Small Earthquake Rolls Through Rivers...

Small Earthquake Rolls Through Riverside County

There are 11 comments on the NBC Los Angeles story from Oct 28, 2012, titled Small Earthquake Rolls Through Riverside County. In it, NBC Los Angeles reports that:

It measured 3.9 and was centered six miles southeast of Valle Vista, according to reports from the U.S Geological Survey.

Join the discussion below, or Read more at NBC Los Angeles.


United States

#1 Oct 28, 2012
I felt it. It was soft rolling shake that maybe lasted about 10 seconds. I couldn't find any information on recent quake information.
James Marple

San Diego, CA

#2 Dec 25, 2012
A majority of residents in Southeast Riverside County live with the reality that the overdue "Superquake" could bring down the experimental "jelly-fill" dams of the Diamond Valley Lake reservoir, releasing a tsunami wave far more destructive than hurricane Sandy's surges.

Most don't know about this and many just ignore hazards they cannot see but those who do realize the potential for another St Francis Dam massacre tense up whenever quakes strike the San Jacinto Fault Zone.
Their concern is that these may be "precursors" to the 'Big One' that seismologists predicted "within the next 30 years" back in the early '90s,
Some remember the words of TV Geologists Lucy Jones and Kate Hutton who reports that large quakes trigger small ones on nearby faults. like the one that runs directly under that East dam, for instance, that has been producing small slippage quakes despite claims of the dam builder that it is "inactive".

Some will evacuate for high ground the moment a large quake hits but most will become victims because no evacuation plan has been set up.(Officials have been amazing;u blind to the disaster potential, ignored State Law that requires an inundation map be published, new schools not be built in the flood areas, and evacuation plans be set up.) Some who can afford it have invented reasons to go on vacation for the next few weeks until these quakes did down.

In 1995 Geological Survey seismologists rated the San Jacinto fault with a 61% chance of a magnitude 6.7 quake or stronger within 30 years. No big deal unless you have family or friends in Hemet, Menifee, Sun City, Canyon Lake or Lake Elsinore. Folks in Murrieta and Temecula will be OK unless the west dam collapses. No faults were recorded under it but federal geologists raised questions about this.
James Marple

San Diego, CA

#3 Jan 9, 2013
This website < ; shows San Diego County's two dozen risky dams and, at its top, where thousands of acres in Temecula and Camp Pendleton could be flooded if the west dam of the Diamond Valley reservoir collapses or a landslide plugs the river gorge during a major rainstorm..

Flood control channels will not prevent massive damage if that dam fails during a major quake, and evacuation is not an option, the roads will become instant parking lots when a major quake hits.

State Law says land buyers must be notified if a property is in a flood hazard area of a State-approved "inundation map". How many of us have seen this map so that we know if our homesite or school is in the path of destruction from 400 million tons of floodwater pouring out of the reservoir if a major quake in the San Jacinto fault zone dissolves its "jelly-fill" dam? And what can we do as a precaution if we are in harm's way?
James Marple

San Diego, CA

#4 Jan 16, 2013
An ancient engineer called to point out a tiny quake two miles south of Hemet. Not good news, he said, because that puts it in the fault under the East dam of the Diamond Valley Reservoir. Very deep, though, about 12 miles down.

What's going on with that crack in the geologic understructure directly under and aligned with the dam? Probably not a significant concern because it is so deep, but the dam builder said that fault was 'inactive', yet it keeps slipping.

With the San Jacinto Fault Zone just six miles to the east, concerns about this fault being 'triggered' into severe movement by the overdue "Superquake" are not unreasonable. In 1995 Geological Survey seismologists rated the San Jacinto fault with a 61% chance of a magnitude 6.7 quake or stronger within 30 years. No big deal unless you have family or friends in Hemet, Menifee, Sun City, Canyon Lake or Lake Elsinore. Folks in Murrieta and Temecula will be OK unless the west dam collapses, then they are in a world of trouble.
James Marple

San Diego, CA

#5 Feb 3, 2013
The cluster of 7 small quakes 10 miles east of Hemet yesterday, deep below the deadly San Jacinto Fault Zone, may be no more than a minor readjustment of its complex structure, But then again, it just might be a precursor to a significant slip that could bring unpleasant consequences.

