"Not comforted": new So Cal earthquake data

I’ve long noted that, though individual humans are often dazzlingly perceptive, humans qua groups are dizzyingly stupid.

Our doltish Group Being is a sort of Svengali to most people, and so there you are.

As individuals, we are entranced; we are stupefied.

We are idjits.

This is one reason why, over the years, I’ve occasionally done stories about the real possibility of natural disasters, such as tsunamis, floods. Boy, when it comes to nature’s wicked but predictable ways, societies are way knuckleheaded. Way, way. And Southern Californians are no exception. They'll stare straight into the face of imminent disaster and blithely discuss their next trip to freakin' Disneyland.


Study finds troubling pattern of Southern California quakes (In this morning’s LA Times):

By Jia-Rui Chong

…The Carrizo Plain section of the San Andreas has not seen a massive quake since the much-researched Fort Tejon temblor of 1857, which at an estimated magnitude of 7.9 is considered the most powerful earthquake to hit Southern California in modern times.

But … new research by UC Irvine scientists … found that major quakes occurred there roughly every 137 years over the last 700 years. Until now, scientists believed big quakes occurred along the fault roughly every 200 years.

The findings are significant because seismologists have long believed this portion of the fault is capable of sparking the so-called Big One that officials have for decades warned will eventually occur in Southern California.
…
Many scientists thought the Carrizo area produced relatively infrequent but large-scale earthquakes such as the Fort Tejon temblor. The new work suggests the area produces more quakes but also ones of a smaller magnitude than Fort Tejon, said Ray Weldon, a University of Oregon geologist….

Such temblors, experts warned, would likely be at least as big as the 1994 Northridge quake, which had a magnitude of 6.7.
…
… About 100 miles northwest of Los Angeles, the Carrizo area was one of the main sections that ruptured in the 1857 quake. That rupture, roaring southwest into the Los Angeles Basin, rocked parts of the region so hard that men were thrown to the ground.
…
By looking at the pattern of soils and using radiocarbon dating on charcoal deposits, [Lisa Grant Ludwig, a principal investigator on the study] found evidence of five large earthquakes dating back to the early 1200s. She found a gap of some 400 years between the 1857 earthquake and the one before, but only about 100 years separating the three preceding quakes.

Back then, the earthquake age estimates were very rough and the samples had to be fairly large…. Ludwig saved field notes and hundreds of soil samples in glass vials in her garage for more than 15 years, hoping that radiocarbon dating techniques would improve.
…
[When that finally occurred, they] went back to her archive, and the redating effort, led by scholar Sinan Akciz, found that the four big earthquakes before the 1857 temblor probably occurred around 1310, 1393, 1585 and 1640.

…
Because they are looking at only a handful of earthquakes, scientists can't be sure that the pattern will hold, Ludwig said.

"But we know it increases the probability of an earthquake," she said. "There's not any way I can look at the data and be comforted by it."….

BE PREPARED:

• OC Red Cross Urges Earthquake Preparedness, Awareness

• Earthquake Preparedness Tip Sheets (Governor's Office of Emergency Services)

• Southern California Earthquake Center