28 January 2004
Temblors along central San Andreas Fault peak every three years
A study by campus seismologists shows a higher probability of moderate to large quakes — magnitude 4, 5 and 6 — just as the frequency of smaller quakes, called microquakes, begins to increase along the northern half of a 110-mile segment of the central San Andreas Fault. The frequency of these repeating microquakes along the fault segment rises and falls over a three-year period, and moderate to large earthquakes are six to seven times more likely to occur at the upswing of this cycle.
“Larger earthquakes along the northern portion of the central San Andreas occur preferentially when the pulse starts up,” said Robert Nadeau, an assistant research geophysicist at the Berkeley Seismological Laboratory. “Quakes greater than magnitude 3.5 tend to happen within one year of the pulse’s initiation or start.”
Among the earthquakes that occurred at an upswing in microquakes was the destructive 1989 Loma Prieta quake, a magnitude 7.1 temblor. Assuming the three-year cycle has continued, the next upswing in microquakes should occur in late 2004, Nadeau said.
The phenomenon noted “has promise for forecasting larger quakes,” Nadeau said, “though this is our first look and it needs to be refined more.”
He reported the findings in the Jan. 9 issue of Science in a paper coauthored by his late collaborator Thomas McEvilly.
Microquakes are quakes that cannot be felt, typically lower than magnitude 3.5. From a study at Parkfield, Calif., at the southern end of the fault segment, McEvilly and Nadeau discovered in 1999 that repeating microquakes could be used to predict the rate at which the fault is slipping deep underground. They then looked at the central San Andreas Fault.
Nadeau said it is unclear whether quakes as large as or larger than the Loma Prieta quake will always correlate with upswings in microquake activity and whether larger quakes on the Hayward Fault correlate similarly with upticks in microquake activity there.
— Robert Sanders
New study looks at Bush school reforms
A new study shows that thousands of California schools are falling short of new federal standards because their diversity presents more hurdles than are faced by schools serving a more homogenous student body. Failing to measure well in a single category can spell “failure” for the entire school, the report says.
The new federal standards — championed by the Bush White House and approved with bipartisan support in the No Child Left Behind Act — aim to pinpoint schools that fail to raise children’s achievement. More than 3,000 of California’s 7,669 schools were characterized as “needing improvement” under Washington’s new rules this fall.
Washington requires public schools to test 95 percent of each student subgroup — such as students with disabilities, students by racial group, youngsters with limited English, and those from low-income homes. By these measures, half the schools in Los Angeles and Sacramento fell short.
Under Bush-administration reforms, any student group comprising 15 percent or more of a school’s population must meet testing and growth targets. When a school misses a target for any one group, federal sanctions kick in — allowing parents to move their children to another school and requiring the creation of school-funded tutoring programs. If student performances continue to lag, teachers can be replaced or the school handed over to a private manager.
Just half of California’s suburban high schools were deemed effective by Washington’s new standards this fall, according to the researchers. They said the odds of falling short and of federal penalties coming into play doubled for middle-class high schools that enroll three subgroups, such as whites, Asian Americans, and learning-disabled children.
The study was conducted by Policy Analysis for California Education (PACE), a research center based at Berkeley and Stanford, in collaboration with the Long Beach public schools.
“We discovered hundreds of middle-class schools that the feds began to penalize this fall, schools that are only guilty of enrolling diverse children,” said study co-author John Novak of the Long Beach school district.
Bruce Fuller, a co-author, a Berkeley professor of education and public policy, and co-director of PACE, said the study’s findings suggest that the new federal rules “are yielding unintended and demoralizing effects inside many local schools.”
— Kathleen Maclay