A small self-inflating raft could be a prudent investment for residents in the flatlands of western Hemet, Wnchester, Menifee and south Sun City because evacuation will not be an option. Canyon Lake and Lake Elsinore residents can just run up; a hill to avoid floodwaters should one of Diamond Lake's wet rubble dams collapse due to repeated shaking.

Of course, if their officials have not provided an inundation map and evacuation plan, and don't warn them with a powerful siren, most folks will just sit around wondering how much damage the quake did instead of using the brief time they will have to escape a wall of floodwater.

In that case there would be a lot of bellybuttons winkin' at the moon.
James Marple

San Diego, CA

#6 Feb 27, 2013
Another cluster of small quakes, up to 1.7 magnitude, is stirring up worries of folks who live below the huge dams holding 400 million tons of water in the Eastside Reservoir.
(It was renamed Diamond Valley Lake to make it seem less of a hazard to the people who expect one of its dams will fail if a major quake happens.)

The simultaneous 3.6 quake a few miles to the north on the same fault makes this swarm of shakes more worrisome than the last one.

Science Daily has been running a series of stories with new information about how quakes trigger others, and today's quake map shows this is happening.

Let's hope the fault under the East dam does not get excited and slip again.
James Marple

San Diego, CA

#7 Mar 18, 2013
An unusually high level of activity along the San Jacinto fault this week tells prudent residents from Hemet to Lake Elsinore to Temecula they should be prepared to find high ground immediately should the long-overdue Superquake arrive. Waterwings won't be sufficient for most folks because the outflow from their reservoirs as dams collapse will be a high-speed mass of mud and debris.

Officials in this corner of Riverside County have been persuaded by the highly skillled professional liars who serve land developers to not provide evacuation plans or a warning system for this hazard but then, it seems probable most dams are tough enough to not fail suddenly.

Of most concern is that East dam of the Diamond Valley reservoir. It's only six miles from the San Jac fault zone and the deep fault under and parallel to it has already shown activity so will be a prime target for "triggered" slippage.

Just after the dams were completed a Professional Engineer in Temecula confided that his main concern would be a big shake that lasted for several minutes. He thought it possible this would 'slosh' that long body of water enough to send a wave over the end dams that could overtop and cut through them, causing 'instant' failure and that would be disatrous for his family near Warm Springs Creek.

Lucy Jones didn't seem much concerned when I contacted her then, even though she and Kate Hutton had published a paper pointing out that big quakes could trigger little ones in nearby faults. So perhaps there's really not much to worry about. But it still seems likely that prudent people won't wait to see if the dams survived before getting out of harms way immediately if a big quake hits.
Robert da Silva

Plymouth, MN

#8 Apr 22, 2013
I'm thinking of moving to Canyon Lake but didn't realize that the Diamond Valley Lake Dam would affect the Canyon Lake. I thought it would just affect Hemet/Temecula/ but had no idea of how it will affect Canyon Lake. Is Canyon Lake a remote possibility? Is Canyon Lake less of a threat then say Hemet or Temecula?
James Marple

San Diego, CA

#9 Apr 26, 2013

When the DVL was being planned State and federal laws required that an "Inundation Map" be prepared so that residents could judge how they would be affected by the failure of one of its 3 'experimental' dams. Inexplicably, local, State and Federal officials did not bother to enforce this requirement so folks downstream from this giant pond - and most area homes are - had no idea they would be put in harms way.

An extremely concerned Professional Engineer with a major firm in Temecula worked with our CRWM group to delineate areas that would be flooded, estimating flood speeds and depths on a map we left on file in the local Resource Conservation District. He and others were concerned that schools and retirement homes would be built where evacuation would be impossible and survival unlikely.

After the dam was built members of the CRWM group and the RCD pointed this deficiency out to local officials and discussed it on a local forum. Their concerns went unrecognized by news services but the design capacity of the dam was quietly lowered by 50 billion gallons to lessen the potential for catastrophic failure.

