Will the Big One actually be just the sum of a million little ones? Will California slowly shake-and-slide into the Pacific like a frog cooked in a slowly heating pot of eventually-boiling water? More evidence suggesting that will be the case can be found in a new study using an old technology in a new way to discover fingerprints of strange little quakes that have never been mapped before … and the road they expose is terrifying. Did you just feel something?
“To overcome these limitations, we applied a template matching detection technique to the entire waveform archive of the regional seismic network in southern California. This effort resulted in a catalog with 1.81 million earthquakes, a factor of 10 increase, which provides important new insights into the geometry of fault zones at depth, foreshock behavior and nucleation processes, and earthquake triggering mechanisms.”
“A factor of 10 increase” is a good thing to hear from your stockbroker, but not from your seismologist. (Since when do you have a seismologist? Do you know something we don’t? What’s his number?) According to “Searching for hidden earthquakes in Southern California,” a study published recently in the journal Science and reviewed by the Los Angeles Times, Caltech seismologist Zachary Ross and his team for the first time developed a way to identify earthquakes of less than magnitude 1.7 all the way down to magnitude negative 2 over a wide region and over a period of years, in this case over southern California between 2008 and 2017. That level of details-over-time exposed evidence of undiscovered faults, patterns of moving earthquake swarms and faint clusters of foreshocks before larger quakes.
“You can really see the extent, now, to which this one big earthquake is able to affect this huge region that we just couldn’t see before. It shows in a lot of ways that these fault systems are related to each other. … The more that we dig deeper, the more it seems there’s some connection there.”
In one instance – the Easter Sunday magnitude 7.2 earthquake of 2010 – the team was able to track its aftershocks from its epicenter in Mexicali, Mexico, all the way up through connecting faults to micro-quakes 170 miles away. However, “I told you so” doesn’t help much when you’re buried in rubble. What Southern Californians need is a “Guess what’s coming?” and the new way of analyzing seismic data may ultimately provide it.
“Why do they start the way they do? Is it really just one mainshock that hits, or is there more stuff leading up to it? Potentially, this could provide more information about how earthquake sequences start.”
It already provided the first aftershock about foreshocks – that they’re occurring every three minutes, not every 30 minutes as had been previously thought. Is this new picture of the whole lotta shakin’ goin’ on in southern California bad news? What do you think?
“If you look at the San Andreas, the San Andreas has been unbelievably quiet. It does not produce micro-seismicity like this in almost all the locations in Southern California.”
In other words, the forecasters studying faults and plate tectonics in California may be looking for shoves in all the wrong places … the real danger zone is Los Angeles, not San Francisco. Ross may want to move the supercomputer running his new seismic shake seeking software from Caltech in Pasadena to someplace east … far east.
If Jerry Lee Lewis were to write another of his iconic “shakin’“songs today, he’d look at this new data, change one word and blame the “You shake my nerves and you rattle my brain” micro-quakes on “slight balls of fire.”