A strong earthquake magnitude 6.4 hit the Philippine province of Negros Occidental
A strong earthquake magnitude 6.4 hit the Philippine province of Negros Occidental on early Tuesday morning. No tsunami warnings were issued. The 6.4 -magnitude earthquake struck at 4.47 a.m. local time (2047 GMT Monday) and was centered about 73 kilometers (45 miles) south-southwest of Kabankalan, a city in Negros Occidental. It struck about 19 km (11.8 miles) deep, making it a relatively shallow earthquake.
The Philippine Institute of Volcanology and Seismology (Phivolcs) has been closely monitoring the Negros trench following five earthquakes, the strongest one at a 5.2-magnitude, that hit Negros Occidental. Ishmael Narag, Phivolcs Seismology Division officer-in-charge, said Monday afternoon that the 24-hour watch started when the last tremor hit at 10:10 a.m. The epicenter of the earthquakes was offshore and believed to have been caused by sudden movements along the earthquake-generating Negros Trench.
“We believe a subduction occurred where heavier denser plates dove into the interior of the earth, triggering five earthquakes recorded in Cauayan town and Bago City in Negros Occidental,” Narag said.
A subduction occurs when two oceanic plates collide, with the younger plate riding over the older one. Narag explained that as a precaution, they were monitoring the Negros Trench. (Inquirer)
Edgar commented on The Watchers:
The Negros tremors has the same characteristics as the Japan quake, shallow and offshore and right along the trench. Japan island literally moved around 25 meters to the east after its devastating earthquake.
Phivolcs reported two (2) tremors along the Bohol trench (which is almost perpendicular to the Negros trench on July 18), an adjustment response due to the ongoing Negros tectonic movement. Prior to that, series of quakes were recorded along the Cotabato Trench and neighboring onshore faults, recently. Also, land cracks were reported in Bohol & Cebu sometime March-April 2011 (which according to Phivolcs was due to the incessant rain?).
The Philippines is compressed by the Sunda plate in the west and the Philippine Plate in the east. Both plates are subducting under the Philippines.
Edgar commented on The Watchers:
Phivolcs said they are closely monitoring the Negros Trench. One website quoted from the Philippine News Agency that Sibuyan Phivolcs reported 103 tremors as of July 13 but Phivolcs website only listed 30 earthquakes as of July 22? Is that what you call close monitoring?