M7.6 Earthquake Offshore Philippines, Little to No Insured Losses
A magnitude 7.6 earthquake occurred about 100 km offshore the Philippines on August 31, 2012. A preliminary tsunami warning from the Pacific Tsunami Warning Center was subsequently cancelled. Insured losses are expected to be little to none because strong shaking was limited to remote and rural islands in the eastern part of the country.
USGS Shakemap - August 31, 2012
Source: U.S. Geological Survey (USGS)
Shaking was felt widely throughout the Philippines, including the capital of Manila, almost 800 km distant, but with a maximum intensity of light to moderate. Accordingly, little to no damage is expected throughout most of the country, including Manila. Limited damage can be expected to vulnerable buildings on the islands closest to the epicenter, which experienced moderate to strong shaking.
Today's earthquake occurred on the Philippine Sea Trench with a thrust mechanism. The Philippine Sea Trench is a subduction zone capable of generating tsunamigenic earthquakes with magnitudes exceeding 8. On March 9, 2011 an M7.3 earthquake on the Japan Sea Trench was later identified as a foreshock to the M9.0 Tohoku-oki earthquake two days later.
Today's earthquake occurred on a segment of the Philippine Sea Trench with no historic record of rupture. The segment to the north last ruptured in 1897 with a M8.1 and in 1925 with a M7.3, and the segment to the south last ruptured in 1991, 1989, 1929, and 1924 with magnitudes ranging up to 8.3. This indicates that today's earthquake occurred in a potential seismic gap.
Earthquakes in the Philippines with MMI exceeding VII between 1599 and 1993
Source: Thenhaus, et. al. (1993) Estimates of the Regional Ground Motion Hazard in the Philippines, USGS/PHIVOLCS workshop; modifications by EQECAT.
Economic development in urban Philippines has expanded rapidly in recent decades. If a large megathrust earthquake were to occur on the Philippine Sea Trench, it could cause insured losses in the billions of dollars. The 1990 M7.7 earthquake near Luzon, and coincident volcanic eruption, caused economic damage of $500 million in 1990, according to a 1990 UN report.
EQECAT will continue to monitor this event and region and provide additional information as it becomes available.
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