FACT CHECK: ‘Big One’ earthquake cannot reach magnitude 10

Claim: The “Big One,” the strong earthquake that can possibly hit Metro Manila on the West Valley Fault, will be a magnitude 10 earthquake. 

Rating: FALSE

Why we fact-checked this: Several posts bearing variations of the false claim have been circulating on Facebook, with the most popular one gaining 1.2 million views, 17,000 reactions, 5,300 shares, and 1,200 comments. 

The pages that posted these claims present themselves as part of the Department of Social Welfare and Development as its supposed television network.

The posts use similar captions, with some using videos of supposed news anchors and others attaching graphics. The posts all say that classes will be suspended to prepare for the looming magnitude 10 earthquake. 

Users are directed to click on the post’s links for more details. These links claim to show a list of areas where the earthquake will hit and where classes have been suspended.

The facts: Earthquakes with magnitudes 10 or larger cannot happen, according to the US Geological Survey (USGS). This is because the magnitude of an earthquake is directly related to the length of the fault on which it is expected to occur.

“No fault long enough to generate a magnitude 10 earthquake is known to exist, and if it did, it would extend around most of the planet,” the USGS explained.

According to the USGS, the largest earthquake ever recorded was a magnitude 9.5 on May 22, 1960, in Chile on a fault that is almost 1,000 miles, or about 1,600 kilometers. In comparison, the West Valley Fault runs roughly 100 kilometers.

Not magnitude 10: The “Big One,” which refers to the earthquake expected to happen along the West Valley Fault, is also projected to have a magnitude of 7.2. This is according to studies conducted by the Philippine Institute of Volcanology and Seismology (Phivolcs) and Japan International Cooperation Agency.

Phivolcs’ data, published by the Philippine Statistics Authority, also says that the maximum potential magnitude of an earthquake generated by the West Valley Fault can only reach 7.4. (READ: What dangers await when the West Valley Fault moves?)

The West Valley Fault moves roughly every 400 years. Because of this, experts say the “Big One” could happen in our lifetime. However, it is not possible to predict exactly when or where the Big One could occur. (EXPLAINER: Is it possible to predict earthquakes?)

Phishing risk: A URL scanner shows that the links attached to these posts lead to unofficial blog sites. Interacting with these websites may expose users to phishing risks. (READ MORE: Phishing 101: How to spot and avoid phishing) 

Recent earthquakes: The false claim began circulating after a series of earthquakes hit northern Cebu and Mindanao from late September to October this year.

The magnitude 6.9 tremor that struck Bogo City, Cebu, on September 30 was caused by a previously unmapped fault called the Bogo Bay Fault. At least 79 people were killed, 559 were injured, and nearly P6.8 million in damage to infrastructure were recorded, according to data from the National Disaster Risk Reduction and Management Council.

Days later, on October 10, doublet earthquakes hit Davao Oriental with magnitudes of 7.4 and 6.8. While less destructive than the Cebu tremor, the quakes still caused at least eight casualties.

Previous fact-checks: Rappler has previously debunked several false claims about earthquakes

– Shay Du/Rappler.com

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