Folds are undulation or waves in the stratified rocks of Earth’s crust formed when rocks deform. The formation of folds is associated with Convergent boundaries. Convergent plate boundaries or compression zones are sites of collision, where tectonic plates move and crash to each other. When two tectonic plates that make up the Earth’s crust collide together, rocks and debris bend, curved, or form jagged patterns in the rocks, which are known as “Folds.
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Faults are fractures in Earth’s crust where rocks on either side of the crack have slid past each other. A fault is formed as a brittle response to stress. In general, the movement of the tectonic plates is the main cause for providing stress; as a response to this, rocks at the surface break. There are three kinds of fault: strike-slip, normal, and reverse faults. Strike-slip faults form when rocks or plates slide past each other horizontally. Normal faults are formed when two blocks of crust move away, stretching the crust. On the other hand, Reverse faults which are commonly found in collision zones, slide one block of crust on top of another.
Trenches are long and narrow depressions on the seafloor. They are commonly found in subduction zones where Earth’s tectonic plates dive back into the mantle. Ocean trenches are a result of the movement of tectonic plates. When an oceanic plate at a subduction zone converges and moves under a continental plate, the seafloor and the outermost crust bend and form a steep.
A volcano is a rapture or vent in the Earth’s crust through which lava, volcanic ash, and gases escape from the magma chamber. Most volcanoes are usually located along tectonic plates margins where plates are constantly in motion. Land volcanoes form when two tectonic plates collide. One with greater density usually plunges below the lighter plate. When the descended plate sinks deep into the Earth, the temperature and pressure rise where it squeezes the trapped water out. The water reduces the melting point of the rock, forming a magma that can climb its way to the surface, resulting in a volcano.
A rift valley is an elongated lowland region formed by the interaction of two plates. It has usually a long, narrow, and deep formation. Rift valleys can be found both on land or at the bottom of the ocean, where they are created through the process of seafloor spreading. It generally forms in a divergent plate boundary. Ocean rift valleys are formed when two oceanic plates move away from one another creating a deep crack in the center of the ridge. Rift valleys on land, on the other hand, are created when layers of rock that are subjected to stress subside form a depression with steep sides. Rift valleys can also form at transform faults where tectonic plates grind past each other.
Mountain ranges are a group or series of mountains ranged in a line and connected by higher ground. These ranges are usually formed and located at convergent plate boundaries. When two continental plates collide with each other, there will be little to no subduction since both of the plates have equal or close densities. As a result, the plates are pushed together and the rocks have been compressed creating a mountain range.
The West Valley Fault (WVF) is one of the two major fault segments of the Marikina Valley Fault System (MVFS), also known as the Valley Fault System (VFS), which extends across Metro Manila to the cities of Quezon City, Marikina, Pasig, Makati, Taguig, and Muntinlupa. The West Valley Fault segment travels across from Doña Remedios to Calamba Laguna having a length of 129.47 kilometers. This fault exhibits a dextral strike-slip motion in which fractures are vertical and blocks move horizontally.
The Marikina Valley Fault System, in which the West Valley Fault branches is considered to be almost fully locked, meaning it has almost no movement, and currently accumulating and loading elastic strain at the rate of 10 – 12 mm/yr. Historic records suggest that it has slipped with a sudden jolt every 200-400 years, and it has moved 4 times in the last 1400 years. The last major earthquake generated by this fault occurred in 1658, about 357 years ago. The West Valley Fault is known to be capable of producing large-scale earthquakes with a magnitude of 7 and above.
The West Valley Fault, which runs through Metro Manila and neighboring provinces, is expected to be severely affected because these areas are not only densely populated but also hold the country's business capitals and the government's seat of power. The West Valley Fault is considered to be a shallow fault, thus the severity of the earthquake having a 6.0 Richter scale will feel very strong to people within the National Capital Region.
Metro Manila is said to be the most developed region in the country however, it appears to be the most dangerous place when a disastrous and inevitable earthquake strikes. In one of the presentations of the 17th Science Council of Asia Conference, Dr. Renatu U. Solidum said that when the West Valley Fault moved and generated a 7.2 magnitude earthquake, at least 34,000 people may die, and may damage various lifelines such as water, electricity, road, infrastructure, and telecommunications.
An MMEIR study predicted that 38.3% of residential buildings would be partly or severely damaged, which is approximately 508,100 buildings in total. The construction quality and the type of materials used have a major role in buildings’ chances of surviving an earthquake, unluckily most of the houses do not follow the standards.
At the time the MMEIR conducted a study, 30 kilometers of 4482 kilometers electrical power lines connected to the main electrical power sources will be massively damaged if a 7.2 magnitude earthquake strikes Metro Manila. As a result, fire outbreaks by electrical short circuits will happen and explosions of petroleum and gas tanks may cause fire spreading.
In addition to the MMEIR study, Angat Dam, where 97% of Metro Manila gets its water supply, may also be severely affected since the fault is located beneath the dam. After a strong and large quake, it may result in immense water leakage.
Lastly, based also on an MMEIR study, in the earthquake’s aftermath, 95 kilometers of telecommunication cables both aerial and underground cables will be damaged, making communication impossible.
https://www.nationalgeographic.org/encyclopedia/fold-mountain/
https://www.e-education.psu.edu/earth520/content/l7_p3.html\
https://www.nationalgeographic.org/encyclopedia/ocean-trench/
https://www.nationalgeographic.com/environment/article/volcanoes
https://www.nationalgeographic.org/encyclopedia/rift-valley/
https://www.nationalgeographic.com/science/article/mountains
https://www.rappler.com/moveph/93746-maps-west-valley-fault-earthquake-scenarios/
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