earthquakes in the Philippines

EXPLAINER: Is it possible to predict earthquakes?

Lorenz Pasion

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EXPLAINER: Is it possible to predict earthquakes?

DAMAGED. Bureau of Fire Protection shows Luzon earthquake’s damage to houses, properties in Vigan City.

Bureau of Fire Protection

An accurate prediction of exactly when and where an earthquake will occur is currently impossible and will still be impossible in the foreseeable future, experts say

MANILA, Philippines – Immediately after the destruction and deaths caused by the magnitude 7 earthquake that struck the province of Abra and was felt in other parts of Luzon on Wednesday, July 27, Filipinos started to look for tips on how to properly prepare for an earthquake and mitigate its effects.

Following the queries about preparation, another common question that resurfaces whenever a major earthquake occurs is this: Can earthquakes be predicted?

Pinpoint prediction impossible

The Philippine Institute of Volcanology and Seismology (Phivolcs) always reminds the public that the exact time and place where earthquakes would occur cannot be predicted.

“At present, no one has the capacity to determine when an earthquake will strike, at what precise magnitude, and where the strong one will hit,” Phivolcs Director Renato Solidum told Rappler in 2017.

The Phivolcs reiterated this in 2019 when a rumor of a magnitude 7.1 earthquake was predicted to strike in Metro Manila.

On its frequently asked questions page, the United States Geological Survey (USGS) also said that neither USGS scientists nor any other scientists know “how to predict” major earthquakes and they do not expect “to know how anytime in the foreseeable future.”

Why earthquake prediction is impossible

In a BBC interview with USGS scientist emeritus Ross Stein, he explained that “the mass, elasticity, and friction of the plates vary in different areas.”

The plates that Stein was referring to are the Earth’s tectonic plates. According to the USGS, these plates get stuck at their edges due to friction that causes stress to build up. 

Eventually, the stress overcomes the friction that keeps the plates together, causing an earthquake that releases energy in waves that travel in the Earth’s crust.

Stein said that mass, elasticity, and friction can vary even in different parts of a fault. These small variations influence where and when an earthquake happens and how strong it will be.  

Limitations of modern science

What the USGS and other earthquake-monitoring agencies such as the Phivolcs can only do is calculate the probability of a major earthquake happening in a specific area within a certain number of years. This is shown in the hazard mapping of the said agencies.

However, hazard mapping cannot predict the exact time an earthquake would occur.

Solidum said in an interview with Rappler that the Phivolcs could tell “what magnitude and its effects” could be in an area where they have identified a fault.

Earthquake hazard maps of the Philippines can be downloaded at the Phivolcs’ website

The public can also request the following hazard maps from the Phivolcs’ Seismological Observation and Earthquake Prediction Division: 

  • Probabilistic Ground Shaking Hazard Map
  • Deterministic Ground Shaking Hazard Map 
  • Seismicity Map 

These hazard maps can provide details about the level of seismic activity of a certain area as well as how the ground of a specific area moves during earthquakes.

Other things scientists develop to prepare for earthquakes

Due to exact earthquake prediction being impossible in the current and foreseeable future, scientists are using other technology and probabilistic prediction methods to help the public prepare for earthquakes.

One example of such technology is the earthquake early warning system. According to the USGS, an early warning is a notification issued after an earthquake starts to alert the public when the shaking waves of a temblor will arrive at a specific location. 

The early warning system gives people a few seconds of advanced warning that can give them time to protect themselves. An example of this is Japan’s Earthquake Early Warning System managed by the Japan Meteorological Agency (JMA), which issues prompt alerts.

However, according to JMA, there are limitations to the early warning system, such as timing from when a warning is issued to the actual arrival of the main tremors. JMA said that the warning may not be transmitted to areas close to the earthquake’s focus.

In the Philippines, the National Disaster and Risk Reduction Management Council sends free mobile alerts during disasters such as an earthquake, although there are still discrepancies in the speed with which the alerts are sent, ranging from minutes to even hours.

Earthquake forecasts are used by scientists to predict aftershocks, as most of them have the same pattern. Earthquake probabilities, meanwhile, are used to describe the long-term chances that an earthquake of a certain magnitude will happen during a particular time window.

Due to the current limits of science, both scientists and government officials advise the public to prepare for earthquakes and encourage them to participate in earthquake drills such as the Nationwide Simultaneous Earthquake Drill, a quarterly event last conducted in June 2022. – Rappler.com

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Lorenz Pasion

Lorenz Pasion is a researcher at Rappler and a member of its fact-check team that debunks false claims that spread on social media.