The California earthquakes silently rocked the US state between 2008 and 2017. Geologists at the California Institute of Technology (CALTECH) trawled through 10 years worth of seismic data to pinpoint the new tremors. The incredible earthquake discovery has expanded South California’s catalogue of known quakes from 180,000 to an astounding 1.8 million. Caltech’s geologists published their findings on April 18 in the peer-reviewed journal Science.
Zachary Ross, the study’s lead author, said: “It’s not that we didn’t know these small earthquakes were occurring.
“The problem is that they can be very difficult to spot amid all of the noise.”
The California earthquakes were numerous but relatively week – between magnitude 1.7 and -2.0.
According to the US Geological Survey (USGS), any tremor between magnitude 1.0 and 3.0 is “not felt except by a very few under especially favourable conditions.”
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The earthquakes were so small, they were practically indistinguishable from construction work or the rumble of cars.
But the new data shows earthquakes across Southern California are a much more frequent occurrence than previously thought.
Until now, an earthquake was estimated to erupted somewhere in the east coast state once every 30 minutes on average.
With the 10-fold spike in frequency, geologists now estimate seismic events are triggered in California every three minutes.
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This, in turn, translates to about 495 earthquakes in Southern California every single day.
In order to detect the minor tremors, the geologists used a technique known as template matching.
Caltech explained in a statement: “To overcome the low signal-to-noise ratio, the team turned to a technique known as ‘template matching’, in which slightly larger and more easily identifiable earthquakes are used as templates to illustrate what an earthquake’s signal at a given location should, in general, look like.
“When a likely candidate with the matching waveform was identified, the researchers then scanned records from nearby seismometers to see whether the earthquake’s signal had been recorded elsewhere and could be independently verified.”
Scientists are now positive the discoveries will help institutions like the USGS better prepare for and detect earthquakes.
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According to the USGS, California is the leading US state in terms of the damage sustained by frequent earthquakes.
And California and Alaska both top the list for the highest number of natural, not manmade, tremors.
The geological agency said: “It’s well known that California, the Pacific Northwest and Alaska all have frequent earthquakes, some of which are quite damaging.
“It’s well known that California, the Pacific Northwest and Alaska all have frequent earthquakes, some of which are quite damaging.
“Some areas of the country are more at risk than others, but, in fact, 42 of the 50 states could experience damaging ground shaking from an earthquake in 50 years and 16 states have a relatively high likelihood of experiencing damaging ground shaking.”