Most homes in Canyon Lake would be overrun by water carrying the debris of many thousand homes if either the East or West dam failed. Eastern Hemet homes would probably be unaffected but those on the west side would be demolished within less than ten minutes if that dam was overridden by a seismically generated wave or if the fault under it 'twitched' significant, as predicted by the Earthquake Ladies of the USGS before the dam was built.

Temecula would not be affected significantly by this but if the larger and similarly 'soft' West dam failed it would receive half or more of the 800,000 billion gallons stored in the lake to enrich Upstate water profiteers, with major loss of life.

If you locate in any of the communities below this dam it would be smart to have your homeowner's insurance specify dam failure flood damage even if the home is not in a FEMA flood zone. If local insurers are competent the cost will be high but you or your survivors would suffer badly from having to pay for a home washed to the ocean.
James Marple

San Diego, CA

#10 Aug 20, 2013
A tiny quake under the Diamond Valley reservoir's East Dam yesterday may seem unimportant but two areas of ongoing movement along the San Jacinto Fault Zone several miles east of that huge mound of saturated soil make any slippage under it worth considering. The quake swarms near Anza and southeast of Hemet indicate significant movement along that primary fault line, increasing the pressure on points between them and thereby generating a potential for sudden slippage - such as the "Superquake" geologists predicted would happen during the past 30 years.

The fault beneath and parallel to this dam, described as "inactive" by MWD planners, has been slipping frequently since the dam was built, a common feature known as Reservoir-Induced Seismicity.(RIS) caused by filling Diamond/Domenigoni Valley with 400 million tons of water. The chance of dam failure, was reduced by MWD lowering the new lake's "design depth" shortly after it was first filled.(A response to facts posted by CRWM) Yet the two main dams, mounds of partially saturated soil and rock rubble, are still vulnerable to extreme shaking by the "Big One". Compounding this is the prediction of prominent geologists Kate Hutton and Lucy Jones before the dam was built that a large quake can cause a nearby parallel 'inactive' fault to give way suddenly.

Is a public warning system in place?
Most residents of south Hemet-Winchester-Menifee-Sun City would not have time to evacuate, the wall of floodwater would move fast and be overwhelming, but many lives could be saved farther downstream if County officials have done their work properly.

If the East Dam fails it would look like this < ; in the first few minutes. After that the collapse would be quick and complete due to erosion by the enormous weight of water bursting through.
James Marple

San Diego, CA

#11 Sep 13, 2013
A Murrieta resident stopped by our weekend discussion to ask why we stopped posting CRWM's facts and figures about the high cost and poor quality of his water supply. We pointed out that members of this forum did not seem much interested in facts and figures about planning alternatives that would give them cheap and plentiful pure water while eliminating need for the proposed flood control project.

He replied that he and his neighbors were very interested but either "not good with words" or afraid of retribution from city and county officials if they spoke out. So we promised to do better just in case some citizens who browse this forum might be concerned enough to do something about losing more the $5,000 per home yearly to extortion by public officials and water suppliers because land developers who own their news services and use these to keep them dumbed down.

Todays fact:

The continuing series of tiny quakes at the East dam of Diamond Valley Reservoir are not merely harmless "RIS" (Reservoir Induced Seismicity), they reveal that the supposedly "inactive" fault directly beneath it is moving in response to swarms of quakes along the nearby San Jacinto Fault, our nation's most active. <> ;

And this reveals that false and misleading information was published by MWD to quiet fears of a dam failure that would wipe out most south Hemet-Menifee-Sun City-Canyon Lake residents. Those folks should at least be given a warning if this experimental dam begins to fail so that they know which way to run.

How soon will the pressure on this fault cause a sudden slip that releases a tremendous shock wave to the dam above, destabilizing the 'jelly-fill" dam? When the similar Teton dam broke even though it was only partly filled residents had 2 1/2 hours to evacuate so the loss of life was minor.
When the East dam breaks the loss of life will be in the tens of thousands
if there is no warning system.

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