Hella Earthquakes Hit Headlines Around The World

From the island of Mindanao in the Philippines to Miami, Florida, to locally in Moraga, California, earthquakes are making headlines. This most recent spate of seismic activity is but the latest in a parade of notable quakes around the world. The ground has been shaking in Italy, Hawaii, and the anxiously monitored Cascadia Subduction Zone. Vegas got in on the action. Even Louisiana felt a tremor in April, and in March, a M4.0 rumbled Missouri’s Cooter. It seems no matter where you are lately, somewhere nearby, the Earth is on the move. 

First, the mildest shock, the M3.6 centered in the rugged, rolling terrain east of the Oakland Hills. The Bay Area, like all of California, is no stranger to seismic activity. Sunday’s tremor occurred in a tangled mess of faults and folds in the hill country just east of Moraga. Seismicity is by far the Bay Area’s most influential landscaper. Here, every valley, hill, strait and narrow has been shaped by an unseen force that works in fits and starts. It’s like Dr. Lucy Jones says: “In California, when you see mountains, think ‘earthquakes.’” 

This quake was too minor to disrupt BART service. It did not take place on a major fault such as the Hayward (~6 miles away) or Calaveras (~2 miles). The USGS established a hypocenter at 13 kilometers, meaning the nearest population lives at least eight miles from the source. While this quake is unlikely to herald stronger tremors, the San Ramon Valley has been a hotbed of seismic activity lately. 

Sunday’s M7.8 approached the caliber of the 1906 San Francisco earthquake, which geologists agree was probably M7.9. It was horrible, but seismologists and Filipinos residing on the island of Mindanao know this could’ve been worse. Mindanao rests on a complex web of overlapping plate boundaries that make the Bay Area’s faults seem neat and tidy. 

One nightmare earthquake scenario in the cards for the Philippines is a rupture of the Cotabato Trench. The trench is a subduction zone, and the ruptures they generate are called megathrust quakes. It’s the same threat facing the Pacific Northwest, responsible for the worst shaking and tsunamis on Earth. Preliminary reports for this earthquake placed it at M8.2, landing it squarely in megathrust territory. 

Seismologists soon determined it wasn’t the quake they feared, but one that occurred within the subducting plate: an intraslab earthquake. While less severe than a megathrust event, the M7.8 still generated tsunamis, the tallest reaching 4.6 feet. That’s equivalent to the tsunami that sent boats in Santa Cruz Harbor crashing into one another in 2022. USGS estimates up to a hundred casualties from this tragedy, potentially more. 

The past 72 hours were lively, especially for seismograph stations worldwide. These quakes are fascinating, but don’t be fooled by their close succession. It’s the only trait they share. Remotely triggered earthquakes are documented phenomena, but these happened too far apart to impact one another. You don’t have to worry about a tremor in Mindanao causing another in Berkeley. 

This one set some records. As geologist Dr. William Barnhart told the Associated Press, it’s “one of only five or six earthquakes of magnitude 5 or greater that we’re aware of in the entire Gulf.” It isn’t often this cold, muddy corner of the North American Plate gets earthquakes, especially one so great. By comparison, the M6.0 that struck Napa in 2014, killing one and injuring dozens, was 1.41 times weaker. Monday’s quake is the strongest quake to rock the Gulf since records began. 

Brittle old bedrock underlying the sediment-rich Gulf of Mexico transmits seismic energy farther and wider than California’s younger, plastic terranes. That means this genuinely rare occurrence had a way larger audience than a similarly sized event in California. Millions of people live in the Golden State. About as many ring the Gulf of Mexico. From Havana, Cuba to the resort towns of Cancún, Cozumel, Playa del Carmen, and Tulum, Mexico, to Orlando and Miami, Florida, millions of people felt this quake. In Miami, skyscrapers swayed, sending occupants running outside. 

Earth’s interior is grander and more complex than our best scientists could say. So far, we found that currents well up from a rotating, white-hot core, driving continental drift, building mountains, fueling volcanoes and yes, triggering earthquakes. More undoubtedly lies beneath. Since we can only peer so deeply, we can only know so much. But who knows. Some horrible mining company may inadvertently usher in technology that allows us to scan the whole planet’s insides for gold. Til then!