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The mysterious power of the seafloor: Why does the Philippine Sea plate cause such violent earthquakes?
In the heart of Southeast Asia, the Philippine Islands not only boast beautiful beaches and rich culture, but also hide amazing geological dynamics. The land is prone to seismic activity, and many experts believe it all stems from tectonic forces buried deep beneath the ocean floor — specifically the movement of the Philippine Sea Plate.
Philippine Fault System and Seafloor Forces
As a major geological fault system, the Philippine Fault System runs through the entire Philippine Islands. The tectonic forces caused by orogeny have compressed the Philippines into what geologists call the "Philippine Active Zone." The most well-known faults in this system include the Quinnangan, Masbate, and Leyte faults.
"The Philippine active zone is not just an isolated fault, but an interconnected mechanism in the overall fault system."
Structure of Philippine activity belt
The Philippine active zone consists of a large number of collage blocks and strata. Long strips of strata, such as the Zambares Peridotite, are up to 400 kilometers in length and 50 kilometers in width. These formations generally run north-south, and fusion areas are often marked by fault lines. The west side of the Philippine active zone is compressed by the Eurasian plate and the two Sunda plates, while the east side is affected by the Philippine Sea plate.
Philippine Fault Area
The Philippine Fault Zone (PFZ) extends 1,200 kilometers across the entire Philippine Islands and is closely related to the subduction movement of the Philippine Sea Floor. This left-slip fault moves in a NW-SE (N30-40 W) direction to accommodate subduction motion. PFZ activity can be observed in Holocene sandstone outcrops in the eastern islands of Mati and Davao, with slip rates of approximately 2-2.5 cm per year.
"Observing the current activities of PFZ will help reveal the fatal factors in earthquake occurrence."
Generation mechanism of earthquakes
The central fault zone of the PPF, including the Quinangan, Masbate and Central Leyte faults, is the area with the most seismic activity. Moderate earthquakes around the Masbate Fault show persistent displacement and regional slip. Historical data shows that the Quinangan Fault produces the largest earthquakes every 30 to 100 years, with epicentral slip rates of 20 to 33 millimeters per year.
Other active fault systems
In addition to the Philippine Fault System, there are several active fault systems. For example, the Valley Fault System, the Maclode Corridor, and the Lubang-Verde Pass Fault System are important geological features that may also trigger earthquakes. Each fault system has different characteristics and activity patterns, which are important for future earthquake risk assessments.
Summary
Through an in-depth study of the Philippines' seismic activity and the geological forces it implies, we can better understand the dynamic nature of the land. After all, how do these mysterious underground forces quietly shape the landscape of this land while affecting our lives?
