Department of Water Resources
A daily compilation for DWR personnel of significant news articles and comment
November 1, 2007
1. Top Items
Quake a reminder of risk for levees - Sacramento Bee
Earthquake prompts levee inspections in California's delta - Associated Press
Californians Reminded of Danger to Come - Associated Press
Quake a reminder of risk for levees
By Carrie Peyton Dahlberg, staff writer
The 5.6-magnitude quake that shuddered through the hills northeast of
The temblor, though, did send a reminder jolt about quakes and floods in a state where levee engineers have long considered it too costly to build a system that could withstand both at once.
The U.S. Army Corps of Engineers and the state Department of Water Resources recently began re-evaluating how much quake protection a levee truly needs.
The issue will take on new importance as the state begins to spend billions in bond money aimed at reinforcing a system of aging earthen walls that protect
"We have been trying to decide how to come to grips with seismic issues for levees," said Les Harder, the state's deputy director of Water Resources.
As recently as last year, John Hess, a top engineer with the Army Corps of Engineers in
Now, though, the corps is working on a technical document that will revisit that view, and probably change it, setting new guidelines for how levees should be certified, said corps spokesman Dave Killam.
In addition, the Water Resources Department expects to come out in the next two to three years with updated quake safety guidelines for urban levees that protect the biggest population centers. That will be followed by a statewide plan for 1,600 miles of levees by 2012.
"It could be we decide it's still not worth fixing thousands of miles of levees," said Harder. Instead, the state might opt in some areas for "a more robust repair scheme" that could mobilize quickly on post-quake levee fixes.
One area that's especially vulnerable to earthquakes is the Delta. Unlike
The state has estimated a massive quake near the Delta could flood as many as 20 or 30 islands, with an in-rush of saltwater that could disable the system that pumps drinking water to much of
Moderate quakes like Tuesday's aren't what the state worries about.
"We don't expect to see serious damage until we're up in the 6-magnitude, or 6.5, and that would have to be fairly close ... either within the Delta or on the western edge," Harder said.
Still, the Water Resources Department did coordinate with local levee districts and sent a few engineers out on patrol in the Delta on Wednesday. No damage was found.
Inspections also were conducted along south bay and coastal roads by about two dozen state Transportation Department workers immediately after Tuesday's quake, but no problems were found, spokeswoman Lauren Wonder said.
The 5.6-magnitude quake, centered in rolling hills about nine miles northeast of downtown
There were some toppled chimneys on ranch buildings in what's now a park, and some broken windows, but overall "we got a little bit lucky," Boatwright said. The quake's force "was sort of pointed away from where people live."
The quake, on the Calaveras Fault near its juncture with the
The state Office of Emergency Services said the temblor has "significantly increased" quake prospects along the Hayward Fault, which slashes through densely populated
http://www.sacbee.com/101/story/465072.html
Earthquake prompts levee inspections in
Associated Press – 10/31/07
By Samantha Young, staff writer
Experts said the magnitude-5.6 earthquake, centered about 9 miles northeast of
"Last night's jolt was not large enough to cause extensive damage, but it's a reminder of what will come," said Les Harder, deputy director of the state Department of Water Resources.
The quake's epicenter was at least 30 miles from the southern point of the Sacramento-San Joaquin Delta, but tremors were felt within an 80-mile radius, as far away as
It marked the largest earthquake in
Studies in the last few years have shown large parts of the delta's 1,600-mile levee system could crumble during an earthquake of magnitude 6.5 or greater.
The energy of a major earthquake along the
A massive levee failure in the delta would cripple
In an effort to prepare,
Gov. Arnold Schwarzenegger also convened a task force to devise strategies for managing the delta.
As a precaution, the Department of Water Resources dispatched inspectors Wednesday to the delta and instructed several dozen water districts to visually inspect the levees for cracks or water seepage, Harder said.
"It's probably the prudent thing to do, and it's good practice," he said.
He said more high-tech inspections would not be needed because of the earthquake's low impact on the delta. The agency also planned Wednesday to inspect its pumping plants, reservoirs and canals in the region.
Preliminary surveys immediately following Tuesday's earthquake showed only superficial damage at Dos Amigos Pumping Plant, about 85 miles southeast of
http://www.mercurynews.com/news/ci_7332570?nclick_check=1
Californians Reminded of Danger to Come
Associated Press – 10/31/07
By Scott Lindlaw, staff writer
SAN FRANCISCO (AP) — The largest earthquake to hit the
Tuesday's magnitude-5.6 quake, centered about 9 miles northeast of
The quake and the more than three dozen aftershocks that followed — the largest registering magnitude 3.7 on Wednesday afternoon — produced no reports of serious injury or damage, officials said. Tuesday's quake was felt as far away as
Even so, it paled in comparison to the larger one that experts anticipate. That quake will hit one of the seven major faults and pack 60 times the force of Tuesday's quake, said Tom Brocher, a senior U.S. Geological Survey seismologist.
Tuesday's quake originated along the Calaveras Fault, which is not thought to be as dangerous as a fault it intersects, the Hayward Fault. Scientists estimate the Hayward Fault has a 27 percent chance of causing a quake of magnitude 6.7 or greater.
Historically, severe quakes have occurred on the Hayward Fault every 151 years, give or take 23 years. The last one to hit was in 1868, meaning another could strike soon.
The Association of Bay Area Governments estimates a powerful
Tuesday's quake, which struck shortly after 8 p.m., raised questions about whether a quake hitting the Hayward Fault was now more likely.
Under certain circumstances, a quake on one fault can transfer energy to another, adding instability and potentially triggering events on the other fault, seismologists said.
By Wednesday morning, a consensus emerged at the U.S. Geological Survey that the previous night's quake did not significantly elevate the likelihood of a dreaded Hayward Fault quake. Tuesday's quake sent ripples of energy largely to the south, while the Hayward Fault extends north from the epicenter, Brocher said.
Still, state officials issued an alarming warning.
The California Earthquake Prediction Evaluation Council, a panel of scientists that advises the governor on earthquake forecasts, warned that Tuesday's earthquake "has significantly increased the probability above the normal level for a damaging earthquake along the Calaveras and/or
However, the panel said, "the overall likelihood of such an event is still low."
In addition to the seven major faults, hundreds of smaller faults form a latticework of cracks beneath the region, perhaps a dozen of which could snap and generate moderate quakes, said David P. Schwartz, chief of the U.S. Geological Survey's Bay Area Earthquake Hazards Project.
A hypothetical trench dug around the Bay Area would reveal hundreds of these small fissures, Schwartz said.
"The Earth's crust, which has been around for millions of years, has been pushed and pulled in all different directions, and is very broken up," he said. "It's literally cracked up."
Meanwhile, state and local inspectors examined sections of
"Last night's jolt was not large enough to cause extensive damage, but it's a reminder of what will come," said Les Harder, deputy director of the state Department of Water Resources.
A massive levee failure in the delta would cripple
In an effort to prepare,
http://ap.google.com/article/ALeqM5g-JQC5ESySZKfb7WpG_XRBRxNNYwD8SKIDR00
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