Warnings About San Andreas Earthquakes Are Necessary

My husband is in the hospital again for observations and tests.  I hope all is well in the end.  As for California: massive number of quakes have occurred in the southern end of the Salton Sea.  California-Nevada Fault Map centered at 33°N,115°W

More than 400 earthquakes rattle California as the lower end of the San Andreas Fault system shakes like jello.  The stresses there are tremendous but ever since the fault shifted recently in the Gulf of California, the lower end has been having frequent bouts of activity.  These are increasing, not decreasing.  Whenever there are multiple clusters of 4.0 or less quakes in a region along the Ring of Fire, there usually is a major quake brewing.

Earthquake swarm puts California areas on edge | Nation & World | The Seattle Times

A magnitude-4.2 earthquake rattled communities 100 miles east of San Diego on Monday night, despite observations from earthquake experts that a series of small to moderate earthquakes seemed to be slowing down and getting smaller in magnitude.

That may be true for San Diego.  The latest round of quakes are not damaging for anyone in the near vicinity.  The problem is, this shows that both the top and the bottom of the entire fault line system has been reset repeatedly while the entire middle section is frozen in place.  This is bad.  Very bad.

Here is a previous story I wrote about the possibility of a major quake in central California:  Earth news: Geologists Warn San Andreas 99% Chance Big Quake Next 35 Years.  The map below is from 2008.  It is very similar to the map today.

Since then, we have had a very active quake session all along the entire coastal west except for just above LA.  IRIS Seismic Monitor – Recent Earthquakes

We can see this clearly in the map above.  The quakes at either end of the San Andreas system and the Juan de Fuca plate are all very, very active while the center is still.

Many of these quakes are at the critical 10km level which is where  many of the great quakes operate.  The chances of a great quake bigger than a 7.5 is very high for Los Angeles and the midsection of California.  Ten years ago, quakes were so seldom on this map below, there were, at most, only three or four at a time.  As I demonstrated with my 2008 link above, the tendency is for more and more clusters of quakes that shake the entire region.  As it is today.   This year, there are many days when there are hundreds.  The shaking has expanded to Nevada which is another sign that stress is building.

With many quakes, stress is relieved.  But the nature of the swift slip/slide northwards of the entire coastal region from the Gulf of Mexico to northern California means that if the middle section hasn’t slip/slide along with the rest, it will be forced to catch up violently and suddenly.

We have no idea why the middle section has stayed so frozen in place while the other parts have been yanked around so much.  Something around Fort Tejon is doing this.  Several fault lines converge on this site.

This close up map above shows clearly that there are no quakes happening in this entire region.  This is bad news.  Not good news.  People living in the Los Angeles basin as well as all the communities to the north and east should make urgent preparations for a possible quake.  Since geological forces move at their own pace, we have no way of exactly predicting when an event will happen.  But we can calculate roughly the odds of an event happening and there is a 100% chance the middle section of the San Andreas will violently reset itself and the chances of it happening in the next few years is extremely high.

This is a map showing the northern end of the frozen portion of the San Andreas and it is having small quakes this month.  I take this as another warning sign that there is a lot of stress to the south of Parkfield.  Parkfield was where the Great San Francisco Quake stopped 100 plus years ago.  The Fort Tejon quake as 70 years before that and since then, hasn’t happened so it is overdue.  AFP: US overdue, under-prepared for huge Pacific quake:

“All preparedness is local and it varies dramatically over the length of the coast,” said Tom Tobin, president of the Earthquake Engineering Research Institute.

For instance, California has a state law that says all hospitals should be constructed so that they can withstand a major earthquake and still function, Tobin said.

But “since 1971 only one new hospital has been constructed in San Francisco to that higher standard. All the other campuses are in older buildings, some of them dating back to the early 1900s,” he said. 

That is, there is little done to fix the weaknesses inherent in how things were built in the past.  The chances of grave hazard for people is quite high, not low.  Tokyo survived the recent giant quakes that shook and for the most part, destroyed a good part of the east coast of Japan but the effects in Tokyo were much lower due to it being further away from the epicenters of the quakes.  A 9.0 quake in Tokyo bay is another story.  We don’t know if the redesign/retrofitting done there works.

I do know that all schools have diagonal steel struts added to prevent the buildings from pancaking.  The collapse of cement floors in buildings is a huge hazard.  Many, many people have died all over the earth in these very dangerous modern buildings when they suddenly lose the ability to support the cement slabs above.  LA has many buildings like this and I believe virtually none have any diagonal steel beam support structures.

Most of the deaths in Christ Church, New Zealand was from several cement floor buildings pancaking.  This is sadly all too common and the engineering beliefs about these buildings has been very sadly misplaced.  All of them are quite unsafe.  Alas, most parking garages are exactly that: death traps in earth quakes and LA has a good number of these.

 

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