTC (on August 17, 1976), near the islands of Mindanao and Sulu, in the Philippines. Its magnitude was calculated as being as high as 8.0 on the moment magnitude scale. The epicenter was in the Celebes Sea between the islands of Mindanao and Borneo. The Pacific Tsunami Warning Center's preliminary magnitude was given as 8.0 on the Richter scale and as 7.9 by other sources. There were many aftershocks following the main earthquake. A major aftershock on August 17 (local date) had a magnitude of 6.8. It was followed by at least fifteen smaller aftershocks.

 

Tsunami damage at Lebak, Mindanao 

Effects:
The initial earthquake was widespread and was felt as far as the central Philippine islands of the Visayas. A massive tsunami devastated 700 kilometers of coastline bordering the Moro Gulf in the North Celebes Sea, resulting in destruction and death in the coastal communities of the Sulu Archipelago and southern Mindanao, including Zamboanga City and Pagadian City. At least 5000 people died during the earthquake and tsunami, with thousands more remaining missing.[4] Some reports say that as many as 8,000 people lost their lives in total, with ninety percent of all deaths the result of the following tsunami.

Initially over 8,000 people were officially counted as killed or missing, 10,000 injured, and 90,000 homeless, making the 1976 Moro Earthquake and Tsunami one of the most devastating disasters in the history of the Philippine Islands. After the initial earthquake the people were unaware of the need to move to higher ground; when the tsunami hit it sucked most of the victims out to sea. Based on the investigation on the affected region it was confirmed that the waves reached up to 4 to 5 metres (13 to 16 ft) when they hit the areas. There were reports of weak tsunami activity as far as Japan, as well as Indonesian Hydrographic Office reports of unusual wave activity affecting the islands of Sulawesi (Celebes Island) and Borneo.

In Zamboanga City, 14 buildings were partially damaged. Zamboanga City was spared from serious damage of the tsunami triggered by this earthquake because the Basilan Island and the Santa Cruz Islands served as a buffer and deflected waves.

Warnings:
The Pacific Tsunami Warning Center (PTWC) in Honolulu issued a Tsunami Watch for the Pacific and queried tide gauge stations in Okinawa, Yap and Malakal. Based on negative reports from these stations, the watch was cancelled. Unfortunately, minutes after the earthquake, a large local tsunami struck the region. There was no time to issue a local warning.

Aid response:
The Philippine Government sent out aid and support as soon as news reached Manila. Later a team of US and Filipino geologists and officials surveyed the disaster zone with the help of the Philippine Air Force. The objective of the survey was to obtain measurements of the tsunami wave heights, extent of inundation and gather additional information on the earthquake and the tsunami and its effects in the region.

Aftermath:
The earthquake occurred at night, when offices and schools in Cotabato, Zamboanga and other cities were unoccupied, therefore the loss of life was greatly reduced. Pagadian, on the other hand, was the only city hardest hit by the tsunami that followed. Although the earthquake had a large magnitude, surprisingly, it produced little ground deformation on land areas. However, there was extensive earthquake damage to buildings, bridges and roads in Mindanao and particularly in the city of Cotabato.

Reference: http://www.ringsurf.com/online/2412-tsunamis_through_history.html