“We learn geology the morning after the earthquake.”—Ralph Waldo Emerson
***
While thousands of Filipinos attended the prayer rally and birthday celebration of former president Rodrigo R. Duterte, some 153 individuals have lost their lives following a powerful earthquake measuring 7.7 on the Richter scale that struck central Myanmar last Friday (March 28), causing tremors felt as far away as Bangkok and leaving buildings in the area in ruins.
The governing military junta in Myanmar claims that the earthquake caused 144 deaths and 737 injuries nationwide, prompting the declaration of a state of emergency in both Thailand and Myanmar.
In Bangkok, designated as a disaster zone by local authorities, a high-rise structure that was still under construction collapsed, causing a huge dust cloud to form. The commotion was documented in dramatic social media footage, which showed terrified individuals as the building collapsed, covering the surrounding area in dust as bystanders yelled and ran away.
What happened in Thailand and Myanmar may also happened in the Philippines, which is ripe for the “Big One,” a hypothetical earthquake of a 7.2-magnitude or greater.
The Philippine Institute of Volcanology and Seismology (PhiVolcs) says any active faults that have not generated any historical surface-rupturing events have higher potential to generate “The Big One.” The large quake can significantly affect the region and surrounding areas where it happens.
There are some reports that Metro Manila is apt for another big earthquake. In an interview with the Philippine Daily Inquirer, Emmanuel De Guzman, United Nations International Strategy for Disaster Reduction Advisor for Asia-Pacific, was quoted as saying: “The big earthquake is certainly coming. The question is when? No one can tell. It can happen today, tomorrow, or next year. But certainly, there will be an earthquake.”
Davao Region is not spared from such a calamity. A study done by PhiVolcs said “Big One” may be triggered by the Surigao-Mati fault. The newly discovered fault line which stretches from Surigao City to Mati City has a distance of 320 kilometers.
Based on the recent Philvolcs study, it was found that a 7.2 magnitude earthquake hit Compostela Valley in 1893. On April 15, 1924, another earthquake with 8.3 magnitude happened somewhere in Sigaboy, now known as Governor Generoso in Davao Oriental.
In an interview with Edge Davao, PhiVolcs official explained that an earthquake with an intensity of 7.2 that happened in Compostela Valley will immediately be felt in Davao City “within less than a minute” and the magnitude will be about 7.
The Philippines is described as “one of the world’s most disaster-prone countries.” We are often hit by earthquakes due to our location on the Pacific “Ring of Fire,” an arc of seismic faults around the ocean.
An earthquake (also known as a quake, tremor, or tremblor), according to a PhiVolcs monograph “is feeble shaking to violent trembling of the ground produced by the sudden displacement of rocks or rock materials below the earth’s surface.”
The Philippine Archipelago lies between two major tectonic plates: the Philippine Sea Plate and the Eurasian Plate. “Philippine Sea Plate is moving towards the Philippine Archipelago at the rate of about 7 centimeters every year,” Phivolcs explains. “The Eurasian Plate is being subducted along western side of Luzon and Mindoro at the rate of 3 centimeters per year except on Mindoro and northwest of Zamboanga where collision is taking place.”
At the intersection of the two plates is the Philippine Fault Zone, “which decouples the northwestward motion of the Pacific with the southwestward motion of the Eurasian Plate.” Movements along other active faults are reportedly responsible for the present-day high seismicity of the Philippine Archipelago.
According to PhiVolcs, at least 5 earthquakes per day occur in the Philippines. For almost four decades now, the country has been affected by 10 earthquakes with magnitudes greater than 7.0. As such, the possibility of these destructive earthquakes occurring again in the future “is very strong.”
After an earthquake, aftershocks are likely to follow. In seismology, an aftershock is a smaller earthquake that follows a larger earthquake, in the same area of the main shock, caused as the displaced crust adjusts to the effects of the main shock.
“Communities should prepare for aftershocks,” Phivolcs urges. In case of another strongly felt earthquake, it is recommended that people protect themselves by doing the “drop, cover, and hold.”
In homes and offices, heavy furniture and appliances should be strapped to the walls, and hanging objects securely fastened to prevent these from causing injuries.
People should be cautious of structures visibly weakened or having signs of damage caused by a strong earthquake event, as these may further be damaged by succeeding earthquakes and injure building occupants.
“It is best to contact the concerned municipal/city engineering office for inspection and advice,” PhiVolcs suggests. “Civil engineers from the local government and other organizations are strongly enjoined to inspect buildings and infrastructure to determine their structural integrity and recommend appropriate actions.”
Structurally compromised buildings should not be reoccupied unless certified safe by structural engineers. Slopes should be checked for tension/incipient cracks that may have resulted from the strong ground shaking.
