A series of strong earthquakes has struck different parts of the world within hours of each other, rattling communities from Northern California to Japan and Venezuela and prompting questions about whether the events could be connected.
On June 24, at 15:10 GMT, a 5.6 quake rattled Northern California. Hours later, at 22:04 GMT, Venezuela was hammered by a 7.2 foreshock, followed just 38 seconds later by a savage 7.5 mainshock. Barely 25 minutes after that, at 22:30 GMT, a 6.9 quake struck offshore Japan. Three separate tectonic blows, within hours.
The quakes that struck Venezuela's northern Caribbean coast caused widespread damage and triggered tsunami warnings across the region, killing hundreds.
More casualties are feared as search-and-rescue operations are underway.
The following day, Acting President Delcy Rodriguez declared a national state of emergency, with the US Geological Survey (USGS) estimating a 42% chance that the final death toll could be very high.
In Japan, a magnitude 6.9 earthquake struck off the coast of Iwate, according to the Japan Meteorological Agency.
The quake occurred about 42 kilometres (26 miles) from the coastal city of Kuji, at a depth of 50 kilometres (31 miles).
In the US, seismic activity was also recorded when a rural area of Northern California experienced its strongest earthquake since 1940 on Wednesday morning.
The magnitude 5.6 quake was centred about 7 miles (12 kilometres) northwest of Willits, according to the USGS.
“Statistical coincidence”
Experts say the close timing of the seismic events does not necessarily mean they are connected.
They concede that close timing of the earthquakes is striking, but not unusual given global seismic activity patterns.
Peter Stafford, a professor of engineering seismology at Imperial College London, said such events are expected to occur independently in different regions.
"California experiences 2-3 events like this every year, on average. Japan experiences an event like the recent one, on average, roughly once per year. These are both ballpark estimates. Rates in Venezuela are harder to constrain, but these large events occur far less frequently, more like once every 50-100 years..."
According to Prof Stafford, in each region, events like this have happened, are expected and are inevitable.
"The fact that they happen to have occurred in close temporal proximity is almost certainly just a statistical coincidence."
Stafford said that the models for triggering events are usually based on concepts related to static or dynamic stress transfer, adding that the stress changes are very small when considering teleseismic distances relevant to California, Japan, and Venezuela.
He questioned whether these events were somehow related through some sort of triggering process. Why have there not been many other events occurring on faults that are located between these areas?
"If the statistical clustering was really due to physical processes, we would expect to see a more diffuse distribution of triggered events rather than localised instances at great spatial separation," he said.
Are powerful earthquakes increasing?
Scientists say there is no clear evidence that large earthquakes are becoming more frequent.
According to the USGS, short-term increases or decreases in seismic activity are part of normal fluctuations in earthquake rates and do not indicate an approaching major event.
The USGS ComCat earthquake catalogue shows an increase in recorded earthquakes in recent years, but scientists say this reflects improved detection rather than a rise in actual seismic activity.
The National Earthquake Information Centre now locates about 20,000 earthquakes globally each year, or roughly 55 per day.
Long-term records suggest about 16 major earthquakes (magnitude 7.0 or higher) occur annually on average. However, yearly totals vary significantly: 2010 recorded 23 major earthquakes, while some years, such as 1988 and 1989, recorded far fewer than average.
Major earthquakes in modern history
According to the US Geological Survey, the strongest recorded earthquakes in modern history include the magnitude 9.5 Valdivia earthquake in Chile in 1960, which killed 1,655 people and left millions displaced.
The deadliest earthquake on record remains the 1556 Shaanxi quake in China, an estimated magnitude 8.0 disaster that killed about 830,000 people. It was followed by the 1920 Haiyuan earthquake, which left roughly 273,000 dead, and the 1976 Tangshan quake, where the toll reached as high as 300,000.
The 2004 Indian Ocean earthquake off Sumatra, Indonesia, remains the deadliest disaster of the modern era. The massive 9.1–9.3 quake unleashed a tsunami that tore across 14 countries, killing about 228,000 people.
Other catastrophic earthquakes include Haiti in 2010, where a magnitude 7.0 quake killed between 160,000 and 316,000 people, China’s 2008 Sichuan disaster and the 2005 Kashmir earthquake, both of which left around 87,000 dead, and the 2023 Türkiye-Syria earthquakes that claimed roughly 60,000 lives.
Some quakes became defining global disasters not only for their death tolls, but for their scale and aftermath.
Japan’s 2011 Tohoku earthquake triggered a tsunami and the Fukushima nuclear crisis, while Chile’s 2010 magnitude 8.8 quake caused vast economic destruction despite a lower death toll.
