12/10/2025
A subduction earthquake is a powerful type of earthquake that occurs at a subduction zone, a region where two of the Earth's tectonic plates collide and one slides beneath the other. These are the planet's largest and most destructive earthquakes, often responsible for generating devastating tsunamis.
Here's a breakdown of how they happen and their key characteristics:
The Process: How Subduction Causes Earthquakes
Plate Collision: The Earth's surface is made of large, moving pieces of rock called tectonic plates. At a subduction zone, a denser oceanic plate collides with a less dense continental plate or another oceanic plate.
Subduction: Due to its greater density, the oceanic plate is forced to bend and slide, or "subduct," into the Earth's mantle beneath the overriding plate.
Stress Accumulation: This movement is not smooth. The two plates can become locked together for extended periods—decades or even centuries. As the plates continue to try to move, immense stress builds up in the locked section, causing the overriding plate to deform and bulge.
Sudden Release: Eventually, the stress overcomes the friction holding the plates together. The overriding plate suddenly slips and snaps back into place, releasing a tremendous amount of stored energy in the form of seismic waves. This violent release is the subduction earthquake. The specific fault where this rupture occurs is often called a megathrust fault.
Key Characteristics of Subduction Earthquakes
High Magnitude: Subduction zones are responsible for the most powerful earthquakes ever recorded, often referred to as "megathrust" earthquakes. They are the only known source of earthquakes with a magnitude of 9.0 or greater.
Tsunami Generation: When a subduction earthquake occurs offshore, the sudden upward or downward movement of the seafloor can displace a massive volume of water, generating a series of powerful waves known as a tsunami.
Deep and Shallow Quakes: Earthquakes can occur at various depths within a subduction zone. They can be shallow, happening at the interface where the plates are locked, or very deep, occurring within the descending slab as it sinks further into the mantle.
Volcanic Activity: As the subducting plate sinks deeper, heat and pressure cause water to be released from the oceanic crust. This water lowers the melting point of the overlying mantle rock, creating magma that can rise to the surface and form chains of volcanoes, like the "Ring of Fire" around the Pacific Ocean.
Aftershocks: A major subduction earthquake is typically followed by a series of smaller earthquakes, known as aftershocks, which can continue for days, weeks, or even months.
Because the Philippines is located along the Pacific Ring of Fire, it is particularly susceptible to subduction zone earthquakes and their associated hazards.
Source: Google Gemini
